Build on a slope: Building a House on Sloped Land

A grass-covered hillside makes for a picturesque setting for your dream home, but the process of bringing that picture to life is more complicated than it would be for the average dwelling. Building a house on a sloped lot presents unique challenges that you need to be aware of to ensure the rewards for you are worth the additional costs and longer construction time.

How Do You Build on a Sloped Lot?

There are two ways to build a house on a sloped lot: using the “cut and fill” method, or making use of stilts.

Cut and fill refers to the process of leveling out the ground for the foundation by adding soil, removing it, or both. Soil may be brought in to “fill” the plot and make it level, or it can be dug (“cut”) from the slope and either trucked out or used to shore up retaining walls for the home. Depending on the grade, soil conditions, and other factors, cutting and filling can make construction multiple times more expensive than that for a home on a flat site.

Using stilts is an alternative to cutting into the slope that involves using a crane to lift the home onto supporting wood or steel columns. This can be a much more cost-effective method than cut and fill and can also open up the realm of possibilities for home placement, such as building out over trees or water.

Why Build on a Sloping Site?

It’s no accident that some of the most coveted homes in the world are built on slopes. Here’s why:

• The views. You can enjoy stunning vistas of green valleys or wooded forests below, clear sky views above, and uninterrupted lines of sight for miles in some cases.
• The landscaping. For many, the main appeal of having a home on an incline is the striking aesthetics it presents, which includes the opportunity for breathtaking landscaping.
• The space. Lots with steep slopes allow for the extra space of a walkout basement that serves as another floor of the house.
• Natural lighting. When you’re making your house plan, don’t forget the bay windows! Houses situated on the side of a hill are often perfectly situated to maximize lots of natural light, a prized feature that carries the bonus of tons of health benefits, such as better mood, better sleep, and higher productivity. 
• The seclusion. For those who place a premium on privacy, building on a slope allows you to select a location far off the beaten path.

What Are the Major Challenges of Building on Sloping Land?

The biggest hurdles boil down to two main factors: the gradient of the slope and whether the lot is upslope or downslope. 

You can get a rough idea of how challenging a particular site will be to build on by its gradient rating. Less than 10% incline is considered slight and is the easiest to build on, while 11-20% is considered moderate. Anything above 20% is deemed steep. Beyond about 15%, costs begin to increase significantly as the risks become greater and the work becomes more difficult.

An upslope plot (where what will be the front of the house rises up to the back) is also more challenging than a downslope plot. These types of plots usually require some amount of cutting or even blasting, plus transporting and disposing of rocks and soil.

Additional Foundation Work – Time & Cost

It’s not unheard of to have houses built on grades of as much as 50%; however, the cost of the complex foundation systems required for such houses is often more than the cost of an entire house on flat ground.

But even moderately sloped sites typically require more concrete, deeper excavation by specialized excavation equipment or blasting, retaining walls or terraces, and specialized solutions for drainage and septic systems. All that extra labor and materials needed to ensure the house is up to code and safe to inhabit mean higher costs and longer construction times.  

Water – Drainage & Sewage

If you’ve ever seen footage of the effects of mudslides, you’ll understand why proper attention to drainage — for both surface and subsurface water — is absolutely crucial to building on a slope. 

Rainfall runoff has to be redirected away from your home’s foundation, without endangering any neighboring properties with water flows and without flooding public roads. Retaining walls have to be “tanked” (waterproofed) and drained to prevent water from pooling there. Swales and culverts can usually be used to channel the runoff to stormwater drains or soakaways (holes dug in the ground and filled with rubble that allow surface water to percolate back into the ground).

If your home will have a full basement that will be located below the seasonal high water table, subsurface water leaking in can become an issue. Workarounds range from the elegant (French drains and/or crushed stone beneath the foundation) to the functional (a sump pump in the basement during rainy season).

Finally, sewage treatment can be tricky depending on where your home is relative to the sewage line. If the line is uphill, you may need to install a pump, and if it’s downhill, you may have to install tumble bays to slow the flow to a reasonable rate.

Storage of Fill Soil & Staging Areas

If your plot requires cutting, the resulting extra soil will either have to be transported out or stored somewhere nearby if it is to be used for filling. Even if you’re not cutting, you’ll need a staging area for vehicles, equipment, and deliveries. If you’re only filling, you’ll have to have soil trucked in to the site, a costly expense that varies widely with geography, so we highly recommended getting estimates.

Access to the House

Access to the property — for both you and your contractors — is an important factor to consider in your calculations, as well. Property that may seem like a steal initially could run up high costs for additional grading if there’s no good way to access it. Switchback and curved driveways are helpful and attractive, but small properties that don’t have room for them may have no choice but to install a steep driveway that can be hazardous in inclement weather.

Replenishing the Construction Site

Over the weeks or months it takes your home to be built, as trucks come and go, heavy equipment is parked, and construction materials are scattered about, any natural plants on your new home site are going to take a beating. Replanting with cultivated plants or waiting for the natural flora to grow back may require many months of waiting before the property gets the look you’d imagined when you first began the new home-building process.

Soil Type

The type of soil of a sloped property can be easily overlooked but could pose a problem for home builders. While granular soils (gravel, sand, or silt with little or no clay) drain well and can bear high loads, soils with high clay do neither well. Certain clays can damage foundations by swelling or expanding when wet or frozen and may require expensive engineering fixes or additional fill of granular soil.

Rock ledges near the surface can also present difficulties with drainage and septic systems. Often the most budget-friendly solution is to work around them, as blasting them out is costly and carries a liability risk to neighboring foundations.

Landscaping

Flat ground is of course easier to work with, but with the right planning, a sloped lot can be the canvas for landscaping that sets you apart from ordinary front yards. You’ll want to put down plants that can take root on an incline. Ground cover plants with deep roots such as English ivy and Euonymus vines can help reduce erosion and prevent weeds. For planting in retaining walls, Better Homes & Gardens recommends plants that grow well in crevices such as creeping phlox, thyme, and candytuft. They also suggest waterfalls, potted plants, and decorated switchbacks for sprucing up sloped yards.

Legal Eagle Contractors is an award-winning full-service building and remodeling company for residents of Houston, TX with decades of experience in building custom homes and home additions.

What You Need to Know About Building on a Slope

This Montana cabin takes advantage of its sloped lot with a walk-out basement on the backside. See more of this home here. Photo: Joseph Hilliard

Question: My wife and I own property with a gentle slope. I’ve heard it’ll cost a fortune to build up the ground for a slab foundation. Would I save more by building a house with a basement?

Answer:

Slabs and slopes often don’t play well together. It isn’t just the cost; there are other problems as well. Bringing a slope up to level for a slab usually requires building a stem wall or retaining wall on the lower edge of the foundation and adding fill dirt to provide a level base. But be careful: Placing a slab on fill opens the door for cracks and settling. Make sure your builder or excavation team takes great care to compact the fill.

Another issue is drainage. Building codes require that non-masonry building materials be at least 8 inches above the soil surface. I recommend doubling this height to protect log walls from damaging rain and drifting snow. This means adding even more fill. If you’re trying to avoid a basement, consider using a crawlspace. This will require a footing and short wall. If you’re building where winters can be severe, normal footings must be several feet deep.

Also, ask your building about frost-protected shallow footing (FPSF) to reduce the amount of digging and concrete. This building technology has been used in Scandinavia for half a century and provides a more energy-efficient foundation system for less money. As an added bonus, your crawlspace will offer some storage and allow you to run electrical wiring and plumbing—a much easier route than running these through a slab.

Photo: Elk Ridge Builders

Question: What are some pros and cons of building on a slope?

Pros

Building on a slope offers the possibility of a walkout or lookout lower level. This means daylight instead of the dark mustiness of a subterranean basement. Being able to finish all or part of the lower level allows you to build more home for less money.

Sloping lots offer a lot of aesthetic advantages, too. In a forest, a home built on a slope may mean that windows on one side will take in views of a forest canopy and provide a sense of living in a tree house. In more open country, a slope can provide your home with a commanding view of mountains, lakes or meadows.

Cons

Slopes have two potential drawbacks that can cause some anguish to your builder and pocketbook: accessibility and drainage. Steep slopes are difficult to access with the heavy equipment needed to build your foundation. The time required to build your foundation is often increased, and it may be necessary to pump concrete to your foundation. This can mean increased costs.

Sloped home sites also present drainage challenges. If you build at the top of the slope, chances are you won’t face any issues. But if your site is on the side of a slope, you need to pay special attention to the amount of water that can flow toward your home and its foundation. Building codes require that the land immediately around your foundation slope away from it. This may mean your builder has to create a foundation that is partly exposed on the “upslope” side with fill dirt added for a slight counter slope against the house. This step has a positive side: less digging, and the so-called waste soil from excavation may be used as fill.

See also: How to Choose the Best Possible Site to Build

These Ohio homeowners took saw their sloped lot as an opportunity to take advantage of the view. See more of this home here. Photo: Richard Lee 

Question: Our lot has a 15 percent slope. Does this type of grade require a special type of home design?

Answer:

A 15 percent slope means that, for every 100 feet of horizontal distance, elevation changes 15 feet. This may not seem like a lot, but let’s consider how building on a slope like this affects your foundation.

Imagine that your home has overall dimensions of 28 by 60 feet. If you orient the house so that the 60-foot dimension is in the same direction as the slope, the lower corners will be 9 feet lower than the upper corners. If you orient the house so the 28-foot dimension is along the slope, the lower corners will be about 4 feet below the upper corners. As you can see, the latter case involves much less digging.

You can easily determine your home site’s slope with some string, a tape measure and an inexpensive “string level”—a small level vial that hangs from the string and is available from hardware stores. Simply stake one end of the string and measure off a distance down the slope with it. Hold the string taut and level and measure the distance from the string and the ground. Transfer this information to a sheet of graph paper and sketch in your foundation to see how the slope will affect your foundation.

See also: How to Pick the Perfect Piece of Land

Question: Is building on a slope more expensive? Will there be extra excavation costs?

Answer:

Usually, building on a slope requires less excavation than building on a site on level ground. However, if the slope is steep, the excavator may have to do some grading around the side in order to gain access. Also, steep slopes may require the use of more specialized equipment designed to operate in rougher terrain. Steep slopes may require a lot of final grading to re-direct water flow and protect your foundation. This occasionally requires your builder to haul in and spread more fill dirt, which can increase the cost of your foundation significantly.

See also: Your Step-by-Step Guide to Log Home Construction

Question: We have a 2-acre gently sloping lot in a gorgeous area that’s sometimes prone to mudslides. What major factors should we consider before we build?

Answer:

If you’re in mudslide country, you don’t want to find yourself upon the ground that may slide or be in a mudslide’s path. Study your site carefully to determine where water and mud have gone in the past. If possible, visit your site during a heavy downpour and see what happens to the water. Gentle slopes don’t usually pose a great threat, but building your home on the lip of a steep slope raises the possibility that rushing water may scour under your foundation and send your home sliding. If your building site presents any risk of mudslides, it’s best to talk with a civil engineer or an experienced excavator.

This log home built along a slope takes in 270 degrees of scenic North Carolina wilderness. See more of this home here. Photo: Joseph Hilliard 

Question: We want our sloped property to have gorgeous landscaping. What can I do with a sloped lot?

Answer:

Landscaping on slopes requires some attention to detail. First, make sure that the landscaping you have in mind can handle the slope. If some of the plant species you’ve chosen have difficulty establishing their roots in sloped areas, you may want to create a series of retaining walls. The construction of retaining walls is both an art and a science. Not only does it require a feel for the aesthetics of the landscape, but you must understand the forces that affect the wall and the construction required to control them.

Short retaining walls (2 feet or less) are fairly simple, but as the walls exceed 2 feet in height, the weight bearing on the back of the wall makes construction more challenging. It’s important to build the walls to resist the forces of the soil they hold. This may mean extra reinforcement and the use of “dead men,” which are anchors for the wall.

Sloped lots usually offer a world of design and building possibilities. If you plan correctly and work with your builder to properly map out and excavate your home site, you’ll get the best of both worlds: an efficient home plan and some amazing views.

See also: Five Tips to Hardscaping Your Property

Seven Quick Tips for Success When Building on a Slope

Create a daylight basement in the excavated wedge area under homes on the downside slope.

You’ll create a great view with an additional room, instead of an underused crawl space, and without enlarging your home’s footprint.

Reverse your layout.

Sloping sites allow a more modest appearance from the front and a grander one from the rear, especially with dramatic windows, such as prows. When building on a slope, it is often best to put your “front” door behind the house.

Have your driveway access the home from above, not below.

You’ll avoid having to cut the driveway into the side of the hill and build retaining walls to keep dirt and stone from falling onto it. Placing your garage at the front of the top level opens up views at all levels in back of the home.

Build tall.

Taller homes with smaller footprints require less excavation and grading, both of which are major construction expenses. And a narrow, stacked house with an open floor plan can bring views to all or most rooms.

Avoid building on the very top of a hill or mountain.

A panoramic view is great, but it will also raise your heating costs by exposing the home to cold winds in winter. Use the slope to shelter the house and narrow the view’s focus.

Properly site your home.

Site your house to avoid winter shade and summer sun as much as possible.

Make the house part of the view.

Build to conform to the land’s contours, and blend rather than clash with the topography.

Learn more about building on a slope:

• Sloped Sites Vs. Flat Lots: Which Is Right For You? 
• Is a One-Level Log Home Cheaper Than Two Stories? 
• Your Guide to Daylight Basements

Smart Solutions for Steep Slope Building — warmmodern living

Building into a gentle slope can enhance the efficiency of a design by providing living space inside the foundation and requiring less additional material and labor than the same amount of space above grade. And if properly designed, the in-ground living area can be bright and spacious.  

Environmentally responsible site design begins with minimizing disturbance to any site, and working with the existing topography is an essential ingredient. A more measurable benefit of building into a slope is often reduced heating and cooling expenses -and added comfort- that result from the temperature of the soil five feet below grade (the “outside air temperature” of these spaces) is a constant 52 degrees year-round. 

The ideal slope for in-ground building is a slope of 5 to 7 feet through the width of the house, or 15% to 20%.  Building on steeper slopes often presents challenges, and this type of construction is carefully regulated by local jurisdictions that vary, as do local soil types.

Codes that restrict building exist to protect the environment and the people who share it. What are the concerns with building on a steep slope; how are they addressed; and what is the cost of addressing them?

This is a long post, so if you don’t have the time to read this over a nice cup of tea, go directly to the last section, “Tips for building site hunters regarding steep slopes”  … and please return later to read the entire piece!

What are the issues of building on steep slopes?

Soil stability
Soft soil not retained by ledge or deep-rooted trees on steep slopes is prone to dangerous landslides that can affect areas tens of times larger than a single home site and may impact hundreds of lives. Landslides occur when these soils become saturated and heavy, and gravity beckons. The steeper the slope, the greater the danger.

Construction activity
Any disturbance to the ground during construction- excavation and backfilling, especially during spring  or any rainy period – disturbs the site’s static state and may pose a real and sudden danger to construction crews.

Foundation stability
In these environments, special care must be taken to ensure that foundations are supported by more stable soil or bedrock  and that the foundations are designed with adequate strength to resist the forces of shifting soil around them. 

Water management
Since the footprint of every house (and its driveway and sidewalks) replace permeable (absorbent) ground surface with impermeable surface, water running off the impermeable surfaces can cause the soil to become over-saturated, weaken, and slide. Managing the runoff is a matter of great concern and may affect the safety of hundreds of people nearby.

How are these issues addressed

Let’s use a real example.

My clients purchased a site in a well-established neighborhood in a Seattle suburb. Neighboring houses built over the last fifteen years are typically over 3000 square feet with attached two and three car garages built on hilly terrain.

The site slopes down from the street, the portion closest to the street being the steepest. The ground falls 40 feet over the first 70 feet from the street, In the last several years as the pace of development in the area quickens, small landslides have occurred. The county now defines a steep slope as 30% or more and requires a  special permit that imposes specific restrictions on developing steep sites. 

The process, not yet complete, has gone smoothly:

Initial site visit

I study the regs and visit the site with the client. I advise:

1. Site the house about 50 feet from the street where the ground slopes only 10’ over a house depth of 27 feet.

2. Build a compact vertical house in which the floor levels match the contours and minimize disturbance to the site. Three full living levels, (the clients are young and energetic): enter the house on grade on the middle level, a 900 square foot great room with expansive views to the southwest through the treetops. 

3. The upper level will be the primary bedrooms and a 400 square foot roof deck above the treetops, which I refer to as the” home’s, backyard,” since development of a ground-level yard for outdoor entertaining will likely be forbidden.

4. The lowest level will include a private guest suite, a large art studio, both with on- grade walk-outs , and mechanical and storage rooms .

5. Detach the garage so its elevation can be independent of the house.

Investigate

 We schedule an exploratory meeting with the City Engineer and senior members of the zoning and building staffs and the fire chief.   

 We preset our site plan concept, a sketched house plan and house plan, and a 3D massing model.  They pronounce the concept sound with some reservations:  

• They warn us not to cross an on-site sewer easement with cars. It runs the full width of the site half way between the street and the proposed house location. 

• We’ll need to install a sprinkler system since the nearest fire hydrant is over 500 feet from the house location. 

• They express concern over where and how to channel rainfall from the impermeable house and garage roofs and driveway, potentially destabilizing the slope. And the nearest municipal storm sewer is over 200 feet away uphillfrom the site.

• They remind us of the requirement to engage a geo-tech engineer who would take soil borings and advise us and the City on the design of a foundation that would bear on stable soil.  

• When approved, there will be a buffer of 15 feet around the structures and driveway that may be landscaped, but no alterations of any kind can be made to the remainder of the site.

From the southwest

Dig deeper

My client had already engaged a geotechnical engineer. Soil borings are taken in several locations at and near our proposed house location.  My client and I meet with the engineer to get the results and to strategize on the issues raised by the City. His report was mixed: 

• The soil is stable enough to support the foundation without many extra bells and whistles. The design of the house and the proposed siting fit each other nicely, with only a portion of one wall requiring a pour of over 8 feet.  The geotech will work with Lindal’s structural engineer on a foundation design that will take the site conditions into account: a base for the house that is well supported (vertically) and also resistant to shifting soil from uphill (laterally).

• The sewer line is near the surface. Making the necessary cuts for a driveway might in fact expose the line. The only way for cars to access the house will be to replace about 40 feet of the line with a deeper line at a huge cost borne by my clien

• Rainwater from the impermeable roofs and driveway cannot be drained anywhere onto our site. The soil is not stable enough. And the nearest city storm sewer is over 200 feet away, uphill from the house (pumping required)! 

From the northwest

From the southeast

A creative and realistic approach

This is a moment when some clients give up, and others   angrily lash out and vow to fight the restrictions (they mean that) at any cost (they don’t mean that). Fortunately, this client wants to satisfy the City by addressing each issue proactively and creatively. Our case for the special permit includes:

• We are designing a “vertical” house with a 900 square foot compact footprint that is roughly 40% of the size of  the other homes in the subdivision. many of which are on sites now defined as steep slopes.

• The foundation will be built to the spec advised by the geotech and approved by the City. No cutting corners here.

• The idea of crossing the sewer easement Is nixed, and the client decides to create a parking area on the street side of the easement.   This decision precludes a garage and a long driveway reducing the added impermeable surface on site by about 1200 square feet. Our total impermeable surface will about 25% of the neighborhood norm.

• Rather than arguing for larger area around the house to develop, we’ve planned a 425 square foot “roof yard” that will enjoy full-day sunshine and be ideal for family activities and entertaining. The roof yard is also an appealing anecdote to parental concerns regarding the security of children playing alone in their yard.

• The house will be built with a catchment system that will also purify the roof runoff so that it can be used for all domestic purposes. This will alleviate the concern of adding water to the site and the expense of under-street piping and pumping to a remote storm sewer. The system will cost $35,000-$40,000.

A schematic of our proposal

We have addressed the concerns of building on a steep slope, and the client will enjoy benefits from several aspects of the proposed solution.

What is the added cost of steep-slope construction? 

By now you’ve figured that all the testing, proposal preparation, the precautionary measures to construct, and the inspection of this work of community-wide importance carries a substantial price tag. While many of the cost centers cannot be determined until the work is actually done, clients need to budget for these expenses. In this case, I’ve estimated:

Often the added expense is more than the money you saved by purchasing a “site with issues” And the “expense” of added time to permit can also be considerable if you choose to “fight city hall”. 

Ahhhh… but the result can be magical when a house and its site are in perfect harmony.

3500 square foot steep slope design: Sammamish, WA

Warmmodern Living’s tips for building site hunters regarding steep slopes

The first seven tasks should be completed during the feasibility period of your site purchase… before closing on the site.  

1.  Ask the seller’s agent if there are any known issues that will require a special permit (that covers more than steep slopes).

2.  If your state requires seller disclosure forms, obtain one from the seller’s agent.

3.  Research the permitting jurisdiction’s website for their definition of a steep slope (e.g. any area that exceeds 30%) in the area you intend to place the house or any other area of the site that will be developed(driveway, landscaped yard, pool area etc.). Then check the site using a topographical study if one has been done or if there is no topo plan, hire a surveyor for the   hour it will take to  come to the site to measure the incline.

4.  Meet with city or county zoning and building officers to gain insight into their concerns and suggested remedies

5.  Hire a geotechnical engineer to test the soil and explain issues and possible remedies.

6.  If the site is priced comparably to nearby sites with no issues, try to renegotiate the price. If there is a feasibility period, extend it to six months or a year.

7.   Identify remedies, estimate their cost, and make sure you are still within your budget. 

8.  Design your home with an experienced professional who will guide you through this process and can guide you creatively.

9.  Begin the special permitting process as early as possible. Agree upon deadlines with the professionals you rely on to contribute to an approval. Don’t hesitate to be aggressive with laggards. 

Steep slope design, New York

Steep slope design, Washington

An upcoming blog post will shed some light on catchment systems, why you may want to consider one, how they work, and when to begin planning one.

What to Consider Before Building on a Steep Slope

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Building a home on a hillside or steep slope offers unique design opportunities and stunning views — but it’s not without challenges. A successful steep slope construction project requires thorough planning and research to ensure you…

1. Select the right piece of property
2. Can construct a rock-solid home that’s built to last

Keep reading to learn 8 important soil and site factors your design-build team will help you consider before selecting a homesite for your steep slope construction.

1. What is the property’s slope? 

The steepness of your property can be expressed in degrees or percentages. Accurately calculating the slope of your property is critical for many reasons:

• It’s important to understand and apply code requirements
• Will help you determine your foundation wall heights
• Determines fill and grade quantities
• Determines overall site stability
• Helps with surface runoff calculations

2.

What’s the surface texture of your soil?

Surface texture refers to the amount of sand, silt, and clay in the soil. It’s important to gauge the surface texture of the soil on a steep sloping property as it will affect your foundation and landscaping abilities.

You can get a general idea of the surface texture of the soil by rubbing it between your fingers or hands — what do you feel?

• Silky clay texture — This type of soil is sticky when wet and very hard when dry. It is very difficult to work with, both when landscaping and constructing a foundation. 
• Floury (loamy) feeling — This texture of soil is easy to excavate and ideal for landscaping and gardening. It absorbs wastewater quite well. 
• Rough and gritty — This texture of soil will need significant moisture improvement if you want to use it for landscaping and growing. While this texture of soil is easy to excavate and absorbs wastewater quite well, erosion is a concern.

3. Have you measured soil permeability?

Soil permeability is the rate at which water enters and passes through the soil. Permeability will play an important factor in choosing a wastewater treatment system. You must take soil percolation tests before choosing the right system for your property.

For example, septic system costs can increase significantly for soil with a very slow permeability. This type of land requires extensive lateral drains or other expensive modifications.

4. Is the property at risk for mudslides or flooding?

You need to understand the rate that water flows off your site as well as the depth at which water occurs in the soil — both seasonally and permanently. This information will be based on the slope of your property, soil permeability, and soil texture. You should also consider the potential for landslides and flooding hazards.

While a geotech engineer is needed to accurately assess these conditions, you can contribute by:

• Noting if there are any streams or other surface water on the property
• Viewing the property in multiple weather conditions and seasons to see if the property is at greater risk of water issues at different times of the year
• Asking nearby residents about site conditions

5. Are there any erosion concerns?

Measuring topsoil is important for understanding the future potential of erosion. Ideally, you want topsoil that’s at least 6 inches thick. In extreme cases where topsoil is less than 3 inches (or even non-existent), you’ll need to plan for…

• Extensive filing and leveling
• More costly septic system installation
• Extensive landscaping modifications

Whether or not you have a thick layer of topsoil, it’s important to take erosion control measures during construction to ensure a rock-solid home.

6. Can you achieve the design you want on the property?

All the factors above combined with the size and location of the land will help to determine what may or may not be possible in terms of design and landscaping. 

For example, steep slope homes are often designed with daylight basements — but perhaps that’s not something you envisioned for your home. Or maybe you’ve always wanted a swimming pool on your property, but it won’t be possible on this piece of property.

All said, don’t immediately discount a sloping property without first working with an expert. Modern advancements in the design-build industry open up a world of possibilities.

7. What specialized equipment will be necessary?

Sloping properties create a few logistical challenges when it comes to construction — particularly when it comes to equipment. Steep slope construction is often considered hazardous terrain and may require specific tools and machinery to get the job done correctly.

When you work with the right design-build team, they’ll understand what equipment is required. They’ll also know how to conduct any necessary equipment modifications while staying in accordance with industry best practices and manufacturer’s guidelines.

8. Do you understand the timeframe?

Building a home on a sloped lot often requires a bit of extra time — there are extra steps and more labor required to get the land to a safe and stable place. Work closely with a design-build expert to make sure you understand the timeframe, and possible delays, beforehand. 

Always work with a steep slope construction expert

Whether or not you’re building on a steep slope, you should always have it reviewed by a qualified engineer. 

At Westlake Development, we partner with local geotech engineers to investigate the soil and surrounding groundwork, provide essential documentation, and help with the construction process. Our team knows the proper way to place and construct a residence in the most structurally sound and cost-effective way — all while taking advantage of all the benefits the home site has to offer.  

With over 30 years of experience constructing custom homes on steep slopes and other challenging properties, we provide peace of mind and an easy, enjoyable experience.

View our gallery of work or contact us to learn more.

About the Author: westlake

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How to Build on a Sloping Site

(Image credit: /o Roderick James Architects / The Gitcombe Estate; photographer Matthew Heritage )

A sloping site can be one of the reasons you discount a plot to build your dream home on. But, although it can be challenging, complex and therefore add costs to the project, it can be well worth it. The end result? A stunning and interesting home that uses the sloping site to its advantage.  

But what do you need to consider if you choose a sloping site for your self build? From the costs to the construction; from drainage to design — here’s a look at what you need to think about before the project begins.

How Will a Sloping Site Affect Costs?

The use of reinforced suspended concrete floors – most commonly precast beam – and hard landscaping, extra drainage, including perhaps the necessity for a pump, and extra work in stepping the foundations will all cost money. 

A standard foundation for a home on a flat site may take three to four weeks to complete. In contrast, if you are retaining the banking with sheet piles, then building tanked retaining walls, creating basement rooms, and adding a beam and block floor, all while working on a slope, then this could take six to 10 weeks. That will have a massive impact on the length of your project and its cost, both directly and in terms of indirect costs like insurance, welfare facilities and scaffolding.

Building on a budget can be difficult on a steeply sloping site; I would estimate that the same floor area (GIA or gross internal area) of a house on a flat site may be as much as 20-30% less expensive. This, along with potentially adding six weeks on to your timeline, may not work for some self-builders.

(MORE: Foundation Systems and Soil Types)

Cut and Fill

This describes the process of carving out a level plinth on a sloping site, in order to build a home that is essentially designed for use on a level site. Any spoil that is cut from the bank is reserved in order for it to be brought back to make up the levels on the lower edge. 

The foundation costs are always going to increase due to the slope of the land and the requirement that the foundations should find original subsoil bearing. 

If the spoil is piled up against the lower or built up section of the new home then provision will have to be made for the oversite level within the building to be brought up to within 600mm of the proposed external soil level, in order to equalise the pressure on the walling. 

However, carting spoil away from a site is expensive and time consuming and its retention on site is a cost benefit, just so long as there is space to store it.

Drainage and Sewers on a Sloping Site

Having a sloping site may involve extra costs with drainage and sewers — but not necessarily.  

If your site slopes down from a road in which the sewer is fairly shallow then you may have to think of using a pumped sewage system. This can add at least £2,000 to the drainage costs. However, there may be a corresponding saving due to the fact that the 50mm flexible pipe may well be cheaper to lay than a conventional drainage pipe.

If your site slopes down from the road, within which the sewer is quite deep, then the slope may actually represent a saving in cost, as the resulting house drainage will not have to be as deep. Sites which slope up from the road and sewer may seem more attractive so far as drainage is concerned, but if the slope is significant it might be necessary to install tumble bays within the manholes, in order to slow off the fall, so that the effluent can enter the sewer at a reasonable rate.

Surface and rainwater is also a consideration. Sloping up from the road may at first seem the best option, but many local authorities will not allow surface water to go into the public sewers and many require that precautions are taken to ensure that surface water does not flow onto the road. Sloping down from the road means that surface water can collect around the base of the lower floor, or worse still, find its way into the garage. This may mean having to install a drainage channel to divert the water to soakaways.

Employ an Experienced Contractor

Steeper sloping sites can be a challenge, mostly during the construction phase. Most sloping sites don’t have a convenient flat area large enough to use as a contractor’s compound. Therefore, workers either have to build something or continually work on a slope, which can be dangerous and takes up additional time. 

If you have chosen an inexperienced contractor who’s only worked on flat, open sites, then this could be a massive mistake.

Building on a slope often affords you a lot of design flexibility with the mass of the building. A prime example is this riverside self-build project. At the front the building could only have a very small mass, due to planning restrictions, but to the rear Allan Corfield Architects were able to create an expansive two-storey home.   (Image credit: Jeremy Phillips)

Where Should I Position a House on a Sloping Site?

Appraising a site at the initial design stage is a balancing act. It might be that choosing the best location for access would involve cutting or filling too much land. If your designer is using topographical survey data (a must-have for any project) they should be able to recreate the site as a 3D computer model, which will help determine the best, most economical location.

Take your time before settling on your preferred floor levels, as the best choices may not be formed yet or accessible. We use drones to give our clients a glimpse of the views they could get from their new home.

Site Safety on a Sloping Site

Most sites have an area that can be used as a site office and for storage. On a lot of sloping sites you want to maximise the width of the plot, and this can compromise your working space. 

Once the ground floor walls are on, you may also be faced with the challenge of having to build over your home to get access to other parts of the site. This is not only a logistical problem, but also a less than ideal state of affairs from a health and safety point of view. 

Basements

On a costing level a basement is always going to cost at least the same amount per square metre as any other part of the home, if not more. In ground with high water tables or in heavy clay, these costs and the sheer physical difficulties presented may make the choice unviable. However, if the lie of the land is such that there is no alternative to either a full or partial basement, then this can be the cost-effective solution. 

Find out more about converting a basement.

The Folding House, designed by AR Design Studio, sits on a steep 18m slope down to the River Avon. A concrete-framed building was founded on a raft slab and pad and strip foundations. Where the building cut into the slope of the site, it was necessary for the perimeter walls of the building to be retaining walls in order to resist the loads from the soil they retained.   (Image credit: c/o ar design studio, photographer martin gardner)

Retaining Walls

Basement walls may have to be strong enough to hold back considerable banks of ground, in which case they become retaining walls in their own right. In other situations, such as building on a level plinth beside a natural or carved out bank, it may be necessary to construct separate retaining walls. Above 1,200mm in height these will have to be designed by an engineer. 

In certain circumstances it may be cheaper, and visually more attractive, to construct a series of lower retaining walls with the ground stepped between them. An alternative is wire cages – known as Gabions – filled with stone, or interlocking concrete blocks that are subsequently filled with soil and planted.

Building On Stilts

One way of building on steeply sloping land is to build out from it on a series of supporting stilts or columns. This gets away from the need to build extensive foundations on sloping ground and it negates the need for tanking. It also leaves the ground relatively untouched, allowing planting to take place over much more of the site. 

In certain situations it can be the cost effective solution and there is no reason why it cannot be employed with multiple level designs.

Mark is the author of the ever-popular Housebuilder’s Bible and an experienced builder. The Housebuilder’s Bible is the go-to hardback for self builders; originally published in 1994, it is updated every two years with up-to-date build costs and information on planning and building regulations, and is currently in its 14th reiteration.

He has written for publications such as Homebuilding & Renovating for over three decades. An experienced self builder, his latest self build, a contemporary eco home built to Passivhaus principles, was created on a tight urban brownfield plot.

Six Advantages of Building on a Sloped Lot

Why Your Dream Home on a Sloped Site is Worth All the Challenges

What if the site you have seriously considered for your potential dream home turns out to have a graded slope? Many people will definitely avoid buying a sloped site. Will you be like this segment of home builders – be faint-hearted and dismiss the lot – seeing only the limitations and not the possibilities the site presents?

Yes, there are challenges with a sloping site – as there are with any property. But think slowly and consult an experienced builder/designer who can guide you through the process. Be certain to weigh all of the pros and cons before rejecting the idea of building on a sloped site. Just remember that an experienced builder can help you overcome some site problems – and with a little imagination, some of these obstacles can become assets.

An example is Fall House – a 3-bedroom residence on a triangular 1.5-acre site in Big Sur with dramatic views of the Pacific Ocean, a breathtaking example of a home built on a hilltop. The home is staggered down a cliffside and features a cantilevered master bedroom suite. As created by renowned San Francisco architect Anne Fougeron, Fall House is embedded within its landscape and becomes a structure inseparable from its environment.  

Why would – should – anyone build on a sloped lot instead of the usual flat lot? Let’s look at six good reasons why building your home on a sloped lot can have advantages.

1.  Spectacular Views

Everyone loves a home with a view. Here’s an opportunity to experience the wonders of nature from your favorite spot. While there may be no nearby lake or snow-capped mountains, you can sit and relax in your rear deck or patio and enjoy unobstructed views of the natural landscape. With a home on a sloped site, you can watch dramatic sunsets, a full moon, and bright stars lighting up the sky on a clear night.

Top: This 2-story, 4-bedroom Contemporary style home built on a sloped site provides wonderful views of the surroundings … green fields and mountain ranges from every window and deck in the house (Plan #161-1000). Bottom: Windows around the rear of this 2-story, 5-bedroom, 5-bath Shingle-style home built on a graded sloping lot afford a magnificent view of the ocean (Plan #168-1132).

2.  Interesting Architectural Features

Want to stay away from the cookie-cutter mold? A house on a sloped site allows the owner to be creative and customize to include certain architectural details. For example:

Walkout Basement

How about the luxury of extra space with an atypical basement that’s still located in a lower level – but with abundant light and functional living areas? Walkout basement floor plans offer many benefits, including adding square footage without increasing the home’s footprint.

Walkout basement house plans also allow a family to convert part of the space into a fully furnished in-law suite or guest quarters – or add a wine cellar, media room, or home gym. It also creates another level of outdoor living with a patio, an outdoor sitting area, and a pathway.

Top: The exterior view of this 2-story, 4-bedroom, 5,023-sq.-ft. Shingle-style home shows its walkout basement, a door to the outdoor patio/sitting area, and a pathway. Bottom: The floor plan of the walkout basement shows the various living spaces utilized by the family – including a fully furnished guest suite with an outdoor sitting area, recreation room, home theater, bar, unfinished space, and outdoor patio (Plan #161-1038).

High Ceilings with Exposed Beams

Tall ceilings can add to the character and uniqueness of the home and make the most of the views provided by the sloping site. No one ever feels cooped up in a space with high ceilings because they open up a room and give it an immediate sense of space, air, and light.

High ceilings with exposed beams and large windows maximize the surrounding natural landscapes views on the lot of this 1-story, 4-bedroom, 3-bath Cottage style home with rustic accents (Plan #198-1012).

Drive-under Garage

Many house plans with a basement have a lower-level garage, and most are ideal for a sloped lot. While a drive-under garage may be considered necessary for a home on a sloped site, it is also another interesting architectural feature. By having the garage underneath the home, the main and upper floors can be raised for better views of the surrounding landscapes.

Down the road, this type of garage can even be converted into extra living space.

This color rendering of a 2-story, 4-bedroom, 3-bath Country home shows a 2-car drive-under garage built below the main living areas (Plan #126-1888).

Panoramic Windows

Don’t forget to install lots of large floor-to-ceiling windows around your home to maximize the natural light that filters into the home and to have ideal vantage points to revel in all the amazing sights around your property. You can choose window trims that can be as simple or as colorful and elaborate to fit your personal taste and the home’s architectural style.

Top: Just the right spot! Sit back and relax on this enclosed deck of a 2-story, 5-bedroom, 5-bath Shingle-style home, and take in the serene ocean view through the large floor-to-ceiling windows (Plan #168-1132).  Bottom: Lake views and lush landscapes around the property are on display through a panel of panoramic windows around this entrance tower of a 2-story, 4-bedroom Mediterranean-style home. (Plan #161-1034) 

3.  Lots of Natural Light

All the windows, high ceilings, and walkout basement in a home on a sloped sight let more natural light in – thus transforming the residence into an energy-efficient and healthy space.

Sunlight streams into this 1-story, 3-bedroom, 2.5-bath vacation home through its many large windows (Plan #168-1001).

4.  Landscaping

With a sloped site, the homeowner has the option of doing away with manicured lawns and simply leaving the natural surrounding as it is – or going all out with hedges, trees, shrubbery, and/or some hard landscaping.

Top: In this 2-story, 4-bedroom, 3.5-bath Transitional home, the landscape is left as it is to focus on its natural beauty (Plan #146-2810). Bottom: This gorgeous 2-story, 4-bedroom, 5,023-sq.-ft. Shingle-style home becomes more attractive with its manicured lawn and shrubs lined up the slope (Plan #161-1038).

5.  Privacy/Seclusion

If you want more privacy than your current neighborhood allows, you can look for a sloped site farther away from the hustle and bustle of city living or busier communities. In your secluded property, you can have all the peace and quiet that your heart desires.

With its location on a hilly lakeside site – surrounded by trees – this 2-story home provides all the seclusion and privacy a family may desire (Plan #160-1015).  

6.  Savings on Excavation Costs

Since a sloped property typically requires less excavation than a flat site does, the reduced costs will help balance the expenses related to drainage and foundation issues. 

Challenges of Building on a Sloped Site

Don’t let what appears to be problematic issues discourage you from building your dream home on a sloped site. The key is to consult/hire an experienced builder who can review all the potential challenges with you and advise you on design and construction possibilities.  

Here are some of the major risks when building a house on a sloping lot:

1.  Drainage and Sewer Hazards

To avoid flooding, melting sleet or snow, mudslides, and other threats to a home on a sloped site, work with your contractor on proper drainage. Be sure your builder understands how to create pathways for water to move past and beneath your home without affecting the structural stability. If possible, a foundation drainage system that exits to daylight is the best possible scenario to avoid flooding in the basement.

2.  Watch Out for Erosion

This gradual loss of soil to rain is one of the hazards of building on a sloping site. So before you build your home, schedule time with your contractor to do a thorough exploration of the soil types on your sloped lot. Information about the soil can guide you and your builder on ways to minimize the risks associated with erosion.

There are different ways of controlling erosion on the property, depending on how steep the slope is, how much money you want to spend, and the recommendations of a structural engineer or architect. Two of the most common considerations follow.

Retaining Wall

Described as a structure that holds or retains soil behind it, a retaining wall can be made of concrete blocks, poured concrete, treated timbers, rocks, or boulders. The retaining wall prevents the buildup of mud or small rivulets coming down the slope and ruining other landscaping. It acts as a drainage regulator and channels water and mud to be less prone to damage.

Mulch

The U.S. Department of Agriculture recommends covering bare soils with mulch consisting of two to four inches of bark chips, pine needles, wood chips, and even stones or river rock to help prevent erosion.   

Design experts also use large rocks as mulch for decorative as well as functional purposes. Among the benefits of mulching are:

• helping to protect and keep soil in place

• increasing water penetration

• keeping the soil cool and maintaining moisture.

3.  Maintenance

If your home is on a gently sloped property, you don’t have to worry about landscaping and mowing issues. However, steeper sites can be a bit problematic – but not totally without solutions. For example, retaining walls work well, as do paved steps. Low-maintenance trees, plants, and rocks can also make the home as attractive and eye-popping as traditional landscaping.

Ultimately, the advantages outweigh the challenges of building on a sloped site. With a creative design, thorough planning, and attention to detail, you can turn something problematic into an appealing and unique asset.

Footnote: The lead image in this article is a 1-story, 4-bedroom, 3-bath Cottage style home with interesting Craftsman details and a spacious walkout basement. For more details, click here (Plan #198-1012).

Building a house on a slope: photos and planning advice, a house on a slope with a basement, design of houses on a slope

A house on a slope in most cases becomes a very expressive architectural structure. Spacious view terraces and large windows, inaccessible to prying eyes, let nature into the space of the house. But, like any big idea, building a house on a slope requires scrupulous research and design. What to pay attention to when you formulate a task for an architect and designers?

Keuka Studios, Inc

Determine the potential of the site
I will not go into mathematical details, give definitions of what constitutes a small, medium and steep slope. Much more important is the ability to distinguish a slope from a ravine.

Archier

A ravine is always formed under the influence of seasonal or rain runoff: on such a slope, signs of soil erosion are visible, or, more simply, gullies (grass grows poorly in them). This slope is crumbling.

READ ABOUT THE PROJECT WITH PHOTOS…
Design World: 9 Smart Energy Efficient Homes in Australia

Denali Custom Homes, Inc.

One should be wary not only of ravines, but of artificial slopes. Before you build a house on a slope, make sure that your slope is natural, that it did not appear as a result of the life of a person who brought soil or waste to this place.

Fact: The first and main task is to conduct geological research. Without them, starting construction on a slope, designing the foundations of a house is a dubious undertaking.

Richard Chivers Architectural Photography

Sun on a slope
The next question is the orientation of the site. It is believed that the southern and southeastern slopes are best suited, while the western and southwestern slopes seem to be too hot. In my opinion, in the conditions of our short summer, the advantage lies precisely with the southern and western slopes, on which it is so pleasant to spend time admiring the sunsets.

ARTifacts/Shanghai Green Antiques

Gikalo Kuptsov Architects

Find the right place for your house
Pay special attention to the location and orientation of the country house. When planning a building on a slope, evaluate the future views from the windows, the movement of the sun, the dominant wind directions. Of course, a professional architect will pay attention to all significant factors, but this knowledge will not interfere with you as a future owner.

Utz-Sanby Architects

The final assessment of the potential of the site should be a practical understanding of the prospects for construction and your living in the house.

Windsor Companies

Hi!arch Architects

Driveway
Driveway during and after construction is a critical issue when building a house on a slope. With large slopes, access is often only possible from one side. This puts a lot of demands on the organization of the construction, when you need to think about all the buildings on the site. Imagine that your house is located at the top of the site, and at the bottom you plan to build, for example, a bathhouse or a guest house. Think about the difficulties in transporting materials and equipment you may encounter after the house is built and occupies most of the site.

Cornerstone Architects

How is the entrance to the house, how is the path from the road to the main entrance to the house – these issues are related to the location of the parking lot, the possibility of access for trucks serving, for example, a septic tank. And of course, with the convenience of your very stay in the house. After all, even the way with packages from the car to the house is no less important.

Land Aesthetic

Master plan in your hands
The result of this stage should be your master plan with the placement of the house, outbuildings, parking, paths, playground. Do not forget about engineering needs, a septic tank and a well, to which it is desirable to have an entrance, bearing in mind that they should not be located nearby.

SEE ALSO…
Good Question: What You Need to Know About Septic Tanks

Thuilot Associates

Think About Communications
Communications on sloping sites is tricky. So, for example, running a sewer in parallel will not work even along the middle slope. A water well located in the lower part of the site will also require taking into account the total height of the water rise, taking into account the height of the house and the difference in relief.

180 degrees

Make a drainage system
But the most important issue is the drainage of stormwater and melt water. The fact is that over time, its own hydrological regime is formed on an undeveloped site. That is, all the water that falls in the form of precipitation or formed during the snowmelt period, leaves in an established way along the slope without washing it away.

CSDesign llc

Important : During the construction process, natural barriers will inevitably appear in the form of platform foundations, fences and much more. And as a result, water flows uncontrollably change direction and will inevitably lead to soil washing out. The worst thing is that this process is fast and you can get the Grand Canyon on your site during the season.

To prevent this from happening, a number of rules must be followed. First of all, it is necessary to organize drainage both from the roof and from all sites.

Artel “Danila, Makar and Brothers”

Conner Landscape Architects

This can be a storm sewer with intercepting storm gutters and wells. If your site is located in the middle part of the slope, observe how drainage is organized from the upper sites. And remember, the lower you are on the slope, the more water will come to you. Here you definitely cannot do without a device for catching drainage and a tray across the slope.

Accurate Landscaping

Donald Lococo Architects

Protect the vegetation
Another important rule is to respect the soil cover, trees and shrubs growing on the site. These are your main allies: by absorbing excess water, they strengthen the slope with their roots. Think over the future landscape until the excavators come to your site. When planning where to build your home, pay great attention to the preservation of vegetation, especially the turf.

SEE ALSO…
Good question: How can the trees on the site survive your construction? The house on the mountainside is integrated into the relief, and by the time construction begins, the project must contain all engineering sections: from the foundation and communications to the territory planning project. Work in stages or “from a sheet” is fraught with financial surprises during construction on any site, regardless of the terrain. And when building on sites with difficult terrain, this is doubly sensitive.