How deep are foundations for a house: How deep should the foundation of a house be?

How deep should the foundation of a house be?

Between basement flooding, pest infestations, and foundation cracks, getting a foundation right is essential to avoid later problems with your home. Your foundation depth will determine how long your home lasts, how your utilities run, and what kind of storage space you’ll have. Do you know the optimum foundation depth for your home?


Before you start planning out your home design, you need to consider what you want from your foundation. Depending on your climate zone or your budget, you will need to make a final decision before you can start the design.

Here is a breakdown of the three major kinds of structures undergirding your home:

1. A full basement

This is one of the most popular foundations in the northeast US. For a full basement, your foundation depth will be below frost depth.

Basements have footings, and typically 8-foot walls built on a 4-inch concrete slab.

The slab will serve as the floor of a room underground, where you can store your home’s mechanical and HVAC system or make use of it as storage. With a little extra work, the space can be finished and made suitable for living.

Whereas basements of older homes must be retrofitted for living, newer home building projects often plan for a finished basement. This is the most cost-effective approach. It’s much harder to ensure your basement has ventilation, light, and plumbing after you’ve already built the house.

Rigid foam beneath the slab will make the space a little more livable. Insulation can help reduce the mold and mildew issues that many basements face.

2. Crawlspace

In areas of the South and the Midwest US, crawl spaces are used to prevent moisture and leave room for plumbing installation and service. It also leaves room for servicing your electrical system.

Crawl spaces need to be sealed and insulated. For the ease of access, they leave the home vulnerable to mildew and rot. In extreme situations, you might see pests begin to make their home in your crawlspace. Well-ventilated crawl spaces keep your moisture out, but can also be an entryway for rodents and insects. Be sure that you crawlspace is sealed with vents small enough to keep raccoons, squirrels, and mice out.

Modern homes are insulated with a concrete slab or polyethylene vapor barrier between the home and the ground. In a big enough crawlspace, the heating unit can be stored, leaving space free inside your home.

3. Slab-on-grade

A concrete slab poured directly onto the grade of the site is another option. This is the shallowest foundation depth. Your slab will be directly beneath your home’s main floor.

These are found in the warmest parts of the US—especially warm places and those where flooding is common.

Once you dig your foundation, gravel is poured to ensure water can escape. Wire mesh is added to limit cracking. Any plumbing or conduits that are to be included in the foundation are set up, and then concrete is poured over it all.

In colder climates, special frost-proofing is needed. Sometimes short walls are added with a layer of foam added for insulation.

If you’re having trouble determining the ideal foundation depth for your new home, contact our team. We will be happy to walk you through it!

Related Posts

Building Guidelines | Requirements for Foundations & Rising Walls

Foundations

Strip Foundations

Foundations to be provided for all brick and block walls, chimneys and load bearing partitions including load bearing stud partitions. All internal foundations are to be the same thickness and depth as the external wall foundations.

Diagram B8 – Typical strip foundations

Standard Dimensions Required for Foundations

Diagram B9 – Standard dimensions required for foundations

Depth Depth of foundation excavation to be at least 600mm below ground level at completion.

Width Foundation must be at least 3 times the width of the wall it supports.

Thickness Concrete to be at least 300mm thick.

The above are min. figures; special foundation design may be required and greater dimensions may be required. Larger foundations are required for larger elements such as chimneys.

Raft Foundations

As raft foundations are a specialist form of foundation design it is important that a qualified engineer designs them. The engineer must be qualified by examination, be in private practice and possess professional indemnity insurance.

Before raft design commences a site investigation must first be carried out, the results of which are to be taken into account in the design. Once designed the construction should be supervised and completed to the engineer’s satisfaction.

Excavation & Filling

Excavate area to a suitable level while ensuring all soft layers are removed.

Diagram B10 – Excavate to suitable bearing

Fill area using appropriate granular fill. Fill in layers not exceeding 225mm in depth. The filling and compaction process must be overseen by a qualified engineer. The engineer must be qualified by examination, be in private practice and possess professional indemnity insurance.

Diagram B11 – Fill using an appropriate granular fill material and compact

Once filled and compacted, first place reinforcement, then shutter raft, pour concrete, vibrate and cure. Steel and concrete to engineer’s specification.

Diagram B12 – Provide reinforcement, shutter, pour, vibrate and cure

DPMs & Screed

DPM must be provided along with insulation and a minimum of 65mm thick screed. DPM must be 1200 gauge; never use recycled material.

Diagram B13 – DPM to be provided, insulation and screed

When placed on top of insulation, screed should be at least 65mm thick with light mesh reinforcement incorporated. Insulation should never be placed under the raft. Water and heating pipes must be above the level of the structural slab.

When Drains Run Near Foundations

When drains run close to foundations they can be subject to loads from the foundation. In order to prevent settlement of the foundations and/or fracturing of the drains it is necessary to take precautions.

There are 2 general precautions to be taken depending on the distance of the drain from the foundation when the drain is at a lower level:

  1. If trench is within 1m of the foundations, trench is to be filled with concrete to the level of the bottom of the foundation.

  2. If trench is greater than 1m from the foundations, the trench is to be filled to the level of the bottom of the foundation less the distance from the foundation less 150mm.

Diagram B14 – Drain less than 1m from foundation

Diagram B15 – Drain more than 1m from foundation

Rising Walls

Services Through Rising Walls

Clearance for service pipes and ducts is important as inadequate clearance or excessive rigidity can cause settlement or fracture. The opening should provide at least 50mm clearance all around the pipe. This opening should be masked with rigid sheet material to reduce the risk of vermin or fill entering. The void should also be filled with a sealant, the purpose of which is to prevent gas seeping in. For further guidelines see TGD H of the building regulations.

For clarity, the ope masking is not shown in the sketches.

Diagram B16 – Services passing through rising walls

50mm clearance should be provided for all services passing through the rising wall. Ducts to be provided where required.

Openings & Lintels

In the case of a large opening, a lintel should be provided. Use of metal lintels is not permitted in rising walls.

Diagram B17 – Lintels to be provided for large openings

Protecting Water Service Pipes from Frost

Guidance on adequately protecting service pipe and fitting and all cold water pipes against damage from frost is outlined in Clause 1. 9 of Technical Guidance Document G – Hygiene, Building Regulations 2008 as amended July 2011:

Underground service pipe from external meter/stopcock must have a cover of at least 600mm. This cover is to be maintained along the entire length of the pipe. When near an external wall the pipe must be insulated with insulation which is impervious to water vapour.

Insulation for a cold water supply through a floor which is in contact with the ground.

Diagram B18 – Protecting water service pipes from frost – floors in contact with the ground

Insulation for a cold water supply through a suspended ventilated floor.

Diagram B19 – Protecting water service pipes from frost – suspended ventilated floors

Level Changes

Rising Walls Changes in Level

When rising wall is 215mm wide, change in level should be between 150mm and 860mm.

Diagram B20 – Rising walls – changes in level 150-800mm

For changes in level between 800mm and 1260mm and when the rise exceeds 4 times the wall’s thickness, the wall thickness should be specified by the engineer. The engineer should be qualified by examination, in private practice and be in possession of professional indemnity insurance.

Diagram B21 – Rising walls – changes in level 800-1260mm

In cases where the change in level is large between both sides of a rising wall, the wall, particularly in the partially built state, will act as a retaining wall. Consequently, wall thickness needs to be increased and great care needs to be taken also when compacting the fill material.

The height of a rising wall should never exceed 4 times the wall’s width. Where the cavity is not filled the thickness of the wall is taken as the sum of both wall leaves as illustrated.

Diagram B22 – Maximum height of rising wall with respect to its width

Diagram B23 – Maximum height of rising wall with respect to its width

DPC must be stepped with changes in site level or slopes as shown below.

Diagram B24 – Damp proof membrane installation on site with level changes or slope

Diagram B25 – Typical stepped DPC detail on sloping site

Diagram B26 – Level changes within a house

Use 1200 gauge polythene laid with joints sealed on binding material which will not damage the membrane in all cases where the DPM is laid under the concrete.

Diagram B27 – Detail A – Typical vertical joints in the DPM or DPC

Minimum lapping of vertical joints for dpm or dpc should be 150mm along the length of the wall. Joints should be taped using double-sided proprietary sealant tape.

In order to prevent dampness travelling beneath the floor of a higher house penetrating through a party wall above the floor level in the next house it is advisable to make these party walls cavity walls i.e. wall between House A and House B below. This wall must be drained to the outside face of the building.

Diagram B28 – Path of flanking dampness

Diagram B29 – Level changes in adjoining houses

Diagram B30 – Detail X – Typical party wall detail with a change in level

It is important in a situation where the ground level is greater than the floor level that measures are taken to eliminate the risk of moisture penetration. When designing the house the engineer or architect should provide barriers sufficient to prevent this.

If a case occurs where part of the house is below ground level, it is recommended that at least the extent of the wall which is underground be built as detailed below or alternatively the entire wall is to be fully tanked where there is a possibility of water pressure building up.

Diagram B31 – Internal floor level partially below ground level

When an entire floor is below ground level, as in a basement, tanking should be provided. In this situation, there should be no build-up of water pressure and the depth of cavity below ground level should be drained.

Diagram B32 – Internal floor level partially below ground level

Diagram B33 – Detail A – DPM installation where internal floor level is below ground floor level

In order to reduce the risk of clogging by migration of fines it is recommended to wrap the perforated drain in a geotextile filter.

How deep should the foundation of a house be?

Questions discussed in the material:

  • Soil type
  • Ground freezing depth
  • Groundwater level
  • Foundation depth depending on foundation type
  • Foundation area

Perhaps the most important question to answer before starting to build a house: how deep should the foundation be? After all, it is he who takes on all the loads, it is he who is the basis of any building. And the foundation must be really strong.

The depth of the foundation depends on certain conditions, you can not use the same principle of construction wherever possible. There are always nuances that must be taken into account when calculating.

Moreover, the slightest mistake in calculations can lead to the most unfortunate consequences: the foundation will crack. To prevent this from happening, you should familiarize yourself in advance with the factors that, to one degree or another, determine the depth of the foundation.

Factors affecting foundation depth

Every building needs a strong and stable support, and that’s what the foundation is made for. The durability of the house largely depends on the depth to which the foundation will be buried. There are three types of foundations: shallow, deep and shallow. These characteristics are most often used in relation to strip bases and columnar ones, but sometimes they are also used for slabs, which are usually made shallow or not buried.

The depth of the foundation is the design value from the beginning of the support, buried in the ground, and to the surface of the earth. This value depends on several factors: environmental conditions (type of soil, depth of its freezing, groundwater level), features of the future building (number of floors, weight, presence of a basement, location of communications that run underground).

In order to draw up a project, first of all, you need to decide on the location of the house on the site.

If you have previously used the services of specialists and carried out geological surveys on the ground, be sure to take into account their results. For the house, you need to use a dry place, that is, groundwater there should pass as far as possible from the surface. Thus, you will be able to avoid all sorts of problems with the foundation, and it will also come out much cheaper.

During the geological study of the soil, several wells are drilled (minimum 5) with a depth of 10 to 40 meters. They are made where the corners of the structure and in the middle will be. The depth of one pit usually depends on the structure of the earth layers and on the mass of the future building.

Type of soil

The type of soil on the site intended for construction affects how deep the foundation is needed. This is due to the fact that the soil behaves differently during freezing – it can be heaving and non-heaving.

The degree of heaving depends on various factors. One of them is humidity. Since it is constantly changing, the earth at one time remains dry, and at another becomes saturated with water (for example, on rainy days). Of course, there are certain types of soils that remain non-rocky under any conditions. These include crushed stone, pebble and coarse-grained soils with sandy aggregate, medium and coarse sands.

If the soil is not heaving, then when determining the depth of pouring the foundation, the level of soil freezing is not taken into account.

Depth of soil freezing

There are maps showing the levels of soil freezing in the regions. Using them is quite simple, and these data will help you.

Of course, the map shows averaged information, in some places there are errors. If you need accurate calculations, then there is a formula by which you can calculate the depth of soil freezing in your area. However, it is important to know the average value of freezing temperatures in winter.

To determine soil freezing (dfn), plug in your values:

  • do is a multiplier that takes into account the type of soil. Each has its own coefficient: coarse soil – 0.34; sands with good bearing capacity – 0.3; loose sands – 0.28; clay, loam – 0.23.
  • Mt is a multiplier that takes into account the sum of average monthly sub-zero temperatures in the region. To add this value, you need to find the statistics of the meteorological service on the Internet and write out the average temperature for each of the five months of the cold period (November – March). Then add up the data and take the square root. The result obtained from the calculations will be used in the above formula.

Let’s try to calculate the depth of soil freezing using the formula. For example, construction is planned on an area with clay soil. We write out the average temperatures of the cold months: -2 °C, -12 °C, -15 °C, -10 °C, -4 °C. Then we add their absolute values: Mt = 2 + 12 + 15 + 10 + 4 = 43.

Next, you need to find the square root of 43. It turns out a non-integer number 6.6. We substitute the values ​​\u200b\u200bknown to us into the formula: dfn \u003d 0.23 * 6.6 \u003d 1.52 m. The calculations do not end there, because you need to take into account the type of room (house, cottage, bathhouse, garage, etc.), it will become whether to heat or not, how long the construction will take. Usually, when calculating, a multiplying factor is added (for a margin of safety). It is equal to 1.1. Therefore, 1.52 * 1.1 = 1.7 m.

If the building is heated, then the freezing of the soil will decrease. Then, when multiplying, we use reduction factors. They are shown in the table:

For example, in our building there will always be an average temperature of +20 °C, warm floors. We calculate the depth of the foundation: 1.52 m * 0.7 = 1.064 m. The value turned out to be less, which means that the costs will decrease.

Do not forget that maps and tables always show average data by region for about ten years. When making calculations, we recommend using information about the coldest winters (take the lowest possible temperatures). Why exactly? No one guarantees you that the foundation, having successfully stood for several years, will not crack due to abnormally cold weather in the winter.

Ground water level

In principle ground water does not pose a risk to a structure made of reinforced concrete. If it is lowered into clean water, then nothing will immediately happen to concrete or reinforcement. However, the level of groundwater at the planning stage simply needs to be clarified.

We have already talked about heaving soils. They can be saturated with water not only by precipitation, but also by groundwater. The soil becomes strongly heaving both below the water level and above (in some strata), namely, within a frost-prone border up to 3–3.5 m thick.

The danger is that concrete tends to absorb moisture. At sub-zero temperatures, destructive processes can begin inside it, because the water in the pores of concrete increases in volume when it freezes.

It often happens that groundwater contains some polluting components. They, in turn, can adversely affect structures.

If we summarize all the information received about the dependence of the depth of the foundation on the location of groundwater, then we can highlight several basic recommendations.

First, you must always remember that the depth of the foundation being laid on a non-rocky type of soil (on rocky, sandy, coarse and medium-sized, coarse-grained with sand aggregate, gravel) is absolutely independent of the level at which there will be groundwater.

Secondly, if there are sands (fine, dusty) under the base of the building, then the depth of the foundation can be any. One has only to take into account an important point: groundwater should be located two meters below the freezing level of the soil, and if they are located higher, then the foundation must be made below the freezing level.

Thirdly, if there are clays, loams, coarse soils with dusty or clay aggregate under the base of the building, then the foundation will need to be laid below the freezing level. The level of groundwater is also not important here.

Depth of laying the foundation depending on its type

Each type of foundation has its own characteristics and is designed so that construction work can begin on terrain with different soils.

Depth of strip foundation

A foundation in which the entire supporting array resembles a tape that repeats the perimeter of the load-bearing walls of a building is called a tape foundation. This also includes logs that serve as the basis for wooden houses. Types of support tapes: masonry (natural stone, rubble), reinforced concrete monolithic, reinforced concrete prefabricated (from blocks).

Today, the strip foundation is widely used in the construction of private houses. It is less expensive and easy to install.

A huge plus is that this type of foundation is characterized by a uniform distribution of the load from the mass of the building. The strip foundation is laid on the ground with homogeneous soil, non-porous. When calculating its depth, everything is taken into account: the type of soil, the level of its freezing, as well as the presence of groundwater and their location.

How deep should the strip foundation be? It depends on the degree of heaving of the soil. If, for example, the ground is with a low degree of heaving, then the level of laying will be from 50 to 60 cm. And with an average level of heaving – from 75 cm to 1.5 m, and maybe more (up to 2 m in cold regions).

Depth of the column foundation

The column foundation is used in the construction of low-rise buildings with a relatively small mass. The base consists of reinforced concrete pillars. This type of foundation has many advantages: easy to install, economical, can be installed even on difficult soils.

There are some limitations that should be taken into account when choosing a columnar foundation:

  • difficulties when installing on moving soils, as well as on clay, peat;
  • cannot be used to build large multi-storey buildings. Such a foundation cannot be a reliable support in this case.

How deep is the foundation for a standard one-story stilt house? It depends on how frozen the ground on the site is. It is recommended to make it deeper than the freezing level by 20–30 cm.

If a brick house is built on stable ground, has one floor, then the standard pile depth is 80 cm.

The foundation depth for houses built from foam blocks usually does not change. Sometimes the value may decrease, as it all depends on the design.

Due to the fact that the bearing layers of the soil are unevenly located, the supports for the building may be at different depths. But this is in theory, in practice it happens differently. Developers are not always ready to spend time on individual deepening of a single column, therefore they determine the maximum value and install all supports in the same way.

Slab foundation depth

A monolithic slab made of reinforced concrete has more advantages. It is large, strong enough, reliable, and most importantly designed for a long service life. Due to its size, a monolithic slab minimizes the specific load per unit of the supporting area of ​​the soil. That is why the price of installing a slab foundation is much higher.

This type of foundation is used in the construction of buildings in areas with weak soil. The depth level can vary from a few tens of centimeters to a meter. If the region has a bad climate with low temperatures, there is complex soil, then, unequivocally, the depth of the foundation will be at least a meter.

A word of advice: when the level of soil freezing is over 2.5 m, it is advisable to use a slab foundation or a column foundation.

Foundation base area

If the ground is heavily loaded from the mass of the erected building, then the ground sags. This problem can be overcome by increasing the base area of ​​the foundation. For each type of foundation, everything is done individually. For example, for a columnar foundation, it is necessary to increase the number of columns, as well as their length and width (up to a value of 500 mm). And for a tape, it will be enough to increase the width of the foundation itself.

As for summer garden houses (one-story, two-story), the size of their foundation is always almost the same, because soils with any bearing capacity can cope with such a load. It cannot be said that the size of the base itself directly depends on the thickness of the walls and on the level of soil freezing. For the construction of summer garden houses, a columnar foundation is laid without thickening it. If the properties of the soil on the site intended for development are unfavorable, then only the lower part of the foundation is made wider.

If it is planned to use brick or reinforced concrete to build the walls of the building, if they want to make a basement in the building, then it is necessary to build a strip foundation. Its thickness will be equal to the thickness of future walls.

For wooden and frame buildings, the walls of which are made light, a columnar foundation is laid. The pillars are placed at a distance of 1,500–2,500 mm in places where the load is most concentrated, as well as at the corners of the building, at the intersection of the walls. The distance between the installed pillars depends on the mass of the building being erected and on the bearing capacity of the soil on the site. A distance of 1,500–2,000 mm is made on sandy soils and sandy loam, and 2,000–2,500 mm on loam, clay, on cartilaginous and rocky soils.

The area of ​​the foundation that satisfies the inequality below will determine whether the foundation will be durable:

S x Rh > M, where

S is the area of ​​the foundation base, cm²;

Rh – soil bearing capacity, kg/cm²;

M – house weight, kg.

The bearing capacity of the soil referred to above is also called design resistance. This coefficient depends on the type of soil under the foundation. In the table you can find the value of the bearing capacity of the soil:

To find out the total weight of the house, you need to add up the mass of everything that is in it. You need to start with the foundation, walls, roof (even snow on the same roof in winter), add the weight of furniture, all items, and then a lot of people.

For example, the weight of snow lying on a roof can be calculated taking into account the specific weight of snow cover in central Russia 100 kg/m².

Using the formula [200 kg/m² x (total area of ​​the room, m²)], you can approximately calculate the weight of people and objects in the house in the country, provided that there is no large crowds of people, billiards, piano or piano, as well as heavy cast iron bath.

Using the formula [400 kg/m² x (total area of ​​the room, m²)], you can approximately calculate the weight of people and objects for an apartment, cottage or country house.

As mentioned above, all heavy items and objects are added to the total weight of the house.

Summing up, I would like to point out once again that the creation of a good building that will not collapse does not require additional financial investments, depends on the presence of a solid foundation with a long service life. Usually 15-30% of the total amount of construction work is spent on it. Don’t skimp on the foundation. Hire professionals, make the necessary calculations, purchase the best materials, otherwise the mistakes made will cost you much more.

Strip foundation: laying depth, tables and calculation

Article content:

  1. Factors affecting the laying depth
  2. Unburied strip foundation
  3. Shallow strip foundation
  4. Buried strip foundation
  5. How to reduce the depth of the strip foundation

Despite the fact that the depth of the strip foundation is not the only indicator of reliability and durability, it plays a huge role in the integrity of the entire house during its operation. Reinforced concrete tape of any size and brand of concrete may burst over time if it is incorrectly placed in the ground, not taking into account its features.

In order not to get confused in all types of foundations and soils, let’s try to understand everything in order. First, we will analyze the types of monolithic tapes, and then, specifically for each type of strip foundation, we will determine the depth of the foundation.

It is probably worth starting with the fact that the strip foundations themselves are divided into three main types:

  1. Non-buried
  2. Shallow
  3. Recessed

Each of these types is laid to a certain depth, which depends on several main factors:

  • Ground freezing depth
  • Soil type
  • Groundwater level

It is worth noting that the depth of the strip foundation is the distance from the soil surface to the base of the foundation, and not the depth to which the trench is dug. In the trench, in addition to the foundation, there may be a pillow.

Now let’s see how these factors affect each type of strip footing separately.

An unburied strip foundation is rarely used in the construction of private houses, because it is a very weak support for the future structure. As a rule, it is all located on top of the ground, and inside there is only a sand or sand and gravel cushion.

I will not write much about the non-buried strip foundation, especially since a whole article was already devoted to it earlier. And in general, the very concept of the depth of laying in such a foundation is absent.

This is the most capricious, in terms of the depth of the foundation. Firstly, it is not as reliable as buried, and secondly, in order for such a strip foundation to withstand the load of the structure, and also to restrain all the heaving forces transmitted from the ground, its calculation must be approached with special responsibility.

I have already described in detail how to pour a shallow strip foundation in one of the previous articles. Therefore, we will not go into details.

Such a strip foundation is laid to a depth that is much higher than the depth of freezing of the soil, which is why it is called shallow. It, in contrast to the buried one, can be largely affected by the forces of heaving of the soil.

Also, an important difference between shallow foundations is that it must be made monolithic not only below the ground level, but immediately, after placing the formwork, pour the above-ground part of the foundation – the basement. This will greatly strengthen the entire strip foundation.

The depth of a shallow foundation depends directly on all three factors described above. In order not to get confused, let’s look at the table.

Table No. 1: Depth of laying a strip shallow foundation (minimum), depending on the type and depth of soil freezing

Depth of soil freezing, m Foundation depth
, m
Slightly heaving soil Rough ground,
hard rock
over 2. 5 1.5
1.5 – 2.5 3.0 or more 1.0
1.0 – 1.5 2.0 – 3.0 0.8
less than 1.0 less than 2.0 0.5

Note: In order to find out what is the depth of soil freezing in your region, look at table No. 2 below, where the values ​​\u200b\u200bare given for some cities, taking into account the type of soil. Click on the table to enlarge.

Table No. 2: Depth of soil freezing in some regions

Note: , which we’ll talk about next.

Dependence of the depth of the strip foundation on the groundwater level (GWL)

There are two options for the location of groundwater – when they are located below the freezing depth of the soil, and when – above.

The groundwater level is below the freezing depth of the soil

This can be considered a good indicator, and in this case, groundwater in most types of soils does not have a special effect on the depth of the monolithic reinforced concrete strip.

The only restriction, in this case, is that in such soils as loams, clays and the like, the tape must be laid at least half the freezing depth of such soil. In other, “good” soils, this factor does not affect the laying of the foundation.

In other words, if the freezing depth in your region is, say, 1.5 meters , then the tape shallow foundation must be arranged at least 0. 75 meters .

Groundwater level above freezing depth

If groundwater is high, then the depth of digging a trench for strip foundation does not depend on their level only on rocky soils, sandy coarse-grained, gravel and the like.

On any other types of soils with high GWL, the monolithic tape will have to be buried below the freezing depth by 10-20cm (). In this case, it will become a deep foundation.

Recessed strip foundation is considered the most reliable of all strips. It is laid below the freezing depth of the soil by 10-20 cm . Another condition for its device is that the ground under its sole must be more or less solid.

In the case of swampy soils, peatlands and the like, the strip foundation is laid to a depth that is below these layers. In some cases, it is enough to dig a trench to hard ground, and then arrange a sand or sand and gravel cushion to a level that is slightly below the freezing depth of the soil in your area.

When the ground on the construction site is very poor for laying a strip foundation, or its installation is very expensive, you can try to calculate another type of foundation, for example, a slab foundation. Perhaps it will be both cheaper and more reliable.

After carrying out all the calculations on the depth of laying the strip foundation, it often happens that, taking into account the soil and the region, it must be laid very deep. This raises the question of how to cut costs and reduce depth.

There are several ways to reduce the depth of strip foundations, all based on reducing the importance of the main factors affecting the foundation.

Reducing the depth of soil freezing

Of course, we will not be able to change the climate in the region, but we will be able to change the depth of freezing, specifically under the base of the foundation, by insulating the foundation itself and the soil adjacent to it from the outside.

In this way, we can reduce the depth of the foundation, as well as reduce the cost of it.

Drainage of groundwater from a strip foundation

Another effective way to reduce the depth of a strip foundation is to drain water from it.

This is done with the help of a good drainage system, which will divert a significant part of the water from the foundation and prevent it from adversely affecting it.

Sand or sand and gravel pad under the foundation

In the case when heaving layers of soil lie deep enough on the site, strip foundation will also have to be laid to a greater depth. You can reduce it by replacing the heaving soil with a sandy or sandy-gravel cushion.

In other words, it is necessary to dig a deep trench to hard ground rocks, and then arrange a massive sand and gravel cushion there, which will distribute the load from the foundation and the house onto the ground evenly and will not allow heaving forces to adversely affect the foundation.