Flooring screeding: What is Floor Screed? Its Types, Materials, Construction and Uses
What is Floor Screed? Its Types, Materials, Construction and Uses
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Floor screed is composed of cementitious materials and sand blended based on a suitable mix design and applied to provide a leveled surface for the floor finish which is introduced to the surface of the floor screed.
So, floor screed is the base for the floor finish and greatly influences the performance of floor finish. In this article, different aspects of floor screed will be explored.
Fig.1: Details of Floor Screed
Fig.2: Floor Screed Construction
Contents:
- Following points regarding flooring screeds are discussed:
- Types of Floor Screed
- Materials for Floor Screed
- What are the Requirements that a Floor Screed Should Meet?
- Procedure of Floor Screeding
- How a Successful Screed Floor can be Constructed?
Following points regarding flooring screeds are discussed:
- Types of floor screed
- Floor screed materials
- What are the requirements that a floor screed should meet?
- Floor screeding procedure
- How a successful screed floor can be constructed?
Types of Floor Screed
There are different types of floor screed that is specified based on the requirements and applications and the functionality of the floor:
- Unbonded screed floor (Figure 3 and Figure 6)
- Bonded screed floor (Figure 3 and Figure 4)
- Floating screed floor (Figure 3 and Figure 5)
- Heated screed floor (Figure 3 and Figure 7)
Fig. 3: Different Types of Floor Screeds; (A) Bonded Screed, (B) Floated Screed, (C) Unbonded Screed and (D) Heated Screed
Fig.4: Bonded Screed Floor
Fig.5: Floated Screed Floors
Fig.6: Unbonded Screed Floors
Fig.7: Heated Screed Floor
Materials for Floor Screed
Following are the materials used for construction of floor screeds:
- Cement
- Clean and sharp sand
- Water
- And occasionally additives are added to obtain specific properties. Polymer materials or metal mesh or glass are likely to be introduced to reinforce the screed.
The above components are adequately blended based on the prepared material proportions. If the thickness of the floor screed does not exceed 40mm, then the recommended mix is 1 Portland cement: 3 sands or 1 Portland cement: 4.5 sand.
However, 1 cement: 1.5fine sand: 3 coarse aggregate (10 mm maximum aggregate size) should be considered if the floor screed thickness is greater than 40mm.
It should be known that drying shrinkage gets reduced as the proportion of cement to sand is decreased.
Suitable amount of water should be specified to provide required workability since excessive water would reduce floor screed strength and inadequate water quantity lead to poor compaction.
What are the Requirements that a Floor Screed Should Meet?
Floor screeds should have adequate thickness which is based on the screed type and application frequencies. Recommended floor screed thickness based on the type of the screed floor and the construction conditions are provided in Table-1.
Table-1: Recommended Floor Screed Based on the Type of Screed and Construction Condition
| Recommended floor screed thickness, mm | Floor screed type and construction condition |
| 12 | For monolithic construction. In this case floor screed will be placed no longer than 3 hours after the placement of concrete. This will guarantee a satisfactory bond between floor screed and placed concrete beneath it. |
| 40 | For screed floor placed on hardened concrete. The concrete should be cut by appropriate means then cleaned, wetted and finally screed is placed. Not only will this ensure good bond but also make the screed to dry slowly and prevent cracks. |
| 50 | For floor screed placed on impermeable damp proof membrane. In this case a bond between the screed and the layer below it would not exist and hence shrinkage is unrestrained. |
| 65 | For screed installed on compressible course of sound or heat insulation material. This is recommended for domestic application only, otherwise the thickness of the screed should be increased. Lesser thickness will suffer from crack development. |
| 75 | For screed installed on compressible course of sound or heat insulation material. This is advised for applications other than domestic utilization. Lesser thickness will suffer from crack development. |
- Floor screed strength should be 20MPa for domestic application and 30MPa for industrial utilization
- It should be solid and compact so as to provide satisfactory base for the floor finish
- It should be curried properly to prevent shrinkage and rapid drying which lead to cracks. So, it should undergo almost all shrinkage, which floor screed might experience, prior to applying floor finish. This will lead to prevent the initiation of cracks.
- Finally, floor screed surface should be flat and smooth.
Procedure of Floor Screeding
- Evaluate the surface of the base
- Estimate materials used for screeding
- Prepare the base
- Prepare the floor screed mixture
- Apply bonding agents such as water or bonding slurry
- Place the floor screed mixture
- Finally, properly cure the placed materials
How a Successful Screed Floor can be Constructed?
- Choose right and suitable screed contractor
- Select suitable screed floor type
- Produce right and suitable floor screed mixture
- Construct floor screed using appropriate and acceptable screed placement process
- Consider right approaches for floor screed protection
Read More:What is Screed in Concrete Construction? Properties and Composition of Screeds
Basics of Screeding For Concrete and Masonry
By
Lee Wallender
Lee Wallender
Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years.
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Editorial Process
Updated on 05/03/22
Reviewed by
Deane Biermeier
Reviewed by
Deane Biermeier
Deane Biermeier is an expert contractor with nearly 30 years of experience in all types of home repair, maintenance, and remodeling. He is a certified lead carpenter and also holds a certification from the EPA. Deane is a member of The Spruce’s Home Improvement Review Board.
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When you’re pouring concrete or laying pavers or stone for patios or walkways, everything has to be perfectly flat and level. With concrete, one of the final stages is screeding. With masonry, paver, brick, or stonework, screeding happens toward the end of the project, before the hardscape materials are laid.
Screeding refers to any action of smoothing out a pliable material into a flat, smooth, and level layer. There are tools manufactured expressly for screeding, but you can also make use of any straight board to do the job.
What Concrete Screeding Is
With concrete work, screeding is the action of flattening poured concrete into a smooth, flat layer prior to finishing the surface.
Screeding is only the first step in finishing concrete, and it is not intended to produce a completely smooth final surface. Screeding fills in large gaps and removes high spots in the concrete material being installed. The final finish will be created by floating the concrete with one or more smooth-faced tools that are designed to draw up fine aggregate and cement to the surface of the slab. For large slabs such as driveways or garage floors, the surface is floated with a large tool known as a bull float.
Smaller wood and metal hand floats are used for sidewalks and other surfaces, but whatever tools are used, they can create a smooth surface only if the concrete has first been screeded to create a uniform layer.
How to Screed Concrete
In the process of pouring concrete, a screed is usually a long length of straight two-by-four board or an aluminum bar manufactured for the purpose.
Whatever object is used, screeding is done by drawing the tool across the wet surface of the concrete.
The screeding tool is generally long enough so that the ends can rest on opposite sides of the concrete form. The screed is drawn toward the workers with a sawing, scraping motion that simultaneously smooths the surface and pushes excess concrete into any gaps or hollows.
It helps to have two workers, one on each side of the screeding tool, especially for large slabs. Aluminum ​screeds are often used where precision is needed, as they provide a straighter edge.
For more professional, faster screeding action, a motorized screed may be used. The tool has a long handle to eliminate laborious bending and tugging.
What Masonry Screeding Is
Screeding also describes the action of flattening out a layer of mortar, sand, or gravel underlayment beneath a surface in preparation for laying pavers.
In this context, screeding is done to help a subsequent upper layer (the concrete pavers, stone, or brick) rest firmly on a smooth, flat layer.
Another context where screeding is used is with leveling compounds. You might have an uneven sub-floor that needs to be filled in with leveling compound. If the compound is not self-leveling, then you must drag a screed across the top to flatten and level the compound, prior to laying the floor covering.
How to Screed a Masonry Base
For masonry items like bricks or pavers, a layer of 1-inch coarse bedding sand is first dumped and shoveled evenly across the area. Since this is the last bedding layer before laying the masonry product, it’s important to get this as smooth and perfect as possible.
One trick to keep screeding consistent is to lay out 1-inch PVC pipes before dumping the sand. As you screed the sand across the pipes, the pipes act as guards to prevent you from screeding any deeper.
After screeding, carefully remove the PVC pipes and fill in the depressions with loose sand. It’s always a good idea to trowel the loose sand to smooth out the filled-in areas.
Screeding With an Assistant
Working with an assistant is critical for perfect screeding. If not, you’re kneeling in the sand layer ahead of the screed tool. The screed tool will help to smooth out your knee and shoe depressions. But it’s best not to kneel in the sand in the first place. When you work with an assistant, both of you can remain outside of the project area.
In addition, screeding tools can be hard to handle. Screeding a 3-foot-wide walkway is manageable by one person. But when the screeding tool is a full-length two-by-four (8 feet or even longer), it is very difficult for one person to effectively handle the tool. You’ll need two people—one at each end—to control this heavier, larger tool.
Leveling layer (screed) for floors and ceilings
Application of screed
Any floor covering that is used indoors as a finishing layer must have a solid and even base under it. To do this, the upper side of the floor is leveled using special mortars or structures.
Such a layer that eliminates irregularities, closes communications, creates the necessary slope and distributes loads, is called a screed.
Tie-down must be provided when necessary: ​​
- leveling the surface of the underlying layer;
- pipeline cover;
- distribution of loads over heat and sound insulation layers;
- ensuring normalized heat absorption of floors;
- creating slopes on floors along slabs.
Screeds are made as a final surface or as an intermediate layer on which a topcoat is applied.
Tie classification
Tie, by design
According to the type of construction, the screeds are:
- monolithic single-layer;
- monolithic multilayer;
- prefabricated.
Monolithic single-layer screeds
Monolithic single-layer screeds are laid in one layer throughout the entire thickness. As a rule, these are cement-sand mixtures or cement-based mortars.
These ties are simple and are made according to the technology known to most builders. It is important that such screeds can be performed on uneven surfaces.
Monolithic multi-layer screeds
Monolithic multi-layer screeds are made in the same way as single-layer screeds, but at the same time they consist of several interlocking layers, which are made in series.
Prefabricated screeds
Prefabricated screeds are prefabricated elements that are ready to be installed.
Prefabricated screeds are coverings consisting of elements that are ready to be laid and are designed to be mechanically connected to each other. Installation is made from sheets ACL, TsSP large size. Boards made of plywood, chipboard, fiberboard, gypsum-fiber (GVL) or glass-magnesite sheets can also be used.
There are no “wet” processes when working with prefabricated screeds, which makes it possible to lay face coverings immediately after installation. However, such screeds must be arranged on a flat surface in order to avoid deformations and cracks in the screed during operation.
Ties according to the method of engagement with overlap
Types of ties according to the method of adhesion to overlap exist:
- connected to the base;
- on release layer;
- on an insulating layer (“floating”).
Bonded ties
Bonded ties are those that are firmly attached to the base. In other words, there are no separating layers between the base and the screed.
This type of screed can withstand heavy loads, but the shrinkage of bonded screeds is uneven, therefore, during operation, these types of screeds are more prone to deformation and cracking. To avoid them, it is necessary to perform expansion joints in the screeds.
Screeds on the release layer
Since the moisture content of the screeds depends on how wet the floor is, it is recommended to use screeds on the release layer to prevent the screed from adhering to the floor.
A waterproofing material can be used as a separating layer, which at the same time will protect the structure from moisture.
For this screed to be strong enough, it must be at least 30 mm thick.
Ties on the insulating layer (“floating”)
“Floating” ties on the insulating layer do not bind to the base. This is an independent building structure. Such screeds can be found most often in new construction. The design of the screed in this case is less prone to cracking during operation.
The underlying layer between the floor concrete and the “floating” screed is made of the following heat and sound insulating materials:
- mineral wool;
- extruded polystyrene;
- cork board;
- fibreboard.
Minimum floating screed thickness 50 mm. The use of a screed on the insulating layer increases the heat and sound insulation of the ceiling. In addition, the moisture contained in the screed will in no way depend on the concrete floor.
Important! In the case of installing a screed in rooms where the operation mode assumes high loads on the floor structure, it is necessary to reinforce the screed with a steel reinforcing mesh with a diameter of 5 mm with a cell of 100 mm.
At the same time, the minimum thickness of the screed with reinforcement must be at least 50 mm. Prefabricated screeds in this case are not used.
Floor screed: what is it, what happens and is it necessary?
As a rule, the screed is already included in the repair list. Customers are confronted with a fact or asked a number of questions about the screed and its necessity. Not everyone knows what it is and why it is needed. So, even if you know everything about the screed, we recommend reading this article. You will definitely find something new for yourself!
What is screed
This is the layer that serves as the base for the floor covering.
Floor screed is almost always done for leveling (sometimes creating a slope), less often to stiffen the surface. The secondary tasks of the screed is to cover underfloor heating, pipes, wires. It is laid on top of the ceiling or on auxiliary, for example, heat or sound insulating layers.
Screeds can be used as a finishing surface, such as floors in garages and parking lots, but this is not our case.
In apartments or houses, the screed serves as an intermediate layer for laying a top coat on them.
Types of screeds
To begin with, we classify according to the method of adhesion to the base:
- Bound floor screed – this screed is placed on the work surface and, as a rule, fastened to it due to adhesion;
- Floor screed on a separating layer – it is separated from the lower layer by waterproofing or thermal insulation, but in contact with the walls of the room. Not common;
- Floating floor screed – this type of screed is installed on a cushion of sound and heat insulating layer, without touching the walls of the room, which ensures the best quality of sound insulation. It is this type of screed that we most often see in new buildings.
According to the laying method, 4 types of screed are distinguished: More often it is called a beacon screed, since the technology involves first installing beacons, and then leveling the mortar. You may need a screed to: You have a new building and a semi-dry screed has already been poured by the builder. In this case, do you need a screed? It is impossible to answer unequivocally, but depending on the chosen floor covering, with a high degree of probability it is possible to say YES – NEEDED.
In fact, the same DSP, only much less water (in an amount sufficient only for the hydration of the cement in the composition), and with the addition of fiber, which performs the function of reinforcement. This type of screed is convenient for mechanized pouring, but it is rational for an area of ​​​​80-100 sq.m. There are many organizational difficulties with this type of screed, for example, with the placement of a concrete pump that prepares the mixture. Why you need a screed
In this case, a screed is poured over the beacons or a semi-dry screed. Consider a typical situation
