Rules for preparing the base for a floor screed

A successful and long-lasting floor greatly depends on the quality of the base for a floor screed. A well-prepared base guarantees that your screed will adhere well and last for a long time, whether you’re installing a new floor or remodeling an old one. Although the procedure may seem overwhelming, if you follow the right steps, you can create the ideal base.

You must first give the surface a thorough cleaning. Clear away any loose materials, dust, and debris. This is a crucial step because impurities could prevent the screed from

1. Clean the Subfloor: Remove all dust, debris, and grease from the subfloor.
2. Check for Stability: En Install edge profiles or perimeter isolation strips to allow for expansion and contraction.

What does the concept mean??

One installation procedure that is carried out during the rough finishing of a public, residential, or industrial space is preparing the base for a floor screed. The following fundamental actions are part of the preparatory work that comes before installing floor screed:

  • Milling or leveling the floor slab.
  • Compaction of the soil base.
  • Partial or complete replacement of soils.
  • Examination of concrete or other span structures, foundation slab for identification of defects.
  • Repair of the span structure when defects are identified that do not allow a reliable screed to be installed.
  • Partial or complete dismantling of an old screed in order to restore or replace it.
  • Processing with penetrating antiseptic compositions of wooden structures to prevent the propagation of bacteria and the development of putrefactive processes in the natural structure.
  • Laying a polymer film on top of a wooden coating in front of the floor screed.
  • The device of gluing waterproofing from bituminous materials or coating liquid mastic on top of the reinforced concrete team or monolithic floor slab.
  • The device of heat -insulating mats, polystyrene or mineral wool plates to increase the energy efficiency of the enclosing structure.
  • Installation of a protective, carrying or soundproofing floor screed before pouring the main structure.
  • Strengthening the external structure using external reinforcement tools to increase the bearing capacity under the weight of the future floor screed.
  • Carrying out other repair and restoration or preparatory activities, in accordance with the instructions of the working design drawings or technological map.

The type of ceiling, the extent of its physical wear and quality, as well as the demands of the operational project, determine the ultimate arrangement and quantity of layers and the technology used to prepare the base.

Whether it is mandatory?

For the following kinds of bases and structures, the floor screed must be prepared without fail:

  1. For wet Concrete screeds or cement-sand solution:
  2. In the presence of defects on the surface of the reinforced concrete floor slab.
  3. In the case of the construction of the underly underwent design on top of the ground,.
  4. When arranging such a screed on wooden floors or flooring on beams from other materials.
  5. During major repairs, partial or complete restoration of the old concrete screed.
  6. In the presence of increased fire requirements for the finished public or dwelling.
  7. For half -dry screeds made of cement-sand mortar, erected by machine:
  8. If such a screed is arranged on top of the old coating of the coating of a black floor or finish coating.
  9. If the floors on soil imply the laying of hidden engineering communications – healing, water supply, electrical wiring.
  10. If the design of the screed involves an increase in the load on the extension element of the building, which was not previously provided for by the working project and static calculation.
  11. For dry Saturation screeds with inert materials and a coating of solid gypsum, OSP, GKL or other sheets:
  12. When installing a constructive element on top of a wooden overlap, whether another extending structure.
  13. When laying hidden elements of the stages in the thumbnail of a dry floor screed.
  14. If it is necessary to adjust the height of the destroyed premises, according to the volume-planning requirements.

Simultaneously, there are situations in which the black floor screed in different rooms can be applied without the need to prepare the base, specifically:

  • With a rough screed already installed, which has no defects or mechanical damage.
  • In the event that a dry screed is installed on top of a prefabricated and monolithic floor slab that does not have any damage, and the room does not require compliance with special temperature and humidity conditions.
  • If this decision is not provided for by the working hire or technical specifications.
  • In the event that a dry floor screed is installed in a dry residential room, which is not subject to any increased operational requirements.
  • If all preparatory measures were previously carried out during the construction of the facility.

Even though it is acceptable to overlook the base’s preparation for screeding the floor covering, a required inspection of the floor slab will be necessary before work on the main structure is begun in order to find any potential flaws and to ensure that the binder material adheres to the surface of the slab in a high-quality manner. Additionally, the floor slab must be cleaned and cleared of dust.

General requirements

Beneath the base of a floor screed within civil buildings The following prerequisites must be fulfilled:

  • Mechanical strength, maximum deflection and crack formation are required to fully satisfy the joint venture.
  • Design load capacity.
  • No mechanical defects.
  • Waterproof design.
  • Sound and vibration insulation of the base under the screed.
  • Increased degree of adhesion to subfloor screed materials.
  • Reliability and durability of the structure after installation of all structural layers of the floor pie.
  • No defects on the supporting structure after restoration operations.
  • Satisfying environmental, sanitary and hygienic requirements during repair and restoration operations.
  • Ensuring the proper degree of waterproofness and fire resistance for the span structure intended for screeding the subfloor.
  • The durability of the prepared base, which can serve no less than the entire subfloor screed structure.

The master finisher formulates a set of implementation-ready solutions that meet the requirements of the regulatory documentation (Sp 29.13330.2011 "Floors," GOST 31358-2019 "Dry construction floor mixtures"), the detailed design drawings, and the results of an inspection of the current foundation. These are developed based on the fundamental requirements that were previously presented.

Necessary materials

The following basic and consumable materials are required for the customer, the facility owner, to prepare the base for the construction of a floor screed in an excellent manner:

  • Self-expanding mortar based on cement binder type NTs for local repair of prefabricated or monolithic reinforced concrete floors.
  • Antibacterial impregnation for wood.
  • Penetrating waterproofing for treating porous concrete surfaces.
  • Polymer film or bitumen mastic, or a waterproofing membrane on fiberglass to protect the base from moisture.
  • Penofol, mineral wool mats or other fibrous roll materials to ensure reliable sound insulation of the floor screed.
  • Porous narrow damping tape with a self-adhesive back side for installation around the perimeter of the room in the lower edge of the walls.
  • Insulation made of mineral wool board or sheets of extruded polystyrene foam for installing a thermal insulation gasket between the screed and the base.
  • Composite or steel mesh for reinforcing a subfloor structure made of concrete or cement-sand mortar.
  • Concrete contact to improve adhesion between the floor slab and the subfloor structure made of cementitious binders.
  • Concrete with a low strength grade for the installation of a primary sublayer under the main screed when constructing floors on the ground.
  • Mounting foam, silicone sealants for conjugation and ensuring the impermeability of insulating membranes.
  • Pipe, cable communications, heating mats and other elements of hidden engineering communications, the diameter, length, materials and quantity of which are determined by separate sections of the design documentation.
  • Galvanized steel beacons or reinforcing bars for installing guides before pouring the floor screed.

All materials utilized in the process of preparing the span structure’s load-bearing portion for the installation of a leveling screed are listed in the project drawings, floor assemblies, floor cross-sections, and the specification for graphic materials, which specifies the precise amount and safety factors of each material.

Tools and accessories

Regardless of the design or thickness of the floor screed, the following tools and electrical equipment are required to properly prepare a sturdy and level base:

  1. Hand tools:
  2. Laser and bubble building levels for monitoring the horizontal floor plane.
  3. Hammer for identifying voids and defects under existing old floor screed.
  4. A trowel and a set of spatulas of wide width for applying repair compounds to cracks, chips, sinkholes, areas of concrete delamination and other defects in the structure of the slab or old rough floor structure.
  5. Chisel for expanding and jointing small cracks to a repairable width.
  6. Roller for applying coating waterproofing, penetrating impregnation for wooden floors and other liquid compositions.
  7. Scissors or a construction knife with a retractable blade for cutting polymer roll materials for preparing the base for a floor screed.
  8. Container for mixing repair compounds, cement-sand mortar for fixing beacons.
  9. Mixer attachments for drills for mixing plastic repair or installation materials.
  10. Plastic heap with an abrasive contact plane for grouting repair compositions after applying them.
  11. Attachments for rotary hammers and drills in the form of disc abrasives, cutters for special equipment for rough mechanical processing of a concrete floor slab before installing a floor screed.
  12. Special cutters for cutting pipe communications or elements of water heated floors.
  13. Electrical equipment:
  14. A hammer drill for complete or partial dismantling of the old floor screed, or a jackhammer if the structure is highly durable and requires significant impact forces.
  15. Drill for grinding concrete floors, or for mixing repair compounds using a special attachment.
  16. Vibrating rammer for compacting bedding made of inert high-strength bulk materials for constructing reliable floors on the ground.
  17. For large volumes of screed in long rooms – a semi-automatic mixer with a powerful electric motor and a receiving hopper with blades with a capacity of up to 150 – 200 l.
  18. A cut hairdryer for fast drying before starting further work on the installation of a black floor structure.
  19. Gas cylinder with burner for reliable fixation of rolled bitumen waterproofing materials on top of the floor slab.
  20. A jigsaw or circular saw with cutting or diamond disc attachments for cutting wooden, steel or other dry floor screeds.

All tools and equipment need to be of the highest caliber, sharpened, in excellent operating condition, devoid of any grease, dust, or dirt residue, and fully prepared for use.

Step-by-step preparation instructions

The owner of an apartment or other property should contact professionals to prepare the foundation for a floor screed, provided that he lacks construction, installation, or finishing work experience. These professionals will complete all necessary tasks quickly and efficiently and then offer a long-term guarantee for the outcome.

If this is not possible, these kinds of work can be carried out independently as long as all safety protocols and technological maps—which are provided in detail with all the subtleties below—are strictly followed. This applies to all common types of floor mockeys.

Priming

Ground floors are the most typical kind of base used for screeding the final layer. To prepare this design, run the following production algorithm:

  • The soil base is examined for its density and sufficient bearing capacity, as well as the uniformity of the granulometric composition.
  • If necessary, the soil is spilled with water and compacted with vibrating rammers.
  • If, after compaction, subsidence of the soil base is detected, additional addition of a certain amount of inert materials is required.
  • On top of the soil base, compacted to the required degree, a protective leveling unreinforced screed made of concrete of class no more than B7.5 or B10 is installed.
  • After polymerization and a set of design strength of concrete, sequentially coating and gluttoen waterproofing with fueling joints from bitumen materials using gas burners is arranged.
  • After waterproofing, thermal insulation from extruded polystyrene foam is cut out and successively installed to cut off all the cold from the street when the ground freezes in winter.
  • The joints between the insulation are necessarily foamed with self-expanding polymer porous compounds – polyurethane foam from cylinders.
  • After the insulation, a rolled porous material must be lined – penofol with a metallized membrane that reflects heat from the heating pipes, which greatly increases the energy efficiency of the subfloor structure.
  • Utilities are installed on top of the penofol – underfloor heating pipes, through which the coolant liquid will subsequently circulate.
  • At the final stage, after the installation of all utilities, beacons are installed, a damper tape along the perimeter of the walls of the strip foundation, inside the perimeter of which the floors are poured on the ground, and reinforcement of the future structure of the rough base for the finishing coating of the first floor of the building is also performed.

It should be kept in mind that inadequately compacted soil, the existence of voids beneath, or lenses of a weak or fluid base always lead to settlement over time. This can result in depressurization of pipe utilities and cracking of the finished floor’s finishing surface in addition to the screed.

Old screed

One of the most complex and questionable subfloor bases that can be utilized is an old cement-sand or concrete screed. As a result, in order to get ready, you must finish the following crucial and required steps:

  • A detailed examination of all planes of the old concrete or cement-sand screed is carried out.
  • All defects that must be eliminated during repair work are identified, classified and recorded in a special list, and these zones are marked on the surface of the screed using chalk or a permanent marker.
  • All identified cracks, chips, holes and other traces of defects, or mechanical damage are repaired using a hammer and chisel.
  • The screed is tapped with a hammer over the entire area of ​​the room to identify voids underneath due to physical wear and tear.
  • All areas with voids are hollowed out from the base under the subfloor screed using a hammer drill with special attachments, after which the ends of this dismantling area are completely cleaned.
  • The entire surface of the old screed is cleaned of all traces of dust and other types of contaminants.
  • In a separate container, a repair high-strength cement-sand or concrete mixture based on a non-shrinking hydraulic binder with polymer ingredients is mixed.
  • The resulting plastic mass is poured into pre-hollowed areas, and also applied with trowels into cracks, chips and other previously identified minor defects of the old screed.
  • Time is waited for complete polymerization of the poured composition and for its development of design strength.
  • After the repair compounds have hardened, the plane of the restored screed is ground with abrasive discs mounted on a drill, and treated with penetrating waterproofing.
  • Before installing a concrete or cement-sand floor screed, depending on the requirements and content of the working project, waterproofing and heat-insulating layers are installed from the materials accepted in the drawings and specifications for them.
  • After laying all the layers of the pie, when preparing the base for the screed, elements of hidden utility lines, beacons and reinforcement meshes are installed to increase the load-bearing capacity of the structure.

The structure may not be suitable for installing a new load-bearing base beneath the finished floor in certain cases, according to the findings of an instrumental and visual inspection of the old screed. According to the project, in such circumstances, the property owner will have to completely disassemble the old covering in order to replace it with a new screed.

Concrete slab

Regardless of the material and thickness of the floor screed, the most dependable and long-lasting structure is a precast or monolithic floor slab or foundation made of reinforced concrete. A minimal amount of work and adherence to the subsequent detailed instructions are needed to prepare such a base:

  • The floor slab is inspected for minor defects that arose during its concreting or careless operation during the construction of the finished object.
  • All previously identified defects are calked with repair compounds using a spatula, using the technology described above, for the previous point.
  • The entire plane of the concrete floor slab is cleaned, washed, dusted and degreased, and then dried with a building hair dryer.
  • Waterproofing and thermal insulation layers are installed sequentially, if such solutions are provided for in the working design.
  • After installing the waterproofing and thermal insulation of the floor, reinforcement is installed, underfloor heating or hidden heating pipes are laid, cable communications are laid, and beacons are fixed, after which the base is ready for installation of the subfloor screed.

The results of all the operations discussed above indicate that it is crucial to wait until all repair compounds have completely polymerized in order to stop moisture from evaporating beneath the future screed. This is because bacterial growth and mold formation almost always result in swelling of parquet, laminate, carpet, or other finishing floor covering in the room that is being finished.

Wood

When laying a screed over such an overlap of natural materials, wood is a very erratic building material that demands adherence to specific safety precautions and consideration of the following steps and nuances:

  • The plane of the wooden floor is examined to ensure the required load-bearing capacity under the weight of the future cement-sand or concrete floor screed.
  • If necessary, the span structure is strengthened in strict accordance with the previously developed design and based on static calculations.
  • All wooden structures are treated with penetrating antiseptics to prevent the development of fungus and rotting of materials.
  • Polymer waterproofing membranes are lined on top of the wood plane, which completely protect wooden structures from moisture.
  • If sound insulation is necessary, logs made of timber or boards are placed on top of impermeable polymer films, between which a backfill of expanded clay or inert materials is carried out.
  • Before installing a wet screed over a wooden floor, you should also lay the base, after the heat-insulating, sound-insulating and waterproofing layers using OSB sheets or asbestos cement (flat slate)
  • The gaps between the sheets are treated with silicone or bitumen mastic to ensure sealing.
  • Cables, heating pipes are mounted on top of the base, reinforcement and beacons are installed, after which the master begins to construct a floor screed from gypsum, cement-sand mortar or other modern materials with minimal volumetric weight.

The property owner must be aware that moisture entering the pores of wooden structures must be eliminated by artificial or natural drying, as this will cause the material to rot and drastically shorten its lifespan.

The base must be ready for a floor screed in order to guarantee a smooth, strong, and long-lasting finish. In order to improve adhesion, this process entails completely cleaning the surface, fixing any cracks or damage, and applying an appropriate primer. The risk of recurring issues, like unevenness or cracking, is reduced with proper preparation, which also lays the groundwork for a premium screed that will successfully support the finished flooring material.

Bugs and difficulties

A home craftsman or property owner lacking extensive experience in finishing and repair processes can make several serious violations and mistakes when preparing a load-bearing base for a floor screed in a residential or public building by hand. These errors almost always result in unfavorable outcomes.

Here is a thorough explanation of the most frequent mistakes that could occur and suggestions for avoiding them, along with the best ways to do so.

  • Neglecting soil compaction – there is a risk of subsidence and, as a result, destruction of both the screed and the finishing floor covering.
  • Installing a screed on an untreated, dusty base – the adhesion of the new plastic material may be impaired, which will subsequently lead to delamination of the entire structure and the formation of voids.
  • Neglecting to inspect the floor slab and old screed to identify defects in order to carry out repair work to restore these structures.
  • In order to completely avoid the risk of depressurization of the covering slab, both at the stage of screed installation and during the operation of the floor covering, the mandatory installation of membrane, adhesive or coating waterproofing of the base is required.
  • Neglecting grinding or milling of beads on the floor slab or building foundations – difficulty in placing beacons, reinforcement, increased risk of the formation of duplicate bumps on the screed itself, which will be displayed indoors.
  • The absence of a damper tape along the lower edge of the walls at the point where they join the floor slab – there is an increased risk of structural noise spreading throughout the room.
  • Lack of static calculations and measures to strengthen the wooden floor – when installing the screed, there is a risk of cracking of the fiber span structures.

Before beginning work, the property owner should familiarize himself with a number of master classes and video lessons from professionals and experts, who frequently share their experience with other users and interested parties on well-known online channels that are open to the public, in order to completely eliminate any errors.

Useful video

We would like you to view the following video about the subject of the article:

The base must be properly prepared before applying a floor screed in order to produce a smooth, long-lasting finish. The procedure begins with a careful examination and cleaning of the current surface to make sure adhesion-affecting materials, dust, and debris are removed. This is an essential step in building a strong foundation.

The next step is to fix any cracks or uneven areas after the surface has been cleaned. Cracks and dips in the floor can be avoided in the future by filling in the gaps and leveling the base to guarantee that the screed is applied uniformly. By preventing expensive repairs, this meticulous attention to detail during preparation can ultimately save time and money.

A primer or bonding agent is applied to the base after it has been cleaned and leveled to improve the screed’s adhesion to the surface.

Video on the topic

Pouring a subfloor over the ground – process and nuances

Preparation of the subfloor / rough screed for heated floors / installation of heated floors

FLOORS ON GROUND ● Preparation of the base ● Rough screed of the floor

🔥 7. HOW TO MAKE / POUR A SCREED UNDER A WARM FLOOR. From A to Z! Warm floor screed screed thickness

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Fedor Pavlov

Interior designer, author of books on residential design. I will help you make your home not only functional, but also beautiful.

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