NHBC Standards 2011

8.3 Floor finishes


This Chapter gives guidance on meeting the Technical Requirements and recommendations for floor finishes, including integral insulation, screeds, ceramic, concrete and similar tiles, flexible sheet and tiles, wood block and asphalt.


8.3 - D1 Design standards
8.3 - D2 Statutory requirements
8.3 - D3 Screeding
8.3 - D4 Ceramic, concrete, terrazzo and similar tile finishes
8.3 - D5 Asphalt finishes
8.3 - D6 Flexible sheet and tile finishes
8.3 - D7 Wood finishes
8.3 - D8 Staircase finishes
8.3 - D9-D10 Provision of information

8.3 - D1
Design shall meet the Technical Requirements

Design that follows the guidance below will be acceptable for floor finishes.


8.3 - D2
Design shall comply with all relevant statutory requirements

 Designs should be in accordance with relevant Building Regulations and other statutory requirements.


8.3 - D3
Floor screeds shall be suitable for their intended use

Items to be taken into account include:

(a) background


Background surfaces for bonded screeds should provide an adequate mechanical key. If necessary, cement grouting or a bonding agent should be specified to provide adequate adhesion.


The floor design should ensure that moisture from the ground does not enter the dwelling. For details, reference should be made to Chapters 5.1 'Substructure and ground bearing floors' (Design) and 5.2 'Suspended ground floors' (Design).

(b) services

Provision should be made for:

  • thermal movement of water pipes
  • protection against chemical attack, for example by using purpose-made pipe sleeves or ducts.

(c) screed mix

Cement and sand screeds should normally be a mix between 1 : 3 and 1 : 4½. Screeds more than 40mm thick may be of concrete.

Proprietary additives should have been assessed in accordance with Technical Requirement R3.

(d) screed thickness

Cement and sand screeds should be not less than the following thickness:

Method of laying Minimum thickness at any point (mm)
Laid monolithically with base 12
Laid on and bonded to a set and hardened base 20
Laid on a separating membrane (eg 1000g polyethylene) 50
Laid on resilient slabs or quilts (screed reinforced with galvanized wire mesh) 65
Above services, reinforcement or insulation to services 25

For concrete ground bearing floors, up to 20mm thickness of monolithic screed may be acceptable as part of the required thickness.

Where service pipes are bedded in the screed, the screed should be deep enough to provide at least 25mm of cover over pipes and insulation.

(e) bay size

Screeds over underfloor heating should be sub-divided into bays not exceeding 40m2 in area. Otherwise, room size laying is preferable. Expansion joints in screeds should be consistent with joints in the slab.

(f) curing

A curing period should be allowed until the screed achieves sufficient strength to resist shrinkage stresses and other damage.

(g) surface quality


Screeds intended to be covered with floor finishes should provide an even surface as appropriate.

Recommendations for screeds suitable for various floor finishes are given in the British Standards referred to in Materials clause 8.3 - M2. BS 8204 gives recommendations for screeds to receive in-situ floorings.


Concrete floor slabs may be suitably finished to serve directly as a wearing surface without the need for an additional topping, in accordance with recommendations of BS 8204.


If required, surface sealers or hardeners should only be used in accordance with manufacturers' instructions.

(h) moisture content

The moisture content of screeds to receive other finishes, should be:

  • generally in accordance with relevant British Standards
  • in accordance with floor finish manufacturers' recommendations, where available.

(i) thermal insulation material below screeds

Insulation below screeds should provide adequate compressive strength to support wet construction screeds and floor loads.

Suitable materials are described in clause M8. Insulants should be compatible with any dpm in contact with the insulation.

(j) sound insulation material below screeds

Screeds above compressible material in sound insulating floating floors should be laid on an isolating membrane (for example building paper) and reinforced with galvanized wire mesh.

Suitable insulation materials are described in clause M7.


8.3 - D4
Tile floorings shall provide a suitable surface for the intended use

Items to be taken into account include:

(a) background


The substrate should provide a plane surface. Falls should be specified where required.


Where floor tiling is laid above ground bearing floor slabs, a dpm should be incorporated below or above the floor slab.

(b) application

Floor tiling should be in accordance with the recommendations of BS 5385 : Part 3.
Care should be taken to ensure that:

  • the concrete base or screed is true and level
  • sufficient drying time has been allowed, ie at least 6 weeks for concrete base, 3 weeks for screed.


The floor should be designed to take the additional loads of tiles and any other materials (e.g. overlays). Tiles should be suitable for laying over a timber base.

The floor decking should be:

  • plywood for use in exterior conditions (minimum 15mm for joists at 400/450mm centres and minmum 18mm  for joists at 600mm centres) screwed to the joists at 300mm centres with all square edges supported on joists or noggins. Plywood should be laid with a 1.5-2mm movement gap between boards and at abutments
  • chipboard floor decking overlaid with minimum 10mm plywood suitable for exterior conditions and fixed as above, or proprietary separating/de-coupling layers, tile backer boards or tile bedding reinforcement sheets used in accordance with the manufacturer's recommendations.

Deformable (flexible) tile adhesive (e.g. C2S1) and grout should be used in accordance with the adhesive manufactuer's recommendations.


8.3 - D5
Asphalt finishes shall be suitable for their intended use

Asphalt floor finishes should be in accordance with BS 6925 (limestone aggregate). Suitable thicknesses and grades include:

Use Thickness (mm) Grade
Floor finish 15 to 20 I or II
Underlay for other finishes (in one coat) 15 to 20 I or II

Suspended floor system manufacturers should be consulted where mastic asphalt floor finishes are to be used with such systems.


8.3 - D6
Flexible sheet and tile flooring shall provide a suitable surface for the intended use

Items to be taken into account include:

(a) background

BS 8203 gives recommendations on the use of flexible sheet and tile floorings.


Substrates should be sufficiently level to achieve an acceptable floor surface. If necessary, a levelling underlay should be provided.

Acceptable types of underlay for boarded surfaces include the following:

Type of underlay Minimum thickness (mm)
Hardboard 3.2
Plywood 4.0
Chipboard 9.0
Oriented strand board 6.0


Where flexible sheet or tile flooring is laid on ground bearing concrete floors, a dpm should be incorporated to prevent rising moisture adversely affecting floor finishes.

Screeds or concrete surfaces should be sufficiently dry to avoid any adverse effects on the flooring.

Where there is a risk of trapping moisture from spillage or interstitial condensation, permeable finishes should be used.

(b) laying and fixing

Flexible tiles and sheets should be laid, using the adhesive and the method recommended by the manufacturer.

Special precautions, such as welded seams, may need to be specified to prevent curling, bubbling and lifting.

(c) accessories

Skirtings should be specified, where appropriate.


8.3 - D7
Wood and wood-based flooring shall be designed to provide a suitable wearing surface for the intended use

Items to be taken into account include:

(a) background

BS 8201 gives recommendations on the use of wood and wood-based floorings for directly and indirectly applied finishes.

BS 5250 gives recommendations on the use of vapour control layers with wood and wood-based floorings.

Screeds or concrete to receive wood flooring should be sufficiently dry to avoid any adverse effects. Tests for moisture content are given in BS 8201.

A damp-proof membrane should be incorporated as appropriate.


(wood blocks, parquet, wood mosaic, etc)
Floor finishes should be applied with the correct adhesives, for example:

  • bitumen rubber emulsion (in accordance with BS 8201)
  • proprietary adhesives (assessed in accordance with Technical Requirement R3) in accordance with manufacturers' instructions.

Screeds or concrete surfaces to receive wood finishes:

  • should be treated with a suitable primer where recommended by the adhesive manufacturer.


(softwood boarding, wood-based panel products)
The following precautions should be taken:

  • vapour control layers may need to be incorporated above the insulation
  • battens should be preservative treated in accordance with recommendations given in Chapter 2.3 'Timber preservation (natural solid timber)'
  • provision should be made for local support for heavy items such as storage heaters, boilers, etc
  • battens should be at appropriate centres, generally in accordance with the following:
Thickness of finish (mm) Maximum batten centres (mm)
Chipboard (type P5)
18/19 450
22 600
12 450
16 600
Oriented strand board (type OSB3)
15 450
18-19 600

  • fixings to battens should prevent excessive movement and should be in accordance with manufacturers' recommendations.

(b) services

Wherever possible, services beneath the floor finish should be tested before floor laying is commenced.

(c) sound insulation

Floating floor finishes should be designed to:

  • isolate the floor finish from the supporting floor and all walls
  • avoid excessive movement or squeaking
  • avoid the use of fixings which penetrate the insulation layer.

Floors should be designed so that there are no airpaths, especially at the perimeter. This limits the transfer of airborne sound and avoids flanking transmission.


Where a floor relies on a soft floor covering to provide the minimum standard of sound insulation, the covering should be fixed permanently in position.

(d) thermal insulation

Methods of providing insulation include the following:

  • insulation above in-situ concrete slab (dpm required)
Insulation above in-situ concrete slab

  • insulation above dry, precast system (dpm NOT required).
Insulation above dry precast system

Proprietary insulated flooring should be assessed in accordance with Technical Requirement R3. Manufacturers' recommendations regarding provision of vapour control layers and damp-proof membranes should be followed.

Further information can be found in BS 5250 and the BRE Report 'Thermal insulation: avoiding risks'.


8.3 - D8
Staircase finishes shall allow safe use of the staircase

Items to be taken into account include:

(a) rise and going

Staircase pitch and tread dimensions are specified in Chapter 6.6 'Staircases' (Design). It is important that rise and going remain consistent and are not affected by the staircase finish, particularly at the top and bottom of the flight.

(b) slip resistance

Guidance on staircase finishes of flexible sheet or tiles is included in BS 8203.

Communal staircases, such as those providing means of escape in fire, should be provided with a non-slip surface or nosing.


8.3 - D9
Designs and specifications shall be produced in a clearly understandable format and include all necessary information

Drawings and specifications should cover at least:

  • schedule of finishes
  • screed thickness and mix
  • details of sound insulating floors
  • extent and detail of tiled surfaces
  • location of services adjacent to tiled surfaces
  • details of staircase finishes.
8.3 - D10
All relevant information shall be distributed to appropriate personnel

Ensure that design and specification information is issued to site supervisors and relevant specialist sub-contractors and/or suppliers.