​​Revision 03 - August 2020

A12 - SUBSTRATE PREPARATION

A12-1 General Requirements
​A12-2 Basic substrate requirements
A12-3 Preparing wood substrates
A12-4 New concrete substrates
A12-5 Concrete subfloors requiring special surface preparation work
A12-6 Preparing existing resilient flooring surfaces
A12-7 Removal of resilient flooring
A12-8 Preparing concrete surfaces containing residual adhesive
A12-9 Preparing metal surfaces
A12-10 Preparing poured polymeric and/or epoxy surfaces
A12-11 Preparing existing terrazzo/marble/ceramic surfaces to receive resilient flooring
1 • GENERAL REQUIREMENTS
  1. All substrate surfaces to receive resilient flooring, carpet, hardwood, laminate, and other flooring types noted within this manual shall meet minimum NFCA and flooring material manufacturer’s written requirements.
  2. The General Contractor shall (except as noted below) provide a substrate surface acceptable for the installation of specified flooring materials.  Unless otherwise defined by local trade jurisdiction, or agreed to between the General Contractor and the flooring contractor prior to commencement of the Work, the General Contractor will be responsible for:
    1. Provision of substrate surfaces within level tolerances defined under Part A10 - Acceptable Conditions.
    2. Filling and levelling all substrate surfaces including control and construction joints, structural cracks, grooves, gaps, and other irregularities.
    3. Grinding smooth all ridges, undulations, projections and areas of carbonation and scaling.
    4. Correcting low density or powdery concrete surfaces in order to provide substrate surfaces that are acceptable for the installation of flooring materials.
    5. Major patching or installation of an underlayment using products that are suitable for substrate surfaces, that are compatible with flooring materials to be used, and that are in accordance with NFCA requirements.  Refer to Part A12 - Substrate Preparation.
      1. Note:  Where the contractual relationship is between an Owner and the flooring contractor the contractor shall be responsible for providing surfaces acceptable for the installation of flooring including those items listed above.
  3. The flooring contractor shall be responsible only for minor substrate preparation that includes filling of small chips and dents, removal of minor protrusions and vacuuming of an otherwise acceptable surface in accordance with NFCA requirements and as defined by local trade jurisdiction requirements. General Contractor or Owner shall include for the additional substrate preparation work (shot-blasting, grinding, levelling, skim coating, crack filling etc.) as required to meet NFCA and manufacturer requirements.
  4. If a substrate surface has been previously patched, the flooring contractor shall ensure that an industry approved Portland cement-based patching compound was used. Unacceptable patching compounds shall be removed and be re-patched using an approved patching compound with the work done by the General Contractor unless otherwise agreed to between the General Contractor and the flooring contractor prior to commencement of the Work.
  5. All low density or powdery surfaces shall be removed and corrected before the installation of any flooring material.  This may be done by using an approved patching compound subject to the requirements noted herein with the work done by the General Contractor unless otherwise agreed to between the General Contractor and the flooring contractor prior to commencement of the Work.
  6. The General Contractor shall ensure and the flooring contractor shall verify that all substrate surfaces required to be patched are structurally sound and are clean, dry and free from alkali, dust, dirt, adhesives, paint, varnish, solvents, oils and grease, waxes, release agents, sealers and curing and hardening compounds detrimental to the installation of patching materials to be used.
  7. Irrespective of any NFCA Quality Assurance Inspection Program requirement, the flooring contractor shall report in writing to the General Contractor or Owner (or Owner’s representative) any unsatisfactory conditions observed at the site prior to installation of flooring materials.
2 • BASIC SUBSTRATE REQUIREMENTS
.01   All substrates surfaces must be dry, relatively smooth, level and free from irregularities or imperfections that may potentially be telegraphed to the surface of the newly installed flooring and thereby detract from the final appearance and possibly impair the longevity of the flooring.

.02   The substrates must be free of any previous surface applications, such as wax, oil, paint, varnish, hardening compounds, old adhesive, etc., that will impair the adhesive bond, or cause staining.

.03   Existing substrate surfaces must be correctly prepared to provide an acceptable surface and bond for the replacement flooring.

.04   Various substrates surfaces may be covered with flooring materials, subject to NFCA acceptance. Some of these are:
  1. Concrete including concrete topping.
  2. Wood subfloors.
  3. Existing epoxy, terrazzo, and tile (stone, ceramic tile) surfaced floors.
  4. Existing resilient flooring surfaced floors.
  5. Metal subfloors.
3 • PREPARING WOOD SUBSTRATES
.01   Basic Requirements:
1.  Wood substrate surfaces must be flat and relatively level, strongly constructed, and free from springiness.

2.  The substructure must be suspended over a cross-ventilated or heated crawl space that conforms to the requirements noted in Part A10 - Acceptable Conditions.

3.  Floor Covering Manufacturers do not recommend the installation of resilient flooring over wood panels attached directly to on grade or below grade concrete subfloors or over sleeper constructed subfloors on or below grade concrete slabs.  Refer to Part A10 - Acceptable Conditions for wood substrate requirements.
.02 Basic Preparation Requirements:
.1    Strip and Plank Floors:  Any loose and squeaky boards must be securely nailed and all broken or unsound boards or board sections replaced.  The entire flooring should be sanded until even and sealed to prevent moisture absorption.  Cracks in excess of 1.6 mm between boards should be filled level.
 
Note:  The installation of an approved wood panel underlayment over strip or plank flooring will minimise the potential telegraphing effect and compensate for the seasonal expansion and contraction characteristics of the boards and is therefore strongly recommended.  Refer to Part A10 - Acceptable Conditions and Part D06 (Hardwood) Installation Guide for further explanation and requirements.
 
.2     Underlayment Panels:  The following types of panel materials are acceptable depending on floor covering material to be applied, floor covering manufacturers recommendations and pre-approval, NFCA requirements, and panel manufacturer’s
  • Plywood.
  • Particle Board.
  • Oriented Strand Board (OSB).
  • Cementitious Board.
 
Refer to Part A10 - Acceptable Conditions for wood substrate requirements.
.03   Basic Underlayment Panel Preparation Requirements:
  1. Ensure that underlayment panels and the fastening procedure employed are in compliance with the floor covering manufacturers recommendations.
  2. Panel thickness differences at joints shall be corrected by sanding until even.
  3. Contaminates which potentially could stain or discolour the new flooring must be removed.
  4. Ensure that the entire area has been thoroughly cleaned and all detachable objects have been removed.
  5. Open knotholes and other imperfections must be patched flush.
  6. Generally only gaps between panels in excess of 1.6 mm should be filled unless otherwise specified.
  7. Refer to Part A13 - Patching and Filling for recommended patching / levelling compounds.
4 • NEW CONCRETE SUBSTRATES
.01  Basic Substrate Requirements:
  1. Concrete subfloors must be dry, smooth, structurally sound, and free of depressions, scale, topically applied sealers or any other foreign deposits.
  2. Ensure that moisture and adhesive-bond test results are in compliance with the manufacturers recommendations.
  3. Depending on environmental conditions and time of the year, new concrete slabs will require at least six weeks drying time before they may be ready for moisture tests.  Floors containing lightweight aggregate or excess water, or floors placed on steel or plastic pan construction, may need a much longer drying time.
  4. Refer to Part A10 - Acceptable Conditions for floor covering installation requirements and for concrete substrates.
  5. Refer to Part A11 - Substrate Testing for moisture and alkali testing requirements.
.01  Basic Preparation Requirements:
  1. All areas specified to receive new flooring materials must be prepared in accordance with the manufactures recommendations, applicable floor covering specification requirements, and minimum NFCA requirements to extent indicated in Parts B05, C05, D05, E05, and F05 - Scope of Work.
  2. Such tasks may include:
  1. The removal of all contaminates which potentially may stain or discolour the new flooring such as grease pencil marks, paint droppings, oil spills etc.
  2. Removal of previously applied concrete hardener or sealer.
  3. Removal of mortar and drywall droppings, or any other surface attachments.
  4. Minor levelling of low areas and transition patching where required.
  5. Filling / levelling of construction joints, holes, cracks etc., using approved patching compound.
  6. Thorough cleaning of entire flooring area and the removal of detachable objects.
    3.   Refer to Part A13 - Patching and Filling for recommended patching / levelling compounds and for General Contractor and Flooring Contractor responsibilities.
.03   Preparing Hydraulic Cementitious Underlayment Surfaces:
  1. The addition of a self-levelling cementitious underlayment over new or existing concrete surfaces to provide a level surface suitable for flooring installation shall be done by others (unless agreed to with the Owner or General Contractor and the flooring contractor) with finishing and curing requirements as noted in to Part A10 - Acceptable Conditions.
  2. After this material is installed it is subject to the same preparation requirements as those for new concrete substrates noted above.
5 • CONCRETE SUB-FLOORS REQUIRING SPECIAL SURFACE PREPARATION WORK
.01  Treating an Alkaline Condition:
  1. Only minor alkaline conditions are treatable.  Excessive alkali deposits are generally the result of moisture migration.  Such subfloors require water proofing prior to any resilient flooring installation.
  2. For temporary relief of minor alkaline conditions, a five (5) to ten (10) percent mix of muriatic acid and water may be used to neutralize the affected areas.  Manufacturers application instructions must be followed and all required precautions and regulations obeyed when working with an acid solution.
.02   Concrete Curing / Sealing Agents and Removal:
  1. Curing agents containing combinations of curing and sealing compounds are designed to retard the rapid hydration of water from the slab.  These materials leave a residue on the concrete surface that has caused a number of flooring and/or installation failures.
  2. Problems encountered with treated slabs have been:
  • Prolonged flooring installation delays due to latent moisture retention of the slab and moisture related flooring failures where installations had been undertaken.
  • Adhesive bonding failures, especially with two component and water-based adhesives.  Generally, sealers by their nature render the concrete surface less porous and thereby less receptive to the necessary bonding or curing requirements of these types of adhesives.
  • Adhesive bonding and/or flooring failures on subfloors previously treated with a wax or oil based curing compound.
     3.   Special Note:  Due to the large number of curing and/or sealing compounds available, specific recommendations cannot be made   regarding their use or need for removal.  Specifiers and Contractors must therefore ensure that the products selected are recommended by the curing / sealing compound manufacturer for the type of floor covering and/or installation system specified.

The responsibility for concrete sealer and curing warranties rests with the concrete treating compound manufacturer / supplier / specifier or building contractor / owner in the event of a flooring and/or installation failure and not with the floor covering manufacturer, supplier, or floor covering contractor.
.03   Removal of Concrete Substrate Surface Treatments:
  1. Due to a potential flooring and/or adhesive compatibility problem, the majority of floor covering manufacturers will recommend complete removal.  Only when bond and stain tests have proven that a satisfactory installation can be obtained may an installation be considered.
  2. Standard Methods of Removal are:
  • Grinding with a terrazzo or concrete grinder.
  • Sanding with a drum sander or edger.
  • Using solvents or dilutents recommended by curing/sealer manufacturer.
  • Abrasive blasting using shot or sand (most effective method).
.04   Preparing Hard-Trowelled Concrete Substrate Surfaces:
  1. On hard-trowelled or polished concrete surfaces, an adequate bond with conventional adhesives may not be possible due to the lack of surface porosity and absorption.
  2. Depending on the surface condition, one of the following correction procedures may be considered:
  • Washing the floor with a strong solution of tri-sodium phosphate followed by clear water rinsing.
  • Treating the floor with a 10 percent solution of muriatic acid followed by clear water rinsing.
  • Grinding the surface with terrazzo or concrete grinder.
  • Brush-shot blasting the area.
.05   Preparing Coloured Concrete Substrate Surfaces:
  1. If the colour is an integral part of the concrete slab, the same preparation procedures used for a regular concrete substrate should be applied.  If the surface has been waxed or varnished etc., all topically applied coatings should be removed prior to any resilient flooring installation, following the surface coating manufacturer’s removal recommendations.
.06    Preparing Painted Concrete Substrate Surfaces:
  1. Depending on the type of resilient flooring specified, the type of paint used and the condition of the painted surface itself will dictate the extent of the actual preparation work necessary.  In all instances the floor covering manufacturer’s recommendations must be followed.
  2. Complete Paint Removal:  The painted area should be ground, using a terrazzo or concrete grinder or should be shot blasted (most effective method) until complete removal is attained.
  3. Preparation of Painted Surfaces:
    1. All loose and scaly paint should be removed by scraping, sanding, or grinding.
    2. The entire painted area should be sanded, using drum-sander, belt sander, edger, grinder, etc.
    3. Depending on the type of paint used, washing the floor with a solution of tri-sodium phosphate, followed by clear water rinsing may be sufficien.
    4. Special Note:  The remaining paint must be well bonded to the concrete surface, as any remaining loose paint will lift once covered with flooring, resulting in buckling, edge peaking, or other flooring problems.  Be aware, some flooring lines cannot be installed over painted surfaces.  Check with floor covering manufacturers for the types of flooring that can not be installed over painted surfaces.
4. Special Note:  The remaining paint must be well bonded to the concrete surface, as any remaining loose paint will lift once covered with flooring, resulting in buckling, edge peaking, or other flooring problems.  Be aware, some flooring lines cannot be installed over painted surfaces.  Check with floor covering manufacturers for the types of flooring that can not be installed over painted surfaces.
.07    Preparing Existing Terrazzo / Marble / Ceramic Tile Surfaces:
  1. Remove dust, wax, paint, oil, grease or any other foreign substance from the surface.
  2. Remove loose tiles and wash the substrate with a tri-sodium phosphate (TSP) solution and rinse until clean.
  3. Glazed tiles or very smooth surfaces should be abraded, using concrete grinder.  Grouted joints and any other worn or low areas should filled and levelled using industry approved patching /levelling compound.
.08    Preparing Oil / Grease / Wax Contaminated Monolithic Surfaces:
  1. The surface area should be scrubbed with a strong solution of tri-sodium phosphate mixed in hot water, the residue picked up and the procedure repeated until the area is free of all contaminates, then rinsed until clean.
  2. The surface area may be treated with 10 percent solution of muriatic acid, its residue picked up and the area rinsed until clean.
  3. Special Note:  Areas should be allowed to dry for at least 24 hours.  An adhesive bond and stain test is recommended, prior to any flooring installation.
6 • PREPARING EXISTING RESILIENT FLOORING SURFACES
.01   In general, floor covering manufacturers recommend complete removal of resilient flooring prior to any new flooring installations.
.02   Those manufacturers that endorse installations over existing resilient flooring impose certain limitations.  These include:
  1. Installation is acceptable if the existing resilient flooring is not a cushion or foam backed type, was correctly installed over an industry approved subfloor, shows no evidence of moisture or alkali, is completely and well bonded, has a non interrupted surface structure or texture, if all surface treatments have been removed, and all surface damaged areas have been repaired.
  2. Installation is not acceptable over asphalt tile, rubber flooring, or static control flooring.
  3. Installation of flexible PVC and linoleum flooring should not be installed over on or below grade vinyl composition tile or other flooring.
Note:  For complete information regarding the suitability of products and installation procedures over existing resilient flooring contact floor covering manufacturers.
.03    Basic Surface Preparation Procedures:
  1. All damaged areas must be repaired, all loose flooring re-bonded or closely nailed where needed.
  2. Noticeable peaked seams or joints should be cut out and patches from leftover flooring inserted.
  3. Surface applied treatments, such as wax, sealer, or floor finishes should be removed, using recommended chemical stripper.
  4. For effective stripping, a heavy-duty mechanical scrubber or polisher with coarse steel wool or coarse scrubbing pad attachment may be used.  Residue can be picked-up with wet vacuum and area rinsed with clean water.  The area should be allowed to thoroughly dry before taking further action.
  5. Holes, cracks, gouges etc., should be patched / levelled where needed, the area thoroughly vacuumed, or damp moped to remove all surface dust, grid, etc.  Note that the use of  “embossing levellers” for skim-coating embossed resilient flooring surfaces is generally only recommended in residential situations.
  6. Adhesive bond-test should be conducted, if successful, installation of new resilient flooring may proceed in accordance with the manufacturers recommendations.
  7. Caution:  Certain flooring materials (e.g. resilient flooring) are non-absorbent.  Therefore, the type of adhesive applicator used and the adhesive open time require careful consideration.
  8. Special Note:  It is the responsibility of the flooring contractor to determine if the existing resilient flooring is suitable for use as a substrate for the new flooring.  Refer to Part A10 - Acceptable Conditions for Existing Resilient Flooring and for complimentary information.
  9. Warning:  Do not sand existing vinyl asbestos tiles or resilient flooring containing asbestos fibre backings.  Sanding of asbestos containing materials can place fine particles of asbestos in the air, if inhaled may cause serious bodily harm.
7 • REMOVAL OF RESILIENT FLOORING
.01    To avoid dimensional instability, excessive indentation or bonding problems with the replacement flooring, the existing resilient flooring regardless of type or condition should be removed.

.02    The removal of the old flooring and the required preparation work is generally very time consuming and often will take longer than the replacement installation.

.03    Although many different devices are used to remove resilient flooring, no efficient method has been developed by floor covering contractors that will work satisfactorily under all conditions.

.04   The actual method of removal selected will depend on the location of the flooring and the familiarity with the removal procedure of the individual contractor.  The selected method of removal must also comply with NFCA requirements, the new floor covering manufacturers recommendations, and applicable WCB requirements.

.05   Removing Resilient Floor Tiles:
  1. Vinyl composition tile (VCT) that has been installed over concrete substrates with an asphalt or resin-base tack adhesive can be removed by:
    • Freezing using dry ice.
    • Heating, using blowtorch or propane torch.
    • Using infrared lamps.
    • Using special scraping or chipping tools.
.06   Removing Sheet Goods:
  1. Sheet goods are generally removed by cutting the flooring into approximately 300 mm (12”) wide strips.  With the aid of heat, except when removing linoleum flooring, the strips are individually pulled or rolled off the substrate.  Any remaining backing will generally require wet-soaking followed by scraping until removed.
.07    Warning:
  1. If it is discovered or suspected during removal of existing resilient sheet of tile materials that the flooring material and/or adhesive contains asbestos, all removal work must cease immediately in that area.  The General Contractor and/or Owner must take appropriate action to either verify or disclaim the presence of friable asbestos.
  2. If it is determined that the flooring and/or adhesive contains asbestos or is in any way hazardous to workers, the General Contractor and/or Owner will arrange and pay for an Asbestos Removal Contractor to remove all such flooring materials and adhesive from the subfloor and site.
.08    Information Update on Resilient Flooring Removal:
  1. Certified Removal Contractors using newly developed floor covering removal equipment are able to efficiently remove all lines of resilient flooring and glue-down carpets.  Contact the flooring contractor for further information.
8 • PREPARING CONCRETE SURFACES CONTAINING RESIDUAL ADHESIVE
.01           In accordance with the manufacturers recommendations, remaining adhesives residues must be removed or sealed, prior to any new flooring installation.
.02           In accordance with the prevailing work practices:
.1       Non-asphaltic adhesive residue that is compatible with the replacement adhesive and flooring materials may remain providing that the remaining adhesive residue is reduced to a thin, smooth even film.  Adhesive bond tests must be conducted prior to any new flooring installation.
 .2       Asphaltic-based adhesive residue must be removed or sealed prior to any new flooring installation, except when installing vinyl composition tile (VCT).  If VCT flooring is to be installed the adhesive residue must be reduced to a thin, smooth even film.
.03    Basic Asphalt Adhesive Removal Procedures.
.1       Removal may be accomplished by wet grinding / sanding, using floor polisher with plastering-lath wire attachment, concrete or terrazzo grinder.
 
.2       Shot blasting area (a very effective removal procedure).
 
.3       Using chemical adhesive removers.  Caution:  Most chemical adhesive removers are flammable and/or toxic; therefore, their use may be restricted.
 
.4       Special Note:  The use of solvents to remove asphalt-base adhesives is not recommended.  Solvents tend to carry adhesive residues deeper into the surface of concrete slabs; thereby causing bond failures and potential staining of newly installed flooring.
.04    Applying Coatings and/or Mastic Sealers Over Adhesive.
.1       There are a number of manufacturers that are marketing trowelable, high bond strength, polymer modified Portland cement base sealing compounds that are recommended for the direct installation over asphalt base adhesives.
.2       To prevent adhesive migration discolourations and to insure proper bond, these types of coatings must be applied in strict compliance with the manufacturer’s recommendations.

.3      Basic Application Procedure:    
.a       Following tile removal, the remaining adhesive residue must be reduced to a thin, smooth, even film.  Signs of adhesive flaking or breakdown will warrant complete adhesive removal.
.b       Sealing compound must be mixed and applied in compliance with manufacturers recommendations.
.c       Sealing compound should be applied even, level with no ridges or gaps showing.
.d       Coverage must be 100 percent with no signs of adhesive residue showing.
.e       Allow for adequate drying time before starting with new installation.
.4      Precautions:
.a       Gypsum based patching compounds applied directly over asphalt base adhesives are not recommended.  The bond of these types of patching compounds is generally inadequate, and they break up from the force of surface loads and will not seal-out adhesive migration actions.
.b       Encapsulating liquid sealers or liquid latex applied directly over asphalt base adhesives are not recommended.
.5     Gypsum based patching compounds applied directly over asphalt base adhesives are not recommended.  The bond of these types of patching compounds is generally inadequate, and they break up from the force of surface loads and will not seal-out adhesive migration actions.
 
.6     Encapsulating liquid sealers or liquid latex applied directly over asphalt base adhesives are not recommended.
9 • PREPARING METAL SURFACES
.1    Occasionally metal subfloors may be encountered such as on ships, raised metal floors, walkways, landings, etc. that necessitate the use of floor covering.  These areas will require the utmost care in all aspects of preparation work.  Forces that effect metal floors differently are:
  1. The relative humidity in the area,
  2. Flexing,
  3. Expansion,
  4. Contraction, and
  5. The lack of absorbency.
.2    Preparation Recommendations
  1. All paint, oil, grease, wax, sealers etc., must be removed by wet stripping, sanding / grinding, or sand or shot blasting if feasible.
  2. All rust, oxide and scales must be removed by steel brushing, grinding, sand or shot blasting.
  3. To improve adhesive bond, abrade very smooth areas by using grinder, disc or drum sander.
  4. Note:  An acid wash is not recommended to clean / neutralize metal surfaces.
  5. All protruding weld ridges, rivets or screw heads and other uneven joints should be ground smooth, filled or levelled, using recommended patching / levelling compound.  (Check with manufacturer for suitable type).
  6. Conduct adhesive bond test when encountering previously primed metal surfaces and proceed according to achieved test results.
  7. Abrade galvanized steel, aluminium, lead, cooper, and brass/bronze surfaces.  Use only those adhesives recommended by the flooring manufacturer for the type of substrate and flooring to be installed.
  8. Special Note:  Conduct adhesive bond test, using recommended adhesive, only if successful proceed with installation.  Metal substrates are non-absorbent, therefore, the type of adhesive applicator and adhesive open time require utmost consideration. For further details, contact floor covering contractor and/or distributor.
10 • PREPARING POURED POLYMERIC AND/OR EPOXY SURFACES
.1    Polymeric and epoxy surfaces must meet the following conditions:
  1. Be well cured and free of any residual solvent, structurally sound, well bonded to the substrate, and have no history of moisture-related problems.
  2. Any loose or damaged areas must be completely re-moved and the resulting voids, patched flush.
  3. If the noted conditions do not apply.  The entire flooring should be removed.
.2     Preparation Recommendations:
.1       Areas should be dry/wet sanded until smooth, using floor polisher with disk attachment, drum sander or any other suitable equipment.
.2       Old remaining floor finishes should be wet-stripped and thoroughly cleaned.
.3       Allow areas to dry before taking any further action.
.4       Surface defects should be spot patched.  Skim coating of entire area is not recommended, as patching material may not adhere reliably.
.5       An adhesive bond test is recommended prior to any flooring installation.
.3     Preparation Recommendations:
Special Note:  The responsibility for determining if the existing polymeric or epoxy flooring is well bonded to the existing substrate and that the remaining surface texture is sufficiently smooth not to impede the final appearance, rests with the floor covering contractor.  The flooring installer is advised to secure a disclaimer from the Owner / Consumer in regard to potential texture telegraphing and/or delamination problems of existing flooring, prior to new flooring installation.
11. PREPARING EXISTING TERRAZZO / MARBLE / CERAMIC SURFACES TO RECEIVE RESILIENT FLOOR COVERINGS
.1 Remove dust, wax, paint, oil, grease or any other foreign substance from the surface.
.2 Remove loose tiles and wash the substrate with a tri-sodium phosphate (TSP) solution and rinse until clean.
.3 Glazed tiles or very smooth surfaces should be abraded, using concrete grinder. Grouted joints and any other worn or low areas should be filled and leveled using industry approved patching /leveling compound.
.4 All preparation work shall comply with the adhesive, cementitious underlayment or floor covering manufacturers installation guid
END OF PART A12