Revision 2: December 2020
A13 - PATCHING AND FILLING
A13-1 General requirements
A13-2 Patching / Filling / Leveling compounds
A13-3 Hydraulic Cement Underlayment (Self-leveling underlayments)
A13-2 Patching / Filling / Leveling compounds
A13-3 Hydraulic Cement Underlayment (Self-leveling underlayments)
Preface: This reference guide covers patching and filling of substrate surfaces in regard to flooring covering preparation. Individuals using this guide should verify all facts relative to the particular project requirements.
1 • GENERAL REQUIREMENTS
- 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.
- 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:
- Provision of substrate surfaces within level tolerances defined under Part A10 - Acceptable Conditions.
- Filling and levelling all substrate surfaces including control and construction joints, structural and non-structural cracks, grooves, gaps, and other irregularities.
- Grinding smooth all ridges, undulations, projections and areas of carbonation and scaling.
- Correcting low density or powdery concrete surfaces in order to provide substrate surfaces that are acceptable for the installation of flooring materials.
- 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.
- 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.
- 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 (shotblasting, grinding, levelling, skim coating, crack filling etc.) as required to meet NFCA and manufacturer requirements.
- 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.
- All low density or powdery surfaces shall be removed and corrected before the installation of any flooring material. This may 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.
- 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.
- 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. PATCHING / FILLING / LEVELLING COMPOUNDS
- Any patching, filling, or levelling compound used must be specifically manufactured for this purpose, be suitable for substrate surfaces that are to be adjusted, and be of a type recommended by the compound manufacturer for coverings to be installed.
- All patching, filling, and levelling materials and workmanship shall be in strict accordance with NFCA and floor covering material manufacturer’s (including adhesive) requirements and approval in order to provide suitable substrate surfaces in accordance with the requirements of Part A10 - Acceptable Conditions.
- There are numerous industry-approved products available for filling joints, cracks, score marks, holes and other minor irregularities, for skim coating, or for levelling situations over a variety of substrates and grade levels. Such products include:
- Cement based compounds: these are Portland cement based compounds with a minimum compressive strength of 27.6 Mpa (4000 psi) after 28 days of curing, suitable for filling, patching, and levelling of all substrate surface types (unless otherwise restricted by the manufacturer). Such compounds shall be dry mixed with water and/or liquid latex / acrylic additive in strict accordance with manufacturer's requirements.
- Gypsum-based compounds: these are non-shrinking gypsum based (calcium sulphate - also referred to as plaster) compounds for patching, i.e., filling joints, cracks, score marks, holes and other minor irregularities.
- Caution: Gypsum based patching compounds are not recommended by most flooring manufacturers because they generally have lower compressive strength, will deteriorate under exposure to moisture or water vapour, and can promote mildew. In addition, gypsum compounds may inhibit some adhesive's capability to properly bond (such as with asphalt based adhesives / mastics).
- Note: Because of the above noted caution, gypsum compounds shall not to be used for skim coating or levelling, except in above grade residential applications with light traffic only, and only if pre-approved by the adhesive and flooring covering manufacturer.
- All compounds used shall be by the same manufacturer throughout the project, be packaged separately in correctly proportioned units, and be mixed in strict accordance with manufacturer's requirements.
- Recommended Usage:
- Commercial applications: Only Portland cement based compounds are recommended for patching, filling, and levelling over concrete / wood substrates at all grade levels for commercial applications.
- Residential applications: Portland cement based compounds are recommended for patching, filling, levelling over concrete / wood substrates at all grade levels. Gypsum based compounds for patching may be used in above grade situations with light traffic applications only if the use of such a compound is pre-approved by the flooring material manufacturer and by the design authority. Gypsum based compounds are not recommended by NFCA for the above noted reasons.
- Priming Requirements:
- Existing and newly patched areas may be porous and highly alkaline, which may prevent adequate adhesive bond. All patching, filling, and levelling compounds therefore shall be primed after application and curing in accordance with NFCA requirements using a primer that is pre-approved by both the adhesive and floor covering material manufacturer before use.
- Level Requirements:
- Patching and filling materials shall be installed to provide a finished surface within level tolerances within requirements noted in Part A10 - Acceptable Conditions.
3. HYDRAULIC CEMENT UNDERLAYMENT (SELF LEVELLING UNDERLAYMENTS)
- Minor discrepancies in new or existing surfaces levels can be adjusted by using patching and filling compounds. This is, within reason, considered part of the work of the flooring installer. (Refer to Part B05, C05, D05, E05, and F05 - Scope of Work within each Flooring section.)
- Where level discrepancies are too large, i.e., where the thickness of patching and filling compounds required exceeds NFCA tolerances noted herein, floor levels must be corrected by using a self-levelling cementitious underlayment capable of bonding to prepared substrate surfaces and being installed from 3 mm (1/8") to 13 mm (1/2") thick in one pour and up to 25 mm (1") thick in small areas. The material must be capable of being feather edged or tapered without fracturing in order to not leave ridges and to match existing elevations. Such material should achieve a compressive strength of 27.6 mpa (4000 psi) after 28 days by air cure only, be capable of being walked on after 3 hours without damage, and be capable of being coated after 24 hours at 21oC (70oF).
- Substrate preparation is critical for bonding of this material and must be in strict accordance with the underlayment manufacturer’s requirements. This requires that all substances detrimental to underlayment installation such as floor finishes including sealers, hardeners, waxes, adhesives, paint, oil, grease, etc. be removed and if necessary slab surfaces be abraded to provide a surface that underlayment will bond to.
- The application of cementitious underlayments shall be done by others (the General Contractor or Owner) in a timely manner before the installation of flooring materials or may be undertaken by the flooring installer as an additional cost to flooring work. Refer to Scope of Work in each Section.
- Self-levelling underlayments shall be installed to provide a finished surface within level tolerances within requirements noted in Part A10 - Acceptable Conditions.
END OF PART A13