Bonding to Wood based Sub-floors
Jun 10, 2009 DIY tips, bonding, how to, wood flooring
Wood-based sub-floors are materials such as floorboards, flooring grade chipboard, plywood, or OSB.
Existing hardwood floor coverings should be removed before installation of new hardwood floors.
Environmental Conditions
- All wet trades must be thoroughly dry before flooring materials are delivered to site.
- Maintain suitable ambient humidity 40 to 60% RH. (Monitor with a hygrometer)
- If necessary employ a domestic humidifier / dehumidifier to maintain suitable conditions.
Moisture condition of Wood based sub-floors
- Ensure that wood based sub-floor materials are not > 2% higher in moisture than the new wood flooring materials being installed.
Suspended wood based sub-floors at ground level
- Voids beneath suspended wood based sub-floor on ground level must be well ventilated to avoid high humidity in the sub-floor void.
- First lay a building paper moisture barrier (e.g. Sisalkraft Moistop), over the existing sub-floor overlapping joins by 100mm and taping with a waterproof tape.
- Then install a WBP ply layer, securely fixing through the building paper to the sub-floor.
Soundness of sub-floors
- Ensure all sub-floors are sound, of load-bearing strength and free from contaminants that may impede adhesion. (Note: If sub-floors are contaminated or affected by adhesive residues seek further advice).
Evenness of sub-floor
- In order to achieve satisfactory contact between wood flooring and adhesive, sub-floors must be even to within 2mm over any 2 lineal meter area.
- Floor boarded sub-floors typically require a WBP plywood covering to be securely fastened to the floorboards before adhesive fixing new wood flooring.
- It is recommended that flooring grade chipboard, OSB & old floorboards are first covered with WBP plywood which is securely fastened to the sub-floor before adhesive fixing new wood flooring to protect against surface contaminants that may impede adhesion.
Adhesive bonding of wood flooring to wood based sub-floor
- Use a purpose made, permanently flexible adhesive such as 1-part polyurethane, when adhesive fixing.
- Always use the trowel type recommended by the adhesive manufacturer for the type of flooring being installed (e.g. solid plank, strip, woodblock, engineered plank etc).
- Replace worn trowels.
- Ensure full contact between the underside of the flooring element and adhesive.
- Any adhesive that that comes into contact with the face of the boards must be cleaned off whilst wet, as residues are not removable when cured.
Provision for expansion
- As a guide only allow a minimum 15mm expansion wherever the floor meets obstacles including perimeters walls, structural supports, hearths etc.
- Create additional expansion breaks in doorways using suitable profiles such as T-section thresholds or transition strips.
- Create additional expansion breaks in large floors.
- Where possible install flooring so that planks, strips run parallel to the longest walls, so the direction of greatest potential expansion (i.e. across the grain) does not coincide with the direction of greatest dimension, esp. in large floors.
- The precise combined provision for expansion must be judged by the installer taking into account environmental humidity, moisture content of wood at time of installation, timber specie and size of the floor.
You can contact us for more information at www.floorcraft.uk.com or call us on 01252 372227/07970 491384 ask for Gavin Winder (we are based in Farnborough, Hampshire, UK and stock all of the above mentioned wood flooring adhesives, latex, underlays etc).
Tags: adhesives, Bona, bonding, DIY guide, Duralay, latex, Sika, underlays, wood flooring
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