The critical importance of plywood in subfloor bases
By GARY SCOTT MANAGING DIRECTOR HANSON PLYWOOD
THE quality of general commercial hardwood plywood has steadily declined as the availability of legal and sustainable high-quality hardwood logs has become more of an issue. This decline in quality became a growing concern for the ﬂooring industry as more and more installation failures were being reported.
The ﬂooring industry invests very heavily and uses the latest technology to produce some highly sophisticated premium quality products, ranging from adhesives and screeds to the actual decorative ﬂoorcovering itself. As an integral component of the subﬂoor, plywood really needs to be able to perform reliably alongside some very high value products.
SP101 is a tailored speciﬁcation which is produced under very strict control and testing at the factory, but also undergoes further third-party testing to give absolute assurance of quality and performance in surface applications.
Key features that are addressed in manufacture and ensure panels are guaranteed ﬁt-for-purpose include:
- thicker outer veneers
- reliable gluing
- strict thickness/dimensional tolerances
- controlled moisture content
- high-quality core
The industry now fully recognises the importance of ﬁt-for-purpose plywood and manufacturers of ﬂoorcoverings and adhesives are always keen to test SP101 alongside their own products to ensure all materials would work in harmony.
Extensive performance testing has taken place since 2013, and SP101 is now widely recognised as being a fully compliant and reliable component in subﬂoor preparation.
BS 8203: 2017 Code of practice for installation of resilient ﬂoorcoverings
Annex A: Guidance on the selection and speciﬁcation of suitable plywood for fabricated underlays.
The CFA Guidance note was immediately recognised as a valued reference document and was widely adopted throughout the industry.
In view of this, further work was undertaken by the CFA, its manufacturing committee and BSi representatives, to introduce the guidance into British Standards. The normative Annex A has now been included in BS 8203 providing a performance speciﬁcation for plywood.
Steps for installation
The following information is advisory step-by-step guidance in the application of plywood for subfloor bases.
Step 1: Humidity and moisture checks prior to installation
The most important factor in the performance of a subfloor is moisture. Care should be taken to ensure the environment and the plywood is equilibrium before proceeding. The moisture test should be carried out using a wood moisture meter. Air humidity and room temperature readings should also be taken. If the moisture reading is within + or 2% of the timber subfloor the plywood can be installed. The installer can then decide on whether the timber subfloor is at the correct moisture content in relation to the humidity and temperature of the room. Once moisture equilibrium is established, the fitter is then able to proceed.
Step 2: Preparation
Before laying sheets, the subfloor should be thoroughly cleaned and checked for removal of debris to ensure the sheets will lay as flat as possible.
Step 3: Laying the plywood sheets
The correct thickness of plywood panel should be selected dependant on the quality of the surface to be overlaid and the overall height of the finished floor. It’s recommended, where possible, that the sheets are laid perpendicular to floorboards with the joints in the plywood staggered.
Step 4: Correct fixings and spacings
Typical fixings for plywood are ring shank nails and countersunk screws. Advice on suitability of fixing process should be taken with regard to the type of covering to be applied and any further surface preparation required. For best results fixings should be countersunk. Fixings should be spaced at a maximum 100mm centres around the perimeter of each plywood sheet, 12mm from the edge and at a maximum 150mm within the sheets.
Step 5: Filling and smoothing of joints and indentations
Once securely fixed, the plywood subfloor is ready for further preparation. Although BS8203 compliant plywood is manufactured to very strict dimensional tolerances, there’s still a need to fill joints and indentations where fixings have been applied to ensure a high-quality finished floor. Dimensional consistency ensures minimal use of filling and smoothing products. When using smoothing and filling compounds which contain water, the plywood and associated subfloor components will again need to be allowed a period to dry out and reach a moisture equilibrium before proceeding.
Step 6: Adhesive application
Once the floor has been fully prepared, a suitable adhesive is applied and the floor is now ready for the LVT tiles.
Step 7: Fitting the LVT
This is the final step and involves fitting the LVT over the plywood. This stage relies on the correct subfloor preparation, which is vital to the end-product.
Fully compliant plywood
Manufactured to ﬂooring industry standards as deﬁned by BS 8203:2017- Plywood Annex A. SP101 Flooring Plywood is a fully reliable component for use in the subfloor base construction for all floor coverings. This makes life much simpler for designers and speciﬁers to work with fully compliant and reliable plywood products. SP101 follows strict installation steps to enable the best outcome for floor fitters. The installation of SP101 relies on a structured process which ultimately benefits the fitting of the LVT and will give you the end product you desire.
Environment and sustainability
The UK timber industry has comprehensive systems in place to ensure legality and sustainability of timber products. Products must be technically sound and ﬁt-for-purpose and have to comply with all relevant environmental criteria.
A FLEGT licence is currently the only licence that ensures full, verifiable compliance with the EU Timber Regulation. SP101 Flooring Plywood was the ﬁrst ﬂooring plywood to be imported into the UK with a FLEGT licence.