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Commercial Flooring News

The Key Element Is The Floor Preparation

IN the November issue of CFJ, I covered the most appropriate way to deal with the difficult and frequent substrate problem, laitance. This month, I will give advice and guidance on correctly preparing a wooden substrate, focusing on wood blocks, wooden floorboards and mosaic panels.

Wooden floors vary from traditional wooden floorboards, plywood, chipboard and other wood composites.
All wooden substrates must be structurally sound, level, smooth, dry and clean before a new floorcovering can be installed.

Wooden subfloors, by nature, are particularly susceptible to subfloor moisture. Damp can quickly have a devastating effect on wood and is, by far, one of the biggest causes of installation failures.
For this reason, it is crucial that wooden subfloors are ventilated from beneath and free from barriers to adhesion such as paint and varnish.

Wood blocks: Laid on ground floors, wood blocks must have an effective damp proof membrane (DPM) incorporated into the subfloor as the plywood overlay and wood blocks must remain dry during the life of

the installation.

The wood blocks must also be well bonded and remain fully secured to the subfloor while securing of

the plywood.

If these conditions cannot be met, the wood blocks must be removed and the subfloor replaced with either a flooring grade asphalt or a modified sand/cement screed which incorporates an effective damp

proof membrane.

Wood blocks are not suitable for direct application of sheet or tile flooring because of the continuous differential movement of the blocks and the risk of the wood block design transferring through the floorcovering sur face.
Providing the wood blocksare smooth, sound,level and securely bonded, they should be overlaid with flooring grade plywood before installing the final floorcovering.

I Further wood substrates: To prepare wooden floorboards, including butt jointed and tongue and groove boards, for installation of a new floorcovering, the substrate must be overlaid with a minimum of 6mm plywood and screw fixed at the centres to provide a rigid substrate.

Following this, they must be primed and a minimum of 3mm of flexible smoothing underlayment, such as Stopgap 700 Superflex, applied.

This product uses the latest micro-fibre and cement binder technology, along with a high polymer to cement ratio to enable the underlayment to provide a high degree of flexibility to accommodate movement.

Worn or uneven floorboards should either be replaced or levelled by sanding, planing or patch filling with a smoothing underlayment such as Stopgap Green Bag or Blue Bag and 114 Liquid, before finally being covered with flooring grade plywood. In all instances damaged tongue and groove floorboards must be replaced.

Wood mosaic panels also require over-pinning with flooring grade plywood in all cases. If panels laid over a flexible timber floor need patch filling, a smoothing underlayment should be used. In all other respects, wood mosaic panels should be treated in a similar way to wooden blocks.

Once the above steps have been made to prepare different types of wooden substrates, you can install

new floorcoverings.

In the March issue I will advise on correct surface preparation for composition floors.

Neil Sanders is technical manager at F Ball and Co.


This article has been reproduced from the Contract Flooring Journal website. You can find them at