Bonded wood floor (full stick down)

Wooden flooring may be bonded (glued) directly to the sub floor, whether it's an old or new timber floor or a concrete screed.

With concrete floors the 'old school' approach is to first build a timber sub frame for the wood flooring to sit on, with secret nailing the preferred choice.

As with all wood flooring installations, first check the moisture level of the sub floor to ensure it has less than 5% moisture content. As a general rule of thumb a new concrete screed takes about 90 days to dry out to this sort of level and this timescale should be allowed for in the construction project plan.

Alternatively, first use a liquid moisture regulator such as Sika MB primer to act as a moisture barrier, which can bring the 90-day timescale down.

However, with modern elastic adhesives such as Sikabond, wooden flooring can be installed in a time saving manner by directly bonding the wood flooring to the concrete sub floor. This elastic bonding ensures an optimal durable bond of the timber flooring direct to the sub floor, while allowing for subtle movement of the floor as a result of climatic changes.

With a moisture-curing adhesive, the top layer will start to 'skin over' within an hour or so once exposed to the air, and this skin would then need to be removed to get to the good glue underneath. Therefore it is advisable to prepare the sub floor and cut all the wood flooring first and have it laid out and ready to go.

Pour sufficient adhesive onto the sub floor, replace the lid onto the tin and then spread the adhesive with the notched trowel at the rate of 0.8KG/m2, which should equate to a level of about 3mm. Place the wood flooring without delay onto the adhesive bed. Complete subsequent rows in the same way using a tapping block where necessary, and clamps and straps to pull the wood flooring tight into the T&G joint. There is no need for PVA wood glue on the T&G joints.

Different approaches should be used where wood flooring is installed in conjunction with under floor heating systems embedded in a concrete screed.

Our recommendation is to use Sikabond T54 adhesive with full surface bonding between the concrete and the wood flooring. This will leave no gaps where air would have to be heated first before the heat can be conducted through to the top surface. It also reduces the risk of any trapped moisture forming and ensures the heat is transferred evenly to the surface without any hot spots.

While these methods are designed for use on concrete floors, they are equally suited to bonding wood flooring onto existing timber floors. Ideally this would be plywood but it can be a particle board such as chipboard - but be aware that while the adhesive will bond to the chipboard, there is always a risk that the chipboard particles of the sub floor may break apart.

With existing floorboards, secure any loose boards first with screws rather than nails to avoid floor squeak, and ensure that old varnishes etc are removed by sanding back. Alternatively, ply the floor out first with thin 3mm or 5mm plywood so that you have a sound level surface.

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> Floated woodfloor

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