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Levelling a wooden subfloor

  |  Levelling a wooden subfloor

Levelling a wooden sub floor

There are many timber sub floor surfaces and it is most likely that a timber sub floor is going to move more than a solid base, even if it has been adhered to a solid surface below. This could be as simple as the expansion and contraction of the timber caused by changes in temperature and humidity. It is probably best if we look at the different types of timber sub floor and provide the best advice that we can.



We appreciate that some timber sub floors will need levelling because of the undulation or depth variation. However, sometimes there are alternative methods that are used and we see their popularity increasing in the future. As an example, we see many contractors needing to compensate for mild surface undulation in timber sub floors and do not like to use products that add moisture to the surface build up. In this case we recommend the use of WAKOL TS102 sound suppression matting. This product is a 2mm cork – polyurethane mat that comes in a 30 m roll. It is glued to the timber subfloor before the wooden floor covering is then subsequently glued to its surface.

This can be a very quick way to build up the sub floor by approximately 3mm without introducing any moisture and secures the overall specification. The additional benefit is the decibel reduction (17db) and the secure under foot feeling. The WAKOL TS102 should always be glued with the same adhesive that will be used later for the final wooden floor covering. Therefore, it is important to keep that in mind before starting. As an example, if you were intending to install engineered plank with WAKOL MS230, THEN THE SAME PRODUCT should be used to glue down the WAKOL TS102 mat first.


Old Floor Boards (Pine on joist)

Ideally, the boards should first be replaced with more structurally sound products of the same thickness such as floor grade specification ply or chipboard. If this is not possible, then you should look at installing a floor grade product on top of the boards. This product should be screwed and glued to the boards below to make it as secure as possible. Ideally the boards below should be sanded back to remove any contaminates, vacuumed and then primed if necessary before applying the adhesive. We would recommend WAKOL PU280 (1 layer) or WAKOL D3055 as the primer coat. We would recommend WAKOL MS260 as the adhesive to be used under the ply or chipboard.

Once you have a timber surface that is ready to receive levelling compound we would recommend WAKOL D3045 as the primer to be applied before installing levelling compound. This will secure the adhesion of the levelling compound and make the job easier. As the base below is likely to move, you will need a fiber re-enforced levelling compound to allow for the movement. We would recommend adding WAKOL AR114 fibers to WAKOL Z520 Thin Screed to result in a flexible product that is strong and will dry in the quickest possible time frame. One bag (250 g) of AR114 fibers is added to each bag (25 kg) of Z520 to achieve the correct ratio. The levelling compound mix can be applied to the dry WAKOL D3045 Gritted Primer.

Always MAKE SURE that the wooden sub floor under the self-levelling compound can vent and is subject to airflow. Joisted floors usually receive air circulation underneath through air- bricks in the external walls.



Please make sure that the ply is secure and free from contaminates before starting the process. Once this is done, we recommend the process above, starting with The WAKOL D3045 Gritted Primer.



Some chipboards can contain adhesive inhibitors or surface contaminates. Usually a layer (I coat) of Wakol PU280 primer will seal out any issues but we cannot guarantee this and you may have to conduct your own tests to be absolutely sure. Once you are happy to proceed, we recommend the process above, starting with The Wakol D3045 Gritted Primer.



This is by no means and exhaustive list of timber surfaces but these are the most common we come across in the UK. If you need help and advice on something that is not covered, please contact us and we will try our best to answer your questions.