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Advice for adhering a sub floor

  |  Advice for adhering a sub floor

HOW TO adhere to a Calcium Sulphate (Anhydrite) subfloor

In this case it’s very important to take into account the condition and the presence of Under Floor Heating (UHF).


With direct adhesion, it is critically important to assess the condition of the subfloor before measuring moisture or other process steps. The contractor needs to look at the structural suitability of the sub floor, the surface hardness and obvious contamination. As an example, any hollow spots would suggest a structural issue. Excessive crumbling on the surface would suggest a hardness issue. Surface staining, plaster residue or discoloration would suggest a contaminate issue. Most problems can be dealt with, but are site specific. Please call us for advice if you have questions at this stage.

The best advice for all calcium sulphate based floors is to remove the surface latents (according to manufacturer’s recommendations) and then take a moisture reading. Industry practice would suggest this is best done with a sealed Hygrometer over a period of at least 48 hours. In this case we would advise that British Standard (65%RH or less) be achieved before caring on with any work.

If there are any large or wide cracks, if the floor surface seems soft or if there are visible contaminates, please call us for further advice.

After sub floor has been assessed as free from cracks and structurally sound and not to be contaminated, it can be primed with Wakol D3055 before the new floor is installed with the relevant Wakol adhesive. If there are hair -line cracks you should apply a layer of Wakol PU280 or Wakol MS330 instead and continue with the adhesive when the primer is dry. If Wakol PU280 Wakol MS330 primer- DPM has been used, you must adhere to it with the relevant Wakol adhesive within 72 hours. If this is not possible (on a very large area), only prime the area that can be adhered to in that time- frame before using the Wakol adhesive. In general terms, we would recommend Wakol MS228 or Wakol MS230 for engineered wooden floors and Wakol MS260 for solid wooden floors up to 180mm in width. However, we would ask contractors to contact us if they have any questions, as each job can be site specific.


Help and advice?

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