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Advice for adhering to a sand and cement sub floor

  |  Advice for adhering to a sand and cement sub floor

HOW TO adhere to a sand and cement sub floor

We really need to look at this in regard to the age of the sub floor, the condition and the presence of Under Floor Heating (UHF). We would also need to consider the exact floor covering that will be installed and the requirements that entails.

General Remarks

With direct adhesion, it is critically important to assess the condition of the sub floor 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.

If you have an existing sub floor in an older property, you will have to check if it has a mechanical DPC installed. You would then need to take a moisture reading. If the RH reading is above 75% and less than 95%, then it must be treated with a moisture suppressant (DPM). We would recommend the use of Wakol MS330 or Wakol PU280 for this purpose. If either Wakol 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. Once that layer is dry, we would then recommend the use of the relevant Wakol adhesive for the specific wooden floor to be installed. 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.

If you have a new build situation then you only need to consider if there is Underfloor Heating (UHF) or not

If there is NO UHF and it has a mechanical DPC (New builds should have this automatically) and the base has been down for longer than 30 days then you don’t need to take a moisture reading. You can apply Wakol PU280 in 2 layers, as directed in the technical data sheet and carry on as detailed above. If you are unsure about anything, Take a moisture reading and follow the steps detailed previously. If the moisture reading is in accordance with British Standards (65%RH or less) then you do not require moisture suppressant. In this instance you can apply Wakol D3055 primer, wait for it to dry and then use the relevant Wakol adhesive to install your new wooden floor.

If the new build has UFH then the advice above is still correct, but you must take a moisture reading first. It is possible to suppress a small amount of moisture in sand and cement sub floors with UFH but the RH reading should not exceed 85% (See also the technical data sheet of the Wakol PU280 and the one of the Wakol MS330). You can use either Wakol PU280 or Wakol MS330 for this purpose. Additionally,if the moisture reading is in accordance with British Standards (65%RH or less) then you do not require moisture suppressant. In this instance you can apply Wakol D3055 primer, wait for it to dry and then use the relevant Wakol adhesive to install your wooden floor.

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

 

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