Levelling 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)
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 65%. 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 (2 coats) for this purpose. Once that layer is dry, we would then recommend the use of WAKOL D3045 gritted primer to promote adhesion of the levelling compound. Once the primer is dry, we would recommend the use of WAKOL Z520 Thin Screed. This system is a very quick way to create your perfect sub floor and is easy to apply.
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 data sheet WAKOL PU280 and carry on as detailed above. If you are unsure about anything, Take a moisture reading and follow the steps detailed previously that includes the Use of WAKOL MS330. 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 D3035 Primer, wait for it to dry and then use the WAKOL Z520 Thin Screed to finish your sub floor preparation.
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% (PU280 and MS330 data sheets). You can use either WAKOL PU280 or WAKOL MS330 for this purpose. If either WAKOL Primer-DPM has been used, you must apply WAKOL D3045 in the next layer before the WAKOL Z520 Thin Screed. 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 D3035 Primer, wait for it to dry and then use the WAKOL Z520 Thin Screed to finish your sub floor preparation.
Help and advice?
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