Insulation Under Screed Floor

Lightweight rigid polyisocyanurate pir foam insulation boards such.

Insulation under screed floor.

Quattro is the ideal insulation material for your floors. Solid floors are normally insulated above the top concrete or screed a mix of sand and cement layer using rigid insulation foam. Hi all i ve been asked to extend the plumbing into a small extension utility room and toilet basin. When it is over insulation it is normally termed as floating.

The insulation should not be stepped as this can act as an anchor point and cause cracking in bridging or on the screed under movement and cause weak spots in a void underneath. I have a new extension being built. They want the pipework concealed under the floor the builder has advised me that on top of the concrete slab there will be 75mm insulation and a 75mm screed. The insulation is then laid followed by a polythene separating layer and either a concrete screed or tongue and groove chipboard ready to receive the specified floor finish.

The polystyrene sheets seem rather soft you can easily push your finger in about 5 10mm. Where insulation is positioned above the slab the slab and dpm can be installed either way round. Ideally you ll want to install 150 mm of rigid insulation depending on the effect this will have on the floor height. Calcium sulphate flowing screed some people call it liquid screed or flow screed.

If we can now look at the floor screed thickness over insulation for different types of screed. Question is i have been recommended the polystyrene by the insulation supplier it has been delivered but i am not sure it is up to the job. I use quattro under the screed or on a suspended floor with or without under floor heating under a sprung floor wood or chipboard floor. You may want to increase the actual kpa value of the insulation to withstand the loadings.

We have 100mm concrete over which we are putting 138mm thickness polystyrene and then 75mm screed. I plan to run plastic pipe. If the screed is on top of insulation there is going to be move give or movement than being laid directly on to a structural substrate. The polythene damp proof membrane dpm generally a 1200 gauge can now be rolled out into place ensuring the perimeter abutments are adequately covered.

When we talk about a minimum thickness we would need to look at the type of floor construction the screed is going onto. There will be a damp proof membrane under the insulation and possibly a second membrane on top depending on the type of screed.