Is sprayed PUR affected by moisture in the base?
Once in place, closed-cell PUR absorbs little water. But it must be sprayed onto a dry base, and it does not replace treating moisture rising from the ground.
Once in place, closed-cell PUR absorbs little water. But it must be sprayed onto a dry base, and it does not replace treating moisture rising from the ground.
This question often comes up regarding old slabs laid without waterproofing. The answer has two parts: how PUR behaves once installed, and the conditions required for spraying it.
The PUR used for floor insulation is a closed-cell foam. This structure significantly limits water absorption, which distinguishes it from open-cell foams. This is also what allows it to maintain its performance over time; see our data sheet sprayed PUR.
Installation specifications require a dry, clean, and dust-free substrate, with a slab temperature of at least 5°C. On a wet surface, the foam adheres poorly and expands unevenly.
PUR is not a waterproofing membrane. If moisture is rising from the ground, it must be treated beforehand: identify the cause, then use a membrane or vapor barrier depending on the situation. Our data sheet pouring a screed on a damp substrate details the diagnostic process.
On a slab permanently exposed to water, an XPS board may be more suitable. The choice is made on a case-by-case basis; see our floor insulation solutions.
Start from the finished floor level set by thresholds and adjoining rooms, measure down to the highest point of the slab, then subtract the floor finish and the screed: what is left is the space for insulation.
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