We wish to lay a suitable laminate floor over a fibre board underlay in our kitchen. We have removed all of the old flooring to reveal bare chipboard flooring. As the house was built circa 1840, there appears to be no bespoke DPC. The chipboard floor appears to have polythene exposed around the edges. Would we need to install a polythene membrane underneath the underlay or would this course the chipboard to sweat and ultimately decay. Some of the information found tends to contradict each other, i.e. to use a membrane over a concrete floor, but not a wooden one, then reading elsewhere, fit a membrane if there may be an issue with damp becoming a problem.
The chipboard is fine. It looks like a polythene membrane underneath and maybe some insulation. Not sure what is beneath the rest. Sorry we cannot be more precise without starting to remove flooring & create more work.
Although acceptable wetness content standards differ, generally speaking, if the dampness content of your subfloor is above the supplier's guidelines for your chosen floor, you're more than likely going to be required to lay a damp proof membrane (DPM).
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