When To Use a Damp Proof Membrane

If you plan to fit a new solid wood or engineered wood floor, it’s essential, before you lay the floor to find out if you need to lay a damp proof membrane (DPM).  Dampness and moisture can play havoc with wooden flooring and there’s little point in investing the time and money required to install a new floor over what may already, or what could potentially end up a damp subfloor.

So what exactly is a damp proof membrane (DPM) used for?  Effectively, a damp proof membrane (DPM) is used to create a barrier between a concrete (or screed) subfloor and a wood floor.  This barrier is intended to stop moisture passing from one to the other.  Damp proof membranes (DPMs) can be used to help resolve damp issues which already exist or to avoid damp or moisture problems in the future.

How do you decide if you might need to include a damp proof membrane (DPM) in your new wood flooring project?  Before you lay a wood floor on a concrete or screed subfloor, it’s really important to measure the moisture content of the sub floor.  Although there are a few different DIY tests you can use to ascertain the moisture content of your subfloor (eg.  The Calcium Chloride Test and The Plastic Film Test), the most reliable results are likely to be achieved using an approved, hand-held moisture meter.  That said, if you do decide to measure the moisture yourself, do make sure that the meter you’re using has been tested and that you’re taking sufficient and accurate readings, otherwise your results may be completely meaningless.

If you are having your floor professionally installed, it is more than likely that your wood flooring fitter will measure the moisture content of your subfloor for you. However, even when it comes to professional installers, don’t just assume that the will test the moisture content of your subfloor, it’s important to make sure they will.  In fact, if your fitter doesn’t mention measuring moisture content as part of the installation process, it might be that alarm bells should start ringing in your head!

Although acceptable moisture content guidelines vary, generally speaking, if the moisture content of your subfloor is above the manufacturers guidelines for your chosen floor, you’re more than likely going to be obliged to lay a damp proof membrane (DPM).  Only by doing so are you sure to prevent moisture passage and damp problems.  In some instances, even if the moisture content is lower than the recommended level, you may still want to consider investing in a damp proof membrane (DPM) to avoid the risk of future damp problems.