With the time-pressures inherent in many construction projects today, it is not uncommon to hear flooring contractors question whether damp proof membranes (DPMs) are really needed, and ask if it might be possible to save time and money by cutting them out of the subfloor preparation process.
The answer to this is a resounding no. While it is rarely certain that floors with more than 75 percent relative humidity (RH) will fail if a DPM is not used, there is a great risk that they will. Taking this risk leaves the flooring open to a plethora of problems that can cost flooring contractors significant time and expense to rectify – as well as reputational damage that they may never recover from.
Here is why flooring contractors cannot afford to cut out DPMs, and how you can ensure that the DPM process does not slow down your projects unduly.
Why DPMs are more necessary than ever
The less flexible floor coverings of the past, such as thermoplastic tiles, had high moisture vapour transmission rates, while the bitumen-based adhesives of yesteryear were relatively moisture-tolerant. This meant moisture was indeed less likely to damage new flooring after it had been laid.
Today, however, things have changed. The most common types of floor covering in modern buildings, such as rubber and highly flexible vinyl, have much lower moisture vapour transmission rates, and some solvent-free adhesives – for all their benefits in terms of reduced VOC emissions that protect the health of installers – do not tolerate moisture as effectively.
Not only do the materials used make projects more vulnerable to moisture today, but modern working habits do too. Whereas, in the past, buildings were put up more slowly, today the trend is for ‘fast-track’ projects. This means the floor coverings are laid very quickly, often when the subfloors still retain a large amount of residual moisture.
“Today the trend is for ‘fast-track’ projects. This means the floor coverings are laid very quickly, often when the subfloors still retain a large amount of residual moisture.”
As a result, those who cut out the DPM stage today are far more likely to get the dreaded call from the customer, demanding to know why the flooring has become warped over time and how soon they will be able to fix it.
Moisture suppression – without the delays
At Bostik, we offer a range of market-leading DPMs that suppress moisture quickly – providing reassurance that the installation is being done correctly, without the inconvenience of long hold-ups.
Our Screedmaster Rapid DPM is a one-part, water-based DPM with a fast-drying time of just one hour. This enables fast access to the site, minimising downtime so you can proceed to the smoothing compound stage safe in the knowledge that residual moisture is not going to ruin your work in the weeks or months after the installation.
“Screedmaster Rapid DPM enables fast access to the site, minimising downtime so you can proceed to the smoothing compound stage safe in the knowledge that residual moisture is not going to ruin your work.”
Alternatively, for where moisture is more of a problem, our Screedmaster One Coat Membrane is a two-part, solvent-free, epoxy surface DPM that contains the exact quantities of resin and hardener ready for mixing together. On a smooth, power-floated concrete base, a single coat of Screedmaster One Coat Membrane will provide protection for subfloors with up to 97 percent RH.
If speed is a particular priority, Screedmaster One Coat Membrane can also be supplemented with our Screedmaster One Coat Accelerator additive, which enables it to cure in as little as three hours.
While it may be tempting to cut costs and save time by not applying a DPM to a wet subfloor, the risks far outweigh the potential rewards. You may get away with it once, but sooner or later you will be found out, and the time and money spent redoing the work – not to mention repairing the damage to your relationship with the customer – will mean it was not worth it. That’s why the only solution is to use high-quality, fast-acting DPMs wherever they are needed.