Navigation Menu+
Commercial Flooring News

DPMs – Always Err On The Side Of Caution

John Alcock on problems in older buildings

DURING the past few months we have been getting more and more calls relating to problems arising where contractors have been fitting floors in older buildings, highlighting some important issues to be aware of.
One recent case involved a house built around the 1920s. A new extension had been added with laminate flooring laid throughout both new and old parts of the ground floor. However, problems had occurred just in the old section, apparently due to moisture.
When the laminate was removed, a quarry tile floor was found underneath. This appeared to have been installed when the house was originally built. It did not have a damp proof membrane underneath.
The lack of a DPM had apparently caused no problem with the hardy quarry tiles. It had therefore been decided that one simply wasn’t needed.
However, this decision had caused problems with the new laminate. Because the tiles were clean, sound and firmly bonded, a two coat application of rapid drying damp proof membrane directly over them solved the problem, but this extra work could have been avoided if a DPM had been put down to start with. It would have avoided the disruption for the building occupants of taking the laminate up and putting down the DPM.
I also recently visited an old hospital building that was undergoing a major refit and extension. Again, the existing floorcoverings were old enough to tell us that there wasn’t a base damp proof membrane in place.
The feedback from the guys on site was that as this didn’t appear to be causing any problems, they were unsure whether they needed to spend time on laying a DPM. However, a visit to the site revealed that it was in a low lying area, which suggested to me that there was a higher risk of moisture problems occurring. So, we advised the contractor to put down a double coat damp proof membrane to minimise the risk of any problems later down the line.
Refurbishing older properties often throws up an unexpected problem, and my advice is always to be better safe than sorry in any aspect of the flooring. If in any doubt about the existence of a base damp proof membrane it’s best to play it safe and apply a double coat DPM.
John Alcock is technical specifications manager at Bostik
T: 01785 272727

This article has been reproduced from the Contract Flooring Journal website. You can find them at