I was asked in my role as an Karndean expert floor witness to look at a Karndean floor that was in the words of the consumer bubbling off the floor in her new Kitchen extension.

The consumer was at odds with the retailer who had supplied and fitted the failing floor who

She claimed was adamant that he had done everything properly. I accepted the challenge and

Agreed to do an independent Karndean floor inspection and provide an unbiased report.

On arrival and after niceties I was shown into the offending room where I was introduced to Graham (not his real name) the retailer.

The floor was indeed bubbling and looked a right mess.

It was obvious that a closer expert floor investigation was needed so I requested that be allowed to take up a tile.

Before I took the tile up the retailer ran through the floor preparation with me  he had latexed the floor then applied a Liquid one coat DPM , 2nd coat latex and finally installed the floor. \he had been using the same fail safe system for years !!

On the face of it as an independent flooring expert I would usually agree with his methods providing certain checks were made ,  he had omitted a moisture check ! but never the less as the floor was warm and had UFH which had been running for some weeks before work started, it is likely that the floor was dry enough to apply a liquid Damp proof membrane.

It was agreed that a tile was to be lifted , as the this one done you could clear see the Latex , DPM, and 2nd Coat Latex it came off the floor as clean as a whistle, revealing the subfloor.

A screed finish, smooth and waxy to touch whitish in colour:  ANHYDRITE FLOOR SCREED !!  Lucky for me as an independent flooring expert I identified the problem immediately.

Anhydrite floor screeds are increasingly being used instead of sharp sand and cement as it is very much quicker and cheaper for the builder to install. This is fine providing it is recognised and the appropriate floor preparation is taken:

The commonly weak layer of laitance on the surface is ground off, find the most at risk (wet) parts of the floor with a radio frequency moisture meter and do multiple moisture tests with a hygrometer.

Apply a compatable smooth compound, Damp proof membrane  second coat Smooth compound.

I asked Graham which products he had used  and agreed with him that they were fine products but was genuinely very sorry to inform him that they were not compatable with what is basically a gypsum based floor screed.

As a Karndean expert flooring witness I increasingly see this type of problem the retailer assumes that all screeds behave the same way “ they don’t”  The first questions that should be asked at the onset are when was the screed laid , how thick and what type ?? expert advice should then  be sought.

Graham did just this

The Karndean was lifted , after seeking advice from one of the many very good floor preparation material manufacturers  carried out the replacement

To the delight of the consumer


Cary Ford  Independent flooring expert