Product category:
Bricks, Blocks and Lintels
News Release from: Schluter-Systems | Subject: Natural limestone tiles
Edited by the Buildingtalk Editorial
Team on 13 May 2005
Essential protection for stone floors
Schluter-Systems troubleshoot at an expensive barn conversion where natural limestone tiles had started to crack within two months of being fixed above an underfloor heating installation.
World market-leader in tiling solutions, Schluter-Systems ., was recently called in to troubleshoot at an expensive barn conversion where natural limestone tiles had started to crack within two months of being fixed above an underfloor heating installation And a range of independent reports appears to clear each of the builder's individual sub-contractors of blame
This article was originally published on Buildingtalk on 11 Apr 2008 at 8.00am (UK)
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Question.
What had happened at the barn conversion?.
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Stone floor cracking or debonding from substrate
Ian Knifton, Technical Manager at Schluter - Systems, says very often stone floors crack or debond because installers have not fitted an uncoupling membrane, or movement joints correctly
Answer.
The floor assembly consisted of an insulation layer, on top of which was a floating screed containing the pipes of a water-based underfloor heating system.
Then 400mm x 400mm limestone tiles with a thickness of 20mm, were installed directly onto the screed.
A combination of movement, and stress cracks being transferred from the substrate into the surface covering caused the tiles to crack and debond, between one and two months after the installation had been finished.
A number of reports were carried out showing: * The adhesive was entirely suitable for the application * The stone had been supplied in good condition * The screed was of the correct strength and specification for what was required of it * The underfloor heating system was functioning properly, and was suitable for the application.
Question.
What did Schluter find? Answer.
The screed was cracked - not a major problem as long as appropriate tile protection measures are taken, but in this case they weren't.
A combination of movement joints with an uncoupling membrane will not only protect a second set of stone tiles laid in the remedial work, but if they'd been used from the outset would have prevented the first ones from cracking.
Unfortunately, the remedial work will cost thousands of pounds.
Question.
How would that combination have prevented this costly damage? Answer.
Movement joints create independent tile fields, absorbing much of the surface movement.
Without them the shear stress builds up between the tile and the screed, causing debonding, bulging and cracking.
Therefore, stress-relieving joints are an essential part of any tiling installation, and should be incorporated at the design stage.
And an uncoupling membrane installed over the substrate, with the tiles anchored to the top of it, will neutralise the cracks in the screed, preventing any stresses being transferred from the screed to the limestone covering.
Stone is a very popular flooring surface nowadays, but suffers the same problems of cracking as ceramic tiling, unless protective measures are taken - and not just on underfloor heating, but with any type of substrate.
In fact, the Stone Federation frequently suggests using uncoupling membranes in its specifications and recommendations.
Question.
So no-one can really guarantee the entire underfloor heating installation? Answer.
Not if a different sub-contractor provides each individual component.
However, there is a new underfloor heating system on the market that includes a modular screed and the heating and control technology.
BEKOTEC-THERM is an entire energy-efficient and quick-reacting radiant heated floor system in one complete package, while also protecting the tiles from damage.
As well as the builder getting a fully guaranteed installation, the work is also much quicker and easier to carry out than conventional underfloor heating systems.
Being modular, the screed is installed very quickly, and incorporates the heating pipes, while taking all shear stress out of the substrate, so no movement joints are needed in the screed.
As soon as the screed can bear weight, an uncoupling membrane is installed, with the tiles anchored on top. Request a free brochure from Schluter-Systems ...
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