Product category:
Floors
News Release from: Schluter-Systems | Subject: Cracking or debonding from substrate
Edited by the Buildingtalk Editorial
Team on 04 February 2008
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
Compensate - or Compensate If a stone floor cracks or debonds from the substrate, flooring contractors could well have to compensate the end-user
This article was originally published on Buildingtalk on 11 Apr 2008 at 8.00am (UK)
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But if the stone fixer compensates for something else when the initial installation is carried out, problems of that nature can be prevented.
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 in line with industry recommendations.
Question: I thought uncoupling membranes protected the stone surface.
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How to ensure stone flooring lasts longer
Ian Knifton, Technical Manager at Schluter - Systems, explains why installers who are not trained in laying stone are going to end up with failures.
Answer: They do.
Last time we looked at how they prevent shear stresses being transferred from the substrate to the surface.
But essential protection of stone - just as with ceramic tiling - also requires movement joints as part of a full systems solution.
Movement joints are needed to compensate for surface movement, which could, otherwise, damage the stone tiles, as well.
Such movement joints create independent tile fields, absorbing much of the surface movement, and should be incorporated at the design stage.
Question: Do all types of stone need movement joints, and is one type of profile suitable for every application? Answer: Stone installations do require protection from movement, therefore movement joints should be included at set distances in accordance with industry guidelines.
Because there are specific joints for specific applications, most problems are generally caused by using ones which aren't suitable for what is being asked of them.
The most suitable ones for stone are maintenance-free profiles with stainless steel, brass or aluminium anchoring legs connected to a soft rubber movement zone.
The amount of movement that can be absorbed - and therefore the degree of protection given by the joint - depends on the size of the profile and the compressible material used.
Therefore, if the wrong one is fitted it may not be capable of taking the degree of movement the stone is being subjected to.
The side sections of such profiles also provide effective protection to the edges of the stone tiles abutting them.
Question: My end-user customer doesn't want movement joints, because of the aesthetics of the installation.
Answer: You should be alerting the customer as to what will happen without them.
An ounce of prevention is worth a pound of cure.
The final responsibility for the correct movement joint lies with the specifier or architect, but trained stone fitters will recommend the right movement joint that's appropriate for the individual application.
And, of course, the Stone Federation of Great Britain's code of practice advises that intermediate movement joints should be installed, along with perimeter joints.
While many specifiers acknowledge that surface movement joints are required to prevent problems, we're often asked if they have to be exactly over the top of joints in the substrate.
They do.
On many occasions we've seen designs where contractors have offset the movement joint in the surface only by millimetres from the one in the screed, and the stone covering has cracked.
Ian Knifton is a Member of the Contract Flooring Association's Manufacturers Committee, and the Stone Federation of Great Britain's Technical Committee. Request a free brochure from Schluter-Systems ...
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