Product category:
Floors
News Release from: Schluter-Systems | Subject: Dealing With Problematic Substrates
Edited by the Buildingtalk Editorial
Team on 20 July 2004
Dealing With Problematic Substrates
How flooring contractors can solve problems associated with a number of different types of substrate they might encounter during building and tiling work.
Not dealing correctly with problematic substrates is one of the major causes behind the failure of many tiling installations, where stresses from the substrate find their way into the finished covering of stone or ceramic tiles Ian Knifton, Technical Manager at Schluter-Systems, world market-leader in tiling solutions, looks at how flooring contractors can solve problems associated with a number of different types of substrate they might encounter during building and tiling work
This article was originally published on Buildingtalk on 11 Apr 2008 at 8.00am (UK)
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Q.
I'm undertaking the flooring work at a major renovation and extension of an old house and need to lay ceramic tiles.
But the screed has several cracks in it, and I'm worried that in time, the tiles will debond and crack.
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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
A.
You're right to be worried.
Because of different thermal expansion and contraction the screed will move at a different rate from the tile, and without the right solution will lead to disaster.
Even if the tile adhesive has a flexible polymer in it, thermal movement in the screed -- particularly at the joint of the cracks -- will be too great for the adhesive to hold the tiles down.
You need an uncoupling system -- also referred to as a separation system -- which allows the tiles to move independently from the substrate.
Q.
How does it work? A.
The Schluter-DITRA has been developed specifically for uncoupling the building structure from the tiles.
It's a pressure-stable polyethylene membrane with a grid structure of square cavities and an anchoring fleece laminated to its underside.
The fleece backing becomes anchored in the tile adhesive on the substrate.
On top of the membrane the adhesive is anchored into the square, cut-back cavities, and the tiles are installed on top.
The membrane neutralises the cracks in the screed, and can absorb up to around 2-3 mm of horizontal movement.
Q.
I also need to tile in the kitchen, where the existing floor surface is vinyl tiles, fastened down with vinyl adhesive.
What's the best way of ensuring a successful and long-lasting installation? A.
If the existing vinyl surface were meticulously prepared, and there was little or no compression in the tiles, it may be feasible to tile straight over the vinyl covering.
But to guarantee the installation's long-lasting success it would be better to remove the vinyl.
However, the timber or concrete substrate underneath is likely to be contaminated by the residue of the vinyl adhesive.
Using a polyethylene membrane means there's no additional preparatory or cleaning work required.
Simply comb a standard tile adhesive on to the contaminated substrate, make sure it's level, anchor the matting down, and tile it! It's ideal for domestic or commercial refurbishment projects.
And as an added bonus, because you're not bonding the tile directly to the substrate, but to the membrane instead, you don't need the same type of adhesion.
Q.
I also need to tile the floor of a new conservatory at the house.
Guidelines are that you shouldn't tile on a new, green, screed, for at least 28 days, but the owners really want me to do it before that.
If I do, is the installation likely to fail in the future? A.
The guideline of 28 days is to allow for movement and shrinkage to take place in the green screed.
But using a membrane such as Schluter-DITRA actually means you can get on to the screed much earlier.
Depending on the weather and time of year it could be as little as a couple of days.
Basically, you're looking at being able to apply the membrane as soon as the screed can support weight.
If you can walk on the screed and your shoe doesn't leave an impression in it, you can install the membrane and tile immediately afterwards.
The membrane actually slows down the drying process of the screed, minimising shrinkage and eliminating most of the cracking which could occur.
Also -- especially over floating type screeds where you've got insulation -- it'll minimise the curling effect of the screed, so all in all, using the membrane on a green screed not only protects the tiles, but gives you a better screed as well.
And if you can get off site three or weeks earlier, because you don't need to wait 28 days before tiling, you can get paid earlier too. Request a free brochure from Schluter-Systems ...
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