Avoid Stress By Avoiding Stress

Ian Knifton, Technical Manager of Schluter-Systems Ltd., looks at how to prevent damage caused by tile movement.

Tiling fitters know how stressful it can be when things go wrong.

The way to avoid such stress over tiling installations is to ensure the tiles themselves are free from strains and stresses.

Ceramic and stone tiles can be subjected to a variety of strains and stresses leading to tiles bulging, cracking or becoming detached from the substrate.

cQ How can I prevent the sort of damage to tiles, as described above? A Use an appropriate movement joint.

Basically, a movement joint is a stress-relieving profile, compensating for the movement of tiles which extends down through the tiles, the bed and screed layer below.

Without them the sheer 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.

Q How do they work? A Movement joints create a tile field which moves independently from those around it, and should be included at set distances in floor and wall tiles, in accordance with recommendations from the British Standards Institution (BSI).

BS 5385 says the maximum tile field should be no more than ten metres in each direction for floors - but in practice, depending on the individual application, it tends to be between five and eight metres for floors, and every three to four-point-five metres on walls.

Q So I simply install a movement joint in line with those recommendations, and that'll prevent tiles from cracking, bulging and debonding? A If you've installed the appropriate joint, yes.

And by "appropriate" we mean one that can do what is being asked of it.

There are different widths of pre-formed movement joints, and the correct width and material - brass, aluminium, stainless steel or PVC - must be specified to take thermal movement into account.

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.

Pre-formed surface joints will usually accommodate movement up to 20% of the movement zone width.

A 10mm joint will extend and compress by approximately 2mm.

Schluter's largest stress-relieving movement joint, the DILEX-KS, which is 15mm wide with a movement zone of 11mm, will accommodate up to 2.5mm of tile movement.

Because there are specific movement joints for specific types of application, most tiling failures are caused by using joints that aren't suitable for what is being demanded of them.

There are many situations, each with their own technically engineered solution in the form of the correct joint.

Q If the problem is caused by using the wrong joint, how do I know which is the right joint? A Generally aluminium is ideal for commercial use; with brass and stainless steel needed for heavy duty commercial and industrial projects such as warehouses, production facilities and airports, and where the tiled surface is cleaned by a scrubbing machine, or where there are rolling loads such as pallet trucks and metal-rimmed trolleys.

Stainless steel is also ideal in places like laboratories and food processing plants where chemicals are used.

PVC can be used for residential and medium duty commercial applications including offices and swimming pools, and areas subject to light mechanical loading such as showrooms and car dealerships.

Many calls to Schluter's technical support service refer to application problems, where no joint or the wrong joint has been used.

Other callers seek advice before the work is carried out - and we would say that it's in everyone's best interests to ensure that ceramic and stone tiles are installed with the correct movement joints.

Prevention is always better than the cure - which is why Schluter is always happy to advise on the requirements of individual projects, as well as delivering a variety of training courses on the use of movement joints.

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