Movement joints - the right one for the right job

The sixth item in our series of ensuring the long-term integrity of tiled floor installations by using protective movement joints

(part two).

This is the sixth item in our series of ensuring the long-term integrity of tiled floor installations by using protective movement joints, and the second part of an item looking specifically at the wide variety of joints on the market.

As Ian Knifton, Technical Manager at Schluter - Systems, explains, the reason there are so many different systems available, is to ensure there is a joint which is suitable for every conceivable individual application.

Q: We know movement joints must be installed in certain areas and positions to prevent tiles or grout from cracking, and in some cases, the tiles tenting and becoming debonded from the substrate.

What features make a particular joint absolutely right for one application, but wrong for another?.

A: Some joints which are designed and engineered specifically for residential, offices, or light commercial use just wouldn't be able to cope with the mechanical stresses of heavy duty applications such as airport terminals and railway stations, for instance.

For those sort of uses, you would need a much stronger profile which is also capable of withstanding greater degrees of shear stresses.

There is a wide variety of movement joints covering every type of different applications.

For example, an aluminium profile with a central movement zone is suitable for commercial and heavy duty applications.

When installed, the visible profile is 6mm wide, which corresponds to the width of the average grout joint.

Many joints come in a variety of metal anchoring legs - either aluminium, brass or stainless steel -- connected to a replaceable rubber movement zone.

It's this zone which actually absorbs the movement, and can be replaced in the future if it becomes worn or damaged, without having to remove either the tiles or the profile.

Q: What's the difference between aluminium, brass and stainless steel?.

A: Each material is suited to different types of applications - whether a heavy duty or lighter duty profile is required all depends on how strong the joint needs to be.

And, of course, that depends on what is being asked of it...namely, it has to respond to the expected mechanical or chemical stresses that the tiled surface will be exposed to.

Aluminium is suitable for areas like shopping malls, supermarkets and offices.

Brass can be used in the same areas, but is much more resistant to high mechanical loads such as vehicular traffic, or those found in production facilities and railway stations.

While stainless steel can also be used in all applications it is particularly suited in areas which may be exposed to chemicals - places like laboratories, chemical production facilities and leisure centres.

Q: What about areas where the stresses aren't expected to be as forceful?.

A: One-part PVC profiles are ideal for residential or light commercial use in offices, retail stores, shopping areas which aren't exposed to metal wheeled traffic, and car showrooms.

These PVC profiles can be safely used for tiled surfaces both indoors and out.

Q: What about coping with structural expansion?.

A: Many structural expansion joint profiles are made of aluminium or brass with lateral joint connections to a sliding telescopic centre section.

This allows the absorption of three-dimensional movement.

Other types of structural expansion joint profiles come with edge protection, consisting of side anchoring legs of brass, aluminium or stainless steel, connected to 20 or 30 mm synthetic rubber movement zone.

Next month - how movement joints form part of a complete systems solution.

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