Tremco illbruck advises on construction gaps

Tremco illbruck's business development manager Steve Wild, considers and discusses joints and gaps in the construction of buildings.

Around one in five housing units is built with a timber frame construction and the sector has been growing in recent years.

One issue arising from this is differential settlement.

When a structure is erected, walls are put in place and windows fitted, and then left for some time before the external envelope is erected, the timber frame will be settling along with other associated movement.

As a result, the window cill is liable to collide with the brickwork below, causing problems.

Designers of timber frame buildings should be aware of what a gap can be and as the build gets higher it gets worse.

On a typical timber framed construction, about 6 mm per floor average movement or settlement is likely.

So on a five or six storey building you could have over 30 mm of settlement.

Wet sealants can not cope with that level of movement.

One solution is the use of Compriband impregnated foam tapes.

Each size selected offers a degree of tolerance or movement capability, typically 5-10mm of tolerance in a joint.

There is a Compriband Timber Max which offers up to 37 mm of movement in one product, designed for use in upper storeys.

The tape is essentially a weather sealing product, impregnated foam that will stop driving rain, but it's also breathable, so any moisture behind it can escape.

Timber settles because it's a natural product and it dries following construction.

Settlement also occurs due to loading of the building during construction.

Different types of timber have different characteristics.

Engineered timber tends to have less moisture so there is less to dry out.

There's Compriband 600, Compriband Timber Max, Compriband Super and Compriband VSA 2, each with subtle differences, either in the impregnation or the movement capability of each product.

Compriband Timber Max, followed by Compriband 600 have the widest movement tolerance, and Compriband Super and VSA are more defined in the type of joint they suit.

In the past, wet sealants tended to be used as a gap filler.

Products today probably cost more than a wet sealant, but can prove more economic to install, particularly when allowing for backer rods and specific tooling techniques.

Finishing off may involve skilled work to make sure that the end result, the aesthetics, is pleasing to the eye, particularly true if the size of the joint varies.

When installing wet sealants, there may also be concern about the weather, especially if the gap is in an exposed location.

Impregnated tapes can be applied in almost any weather.

The Compriband range is expected to last 25 years or more, matching the life expectancy of any wet sealant.

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