Cavity Wall Water Evacuation is Essential

Failure to provide adequate means of water evacuation from a cavity wall causes three major considerations:


External discolouration, salt emission and eventual permanent staining will eventually blemish the appearance of the structure.


If sufficient water is trapped and reservoirs within the cavity, it will permeate inwardly. Water does not discriminate and if it cannot evacuate outwardly easily, it will find alternative routes.


The masonry and mortar joints will suffer premature deterioration. Spalling will occur when trapped water freezes and expands. Masonry cracking, loosening and delaminating will eventually result.

The need to drain cavity walls is not limited to just window and door heads.  

Changes of level, roofing intersections and ringbeams are just three further examples of construction details where functionality is reliant on water being adequately evacuated.

Evacuation can be achieved using preformed caviweeps. Caviweeps ensure water is not trapped within the structure but can exit speedily.

Five versions of caviweep in many different colours are manufactured by Cavity Trays of Yeovil. This permits the Architect to select the most appropriate caviweep to suit the construction. Options include caviweeps with insect screening, discreet external appearance, integral wind baffles, to suit all styles of mortar, masonry etc.  There are even versions to suit masonry with drafted margins or restricted bed and perp joints as encountered with ashlar walling.

Once an external masonry leaf has become saturated and cannot absorb further rain, it acts as a conveyance sponge allowing up to 2.25 litres of water per hour can pass through every square metre of it during ongoing rain. Whilst some styles of masonry are more resilient to ingress, wall design must always anticipate the most extreme exposure possibilities, so evacuation provision is always adequate.  

Cavity Trays of Yeovil will be pleased to assist the optimisation of water evacuation provision upon request.

Where caviweeps are used with cavitrays manufactured by Cavity Trays of Yeovil, the combination benefits a performance warranty for the advantage of Architect Builder and Client.

Cavity Trays of Yeovil is the only cavity tray manufacturer awarded European Technical Approval.

Further Reading in Product Guide 21

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