Removal of moisture from behind panels

No matter which type of joint is used, there is a general consensus of opinion by BRE and panel manufacturers that from time to time moisture will occur on the inner surface of panels as a result of condensation and/or rain penetration, and panels should be designed to include facilities for its removal by weepholes left in the moulding. Condensation is collected in a groove on top of the bottom horizontal ribs. Different weephole designs and condensation grooves are shown in Fig. 1.29.Weepholes should not be less than I 3 mm internal diameter to prevent blocking, and they should project from the face of the building to prevent, as far as possible, any staining of the panel surface. In order to prevent such staining, it is sometimes possible for the weephole to be cast into the panel so that it drains moisture into the horizontal joint.

Site exposure A B

Sheltered 50 75

Moderate 75 100

Severe 100 125

Sheltered 50 75

Moderate 75 100

Severe 100 125

1.28 Heights of upstands and downstands (mm). A - effective lap and B = actual lap or downstand.

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