Technical Manual

Bricks & Pavers Technical Manual
Section 1.3. Brick Masonry Construction
Joint Sizes
Mortar bed joints are required to be less than 10 mm unless the design specifies another thickness. A different
thickness may only be specified after the designer considers the effect on compressive and flexural strength of
the masonry. During construction mortar bed joints are allowed to deviate by ± 3mm. Because of poor practice
or lack of proper direction some slabs and footings are finished at the wrong height. Mortar joints up to 50 mm
thick have been used to get the correct coursing, however, this is not allowed under AS3700.
Perpends are to have a minimum design thickness of 5 mm. In structural brickwork perpends may be up to 10 mm
thicker than the specified thickness but no thinner. In face brickwork perpends may deviate by ± 5 mm from the
average width but in any one wall the maximum difference allowable between any two perpends is 8 mm.
The preceding tolerances do not apply in the case of thin bed mortars and perpend tolerances do not apply where
perpends are not filled with mortar. ■
Weepholes are to allow moisture that collects in the cavity to escape. Weepholes should be spaced at less than
1200 mm centres wherever flashing is built into the masonry to shed water from the cavity. Weepholes are
usually empty perpends (10 mm wide) but proprietary products are available to prevent the entry of insects. In
high wind areas it has been known for water to be blown up the cavity onto the inner wall and as this is very
undesirable, more, narrower weepholes are usually built into the wall. It is essential that weepholes remain open
and render and other applied coatings, where used, must be raked out of the joint. ■