Movement joints
Clay brickwork
Both BRE Digest 164 and British Standard 5628: Part 3 confirm that movement joints should be provided at 12m intervals in continuous brickwork. Movement joints should be provided in the following positions:
- Intersecting walls, piers, floors etc.
- Window and door openings;
- Changes in height or thickness of walls;
- Chases in the wall;
- At the location of other movement joints in the building or floor slab.
The width of the joint in millimetres should be about 30% more than the distance between joints in metres for example movement joints at 12m centres will need to be about 16mm wide. (Unrestrained, un-reinforced walls, but can be applied to walls in all situations to ere on the side of safety).
Wall ties should be provided at 300mm vertical spacing, on either side of the joint. (Masonry is unlikely to develop tensile cracks, except in short returns of less than 1m in length).
Calcium silicate bricks
Movement joints should be provided in external walls at intervals of about 7.5m to 9.0m. The width of the joint should be between 10mm and 13mm.
In internal walls, movement joints are only needed if the wall is going to be plastered before the brickwork has dried out.
Lightweight aggregate concrete blocks
Movement joints at 6.0m to 9.0m intervals, with a 10mm wide joint.
Autoclaved aerated concrete blocks
(Refer to manufacturers literature) Movement joints at 6.0m intervals, with a joint of 10mm wide.
Seals
Materials for joints to BS6213
- 2-part Polysulphide BS5212
- 2-part Polyurethane BS5212
- Bitumen Rubber type A1/A2 of BS2499
- Flexible Epoxide
The depth of the seal should be at least between 2 x width and 1 x width of the joint.
Filling materials: a pressure of about 0.1N/mm2 should be sufficient to compress the material to 50% of its original thickness. Filling materials are usually Polymer Foams. Materials not to be used are: Hemp, fibre board, cork.
Important
For detailed advice please contact the manufacturers of the products you are proposing to use.