Wall Ties and Bed Joint Reinforcement
A single unreinforced brick wall 102mm wide is unstable, in order to maintain stability it must be tied to an inner skin. The inner skin is often blockwork but may be a metal framing system or even wind posts. Detailed information can be found in the BS EN 1996 series of Eurocodes. General information can be found in PD 6697: 2010. Essential background information is listed below. For specification advice information should be taken from the standard, not from this guide.
Embedment in the mortar joint should be a minimum of 50mm in both skins. The wall ties should be selected with an allowance made for tolerances. Wall ties are often available in stainless steel but as cavities grow larger with more insulation basalt ties are sometimes used to avoid cold bridging. Helical ties which can be let into the inner leaf are sometimes used retrospectively where wall tie provision has been inadequate.
Either side of movement joints, windows, doors, or other un-bonded edges including gable walls, wall ties should be placed at 300mm max height (often 225mm to suit blockwork coursing) within 225mm of the edge of the opening.
Wall ties come in the following classifications
- Type 1 Heavy duty often used for high rise and the high winds in the North and West particularly Scotland and Northern Ireland where high winds are frequent.
- Type 2 Up to 15m above Ground Level Wind velocity up to 31m/s
- Type 3 Wind velocity limited to 27m/s.
- Type 4 Light weight lower rise masonry cavity walls in domestic construction.
Bed Joint Reinforcement
Bed Joint Reinforcement is a panacea for much brickwork. With BJR installed every 3rd course or 225mm high Movement Joints can be increased to 17m.
- In the bed joint where the wall consists of different colour brickwork, or different materials such as stone or block are laid in the wall, BJR minimises the possibility of the mortar bed cracking.
- In severely exposed brickwork such as gables or free standing walls where additional durability is required.
- To resist lateral forces, likely to impose point loads such as crowd impact or glancing connections from vehicles.
All construction must conform to the appropriate standards and codes and be reviewed by a competent professional.