External masonry walls

6.1

6.1.18Wall ties

Wall ties of the correct type shall be installed where required, and be suitable for their intended use and location. Issues to be taken into account include:

  1. position
  2. ties for partial fill insulation.

Wall ties should:

  • be in accordance with BS EN 845-1 or Technical Requirement R3
  • be of the type as specified in the design
  • be long enough to be embedded a minimum of 50mm into each leaf
  • be stainless steel or non-ferrous
  • be spaced above and below the DPC in accordance with Table 10.

Position

Table 10: Spacing on wall ties

Maximum horizontal spacing (mm)Maximum vertical spacing (mm)
General wall area900450
Jamb openings, movement joints, etc.Within 225 of openingNot more than 300(1)
Top of gable walls225 (parallel to the top of the wall) Not more than 300
Top and bottom of openings450N/A

Notes

1 The cavity insulation may need cutting to insert the tie.

Water should be prevented from crossing the cavity. Care should be taken to avoid:

  • ties sloping down to the inner leaf
  • drips being off-centre
  • ties having mortar droppings on.

Cavity walls should be coursed so that the wall tie is level or slopes outwards.

Wall ties should be:

  • built in and not pushed into joints
  • bedded into the built leaf (by a minimum of 50mm) so that they can have a minimum 50mm bed into the unbuilt leaf
  • positioned so that the drip faces downwards.

Ties for partial fill insulation

Where partial cavity fill insulation is being used, it should be held against the inner leaf by retaining devices, which may be clipped to the wall ties. Retaining devices should be:

  • compatible with the wall ties
  • used in accordance with Technical Requirement R3.

Where 1,200mm boards are used with partial fill cavities, the wall ties should:

  • be spaced closer to provide adequate support and restraint
  • be spaced at 600mm centres in rows, i.e. not staggered.

Bed joint reinforcements should:

  • be in accordance with BS EN 845-3 or Technical Requirement R3
  • be of the type as specified in the design
  • be sufficiently wide so that minimum cover of 20mm is provided from the external face of masonry
  • be stainless steel or non-ferrous
  • have a minimum lap length of 225mm and laps between lengths should always be staggered
  • be used strictly in accordance with manufacturers recommendations.