Design - Wall Ties

 
Wall ties should be flexible enough to accommodate relative movement between both leaves of a cavity wall but stiff enough to transmit axial loads.
Stainless steel wall ties should be specified, the type according to whether they are for use with traditional mortar or thin-joint construction. Ties should conform to BS 1243: 1978 or BS DD 140: Part 2: 1987.
 
For traditional 10mm mortar construction, conventional butterfly or double-triangle ties should be embedded to at least 50mm into the mortar joint in each leaf.
Driven wall ties should be embedded into the Airtec block to a depth at least matching that when embedded onto the outer leaf mortar joint (when building the Airtec inner leaf first). Positioning will be determined by the coursing levels of the outer leaf.
 
When using partial internal cavity insulation, suitable retaining devices should be used for supporting the cavity batts.
The leaves should be coursed such that the ties are either level or slope outwards to avoid water penetration to the inner leaf. The drip should be positioned so that it points downwards. 
 
 
 

A note on Thin-Joint mortar Wall Ties:

Thin-Joint construction wall ties are the helical twist type that are hammer driven into the face of the aerated block on the inner leaf at the appropriate mortar joint level on the outer leaf as construction progresses.
 
Alternatively, ties that can be face-fixed to the block are also suitable. The tie should be anchored into the Airtec block using an expanding nail or similar fixing. Frame-fix ties must be installed correct side up and placed horizontally or with a slight fall to the outer leaf.
 
 
 

Wall Tie Spacing and Positioning

  • Recommended wall tie spacing and positioning should be in accordance with BS 5628 Parts 1 and 3; a density of 2.5 ties per mē.
  • Ties should be evenly distributed over the entire wall area.
  • Use a staggered pattern when both leaves are greater than 90mm thick.
  • Distance from a vertical movement joint or vertical edge of any opening (door, window) should be no greater than 225mm.
 
 
Cavity
Width
Horizontal Spacing
Vertical
Spacing
50mm
to
75mm
No more than 900mm apart
No more than 450mm apart
75mm
to
150mm
No more than 750mm apart
No more than 450mm apart
 
 
 
 
 
 

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