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GA Fixings
Unit 34
Claycliffe Business Park
Cannon Way
Barugh Green
Barnsley
S75 1JU

Tel: 01226 380779
Fax: 01226 385558

Email: info@gafixings.com

Design considerations for wall ties

 

When selecting which wall ties to use a number of factors must be considered ie cavity size, building type, height and location. To determine the correct wall tie to use guidance must be sought from several main documents covering wall tie usage.

These include:
BS 5628: The Use Of Masonry: Part 1: 1992
Provides recommendations on density, positioning, embedment and length of ties.
Allows ties from BS 1243 and DD140 to be used.

Least Leaf Thickness Nominal Cavity Width Permissable Tie Type Tie Length
BS1243 Shape Type DD140 Tie Type
75 75 or less Butterfly, double triangle or vertical twist Types 1,2 & 4 175
90 75 or less Butterfly, double triangle or vertical twist Types 1,2 & 4 200
90 76 to 90 Double triangle or vertical twist Types 1 & 2 225
90 91 to 100 Double triangle or vertical twist Types 1 & 2 225
90 101 to 125 Vertical twist Types 1 & 2 250
90 126 to 150 Vertical twist Types 1 & 2 275

Least Leaf Thickness Nominal Cavity Width Spacing of Ties Ties Per Metre Square
Horizontal Vertical
65 - 90 50 - 75 450 450 4.9
Above 90 50 - 150 900 450 2.5

BS 5628 recommends that the embedment into each leaf of the cavity wall should be a minimum of 50mm.
Ties at vertical edges of openings or unbonded edges ie: movement joints, should be placed at 300mm centres vertically at a maximum 225mm from the open edge.

BS 1243: 1978: Specification Of Metal Ties For Cavity Wall Construction
Largely a manufacturing standard specifying the size, material and tolerances for three types of tie, butterfly, double triangle and vertical twist. The standard contains no guidance related to the ties performance or recommended usage.

Figure 1: Butterfly Tie
Ref: GA7

Figure 2: Double Triangle Tie
Ref: GA7
Figure 3: Vertical Twist Tie*
Ref: GA5

*Supplied with 3 hole saftety end


DD140: Part 2: 1987: Recommendations For The Design Of Wall Ties
Part 2 of the DD140 document gives recommendations on the design requirements of wall ties used in masonry and timber construction. There are 6 classifications each specifying requirements depending on end use. Class types 1 to 4 relate to masonry construction, class types 5 and 6 relate to timber construction. This document rather than BS 1243 is now used as the primary reference when considering wall tie usage. For more information about DD140 please select this link.