Wall Tie Spacing on a Cavity Wall
A two-storey cavity wall is being built with a 110 mm inner leaf and 110 mm outer leaf, 50 mm cavity, and wall ties at 600 mm horizontal centres and 450 mm vertical centres. The builder has ordered 200 mm ties. On inspection, some ties slope downward toward the inner leaf and a few sit in the cavity without full embedment. The site has a 2.4 m wide window opening and the bricklayer asks whether extra ties are needed around it. The wall is in a sheltered suburban location.
1. Are the tie length and spacing appropriate, and what defects need correcting?
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Tie length must span both leaves plus the cavity with sufficient embedment each side. With 110 + 50 + 110 mm, a 200 mm tie leaves only about 20 mm embedment per leaf once the cavity is accounted for, which is inadequate; ties typically need around 50 mm embedment in each leaf, so a longer tie (roughly 225–250 mm depending on the product) is required. Spacing at 600 × 450 mm is broadly consistent with common guidance for a sheltered suburban site, but the installation is defective: ties must slope slightly downward toward the outer leaf to shed water, not toward the inner leaf, and every tie must be fully embedded, not loose in the cavity. These must be corrected before the wall rises further. The supervisor should verify the selected tie against the manufacturer's and project specification rather than assume.
2. What should be done around the 2.4 m window opening?
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Openings interrupt the continuity of the wall and concentrate movement and loading, so additional ties are normally required around them. The bricklayer is right to ask. Ties should be provided at closer centres around the opening edges, and at the jambs and under the sill, following the project specification and tie manufacturer's instructions. The exact pattern depends on the tie type and the design, so the supervisor should check the drawings and specification. The key judgement is that the standard spacing for the general wall does not automatically apply at an opening; the detail must be confirmed before the wall is built past the window. Any ties already placed at the general spacing that fall within the opening zone should be supplemented, not simply left.