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Cavity wall ties are normally spaced at a maximum of 900 mm horizontally and 450 mm vertically — roughly 2.5 ties per square metre. Where partial-fill insulation is used the horizontal spacing tightens to 600 mm, and additional ties are always required at unbonded jambs, movement joints and openings.
A cavity tray is required wherever the cavity is bridged or closed — over openings, at abutments, above lintels and at changes of level. It needs a minimum 150 mm upstand into the inner leaf, sealed stop ends at each end, and weep holes at not more than 450 mm centres with at least two over every opening. The DPC itself must sit at least 150 mm above finished ground level.
In a dwelling the handrail sits 900–1000 mm above the pitch line or landing floor, headroom over the flight is a minimum of 2000 mm, and the going of a tapered tread is measured at the centre of the flight with at least 50 mm at the narrow end. A stair wider than 1000 mm needs a handrail on both sides.
A cold pitched roof is ventilated with an equivalent area of 10,000 mm²/m at the eaves and 5,000 mm²/m at the ridge, with a clear 25 mm air path maintained above the insulation. In the roof void itself, cavities must be subdivided at a maximum of 20 m and every compartment wall must be carried up and fire stopped tight to the underside of the roof covering.
Floor joists need a minimum 90 mm end bearing on masonry (or a correctly sized and fully nailed hanger), notches no deeper than 0.125 × the joist depth and only between 0.07 and 0.25 of the span, and holes on the neutral axis within the permitted zone. Strutting is provided according to the span.
Cavity barriers are required continuously around the full perimeter of every opening in a cavity wall, at the edges of cavities, and at every compartment junction. Where a service passes through a fire-resisting element, the fire stopping has to reinstate the full fire resistance of that element using a system tested in that substrate.
Gutter brackets are fixed at a maximum of 600 mm centres, with an additional bracket immediately either side of every joint, angle and outlet. The gutter falls consistently towards the outlet and is set so that water running off the roof covering discharges into it rather than behind it.
Lateral restraint straps are fixed at a maximum of 2 m centres at floor and roof level and must be turned down against the inner face of the masonry and fixed over at least three joists or rafters with noggings. Studs are normally at 600 mm or 400 mm centres to suit the panel design and the sheathing fixing schedule.
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