Quality.

    Services penetrations — critical dimensions

    Where pipes and cables pass through structure and fire lines, and the limits that apply when they do.

    Minimum

    Cable depth in a wall before extra protection is needed

    50 mm

    Measured from the finished surface on either side of the wall

    Minimum

    Fire stopping at a service penetration

    Reinstate the full fire resistance of the element

    Sealed with a system tested for that substrate, aperture size and service type

    Minimum

    Flue outlet height at a ridge

    600 mm

    Solid fuel flue passing through a pitched roof at the ridge

    Range

    Gradient of a branch discharge pipe

    18 to 90 mm per metre for a 75 mm or 100 mm branch

    Measured along the branch from the appliance to the stack

    Maximum

    Maximum hot water temperature at a bath

    48 °C

    Hot water supply to a fixed bath in a dwelling

    Maximum

    Maximum length of a WC branch to the stack

    6 m

    For a 100 mm branch serving a single WC, with no more than 90 mm/m fall

    Maximum

    Maximum pipe diameter through a compartment wall or floor

    40 mm

    Nominal internal diameter for a non-fire-rated pipe; larger pipes need a tested sleeve, collar or non-combustible material

    Range

    Permitted notches and holes in floor joists

    Notches: max depth 0.125 x joist depth, only between 0.07 and 0.25 of the span. Holes: max diameter 0.25 x joist depth, on the centreline, between 0.25 and 0.4 of the span, at least 3 diameters apart

    Solid timber floor joists — engineered joists follow the manufacturer's zones instead

    Maximum

    Safe zones for cables buried in a wall

    Within 150 mm of the top of the wall or of a corner, or vertically/horizontally in line with the accessory

    Applies to cables concealed in a wall or partition at a depth of less than 50 mm

    Maximum

    Water efficiency limit for a new dwelling

    125 litres per person per day (110 where the tighter optional requirement is imposed by condition)

    New dwelling water efficiency calculation

    All critical dimensions · All topics

    These entries are our own editorial summaries of publicly available regulation. They are not building control approval, a warranty determination, or a substitute for the full source document.

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