Hatch and chimney openings: Whenever possible hatch openings should be accommodated within the trussed rafter design spacing. When this is not possible the method shown on the left should be used.

D max is equal to twice the design truss spacing less the opening width.

Jack Rafter 25mm deeper than trussed rafter and birdmouthed over wallplate.

Chimney Detail

All timbers must be at least 50mm claer of the chimney brickwork.

Jack Celing Joist nailed to side of jack rafter, size to match bottom chord of trussed rafter

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