Okay, got this from the Australian Domestic Construction Manual, which was written by Standards Australia and Master Builders Construction and Housing Association Australia Inc, in conjunction with major manufacturers of building materials, the Timber Research and Development Advisory Council and several statutory bodies.
Text accompanying the stepped flashing diagrams:
"Cavity gutter detail
A critical area of cavity flashings occurs where exterior brickwork becomes internal below a sloping roof. Proper stepped damp-proof course from brickwork on to the adjacent roof level must be provided in conjunction with a cavity gutter, or alternatively a stepped flashing (laid across the cavity) can be used. One way of creating such a gutter is shown in Figure D7.2 - G."
My emphasis and italics. Note that there's no proviso for not providing such a flashing with associated cavity gutter or stepped flashing for renovations or additions. Manufacturers may give other methods for retrofitting a flashing in such a case, but when the wall leaks and the client sues you you'll need to sue the manufacturer that gave you the advice.
The manufacturer will most likely have deeper pockets than you.
If it's not in the ADCM or the BCA then you use the method at your own risk. Follow all the rules and you and your license are covered. If you cut 60% of the way into a brick wall and sometime down the track it collapses, killing or maiming someone then you'll be getting sued. It will then be up to you to countersue the engineer or manufacturer who gave you that advice. I've even read advice in the Master Builder's magazine that in such cases your estate could even be sued by the injured parties after your death.
The diagram labelled DPC shows the DPC running from under the bottom plate and down the step in the slab to finish under the lower course of bricks.
"Damp proof coursing must be installed as follows-
The full width of the wall
If near ground level, between 150mm and 200mm from the finished ground level."
If the DPC must be installed the full width of the wall it must be installed under the bottom plate as that is part of the wall. If stepping down one brick from the bottom plate sees the DPC being closer than 150mm from finished ground level then the builder has not had the slab formed high enough.
WRT to the brick ties:
"The following precautions should be taken during construction:
...............Bridging may occur at the bottom of the cavity, brick ties and at window flashing..........."
Nowhere is it specified that ties should be fixed at an angle in order to shed water and prevent bridging, but if it was my job I'd be making sure they were, as I wouldn't want any warranty call backs to fix damp spots in plasterboard.
Mick
