Thanks Mick, I was enjoying sitting back and watching.
The greatest occurrence with water penetration in that situation is possibly not with electrocution [point taken] but with water marks or salts appearing on the internal wall in the house. <o></o>
From a builders point of view this type of drop gable is a bastard & there is no one method of flashing that will come up with – ‘do it this way & it wont leak’.
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Firstly<o></o>
Very little water penetrates through bricks. It comes in through the perps. – before I get jumped on by a moderator, bricks do get wet & brickies love laying wet bricks. <o></o>
The higher the brick panel above the abutment flashing the greater the likelihood & amount of moisture in the cavity.<o></o>
The strength of the wind plays an important part, more so with raked or recessed key joints.<o></o>
In an external wall the moisture will have more chance of drying because there is air movement in the cavity.<o></o>
In an internal wall the moisture tends to be drawn through the brickwork because of the temp. difference showing up as effervescence [???].<o></o>
A raked joint will let in more moisture than an ironed joint.
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Yeh ok im getting there.<o></o>
How do you stop it – put in a cavity flashing. <o></o>
As Al showed in his diagram, a stepped flashing with weepholes – a series of horizontal flashings stepping down with the pitch of the roof.<o></o>
But won’t the water run over the edge of the flashing like a waterfall & end up in the bottom of the cavity I hear you say. <o></o>
No. We need to get it into context. We’re talking about moisture not water flowing. If there’s water flowing then its more likely to be a flashing at the very top of the cavity or a couple of bricks left out of the wall [only joking Al] or one of those round grills installed on gable ends to vent the roof space.<o></o>
If you’ve got a single leaf garage you’ll be able to see moisture on the inside of the skin if there’s prolonged rain [& it’s wind driven] If you have say a dry area up towards the top & then water coming in lower and running down the wall it could be more than likely caused by the brickie not buttering the end of the brick fully creating a ‘weak’ perpend.
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In the situation where you have a large expanse of wall above the abutment such as with a full second storey, a full length horizontal flashing as you’d have at the bottom with a slab will reduce the brick area feeding moisture to the stepped cavity flashing. Same as you’d have over a window opening.
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What to do –<o></o>
Reduce the area of the face as much as possible with a ‘normal’ flashing up higher.<o></o>
Ask the brickie to be aware of the potential problem so he will give more attention to perp ends, the installation of the flashings, keeping the cavity clear, making sure weep holes are fully open.<o></o>
Iron finish to the joints if possible.<o></o>
I don’t have much faith long term but clear waterproof coatings work.<o></o>
Liquid damp proof added to the mortar for the entire wall.<o></o>
Use an embossed plastic type flashing in the cavity to maintain a better bond rather than a lead or smooth metal tray/s. - to perform, the flashing has to come within a bees of the face of the brick so you are ‘breaking’ the wall. Either way ensure that wall ties are as close as possible to the flashing.
Whether the abutment flashing is stepped or sloped doesn't come into the performance of the cavity flashing.
As lead will disappear & I think bluescope still have an aversion to laps on their material I may be fulfilled in life yet & see more nice & neat sloped flashings looking modern and not as with their counterparts - left over from the 30's :q
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Ok sock it to me.<o></o>
