Extension over weep holes - What to do?

[warmington_ash]

Good evening all,

 

Hoping someone might be able to help offer some advice regarding our proposed extension.

 

I have crudely marked out the outline of the extension in the below image. It is going to have a concrete tiled pitched roof to match the existing.

 

The question I have is that the extension will cover 3 weep holes (circled in blue). What should I do to avoid any internal leaks? I have read online about fitting cavity trays which I assume would need to involve chasing out the stone above the roof line to fit the trays (which sounds expensive and complex). Is there another simpler way around this?

 

[nod]

You will need to fit cavity trays over the new lead flashings 

Its not a difficult job or that expensive 

Building Control will insist that you do this 

[warmington_ash]

10 hours ago, nod said:

You will need to fit cavity trays over the new lead flashings 

Its not a difficult job or that expensive 

Building Control will insist that you do this 

 

Thankyou.

 

Is this effectively what I need to do?

 

[George]

Yes - you can leave the existing weep holes so long as you close the cavity and put in trays above it. 

 

Obviously in an existing wall you can only remove a few bricks at a time, unless you are able to otherwise prop or support the wall above. 

 

Amusingly I have seen architects who built their own extension say 'ah it'll be fine' when I questioned them on this exact point. 

[Radian]

7 minutes ago, George said:

Amusingly I have seen architects who built their own extension say 'ah it'll be fine' when I questioned them on this exact point. 

 

One house we bought from a developer omitted a tray in a similar location between main house and side extension and within months of moving in, after a heavy rainstorm, we had water cascading down the interconnecting doorway in our living room. The developer had to fix it under NHBC guarantee and, I don't know why, took down the entire outer leaf to install a stepped tray.

 

However, not wishing anyone to attempt to do anything suboptimal, I'm not sure BC will actually insist on a tray in all cases. Porosity of masonry materials, exposure of the elevation and condition of existing lintels/trays all play a part in whether or not there will be problems further down the line. Huge gamble though and even if BC don't insist it is definitely worth doing at the early stage of your build.

[Temp]

3 hours ago, George said:

Amusingly I have seen architects who built their own extension say 'ah it'll be fine' when I questioned them on this exact point. 

 

Sometimes you can get away without one if the bricks are particularly waterproof or its not an exposed location or if you render the wall. 

 

I hadn't realized how porus bricks can be until a few years ago. I filled a bucket with bricks in then filled all the space with water. They fizzed and popped and soaked up all the water.

 

 

 

[Mr Punter]

I have heard of BC accepting an application of Silane/Siloxane masonry cream to the masonry above.

[warmington_ash]

Thanks everyone for your input on this.

 

The one to the right is the one that makes me most nervous, because it clashes with the proposed roof build up for the extension.

I assume that this particular weep hole is serving as the outlet for the cavity tray that runs adjacent to the existing pitched roof?

 

Any thoughts on how to tackle this would be appreciated.

 

See attached pic from a better angle.

 

 

[warmington_ash]

ps excuse the roaming 1 year old in the window reflection 😄 

[dpmiller]

mightn't be for that purpose actually. If memory serves there needs to be weeps above a fire barrier too- are there any more at the same height?

[warmington_ash]

On 25/04/2022 at 07:02, dpmiller said:

mightn't be for that purpose actually. If memory serves there needs to be weeps above a fire barrier too- are there any more at the same height?

No that's the only one.