Alternatives to stepped cavity tray?

[walkern]

Hello,
I know the answer is going to be no, but is there any alternative to fitting stepped cavity trays to a pitched roof extension being built to the side of my existing house. My BC is insisting on getting it done.

It's seems like a massive job and potentially structurally bad to remove bricks all the way across my house just to fit some trays.

thanks.

 

[^woody^]

Clad the wall

 

[walkern]

yeah, like pebble dash

I could alway stick some weep holes in and repoint and pretent I've done it

I don't know why lead flashing and other usual techniques are not good enough when it's worked for years before...

 

[freddiemercurystwin]

How do you know how well the existing wall is performing? Guess you're psychic.

 

[John D v2.0]

Depends if there's water going down your cavity (as per it's design) and whether it'll cause a problem if that water drops down onto your new steels.
It's probably no skin off the bco's nose.

 

[walkern]

The wall it is joining to is only about 5 years old from a previous build. Can somebody explain why it's needed? I'm not talking about my steel, which will have a cavity tray, I'm talking about stepped trays having to be put in with the lead flashing as it joins (like http://www.leeandjackson.co.uk/cavity trays.htm)

But the BC office said they are forcing down on this and I have to have it done. I just want to understand the purpose.

 

[stuart45]

The idea is that water can penetrate the exterior skin of a cavity wall and then runs down the inside and comes out at the weep holes over the frames or runs down below DPC.
When you build an extension the wall then becomes an interior wall so the water can't run away outside.
Lead flashing stops water getting between the tiles or slates and the wall, but not through the cavity.
Don't know if I've explained the theory or have confused you even more.

 

[John D v2.0]

Yes in a cavity wall, the cavity is "wet" and only the inner leaf is "dry". So to keep the water out you have to effectively flash up to the inner leaf.
In a real situation you can get a sheltered or rendered wall, so in actual fact the cavity doesn't get any water in, or vice versa where the water can track through across the wall ties or missing cavity trays etc can cause the inner leaf to be wet too. But that's the general principle.

 

[walkern]

Thanks, makes sense. But we've had it without these trays for years and no issues...

How big a job is this, in terms of money and stress on the wall?

 

[John D v2.0]

fitting stepped cavity trays to a pitched roof extension being built to the side of my existing house. My BC is insisting on getting it done.
s.

Thanks, makes sense. But we've had it without these trays for years and no issues...

Earlier you suggested the extension was new, now you're saying it's been there for years? Why is bc involved all of a sudden? Are you getting retrospective building regs approval due to selling? If so it would have been better to tell the buyer to get an indemnity, as BC are unlikely to enforce anything after many years passed.

 

[walkern]

No, somebody asked about about the quality of the wall it was going onto, that is 5 years old. This is a new extension being built now. Sorry for the confusion.

It's a sun room with pitched roof about 4 metres depth to the side of the existing house.

 

[tony1851]

Did you use a private inspector, or the local authority?

 

[walkern]

I queried my council BC about it and he was pretty vocal about it being done and said waterproofing the walls, etc was not good enough.

If it had to be done, I'll do it, but it seems like a bad idea ripping all the wall apart for something that I think isn't needed and almost all bills in the past have not done.

 

[tony1851]

Private inspectors are usually more realistic, but too late now.
Why not consider some (temporary) PVC cladding?

 

[^woody^]

for something that I think isn't needed

I don't think I need to pay my mortgage every month.