cavity tray

[scurryspice]

Damp wall! Friend has suggested cavity trays? Anyone have a rough idea of what it might cost to have fitted?

Firstly read the Damp section on this website
www.heritage-house.org
They have some great Youtube videos too
Then try to pin down the cause as its usually not damp

Cavity trays stop water running down the inside of the external wall, so you usually see them fitted over single story
‘connections’. Or above old style concrete lintels.
Very difficult to fit retrospectively.
What is the damp issue?

Hi, thanks for that. The 'offending' wall was once an external wall before we had an extension, 20+ years ago, so there is now a flat roof adjoining that wall
Over the past 6-7 years we noticed some damp (nothing major) and we've had it 'fixed' 3 times, and spent a lot of money redecorating.

More likely to be related to the junction of the new flat roof and the wall. Have you had a roofer or surveyor look at it? Post some pictures of the inside and the outside, will help people see what it could be.

I lost the 'new' flat roof on this bungalow in Storm Arwen November 2021. The roofer said it was a blessing in disguise as the join between the tiled roof and the flat roof was wrong, and water had been seeping in at the join since the new roof had been put on. Right over my bed, ceiling could have come in on me.

So rain will be penetrating the brickwork above the extension, running down the inside of the wall and pooling/dripping onto the beam or whatever is there.
Depending on the brickwork, it may just need repointing, or you could render it with waterproof render, or indeed install cavity trays.
With the trays, you chop out 2 bricks, leave 2 bricks, chop out 2 bricks etc, across the width of the wall, install the trays in each hole, put the bricks back with a weep hole for the tray to drain out, then repeat with the other bricks.
Sometimes they take out 2 courses of bricks, a bit at a time.

I eventually got a builder out to look; he can't see any sign of cavity trays but he's quoted me £2400 for approximately a 3 metre bit of wall!!
I thought that sounded a lot?. A couple of other builders didn't bother turning up but I will try some others.

The cost of cavity trays, weeps, bricks/cement, disk cutter blades, drill bits etc is no more than £200. The builder will need to place boards (scaffold or ply) on the roof to protect the felt, and most likely, if you have lead flashing, cut down the new bricks to refit them. And as I said, it’s 2 alternate bricks at a time. It’s 2 days work for 2 people at a push, however he has a business to run, vans, equipment etc etc.
How long did he say it would take?
Anyway, get a few more quotes.
There are YouTube videos, it’s definitely in the realms of handyman territory.

my 1915 semi detached has a flat roof over a bay window. I had the front wall repointed - bay window ceiling still leaking, had roofers out twice to check lead seal & flat roof, still leaking. Finally an honest roofer had a look and mentioned cavity trays, he also recommended a builder. The builder then fitted cavity trays as the old ones had disintegrated. He had to cut through brick work, install trays and repoint everything. I think it was about 3 metres and he charged me £398 incl VAT. This was about a month ago - I’m in the NW near Blackpool if your local I can pm you his details.

Many thanks for all advice, I will get a couple more quotes. I live South East so prices are high!!

Hi, im looking for a builder for similar roofing work, do you still have his contact details?

@scurryspice hi OP - did you get this sorted? It sounds exactly like the problem we currently have that @C4tastrophe described.

I am also in the SE and just wondered if that’s what it was for you, would you mind advising the remedy and the cost just so we have a rough idea ourselves? We have a couple of people coming to look at it and it’s useful to know because we have absolutely no idea what to expect and wouldn’t know if it sounded like a reasonable cost.

Many thanks!

Retrofitting the cavity tray is one option but it costs a few pounds to do when the wall is built and a lot more later so it's not a no brainer. If you look around you might be able to stop water getting into the cavity in the first place, maybe it's a badly fitted window leaking in at the reveal? Or a roof issue? If it's driving rain genuinely coming through the joints then it would be a tray (or fully render it) situation though.