Victorian Cavity Walls, damp (and surveyors!)

[stevebamford]

Hi All,

Can anyone offer advice on the following:

Just bought a Victorian semi with solid 9" walls (according to the surveyor) and a damp issue (again spotted by the surveyor)

We're already lowering the ground level by the wall and installing airbricks, and turning on the heating as the house has been empty for a while

But it turns out that the walls are actually cavity (up to 1st floor level). After having airbricks installed it appears that the bottom of cavity is full of debris. Is this likely to be a cause of the damp ?

Any suggestions on sorting this out, short of taking out every 2nd brick and digging the muck out by hand ? Am guessing that the fact its cavity wall makes this much harder to resolve

And surely the surveyor should have noticed this. A builder pointed out to me that the lack of header bricks (is that the correct term?) is a pretty strong pointer that its a cavity wall ?

Cheers

Steve

 

[JohnD]

if you can take out a brick at a quoin, you can rake out the rubbish towards you. This is very difficult on terraced houses.

I have also had a little luck poking the flexible snout of a powerful vacuum cleaner down the cavity, it can suck up small stuff. Large stuff will get sucked onto the nozzle and block it, but then you can withdraw the hose and clear it.

I have sometimes wondered about using a powerful water jet, but this would make the wall wet, which in a semi would annoy your neighbours.

If you have occasion to take out any door or window frames, this also gives access to the cavity. Sometimes window boards are placed over the cavity, but this depends on regional practice.

 

[^woody^]

The cause of dampness could be either breach of the DPC causing rising dampness or a thermal bridge causing condensation dampness. Either way the the debris will have to come out

The debris is likely to be mortar dropped down the cavity and thus hard to get out without a hammer and chisel.

You wont do this by just taking out every second brick. And you wont do it from just one place

You will probably need to take out patches of at least 6 bricks (2 x 3 courses) every 1m or less, so that you can actually get into the cavity to work. Also get some good gloves, as this job will take the skin off your knuckles.

Just because there are no headers, does not mean that it is a cavity wall. But if the surveyor was specifically looking for the cause of this dampness, then it may ave beome apparent during the investigation. But if this was a basic survey, then it may not have been looked at that closely

 

[stevebamford]

thanks guys - oh Pooh sounds like a job and a half !

 

[AndersonC]

Whatever you do don't sort out your cavity walls then have wall tie replacement work done via anchor bolt insertion.

In some cases wall tie replacement = anchor bolts between the wall layers. So out come the big heavy hilti drills and off come the backs of the bricks from the inside face of the outer course, falling nicely into the cavity and filling it up.

 

[joe-90]

Does the house have a damp course? If so are you sure that the debris bridges it? (lot of debris)

 

[stevebamford]

Whatever you do don't sort out your cavity walls then have wall tie replacement work done via anchor bolt insertion.

In some cases wall tie replacement = anchor bolts between the wall layers. So out come the big heavy hilti drills and off come the backs of the bricks from the inside face of the outer course, falling nicely into the cavity and filling it up.

Cheers chap - is it likely that i need to replace the ties ? No signs of problems with the walls - except the damp issue

 

[stevebamford]

Does the house have a damp course? If so are you sure that the debris bridges it? (lot of debris)

Hmmmmmmmmmm not sure about the damp course. In the past someone has injected a DPC. But the one area I investigated certainly looked as though the debris came higher than that

Presumably there may have been a slate DPC or similar originally - or were these not always fitted ?

 

[joe-90]

My opinion on this is that you've probably got a failed DPC. I really can't see damp rising up the inside of a wall via a pile of brick rubble.
Taking bricks out at the base of a house is pretty risky (to say the least), you just can't get a line of mortar capable of supporting a house back in place. You risk cracking the brickwork.

If I were you I'd inject a new DPC from both sides, then drill right through each brick from one side and give the cavity a good soaking of damp proofing liquid right along. It'll stop any damp rising from the rubble.

 

[Shytalkz]

Uhoh, here we go again....

 

[gregers]

if it is a cavity wall you do not need to drill&inject both sides of the wall,if a chemical dpc is needed then you will have to remove the plaster on the inside to a hight of at least 1m,drill and inject the inside skin,then you need to make some holes in the wall,we used to make the holes at least i brick above the new dpc level,the holes need to be about 2 bricks longx2 bricks high every 2ft then you can use an ads or scutcheon hammer to scrape the silt etc from the cavity to below the new dpc level,then get some bricks and rebrick it up,jobs a good en.

 

[JerryM]

apologies but i've only read the original post and skipping through noticed wall ties.

2 thoughts:

1) i would tank the walls personally - if there is a lot of debris in the cavity it's just pretty much impossible to sort the damp for sure.
2) don't jump to wall ties - a lot of people are making money when it's not needed - u need to inspect an existing tie to be sure it's needed.

 

[chessspy]

It would be almost impossible for a Victorian house to have a cavity wall.
the earliest I ever saw was built in 1926, and was very advanced design for it's day.(the owner claimed it was the first ever built)
There was a form of cavity wall,with the bricks laid on edge, but this still used headers as ties. anyway it was very rarely used.
Either your house is not Victorian, or it's not a cavity wall.
measure it at a Jamb and see how wide it is, you will have to allow for plaster distorting the thickness, about 10" overall for solid, up to 12" for cavity. (with old bricks)
It is possible to hire a camera with a little lens thing on the end of a flexible thingy for looking down cavities etc. with this system you only need to drill through the first skin from the outside and slide the flexible thing in to look.(it also has a little light built in)
The DS can probably advise you and may even come down with his and look

 

[gangman]

It would be almost impossible for a Victorian house to have a cavity wall.
the earliest I ever saw was built in 1926, and was very advanced design for it's day.(the owner claimed it was the first ever built)
There was a form of cavity wall,with the bricks laid on edge, but this still used headers as ties. anyway it was very rarely used.
Either your house is not Victorian, or it's not a cavity wall.
measure it at a Jamb and see how wide it is, you will have to allow for plaster distorting the thickness, about 10" overall for solid, up to 12" for cavity. (with old bricks)

I live in a cottage built in 1900 and it has two brickwork skins with a 3in cavity tied with fishtail ties. A lot of the cottages in my area were built as part of a farm estate around the 1890's to 1900's and they were built with cavity walls. Your "owner" is way out if he thinks he has the first ever cavity walled house.

 

[chessspy]

Thanks gangman,
I stand corrected, and as 1900 is just Victorian, then you have the best of me, on that also.
I still think that cavity walls were essentially a post 1920 phenomena, and the newest houses I ever saw with solid walls were built in 1969, so,~~ (shrugs shoulders)
The point is to measure the wall thickness and determine what is possible and what not.
The rest of my recommendations stand.