Deteriation of cavity wall ties

[Steve]

We are in the process of buying a house that was built circa 1927.

The Surveyor's report has just arrived and mentions some horizontal cracking on one of the walls that could be associated with deterioration of the ties. He recommends a cavity inspection.

What does a cavity inspection entail, is it CCTV endoscope type of thing or is it more intrusive? No rude answers please :-)

Is the repair of failed ties a DIY job?

I was thinking of drilling through both leafs of the wall with very slight gradient downwards to the outside wall and then resin bonding lengths of stainless-steel studding, slightly shorter than the width of the wall - so as to be able to redecorate/point in. Would this be an acceptable repair or is there a better way?

Thanks

Steve.

[Phil L]

an endoscope is often used, yes.

Not really because it requires an insurance backed guarantee

When someone does it it will be from outside, they drill straight through the outer brick and 50mm into the inner brick/block. The ties vary, sometimes they are double mechanical (nut and bolt at each end - the one inside the inner block is tightened first then the outer)...sometimes they are resin bonded both ends, sometimes they are resin bonded to the inner leaf and mechanical outer...in all cases the holes are repointed with a colour matched mortar.

WRT the sulphur damage (the rusting of the old ties which causes horizontal joints to widen) they may need to be isolated, which involves cutting mortar out from around each tie and inserting a plastic sleeve filled with grease over it then re-pointing, a metal detector is used to find each one and an electric or air tool used to cut out the mortar.

HTH

[Phil L]

Forgot to add:

All this work needs to be done by a qualified person in order for most mortgage companies to lend money on a house, if you have not yet purchased the property, the vendor will have to have this work done or knock the price of it off the asking price.

[Andy Cap]

As you appear to know what you are talking about ! Is it usual to repair just the blown courses or would it be normal to re-tie a whole wall or even the whole house, if say one course showed such signs ?

Andy

[Phil L]

Once a lender picks up on it (or more precicely, it's surveyor) they usually want the full house done. The house doesn't even need to be showing signs of sulphur damage neither, they can insist on this even if the ties are in working order but 'at risk', IE not rustproof...modern ties used in building are usually stainless steel and all replacement ties are

[Andrew Gabriel]

They now have to be stainless steel. Galvanised steel were often used until relatively recently, but even these are now no longer allowed.

[Phil L]

I said 'usually stainless steel' because I've worked on newbuild where plastic ones have been used, how effective they are I don't know.

[Steve]

Oh, I see. The mortgage company have not raised this issue. It was because of our Survey that this potential issue has come to light. Our Surveyor recommends that we have the inspection done to ascertain whether work is needed and whether any work can be delayed until the situation worsens.

However, I can see the benefit of an insurance backed guarantee for work of this nature when the mortgage company insists. But as the mortgage company are happy, I still wonder whether to DIY. The ties on <

> would seem to be simple to install (just a 10mm hole) and they supply to private individuals.

I'll forget that idea ;-)

Thanks, your description makes things a lot clearer along with the info on the web page.

This bit, although tedious, seems well within my capabilities.

Yes very much, please also see my answer to your follow up post.

Steve.

[Steve]

As I mentioned, the mortgage company have not raised it as an issue but their survey was less extensive than ours.

If I do the job properly and rid the house of this problem, I am hoping that it will not be an issue in the future.

I think that we will have the cavity inspected and take it from there.

Many thanks

Steve.

[legin]

Just a thought but a cavity wall circa 1927 would be very rare. Check the wall thickness as most were solid 9" construction. Legin

[Steve]

Thanks for the suggestion but the house certainly does have cavity walls. I gather that they were rare before the 1920's.

Cheers

Steve.

[Andrew Gabriel]

Depends on the area of the country, and how wind-swept/wet. In some areas, they were being used from 1880.

[Andrew Gabriel]

[Bob Eager]

Our house is 1903 and has a cavity rear wall! And we had to get the ties done, a few years ago...

[Steve]

How much did it cost Bob?

Steve

[bof]

When we bought our house the surveyor suspected wall tie deterioration, a further (endoscope) inspection showed three[1] of the four walls had a problem, I got a quote for the repairs, as did the vendors which was substantially cheaper, I wanted to use the company I'd found and used the vendors quote to get the price dropped, I then made completion conditional on the vendors having the work completed using my preferred company, and providing an underwritten 50 year guarantee, and kept to the original sale price.

The work entailed fitting stainless steel bolts as tie replacements and putting resin filled socks over the old ties in the exterior leaf to prevent ay further cracking.

[Bob Eager]

Sorry, can't remember. They did other work too, and it was years ago (required by building society).

[Steve]

Thanks very much for that bof. We have not completed yet so there still remains the possibility of negotiating a price reduction. All will be determined by the cavity report.

If you don't mind, can I ask you roughly how much it cost to have three walls done?

Steve

[Phil L]

> would seem to be simple to install (just a 10mm hole) and they supply

Yes you can do them yourself, they are easy, it's just the guarantee that buggers things up a bit but if you don't need one then by all means have a go, they normally go in a diamond pattern at 1 metre intervals, this means you drill a brick, then miss four on the same course, then drill another...5 courses up from this course you do the same again, but staggered so that a diamond pattern is formed, every third brick up each side of each window and door opening, about 1.5 bricks in from the edge....you don't do any solid parts, IE chimneys etc, depending on the size of the house, you'll need about 40 per elevation, you'll also need an sds drill with a depth gauge, don't use the resin bonded ones or you'll also need a dust remover (a blower with a 10mm spout which has to be used on each hole prior to applying the resin)...it sounds like a lot of work but one man can easily do one house per day, those doing it regularly will do two, off ladders naturally!

I've done a quick sketch of a pattern here:

>>>> I was thinking of drilling through both leafs of the wall with very

This bit is probably more important than the replacement ties, if you have (or hire) an sds drill which has a hammer only facility, you can get a thin blade which makes it a lot easier, the sleeves may be available from builders merchants or hire centres, this job should be completed prior to replacing any wall ties (it makes life easier WRT the metal detecting) and you should have a yellow crayon and mark on each joint where an old tie is (they are almost always in rows, usually 6 courses apart), once all the ties are detected and marked, cut each one out with the sds chisel, then when they are all out, go along with a small bucket of sand/cement and a pocketful of sleeves and isolate each one, doing it methodically like this cuts down on hire time for the drill and less trips up and down the ladder (you can probably reach half a dozen on each move of the ladders)

[<me9]

IME cavity walls were common from late victorian times, This may vary around the country, however.