Cavity wall te replacement

[czdbkx]

About a month ago we moved into our new house - it was built in 1904 and is a 5-bed semi in the Davenport Park Conservation area in Stockport.

It was a tortuous process getting through all the surveys and as part of the conditions on the mortgage certain works need to be done during the first 6-months. I'm OK on all of these (tiles, rainwater goods, gulleys, wiring etc) except one. Purely because the house is 104 years old and has cavity walls - the surveyor has insisted that the cavity wall ties will be decayed and need to be replaced - there is no evidence that the walls are distorted - my conversations thus far with specialists say that they will need to drill through the centre of the bricks (2.5 per sq metre to meet modern building standards). The house is half rendered but the bottom half will be disfigured by this process - one alternative would be to drill from the inside out but this would not be possible everywhere - e.g. in the kitchen where fitted units are in the way and it would cause a great deal of mess. I can see no need to this- what do you think?

My only fall-back position was to get in touch with a surveyor recommended by Stockport Conservation Officer who is coming to look at the house on 15th May.
Any ideas would be much appreciated. Clive

 

[andrew gayton]

I would suggest that you investigate the condition of the existing ties via some selected internal opening up, utilising a video camera to monitor screen set-up, to establish exactly what the current condition is; I know that people have used them to look at underground services, so why not in internal walls? unless they have been insulated??

 

[Matt Green]

Just to echo Andrew, it's definately worth opening up a small section. A cavity wall from that period may not have metal wall ties, I've seen a copule of buildings of that era with single bricks bridging the cavity.

Matt

 

[Mark]

And hearsay evidence says that this is another of those things that surveyors are churning out as 'needs doing' regardless of reality. Along with the DPC injection and woodworm treatment.

I would be asking for the evidence of a problem.

 

[Nemesis]

But if there is no sign at all of failure, why do it? Guarding his own back probably.

My only fall-back position was to get in touch with a surveyor recommended by Stockport Conservation Officer who is coming to look at the house on 15th May.

I would go for a second opinion...

 

[chuckey]

My victorian house has no wall ties. I have seen on the telly one house where during a tornado a large part of the outer skin had been pulled off (12' wide X 20' high) because the outer skin does not carry the weight of the roof.
If your contractors are experts, and wall ties need a slope to stop water running along them, why don't they drill slightly uphill through the mortar course in the outer skin, into a brick in the inner skin. Then only the mortar would need colour matching.
Frank

 

[Gervase]

You really do need a second opinion, as your surveyor is almost certainly parroting bunkum merely to cover his 4rse. Nearly all pre-1981 buildings are routinely (and wrongly) regarded as having suspect ties, yet it is rarely a real issue unless it involves a high-rise or cross-wall building - which it ain't in your case. You need to speak to someone like Richard Oxley or a similarly experience surveyor from the 'seeking specialists' section of this website - or hopefully the surveyor suggested by your conservation officer.

 

[andrew gayton]

or.

'if it a'int broke'.................

 

[Nemesis]

I'd certainly be challenging the surveyor for evidence of failure too, and if a second opinion states that there is none - asking for my money back!

 

[PC]

Most wall tie contractors will stick an endoscope into the cavity to inspect the tie. If they show any signs of corrosion then they will recommend replacement. However its the bit between the bricks you need to inspect and even if corrosion exists it doesn’t mean its failed!

It's expansion of the tie that's the problem as this can 'jack up' the masonry (particularly at high level) and this is when the tie fails and the masonry is at risk. Vertical twist ties can, in extreme conditions expand to 7 times their normal size and this can cause cracking and opening of horizontal mortar joints throughout a buildings height.

Investigation needs to be by brick or mortar removal and not just by using an endoscope. Weather conditions and aggresive mortars will also excelerate the corrosion process.

In my opinion a vast majority of the wall tie replacement undertaken in the 80's and 90's was completely un-necessary and more importantly has cosmetically scared many buildings for ever more. Great care must be undertake, particularly when removing or isolating the old corroding / expanding ties.

PC

 

[Gareth Hughes]

more importantly has cosmetically scared many buildings for ever more.
PC

I found Barbara Cartland and Fanny Craddock cosmetically scary

 

[andrew gayton]

come unitary I see a glittering career in comedy for G.H

 

[Gareth Hughes]

come unitary I see a glittering career in comedy for G.H

Anything to get me out of Conservation.

 

[andrew gayton]

and what could i do??

 

[Gareth Hughes]

and what could i do??

Cut a glamorous sequinned female assistant (or failing that, Nemesis) in half?

And rejoin the halves too, of course. Possibly using lime mortar.

"The Great Gaytoni"? Perhaps not.

 

[andrew gayton]

or..............'great pasta with the great gaytoni'

celebrity chef-dom here i come...................

 

[Gareth Hughes]

or..............'great pasta with the great gaytoni'

celebrity chef-dom here i come...................

Vey brave, with Delia on your doorstep - we've all seen what she's like when she's had a couple...

 

[Nemesis]

Cut a glamorous sequinned female assistant (or failing that, Nemesis) in half?

You 're pushing yer luck Hughes.

Watch it. Or I might be 'aving you.

 

[chuckey]

Something else occurred to me, if you drill the the centre of an outer skin brick, the chances are that as the drill exits into the cavity, that a bit of brick will spall off into the cavity. Of course if you don't use a hammer drill and you drill carefully these piece will be small. If you are on a bonus and you use a hammer drill, the piece of brick that spalls off could be 1/2 the face of the brick and about 1/2" thick.
Frank

 

[adrianth]

A related thing I've been meaning to ask for ages:

We too have a 1910-ish cavity walled house. I read somewhere that in this era cavities were more intended to stop wind-driven rain than as insulation, and a surveyor mentioned that similar houses down the road had very chunky iron wall ties. This suggests that adding cavity wall insulation to such a house would be a bad idea, as it could provide a bridge for moisture, or at least slow the ties from drying out if they ever get wet. Is that right, or were the Edwardians just wrong about the function of the cavity, and it works (dry) just like modern ones? And does the lack of zinc coating on old ties make cavity-filling insulation a bad idea in any case?

Interestingly, we were admiring the Acropolis in Athens a few of weeks ago, and they're taking all the temples to bits. They were stitched together with steel pins about a century ago, and the pins are rusting and blowing the masonry apart. It's all being re-done with titanium instead, plus new carved stone to allow all of the chunks that have fallen off over the millenia to be put back in place. Really amazing project!

Thanks for any comments (we aren't actually considering cavity insulation, I'm just curious). Adrian.

PS. I forgot to mention: as far as I can detect, in our case there is only a damp-proof course on the inner leaf of the cavity, and it looks like some sort of tar (applied liquid, then set), definitely not slate. Don't know how unusual that is!