Loose blocks along inside wall


Postby bouncer » Thu Jun 03, 2010 8:17 pm

I have noticed that along two of the faces of my house (south and east) that there are horizontal cracks forming at the top of the inside walls. There are 2 cracks about 1 ft apart and I'm fairly sure they follow the line of the top course of internal blockwork.

In fact I have stripped back the tiles in the bathroom (to redecorate) and uncovered a part of the damaged blockwork. In the corner of the wall, the top block there is actually loose and I can wobble it with my hand. The mortar around the block has turned to dust.

Now I'm unsure what to do. It seems as though the top course of blocks have been affected along the complete two faces of the house.

Some extra info: The house is probably 1950s and the previous owners had cavity wall insulation put in. I think that the internal wall is higher than the external brickwork to account for the pitch of the roof and because of that the CWI stops slightly lower than the top of the blockwork - about to go up in the loft and inspect it.

I'm interested to know if anyone has seen this before. I'm nervous of getting in someone who does not properly assess the problem in case something serious is up. I've included some photos here to help.

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Postby stoneyboy » Sat Jun 05, 2010 11:48 am

bouncer,
If the mortar has become dust then a poor mix is part of the problem.
Fitting the roof and nailing into the wall plate probably disturbed the top row of blocks before the mortar set properly (if it set at all).
end
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Postby bouncer » Sat Jun 05, 2010 7:10 pm

Thanks, that confirms what I have been thinking.
It turns out that a new roof was fitted some time ago, and in fact there are even new timbers along the end of each of the original roof timbers. Presumably, all the banging from the fitting of the new roof has done this.

A builder came round today and suggested the same as you. He says that it is highly likely that everything is in a stable position and putting in slate and new mortar around the top course of blocks would probably be the best course of action. He would plan to do this from the inside only. Does this sound sensible?
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Postby stoneyboy » Sun Jun 06, 2010 8:09 pm

bouncer,
Haven't the faintest idea what slate will do for.
I would suggest wetting the joints, spreading a fine mortar mix along the joins and working this in with a sprayer/trowel.
Removing the top course of blocks and re-setting them will probably do more harm than good.
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Postby bouncer » Wed Jun 09, 2010 8:12 am

I have had two builders in now. One says that the wall was probably disturbed putting a new roof on and everything should be stable. The other is worried that the roof was/is? splaying out and taking the wall with it. He suggests getting a structural engineer in.

I suppose that is the sensible thing to do but is there anything I could look for myself to work out if the wall is stable or not? Other suggestions I have had is to tie the top course of blocks to a few of the low courses to add stability, then finish up with new mortar.
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Postby stoneyboy » Wed Jun 09, 2010 9:48 pm

bouncer,
"The other is worried that the roof was/is? splaying out and taking the wall with it" Very unlikely - if this was happening the wallplate would be moving outwards. Take a level and check that the top of the wall is still reasonably vertical.
If you want to stabilise the top of the wall pin expandmesh along the top 500mm and render over this.
end
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Postby TheDoctor4 » Fri Jun 25, 2010 5:35 pm

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Postby bouncer » Fri Jun 25, 2010 7:24 pm

I've finally got some new information which answers a lot of questions but unfortunately brings about a few more.

What I thought were loose block are actually finlock concrete gutters that were cut off by a roofer, replacing the outside facias and guttering with upvc and leaving the internal finlock guttering between the wall plate and top course of blocks. This was done in 2003

I've read other forums and this is apparently the best way to deal with them but there is no mention anywhere of a problem where they move years later (and I've been in touch with the roofer who claims never to have seen this problem)

Underneath the finlock was some sort of black felt and my best guess is that when the guttering was cut off, the balance point of the gutter left over changed and allowed it to compress this felt in an odd way so that the blocks fell in the way they did. I have been told that the old gutters were likely to have been leaking so maybe another cause is that felt soaking with water, freezing, defrosting and breaking down the mortar beneath the finlock causing it to fall.

I've gone for the option of drilling out the old mortar and packing it with new (a builder did it for me) but only in my bathroom so far. The rest of the house shows this issue and I don't know if I should be paying to get it all seen to - or just leave it alone?

The other thing I've found out is that there is no insulation where they cut the finlock back (celotex should have been used) and now that causes a perfect cold bridge which is why I see condensation at the top of my upstairs ceilings in winter.

Has anyone come across a similar issue where cuting finlock back has resulted in the rest of it moving around - and what did you do about it?
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Postby TheDoctor4 » Sun Jul 25, 2010 7:52 pm

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