Cavity wall insulation - cavity too large ????

Hi,

I've had a company round to do cavity wall insulation this week. They said they couldn't do it because the cavity was "too wide" ?!!

How can this possibly be the case?

The original surveyor who came out said my cavity at the front was massive - and that some companies would refuse to do it simply because of the amount of insulation material that would be necessary. He said those companies would frequently "make an excuse" and say it could not be done.

Well... that's what his company has just done. They said their "brush" that stops the insulation from spilling over into neighbours properties "won't fit in" because the cavity is too large.

hmm.. sounds like BS.

What do other people think? any comments / opinions / recommendations for the Lancashire area would be appreciated.

Pete, Preston.

Reply to
prhubberstey
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Completely true, although 150mm brushes are available, as compared to the regular 75mm ones they normally use

The brushes are put down from top to bottom to stop the insulation spilling into next doors cavity, which by law is classed as trespass, and this is what causes damp, because 'their' insulation will not go from DPC to roofline as yours will - it's only when insulation is stopped halfway up a wall that water can track across from outside brick to inside block.

Have you measured the width of the cavity yourself?- if it's over 150mm, then you may as well forget it.

Reply to
Phil L

It /may/ be true, how wide are your cavities?

You could always get your neighbour to do his walls at the same time then it isn't an issue.

When I had mine done they didn't know the cavities were bigger than the standard and they were worried they would run out and they had another job to go to.

Reply to
dennis

huh? damp? You lost me with that one... I wasn't told that damp was the issue.

Can you explain how damp penetrates through the insulation if only half the wall is done? I presume you mean half done as in vertically? who could it cause damp for - me or the neighbour?

I remember looking through the original surveyor's scope - I would guess it to be around 170mm - not much more than 6" but definately more.

Reply to
prhubberstey

Damp isn't the issue - yet, the issue is trespass, which could lead to damp.

It can't get *through* the insulation because it's waterproof, but it can travel across the top of the insulation if it stops halfway up a wall, which is why it's installed to the top and also why one flat out of a block cannot be insulated, unless it's ringbeamed.

Water naturally passes through the outer leaf, IE the brick, and it runs down the inside of the brickwork until it reaches the DPC or a lintel (which usually have weep holes for this very reason)....if the cavity is partially filled, this water runs across the top of the insulation and soaks into the inner leaf, causing damp.

The neighbour, because yours would be 100% filled, but you would be responsible when it went to court and then instead of paying thousands out in damages, you would naturally blame the installer, which is why he isn't doing it.

The largest brushes I ever seen during 14+ years of installing it were 6 inch (150mm), and these were used in a four inch (100mm) cavity, because they have to stay in place by compresion of the bristles....I suppose they could twist 2 or even 3 of these together as they are only thin gauge wire with nylon bristles

Reply to
Phil L

I once fitted an extractor fan through a brick/brick cavity wall of an Edwardian theatre green room/bar and was amazed to find that the cavity was about 12" at that point. I used a liner of aluminium sheet to span the gap.

Reply to
Frank Erskine

How do these brushes get fitted, out of interest - through holes? How do they get into position?

David

Reply to
Lobster

A hole is drilled at the top of the wall and another at the bottom, a steel chain is fed into the top and allowed to drop down until it reaches the bottom where a hook ( most often a bucket handle bent into a hook shape) is in place....the barrier is attatched to the protruding chain at the top and pulled through from the bottom, so that the barrier follows the chain into the cavity and then the chain is removed.

We were often asked to do a flat out of a pair, or just do 'upstairs because the bedroom's freezing', and could we not put a barrier sideways....no one could seem to understand that gravity wouldn't allow us to drop a steel chain sideways.

Reply to
Phil L

Tell you what guys - just a complete ignoramous comment but I just find this totally beggars belief. In the 21st century we're saying that we can't insulate a gap because it is too big. Totally beggars belief.

Reply to
prhubberstey

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