What is this stuff in our cavity wall?

[gasket]

The boiler is on our garage. We’ve just had it moved.

where the flue went through the wall, the inner thermolite block was always missing. I guess it disintegrated when they drilled the hole.

stuffed into the cavity around where the flue passed through is all this stuff that looks like a long length of bottle brush.

ive never seen it in a cavity and suspect that a previous owner has stuffed it in there for reasons unknown.

I’m just about to replace the missing block and seal it up, before I do I thought I’d better remove it.

the only thing I can think of is that the walls are filled with those little grey polystyrene balls. Maybe this stuff is to stop it all falling out around the old flue.

any ideas?

 

[freddiemercurystwin]

Yes the previous owner was stupid.

 

[cdbe]

Yes, it's put in when they blow in insulation, usually between you and next door, but also round the flue.

 

[freddiemercurystwin]

Well now that's embarrassing.

 

[John D v2.0]

Its very similar to what you can put in your gutters tostopleaves getting stuck in there. But clearly it has more purposes as mentioned above

 

[gasket]

Ace - thanks folks!

As much as I’d love to pull it out, with the risk of getting drowned in insulation balls coupled with the knowledge that it clearly isn’t going to do any harm (no transfer of moisture), then I’ll just leave it be and will brick it in.

Freddie - don’t worry mate, my gut feel after 3 years of fixing the previous owner’s bodges was that he was an idiot and had stuffed gutter-protected down there too.

 

[cdbe]

Quite clever how they do it - drill holes at the top and bottom of the wall, feed a length of chain through the top hole and catch it with a hook through the bottom hole and pull the brush through.

 

[bsr]

It's called a brush seal. As above, a normal part of cavity wall insulation.

I would fill the cavity with a piece of celotex or some expanding foam fixed to the inner skin. Otherwise you might get a damp patch there.