It seems that when our cavity wall cowboys installed the insulation
recently they 'accidentally' drilled into one of our chimneys. They
spotted this and filled in the holes in the bricks/mortar from the
outside. However a gas installer fitted a fire last week and spotted
there was further damage on the inside of the bricks where the drill
had taken a bigger chunk out of the inner side of the brick. The gas
bloke filled in the other side of the brick he could see within the
fire place but said the others further up teh chimney could be
he suggested that the chimney wouldn't function correctly and that
fumes could seep up the bricks somehow and then filter into the loft.
(I'm paraphrasing what my wife has told me the installer said).
What I can't understand is how or why the damaged bricks would affect
the chimney, even if the bricks have vents in them the fumes can only
reach the next layer of mortar surely? Do I need to take out all teh
damaged bricks and replace or is he thinking something else is wrong.
I'm considering dropping a carbon monoxide detector into the loft to
see whether anything is seeping for the time being but just don't
fancy damaging the chimney any more than the cowboys did iin the
The safety is more my concern, however regardless of cost I'm not sure
that I should be paying if the cavity installers have damaged what
was a 'working' lined chimney. As yet though I still couldn't quite
fathom what the potential risk was and how the damaged liner affects
If you could see bricks inside it it wasn't lined mate.
IIRC you have to have it lined with either glazed ceramic flue liners or
a steel pipe these days for it to be considered 'lined'
Now gas fires are not as onerous as wood fires..but even so, there are
regulations that effectively prohibit use of a simple stack made of
bricks or blocks..its all to easy for mortar to crumble out and gases -
toxic OR inflammatory - to leak out.
Normally you would not be allowed to install a gas fore in a flue
without a liner these days. A flexible steel on at a minimum if its pre
It's a 1930's house, looking up inside it appears to be a creamy/sandy
texture which from what I've read is some sort of lime mortar lining.
I can see where the gas bloke has filled in the hole in the 'lining'
using something similar. I guess there are further similar 'holes'
further up. they are sealed from the outside with mortar but I guess
there must be two/three smallish gaps on the inside where the mortared
brick is, probably about 2 inch diameter where the lime mortar will
have come away when drilled. I guess one option is to switch to a
steel flue liner and have done with but as the previous lining was
fine till it got drilled bit annoying, we don't use the fire that
much, it just now seems to be shedding a bit of the lime mortar when
it's very windy.
IN which case I am about 90% sure you can simply use a flexible lining,
dropped in from the top.
I really recommend it anyway..its a sort of point that may conceivably
save the house one day.
Round our parts, there are at least 15 fires a year due to blown mortar
in old stacks allowing flames through to the timberwork - and often
thatch work as well. Our neighbour is a part time fireman..and a damn
useful man to know..he's cast an eye over what I have and pronounced it
Just generally or because of this damage? If it's because of this damage
then a) it's only a potential leak in the outer skin ie to the outside air and b)
as the o/p points out a leak isn't able traverse the wall to somewhere more
critical through the mortar joints. Lining for that reason appears an
Just on principal really. I would not consider a stack that had any
internal surfaces and which relied on mortar joints to be good practice
Originally they would have been lined with a nice coating of soot..but
even then chimney fires could happen and blast pretty hot gasses into
Maybe I am just fussy..brother in laws house burnt down almost to a
shell, and as I said, my neighbour is a fireman. The risk is low, but
the consequences are high. Insurance never covers everything. Why take
the risk when a few hundred quid of steel liner brings the thing
entirely up to standard and probably reduces whatever risk there is to
almost nonexistent proportions?
Gotcha and I'd be inclined to agree if the o/p was doing anything other than
installing a gas fire but the flue gasses just aren't hot enough to cause the
fire risk you're concerned about. Flames licking up the chimney, soot to
catch fire or tars from log burning then fine but for the o/ps use it seems
unwarranted. Going back to the original question, I don't think the chimney
is any more dangerous as a result to the cowboy damage.
And I'd just like to add that they weren't cowboys anyway, how is any CWI
installer supposed to know whether the wall behind the chimney is single
brick, double brick or has a cavity going straight across? - if it's the
latter, it should be insulated as this is where most heat will escape from,
and I seriously doubt the word of the second workman on the premises who has
sold this idea of a damaged chimney to the customer - the largest piece of
brick I have ever known to blow off the back of a brick was no larger than a
matchbox, hardly chimney blocking material, even if he drilled a dozen holes
through - and all holes will be pointed up externally, which means there is
no added, or diminished draught, IE, nothing has changed.
I don't think there's any excuse for breaching the chimney, if it had
previously been found to be leaking and lined with a flexible liner then that
could easily have been breached by the drilling which would have been
seriously bad news.
In the workmen's place I wouldn't have drilled near the line of the chimney
unless I was certain it wasn't single brick. They could have checked that
by depth measurement if the fireplace was open but then again there's no
need to drill on the line of the flue opening, drill either side and the foam or
fibre will flow if it's a cavity and not if it's solid, single or double.
because they install CWI for a living, you'd think they may have come
across a house with a chimney before and give it a bit of
forethought, because after the first time the drill goes through the
cavity they could check, rather than drilling into it four times and
then realising on the bottommost one that they'd filled the fireplace
this was before I discovered they also hadn't replaced/closed off all
the air bricks around the house which were now filled with insualtion
material, they came back out to replace them all a few days later
and just before they did a smoke test and put the 'expired' match onto
the mantelpuece causing it to scorch
So IMO they are cowboys at Snugasabug/Instafoam and Fibre Ltd Woking
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