We have two en suite bathrooms, either side of the central wall in the
house, and on the roof above is a large Victorian four pot chimney. The
bathrooms were installed around thirty years ago, so the walls are
probably now plasterboard rather than original lath and plaster. Within
each bathroom is a recess, either side of the original chimney breast
(one recess in each bathroom).

Due to failure of the flashing (?) on the chimney, water seems to have
run down the inside of the granite wall until it hit both recesses where
it came through - both recess are tiled. The result is that the
plasterboard has swollen, and there is now a crack (1/8 inch or
thereabouts) all around the external angles of both recesses, although
the tiles themselves are still firmly in place.

The chimney problem is being fixed (not by me!), and the plan is to
allow the plasterboard to dry, scrap out the cracked grout and replace.
Does that sound reasonable, and how long should I wait for the PB to
dry?
--
Graeme

The plasterboard will dry but if it has swollen as you imply it will not shrink back. The only real cure is to replace the damaged section of PB. I would make sure that the tiles are actually still firmly glued to the PB and not just wedged in place by the grout. If a repair is not possible and matching the tiles not possible as long as the tiles are secure you may just have to put up with some wider than ideal grout lines.

Richard

On Thursday, 4 February 2016 08:46:56 UTC, News wrote:
We have two en suite bathrooms, either side of the central wall in the
house, and on the roof above is a large Victorian four pot chimney. The
bathrooms were installed around thirty years ago, so the walls are
probably now plasterboard rather than original lath and plaster. Within
each bathroom is a recess, either side of the original chimney breast
(one recess in each bathroom).

Due to failure of the flashing (?) on the chimney, water seems to have
run down the inside of the granite wall until it hit both recesses where
it came through - both recess are tiled. The result is that the
plasterboard has swollen, and there is now a crack (1/8 inch or
thereabouts) all around the external angles of both recesses, although
the tiles themselves are still firmly in place.

The chimney problem is being fixed (not by me!), and the plan is to
allow the plasterboard to dry, scrap out the cracked grout and replace.
Does that sound reasonable,

if they're firmly stuck, but I expect they won't be

and how long should I wait for the PB to
dry?

months, I'd get on & grout, it won't stop it drying. Use waterproof grout.


NT

In message ,
Tricky Dicky writes
The plasterboard will dry but if it has swollen as you imply it will
not shrink back. The only real cure is to replace the damaged section
of PB. I would make sure that the tiles are actually still firmly glued
to the PB and not just wedged in place by the grout. If a repair is not
possible and matching the tiles not possible as long as the tiles are
secure you may just have to put up with some wider than ideal grout lines.

Excellent, thanks. Yes, I realise the PB will not shrink back, and yes,
the tiles seem very firmly attached. The cracks are at the 90 degree
outside corners of a recess, so happy to scrape off where cracked then
refill, even though the join line will be wider than normal.
--
Graeme

News Wrote in message:
In message ,
Tricky Dicky writes
The plasterboard will dry but if it has swollen as you imply it will
not shrink back. The only real cure is to replace the damaged section
of PB. I would make sure that the tiles are actually still firmly glued
to the PB and not just wedged in place by the grout. If a repair is not
possible and matching the tiles not possible as long as the tiles are
secure you may just have to put up with some wider than ideal grout lines.

Excellent, thanks. Yes, I realise the PB will not shrink back, and yes,
the tiles seem very firmly attached. The cracks are at the 90 degree
outside corners of a recess, so happy to scrape off where cracked then
refill, even though the join line will be wider than normal.

If you think they might crack again it might be worth using
sealant instead?
--
--
Chris French


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In message , Chris French
writes
News Wrote in message:

Excellent, thanks. Yes, I realise the PB will not shrink back, and yes,
the tiles seem very firmly attached. The cracks are at the 90 degree
outside corners of a recess, so happy to scrape off where cracked then
refill, even though the join line will be wider than normal.

If you think they might crack again it might be worth using
sealant instead?

Good point. However, the leak above was very much a one off, caused by
heavy rain and wind from an unusual direction. Many other people in the
village had a similar problem. In our case, the problem is poor
flashing (?) around a couple of chimneys. Scaffolding is in place as I
type, so fairly confident the PB will dry over time, and future cracks
unlikely. Fingers crossed ...
--
Graeme