I want to insulate a room which has two exterior walls. These are
solid stone walls around 0.75metres thick. What is the best way to
deal with the job?
I have bought some 3*2" timber to "box in" the slabs of insulation.
The 3" side will be slightly proud of the insulation board, which I
intend to glue to the walls also.
I then intend to screw plasterboard to the timber.
Is this a correct approach.
I do not think there is any rising or penetrative damp, but I have
found that in very cold weather it takes around 4kW of electric
heatingover a period of three hours or so to get what is actually a
small bedroom warm and the condensation can trickle down the two
exterior walls when the room temperature starts to increase.
Our last house had 9" solid brick walls and when renovating it I insulated
all the exterior walls. This was 22 years ago so the materials available
were somewhat limited.
I battened all the walls first with pre treated 2x1" timber. Then nailed 2"
polystyrene sheet over the battens. Next a sheet of polythene (I was told to
do this to prevent interstitial condensation) Finally I screwed on 1/2"
plasterboard then had the whole lot skim plastered.
This system gives an air gap between the insulation and the old wall which
adds to the thermal value. Due to the uneven walls the gap varied from the
1" thickness of the battens up to over 3" inches in places!
We lived in that house for 16 years and it was very easy to heat and never
suffered with condensation. I still keep in touch with the folk we sold it
to 6 years ago and only last week they spoke of how warm they were during
the cold snap.
750mm thick are some walls, I wonder why unless they are chunks of
hewn granite or you live in a castle!
Most random stone/rubble walls have a 225mm inner and outer leaf with
loose rubble between and are normally around 500mm thick.
What you are proposing will work, although depending on how plumb the
interior surfaces are you could save yourself a lot of work by using
insulated plasterboard such as Gyproc Thermaline, or Celotex PL3000
board. You will also not eat into the room space as much either.
Another route is to use multi layer reflective foil blanket such as
Tri Iso super 10. Fix 25x50 treated roofing battens to the walls then
stretch the blanket across, fix counter battens over followed by
12.5mm wall board. This method has the advantage that the Tri Iso acts
as a vapour barrier to prevent any risk of condensation behind.
Without knowing anything about the specifics of your property it's
hard to advise further however.
Many thanks for the reply. The wall thickness is an estimate, it was
around this length of drill that was used when I ran cables through
It is made from various types of stone/ rubble and is typical of the
houses in the SW of Ireland around 150 years ago.
I bought the Quintherm in England, most items I use are taken out from
here as materials can be very very expensive in Ireland.
I did buy the timber over there though as it was a bit weighty and
doesn't seem too out of kilter price wise.
Ditto for the plasterboard.
I have two approaches in mind, the one stated in my previous post
where I frame and glue theQuintherm panels, then apply plasterboard to
the framework. This would leave relatively large sheets of
plasterboard supported only around their periphery.
An alternative would be to adopt a similar technique, but to use foam
on the wall prior to inserting the panels. This would hopefully
produce a completely level surface, i.e the quintherm panels flush
with the frame, and I could screw and glue the plasterboard to the
quintherm and frame.
I presume that the foam and panels would act as a vapour barrier? The
wooden framework just being plugged into the wall. Or would I have to
protect the wood from damp?
Historically the house was very dry, but now some of the rooms [In
this case two bedrooms] are used very rarely.
I gather that these houses are excellent when the heating is
maintained. My ancestors had an unlimited supply of turf though and
never had the experience of the sinking sensation that comes with an
invoice for a delivery of smokeless
It sounds as if your walls are not plumb vertical. If you want the
plasterboard to be vertical then you either need to effectively build
stud framing as planned which is fixed between the floor and ceiling,
then fit Quin between and wallboard over- or you could possibly fix
Thermaline boards back with foam.
While the foam is curing but you would need to hold them in place with
3x2 timbers wedged vertically between the ceiling and floor so that
their faces are against the plasterboard.
Many thanks, I thought this might be the best option.
I wonder, could I trouble you for a suggestion as to the best
foam to use for the application?
I use ductsealing foam at work and in a previous job have used
foam for insulation of instrumentation. Looking at it when it's a few
years old, a lot of the stuff seems to go dark and powdery.
So if you have any suggestions as to brand or what to look for, I
would be very grateful
[Default] On Sun, 12 Dec 2010 02:31:07 +0000, a certain chimpanzee, H.
750mm thick walls! I'm surprised it takes hours to warm it up - I
would have thought weeks would be more like it.
Big thick walls will have a very high thermal mass which will take a
lot of energy to heat. The upside is that they will retain that heat
over a long period (days at least). By having the heating on for short
periods, all you are doing is heating up the air, and if you're lucky,
the first few millimetres of the wall. The condensation is the
moisture in the air coming into contact with the still cold surface.
A highly insulated inner surface will allow the air in the room to
heat up quicker, and not to pass into the structure, but will leave
the fabric of the building cold. Nothing wrong with that per se, but
you need to have a vapour barrier (e.g., polythene) on the warm side
of the insulation and keep the studs clear of the wall to prevent
damage by condensation.
Do you not have some form of permanent heating in that room, such as
central heating or a fireplace? If so, then you may be best to run the
heating at a lower level for long periods/permanently.
"If no-one on the internet wants a piece of this,
Yes! The main room is occupied and if a fire is kept in it does warm
up. It isn't perfect but loft insulation for that part of the house is
on my to do list.
The heating in the bedroom of interest does take hours during winter
to get the room anywhere near habitable. After half an hour of
removing the heat source the whole room is freezing again.
Only electricity at the moment, and as the room is used very
infrequently it would be hard to justify anything more than an
I was thinking about a vapour barrier, but if it's on the warm side of
the insulation wouldn't it be superfluous as the moisture wouldn't
condense on a warm surface anyway?
I have a roll of sheeting that I was going to use on the loft of the
main area of the house. It did cross my mind that it may be
advantageous placed directly on the wall prior to fixing the timber. I
think it may be best to avoid this though if possible, because I would
like to minimise the amount of frame I use by applying foam as a bed/
bond for the insulating board.
I was hoping however that the quintherm and foam would be impervious
to moisture anyway. This would mean that the only direct path of heat
and moisture conduction would be the 3*2 wooden frame and any slight
gaps that I might miss when pressing the Quintherm home.
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