Advice on insulating a granite house in Aberdeen

[rt29781]

After deciding to move back to Aberdeen from SW France we have finally bought a house there after months of trying.  It is a traditional semi detached bungalow in need of quite a lot of renovation.  http://www-r.aspc.co.uk/cgi-bin/public/LiveProperty/293489?ID=FKDJMNDA#picture
Not sure how long that link will stay live for.  These houses are made of granite with an inner skin of lathe and plaster (or plasterboard).  Traditionally, it is said, there is need for a lot of air to flow between the granite and the plastered wall.  Hence they are difficult to heat.  Recently in our quest to find a house we came across a house that had expanded foam in the cavity (for over 20 years) with no apparent issues.  Should we consider that as an option or remove the plasterwork and add insulation before restoring the walls?

We have the ideal time now as lots of work needs done.

The url for our French house that is for sale is in the footer......

[biff]

good morning rt29781,
                    the first thing i would do is put as much between the granite and your living quarters as possible,may i suggest that you strip by the the laths and plaster on all the external walls,point the granite and fill any holes,then errect a radon barrier directly on to the back of the granite surface.the radon can be hung from the wallplate.it is a bit expensive but well worth the money,do not puncture the barrier.
  then step back 50mm and errect 65,, sheets of kingspan right round the perimiter of your new dwelling, the kingspan can be temp secured ,jammed between the ceiling and the floor, then errect a studded partition of 50mm x 75mm@400mm centres,verticles. noggins ever.
    now gently hook a wall tie (you can make these yourself out of s/s) through the kingspan and pull tight to the back of the studwork,secure with a 25mmscrew on every verticle stud.
    infil the stud with precise cut kingspan and clad the lot in 12mmfoil backed plasterboard..
     if you can get up above the ceiling lay at least 15mm of foil wrapped fiberglass between the joists.invest in thermo vynl and cork for your floors and your house should be as snug as a bug in a rug.
 the method describes is clean and healthy,the material is expensive but the labour is semiskilled,especially if you use the tapered edge plasterboard sheets, goodluck with your purchase,,,,,,,,,,biff
   

[biff]

i meant 150mm of foil wrapped glass fibre,,,,,,,,,

[stannn]

Biff
How do you trap the radon barrier at floor level? I thought that this gas percolated upwards through the floor.
Stan

[rt29781]

Hi Biff,

Many thanks for the reply.  I found this :
http://www.radoncouncil.org/BARRIERS.HTM

It suggests testing for Radon so I will do that first.  Looks like I will have to take the inner walls down, thought I would, I hate taping plasterboard........There are also government think tanks that have been looking at insulation of old houses as it is of course a big issue.  May also try to contact them.

Not sure polythene is any good at stopping gases....normally permeable to gases.

[Fintray]

I totally agree with Biff, pull down the lathe and plaster and start from scratch it will be well worth it and if you are going that far get your new walls skimmed with plaster bit more expensive but gives a good smooth finish.

[wookey]

External insulation always better than internal. Better for struture of building and for thermal mass, and you can avoid thermal bridges and rotting joist ends and host of similar issues. Generally less work to fit too, so seriously consider this option.

Standard Radon barriers are just very thick polythene AIUI. That's a separate issue from which side of the wall the insulation is fitted.

[Fintray]

Wookey

Somehow I don't think that rt29781 will get planning permission for external cladding despite its benefits 

[biff]

hi again folks,
           it would be possible to bring the radon barrier 200mm onto the house,underneath the stud and kingspan,leave a 200mm strip and then look to see if the rest of the walls are stud,if this is the case then layer the floor right through in radon barrier,there are different qualities of radon barrier and the type i am suggesting is a red heavy duty reinforced with fibre, its expensive but it is very good, after you stick it,you can lay your vynl on top of it and join the seams at the base of the external wall with the proper adhesive.
                 a sump can be installed underneath the hall floor with a vent running through the sump from front to back,(a100mm drain pipe,black),, the problem is that the internal walls might be solid(i dont think so), the stack wall will be solid for sure and maybe the spinewall. so the last thing you want is a radon barrier finishing at the skirting board, you are better with none than that,
    the main aim is to seal off the granite from the house,meanwhile the house should be well vented.it is possible that the granite comes from many miles away and that the soil is radon free(it that were possible).i would look upon it as a great oppertunity to insulate your house to a high standard but i would not attempt to go for passivehause standards in this case.
                                                                                                    biff

[rt29781]

Hi all,

I realise that external insulation is the best option but the wife would kill me irrespective of the planners.....

Will insulate as much as I can and also see if Radon is seen as a problem in this area of Aberdeen. 

[biff]

the main aim is to seal the granite off from the house,,,,,
                                                          biff

[biff]

rt29781,
       i wobbled a bit with regards to your granite exterior,i reread and realised i was not making myself all that clear.so let me try and get it across a bit better.
       the granite exterior is desirable to some and one can see why, its one of the oldest rocks on the planet and also one of the hardest wearing. however it is not user friendly and not suitable for indooor use and on no account should you clad it and prevent it venting to the open air. this is precisely why the radon barrier should be hung from the wallplate and sealed at the bottom.it would be a good idea to leave vents high up but with an exit that curves up and around the eves and gutter.
 granite is without doubt the perfect barrier against the elements, but you dont need it inside your dwelling.
                                                                                                                     biff

[wookey]

Planners can't stop external insulation unless you are in a conservation area (in general). I thought they could until I checked/asked.
Wall coverings are permitted development AIUI.

But unsymapthetic wall-coverings may well get you extra objections, which won't help.

[dhaslam]

You could cheat a bit with the plaster to look like the original.

http://sherry158.en.made-in-china.com/product/aoVEMTBYaHhl/China-AS-Cast-Finish-Concrete-Stucco-Surface.html

[stuartiannaylor]

Dunno, I just did the front room of our 100 year old stone front terrace. Not enough cavity to be worth while.

I left the old plaster in place as it was structurally fine and "dab & dot" insulated 50mm kingspan plaster board. Whilst doing this I cleared a lot of debris away from the walls that was collating moisture. Went crazy with filler foam.

Yeah there are better ways but for me it was the easiest and cheapest. In fact Travis perkins had an uncollected order of the 50mm boards and got 4 for £25 each.