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Space saving internal insulation

I have an end terrace with solid brick walls. I have suffered with damp caused by condensation as the bedroom walls don't see the sun know the winter, and moisture condenses on the inside surface. I have insulated my loft, but the walls remain very cold to the touch, and any picture hung on them wrinkle because of moisture.
I have bought some 4mm wall rock polystyrene rolls (pre lined with paper), which I have papered one room and the difference is great, warms much quicker and the walls obviously feel better, however I want a plastered finish. Does anyone see a problem with dot and dab general plasterboard on to the walls and fixing with screws into ready placed wall plugs? (I presume dot and dab on to lining paper isn't a great idea?)
I know how proper internal insulation should be done, but I can't afford the loss of space, and I feel this solution will make a great difference with minimal impact on the room.
Should I be concerned about moisture? My thinking is that the polystyrene seals the walls, therefore moisture can't condense on it. The polystyrene is attached to the wall using proper wallrock adhesive.
to summarise:
1)as I am thermally insulating the wall with Wallrock thermal lining (polystyrene with lining paper pre attached) can i dot and dab on to this, or will i need mechanical fixings?
2)as the cold wall is sealed with the paper, is there a risk to moisture causing problems behind the plasterboard? say moist air rising through floorboards then up the back of the board - should I vent the boards top and bottom, just top? even seal the bottom of the board from rising air?
3)would I achieve anything by using thermal backed board, i heard you cant dot and dab foil backed board? i was planning on using plain plasterboard and skimming over the lot once in place.

2 Answers from MyBuilder Insulation Installers

Best Answer

If you are definetely sure that the damp is just condensation coming from the inside of the property and not penetrating damp coming from outside the property then insulated plasterboard put on the walls is definetely your best bet. The best way to install them is the dot and dab method, I have done this on a couple of rooms this year that customers were complaining to be too cold due to old 'solid' walls with no insulation. Dotting and dabbing over lining paper is not a good idea so be sure to remove that 1st before commencing, but you can definetely dot and dab straight over painted surfaces without needing any pre-treatment as long as it is not flakey, loose or really shiney gloss paint, I have done this many a time. Screws are not essential to be honest , the last job i did i dot and dabbed over the painted surfaces and didn't need screws. The plasterboard companies often reccomend screws for fire safety reasons. If you do use screws , just dot and dab your walls as normal and then use hammer in fixings afterwards. Make sure to add in a few airvents at the bottom of the wall after the plasterboarding to let any trapped moisture escape. You can get foam backed insulated plasterboard between 30mm and 100mm, the thicker it is the warmer your room will be, but it depends on how much space you are willing to sacrifice in your room, if it is a really large room then 100mm boards won't make much visibal difference. Boards cost about 30 quid each and one bag of drywall adhesive should be enough to put up two boards. If the problem definetely is condensation from inside then i can guarantee that these foam backed boards will work.

I guarantee your best bet will be to do without the insulation wallpaper fullstop and you definetely can't dot and dab over it, just dot and dab your walls with foam backed 30mm plasterboard, the foam backed boards do not have a foil backed finish that is a different type of board for ceilings etc. You will not get the screws to line up if you are putting in plugs before hand that is not the normal method, you would dot and dab the walls and then put in special fixings afterwards which you can buy from any builders merchants.


Answered 31st Dec 2016

The best solution is to insulate externally and render finish with silicone render, this will resolve problem and reduce heating bill.

Kind regards

Dr Paul D Rogers
PhD Construction Management
Chartered Building Engineer
Expert in Building Defects- Property Refurbishment & Renovation- Client/Contractor Disputes.


Answered 31st Dec 2016

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