plasterboarding on stone walls

[oldgit72]

I am intending to plasterboard the kitchen and bathroom walls in order that I can then tile onto a flat surface. I am using 63x38mm batons to take the boards. My question is, should I insert a barrier between the boards and external stone walls to stop any moisture penetration or will the gap between the walls and boards prevent any damp ingress? I should add that I am planning to use ordinary 13mm plasterboard as the shower I will be installing is the cabin type so no need to tile inside the shower cubicle.

Thanks

[ericd]

Hi, why not use the tile adhesive to make up for any difference? Tiling platerboard directly could cause water ingress and make the job look bad. At a push, slap some concrete on the stones to create an acceptable flat area and tile on top.

[broy]

eh?

[Théière]

Why not use hydrofuge? made for the job and only a little bit more money.

What are your walls made from, limestone, granite?

 

 

[ericd]

Oldgit du 72 wants to have a flat surface to work from for his tiles. Instead of using plasterboard to get back to a flat surface (that could absorb water), he could ciment the same and tile over.

[oldgit72]

Hi, The walls are limestone and I already have a surplus of ordinary plasterboard that I can use as long as I can prevent any moisture getting in. I was thinking that as the bathroom will only have a shower which will be inside an enclosed cabin that the only moisture might be absorbed from the walls through the gap between plasterboard and the outside wall and I was looking for a way of preventing this happening.

[andyh4]

1.  In a situation like yours I would not use timber batonning - use metal studding

2.  You should have a vapour barrier

3.  Because kitchens and bathrooms can become very steamy, you also need ventilation

4.  Irrespective of the shower cabin, I would use the hydrofuge board for the bathroom.  You could "get away with" normal board but over time it will suffer.  By definition a bathroom has a lot of moisture around, this does evapourate and condense on cold surfaces (aka your walls)

[Théière]

[quote user="ericd"]Oldgit du 72 wants to have a flat surface to work from for his tiles. Instead of using plasterboard to get back to a flat surface (that could absorb water), he could ciment the same and tile over.[/quote]

As Andy (oldgit) has stated his walls are limestone and therefore cement cannot/must not be used as it will fall off over time.

As the walls are limestone you must use a vapour barrier between the wall and plasterboard, you could probably paint the plasterboard with sealer to waterproof it as well but in all honesty I would still use hydrofuge.

 

[ericd]

At the time of my answer i was not aware of the nature of the wall. I stand corrected and agree with your advice.

[BIG MAC]

Only my take on this however I agree with the metal stud (You could use ceiling rail if going up tight to the wall to reduce profile) 

I would always use a studded membrane which will allow damp to pass up and down the wall the way it always did this helps maintain the equilibrium in the wall matrix.

The stud will allow the insertion of insulation which again will make things more comfortable and also create a dry  space for running cables etc.

If working to an existing floor I would fasten the bottom rail screws through some plastice (I use the sides of oil bottles or similar) to create about a 3mm gap I also insert off cuts of rail at approximately the level of  3/4s the way up the skirting board.

If you board down (And I would concur use the proper board) but leave about a 5mm gap to floor level and paint the bottom edge of the board with any old oil based paint or bitumastic making sure not to bridge the 'Gap' or come above the level of skirtings.When fitting skirtings you can use either plastic ones (YUK) or if timber the silocone baseboard strip for kitchen plinths (Skirtings should  be primed and painted front and back before fitting, then installed to maintain the gap) you will end up with a relatively cheap well built flat warm wall which will allow any minor condensation to pass below the skirting without affecting it.

The important thing is  as it's well insulated the condensation will be minimal the studded membrane and gap at the bottom will allow it to pass freely.    The boards will be unaffected and electrics safe......sounds complicated but really it isn't and if you compare the cost of retiling because the wall wasn't up to it I am sure you would agree in the long run worth it.

PS. Window reveals foxed me for a long time however if you use cellotex type insulatation and 'Aquapanel' then you should be able to offer up to existing window or door frame, secure by fastening leading edge to your studwork and timber quadrant to frame.

Hope this helps.

[oldgit72]

Thanks all for the advice. I am struggling with 'studded membraine'. Could you please explain what this is and where I could get it from? I also have some bathroom satin emulsion that I was going to paint the reverse of the boards with. Would this help with preventing moisture intrusion?

[Théière]

Studded membrane

http://www.treatdamp.co.uk/ecom-prodshow/oldroyd_xv_damp_proof_membrane.html

[LesFlamands]

There are all sorts of things you can do:

You could use a SPEC on the inside of the plasterboard.

Treated battens will be fine but I would build a wall rather than fix the battens to the existing support.

Ventilation is the key. Upper and lower vents every 1.5 to 2 metres and good airflow in the void and you'll not have any problems

[BIG MAC]

I disagree with the ventilation comment. we do not ventilate the inside of a wall anymore than we ventilate the ground.  What we are looking for in this type of situation is a minimal airspace which allows the free passage of moisture across the face of the rubble wall. The stone is to a degree impervious whereas the mortar is less so...If we keep the inside of our houses warm and dry then in single leaf arrangements moisture is attracted from the wall to the inner surface via capillary action. If we put in a separating medium  (studded membrane) then insulation (Cellotex or similar) The rubble walls will be of a more uniform temperature and less prone to damp coming in in the first place. You will be more comfortable, the surfaces by virtue of boarding will be level and true. Theres no need to ventilate the very small area between stud membrane and wall other than if you have suspended timber floors you may wish to have the membrane protrude below so that any moisture may migrate below the floor. Generally speaking the top doesn't require sealing as in practice there is rarely sufficient warmth to allow water to vapourise and climb the wall, any which does should condense and migrate down the membrane  (If you wanted to you could gun in a small bead of funny foam (Mousse expansif) along the top edge once metal stud is in placeThese are only my thoughts on the matter but I did spend a lot of time talking to barn restorers and preservation specialists before forming my own ideas for economic ways to achieve the same ends.

 

 

[LesFlamands]

Well, I have taken down a number of 'facing' walls usually made of pot brick to find green mould growing on the stone wall behind. There is probably rising and penetrating damp in the wall which is why the facing wall was built in the first place but replacing the wall with plasterboard on a metal frame with insulation and not providing some way for the moisture to escape from the void will only result in reducingthe lifespan of the new wall and insulation. In other circumstances where water is literally flowing through the wall there is little alternative to fitting a channel drain at the base and building a wall in front of it but ventilation is still a good idea if only to protect the new materials.

[Pat and Don]

We are sealing our plaster board prior to tiling by painting it with PVA - although the board is faced onto wooden battened interior non-stone walls. ( We also found PVA was MUCH cheaper in the UK than here.)  

[Anton Redman II]

PVA is much cheaper in UK but it is water soluble. If you have not used the green hydrofuge water repellant board I would find a dedicated sealer or check the instructions on the tile cement. 

[gyn_paul]

Nobody has asked any of the vital questions:

Do these walls have a DPC?

Is damp ingress currently a problem?

Are you planning to heat the room?

Does this shower cubicle have a lid to it?

Is there also a bath in there?

I've installed shower cubicles in bedrooms - and in one case in a box-room in a typical UK 3-bed semi which it shared with computers and printers - without any problems. The only MUST is that the cubicle has to have a lid. If there isn't a free flow of steamy air circulating round the room then the use of the shower injects hardly more water vapour than a tray of 4 cups of tea sitting around. If there isn't a bath, and the room is heated, then condensation really won't be a problem. I'd go for using the available resources you have and forego the hydrofuge !

If the wall doesn't have a DPC then I'd definitely fit a sheet plastic vapour barrier directly against the stone, then pack the space up to the framing with lots of insulation. The plastic will stop moisture from the stone progressing any further, and - since it's well-insulated  - there is no air circulation, so no possibility of condensation.   

 p

[BIG MAC]

I refer the learned gentleperson to my previous postings.

[LesFlamands]

[quote user="gyn_paul"]< - there is no air circulation, so no possibility of condensation.   

 p

[/quote]

Why?

Placing a non breathing membrane against a cold stone/brick wall is just right for creating condensation. If you can hermetically seal the void and then create a vacuum in the space then I would agree that there would be no condensation.

[gyn_paul]

Why ?  Where is this warm, moisture-laden air coming from to continuously condense out ?

If the total volume of air in the void is captured (and held static within a body of insulation) and not circulating (i.e. there are no draughts) then the tiny amount of water vapour contained in that volume of air is fixed and not continuously being replaced and/or added to.

A static temperature gradient will be established between the outside and the inside and - yes - this will vary slightly between the seasons, and within that temperature gradient mols of water vapour will be either 'filming' on the cooler part, or held in vapour state on the warmer part, but this will be essentially a steady state and very slight. - we're talking damp detectable with a meter here, not sopping wet fibre-glass.

On the outside wall side of the impermiable membrane, things will, of course, be much damper, but - unless the stone has been rendered impermiable on the outside - the rain wetting, and rising damp will breath out of the stone.  Unlike plastering directly on the inside of the stone, the Non-breathing membrane will have no 'wicking' effect on the moisture in the stonework.

If there's no source of moisture laiden air then condensation is not a problem, which is why we don't ventilate the space between joists at the first floor level, even with warm living rooms and cold bedrooms the volume of air in the temperature gradient between the downstairs ceiling and the upstairs floor is virtually sealed. No matter how damp the air was when the floor boards were nailed down it's not a problem.

 

p

[ericd]

Gyn-Paul has a point. For moisture to condensate, you need moisture in the first place.

Can i turn this posting into a question for my own usage. There is a great video on YouTube showing you how to insulate/plasterboard your loft area (a commercial video from Isover but the detailed explanations are good) www.youtube.com/watch?v=gn35DzLU_eU

As you see from this very informative video, they put their insulation between rafters first then perpendicularly fit another slice of insulation then seal the whole lot with sheets of heavy gauge polyethene in order to stop draughs coming into the loft area. The plasterboard comes on top of the plastic sheeting.

This in itself is also creating a sealed enclosed area as there will be double glazed roof windows etc......what about internal condensation if only from the basic survival operation of breathing???

Your comments are appreciated. Merci.

[BIG MAC]

The thrust of waht I said was to create an impermeable and a thermal barrier by use of studded membrane and insulation allowing both a dry wall finish and a service void.

Dependent upon floor make up there may be small compromises to be made however the principle is that if you isolate the wall but allow it to breathe across its face (Behind the studded membrane) you create an atmosphere where the wall will be less likely to dry out (Not good with a clay and rubble matrix wall).

These old walls are best repairered using traditional and compatible methods prior to creating the dry compartment. 'Cementitious solutions'   or paint on barriers are rarely appropriate, neither are sheet plastic bodges. You can  in some circumstances get a volume of water sitting between the membrane and wall not neccessarily through condensation but things like water table and ground level can all be factors this is why if possible to extend the membrane down into a solum or even a pumped sump then the scheme should last for a considerable period of time.