Should I point the interior stone walls before insulating and plasterboarding them?

[Rtony]

I've looked through the many posts about interior stone walls but can't find an appropriate answer.

I've removed all the old (rotten) plaster and raked all the joints in the stone walls in the back room of my old house near Fontenay le Comte.

I was going to have all the stone repointed then fit metal or wood studding, insulation and plasterboard with a skimmed finish.

One builder said I should have all the walls 'rendered' with enduit then skimmed. Another builder said don't repoint or render the walls, just fit metal studding, insulate, plasterboard & skim.

Any helpful comments would be appreciated.

[Quillan]

When you say 'rotten' do you mean through moisture?

If there is moisture you need to put a membrane in first with possibly a 'drainage' on the wall side. Then I would use metal studwork at 40cm centers and double up the verticals (two rails screwed together) to give it strength as you won't have plasterboard on the back. If you don't double up the wall will flex a lot, I know because I did this without doubling up and ended up redoing the wall.

Go to Brico Depot and get a catalogue if you don't have one already to work out the price then look at the your first builders solution of rendering and skimming. The problem, if you can call it that, is the cost of labour in France. If you went down the rendering route you might consider rendering yourself, it's a lot easier than plastering, you can use metal or wood to drag across and make it flat. As long as it is virtually flat you don't have to worry to much about the finish as a plasterer will deal with that. You might find that going the latter route might be a little more expensive than going the other way but not so much more considering the labour costs.

[Rtony]

Hello Quillan.

Thanks for that.

The plaster was very old and the house had been empty and shut for over 2 years. I would say that there's no moisture (or very little) in the stone. 3 of the walls are internal.

I think I'd be inclined to have the walls insulated. Isn't it essential to fill the joints between the stone?

[Théière]

[quote user="Rtony"] Isn't it essential to fill the joints between the stone?[/quote]

It depends on the depth of the now missing mortar joints. It isn't necessarily essential as it provides a bigger surface area for moisture to be evaporated away from. I have done this on a soft red brick wall in London to aid the drying out process, later re pointed with lime not cement as previously done which was one of the damp issues. If and with the benefit of being on site they recommend for structural reasons, maybe clay is all that is left in the wall to hold it together then re pointing may be needed but rendering, no really as Q says metal stud etc

[Quillan]

Why insulate internal walls? I don't know your house but you could clean and repoint them and have them as a feature. The outside wall if you want to insulate it (which is a good idea) then there is no point [;-)] in repointing it. It's not the pointing that holds the wall together, pointing is to stop water getting into the joints and possibly what you think is old pointing is just the old plaster forced into the joins from before. It's the 'adhesive' between the top, bottom and sides that holds the wall together.

Having made a suggestion of leaving the internal walls 'natural' there is however a negative side and that is running things like electrical cable for power sockets and perhaps pipes for central heating. If you use studwork you can put all the gange etc in before you put the plasterboard up and nobody will see it.

[Rtony]

In some areas of the walls there are voids at least 15cm deep.

We have some rooms with stone feature walls which are enough for the moment. There are another 5 rooms to do where we could have them.

This is what one of the builders said:

Your walls are dry stone walls and are not suitable for plastering. Also re-pointing will take a long time and the walls will remain cold. The main requirement when renovating houses with dry stone walls is insulation. It is not necessary to point the gaps in the wall before boarding.

The other builder said the opposite!

I've seen no end of stone houses that have collapsed. I always assumed that it was because the pointing had failed.

[Quillan]

I'm no expert but there are plenty of stone walls around that have been there for over 100 years and the bits that fall down are mainly due to human intervention. The pointing would stop air and moisture coming through the joins but if the joints are pointed on the outside I would have thought that would eb good enough. Tell you what if you have had two Divis both saying different to each other then get a third and go with the majority. By the way are these English builders in France?

[mint]

Our first house was a renovated stone building.

The interior walls had plasterboard walls and insulation between the original stone walls and the new plasterboard walls.  It was thus very well insulated and, when we sold it last year, the buyers (French) were delighted to have an entirely new house inside a venerable old stone shell!

Some "stitching" and filling in of obvious gaps in the old stone walls were also done exteriorly.

In fact, in this recent cold weather, OH and I were a bit nostalgic for our well-insulated old house[:D]

[Théière]

[quote user="Quillan"]

Why insulate internal walls? I don't know your house but you could clean and repoint them and have them as a feature.[/quote]

I have assumed, that this is re pointing of the internals before insulation is applied to the walls which I took to be the external walls otherwise yes there would be not much point in insulation on the actual internal walls.

[quote user="Quillan"] By the way are these English builders in France?[/quote] the point being, beurre wouldn't melt in a french builder's mouth? Seen plenty of good and bad work from both.

If there are voids 150mm deep I would certainly look to fill those. We can't see your walls so it's on conjecture from this end.

[Gluestick]

A wall is held up by its own weight. For example, drystone walls can last hundreds of years: if correctly built. Mortar is primarily used to "bed" the stones, bricks, blocks whatever. It isn't glue. It mainly prevents the wall substance from moving sideways.

However, pointing is only, as Q and T have, err, pointed out (sorry! [;-)] ) to prevent the ingress of water and moisture.

If one is covering internal walls with a second fix of insulation and plasterboard etc, then it is wholly pointless (sorry once more) to re-point the wall, beforehand.

One caveat: old stone walls must breath, or they die. This is mainly why "choux" is used, rather than cement pointing and mortar. Therefore when covering old stone walls in insulation and then gypsum based wallboards, do consider ventilation.

[mint]

[quote user="Gluestick"]

One caveat: old stone walls must breath, or they die. This is mainly why "choux" is used, rather than cement pointing and mortar. Therefore when covering old stone walls in insulation and then gypsum based wallboards, do consider ventilation.

[/quote]

Gluey, sorry to interrupt you in mid-flow but the word is chaux.  We have some massive chaux mines near us in St Astier and the stuff is exported all round the world.

You must have been thinking about the pastry you were baking in that fancy oven of yours?[:D]

[crakpot]

Hi

I renovated two houses, now on my third since 1996 , there is no point in re pointing old walls or skimming the plaster boards as for heat insulation I imagine the air is still, ie not moving, behind the Plaster boards so no more need to be done

As for old stone walls need to breath or they die , its odd that they are still here for millions years in the wet and in the dark and still here to day

[Gluestick]

[quote user="mint"]

Gluey, sorry to interrupt you in mid-flow but the word is chaux.  We have some massive chaux mines near us in St Astier and the stuff is exported all round the world.

You must have been thinking about the pastry you were baking in that fancy oven of yours?[:D]

[/quote]

Thanks, mint. Mind not thinking in French at present. Plus laziness, I ought properly to have checked it before posting.

However, I do much like such extravagant delights as Profiteroles, as it happens!

[Rtony]

Thanks all, that's a lot to consider.

To take the advice of the majority I think I'll be doing the following:

Fill the deep voids with a sand and lime mortar, then have studding (wood, or double thickness metal at 40cm centres) erected, fit the electrical wiring in conduit, insulate, plasterboard, skim, fit sockets and switches.

The room is 480cm high at one end sloping down to 240. Is metal studding stable/strong enough for 480cm?

When that's done, the ceiling can be insulated and boarded, leaving the bottom half of the beams exposed.

Have I missed anything?

[NickP]

We built a partition wall that was 15 ft high using metal studding , although we did put double plasterboard either side, solid as a rock no problems at all. We also built a downstairs shower room, to form a cavity wall for water pipes etc.the builder stuck the metal studs to the wall with plaster; nothing has moved or cracked did the job perfectly. Great product .

[Araucaria]

One reason why you might want to do a very rough lime finish over all these walls with open joints - even ones you'll eventually conceal with plasterboard - is to provide less of a home for the mice. Or conceivably sparrows, depending on what kind of stone you have.

One of the problems with stones held together (or if you prefer, apart) with mud is that small creatures can remove it quite easily. The pointing isn't just to keep out moisture.....

[Rtony]

Thanks everyone.

I just need some email addresses of decent plasterers near Fontenay le Comte now.

Regards.

Tony

[Quillan]

[quote user="Rtony"]Thanks everyone. I just need some email addresses of decent plasterers near Fontenay le Comte now. Regards. Tony[/quote]

http://www.pagesjaunes.fr/

 

[Rtony]

Thanks.

I've plasterboarding questions so I'll start a new thread.