dry lining a solid sandstone house

laxeylady

Ive posted before about our damp old house and been given some fab advice, so here I go again. Previous owners of house have lined the rooms by putting up chipboard walls but this has caused damp problems. We have now relined two bedrooms by chipping off the old lime plaster from the external walls and then putting up a wooden carcass a good few inches away from wall and lining with plasterboard. We have made sure the ceilings go to this false wall and not the sandstone one, and chopped back floorboards behind too. We then put some vents in. The theory is that now we will have some air movement behind the false wall. However... we planned on doing same downstairs too but that room has external vents for the suspended floor. Would this cold air coming in get behind our false walls and cause cold spots and condensation on the back of the plasterboard? Are we causing potential problems for ourselves, and how else can we do it?

dlm4473

laxeylady, what brought you to the conclusion that the boarding had caused your damp problems ?

There are many reasons for dampness and unless you identify the problem from the start you may never fix it properly, and waste a lot of time and money - in heating alone - trying.

A sound sandstone wall does not need any ventilation ! While it may appear to 'help' with your damp issues - all you will achieve is to provide a good flow of warm air through your walls which will help dryout damp. But this may push the problem up into the loft space

Have you checked for example roof/flashing leaks, condition of pointing exterior and interior, around window and door openings, level of ground around property has not bridged damp course ?

Ventilation will only be required under lower floor (make sure to insulate between floor boards) and above insulation in attic space.

In short the main habitable parts of your home can ( and should) be as air tight as possible - only windows, trickle vents and fans are required ventilation.

laxeylady

Thanks for the reply. I have reread my original post and realised that I have not explained myself very well. The house has had water getting in from a chimney (which previous owners had repaired) and two badly fitted pvc windows (which we have replaced). This meant that there was very bad damp and mould BEHIND the chipboard walls. The walls themselves did not cause damp. Sorry about that. We could smell it, but had to remove walls to find it. The lime plaster was in a right mess. We have had to line the walls again because otherwise the rooms are flipping freezing!! So you think we needn't have provided ventilation then? We want to make sure we do the ground floor rooms properly so your input will help with that. Cheers again.

owls

If its an old sandstone house with no cavity in the wall there are different options to do it,
chipboard walls thats a new one on me.
why cant you plaster drectly over the existing wall using a plastic membrane system,sand cement render and traditional plastering thus retaining heat in the room and preventng it escaping or condensation appearing,as previously said the wall doesnt need any ventilation, bar under the floor boards on the ground floor wth something as simple as an air brick.
If you have already done it i hope you havnt used standard plasterboard and instead used a vapour check plasterboard or a thermal plasterboard and treated timbers, not only that but you are reducing the size off you rooms installing stud walls.
If the walls are damp there are a number of different tankng systems available,in my opinion errecting stud walls is a last resort.

laxeylady

We have only dry lined the external walls - the internal ones were replastered - so no great loss to size of room. We don't think the walls are damp, all the water that has gotten into fabric of house has come from chimney, windows and roof (all of which have been repaired or replaced). We have been told that using sand and cement on sandstone is a VERY bad idea so have avoided this. We will have to see how the two completed rooms react to our treatment before proceeding on any others.

owls

You miss understand me the sand cement backing is applied direct to the membrane and not to the sandstone,
in any case i dont know why theve told you applying a sand cement backing on a sandstone background is wrong unless it is of very weak substance and crumbling away as ths would fail as the background is weaker than the coat applied.
Im a time served plasterer by trade and ive completed numerous projects over the years of similiar nature on a sound sandstone background,the house i live in now is constructed of york sandstone and i plastered it in this nature years ago and it is fine.
Obiously it is hard to make a proper sound judement without viewing it myself in person,but i suppose like most other buildng issues you will get a wide variety of opinion from different tradesman.

laxeylady

Owls your response is much appreciated, and you're right - we have had so much conflicting advice it makes you frightened to ask! It was a plasterer with a good reputation that suggested the boarding out and adding of vents and subsequently carried out the work. Another told use to use lime plaster, another told us you could not get such a thing these days, and yet another said that since the mortar was lime which allowed movement using sand and cement would be very dodgy indeed. I am intrigued by your suggestion as this one is new on me and could be the perfect solution to our downstairs. Thanks so much for taking the time - you're a gent.:beer:

owls

you can still get lime mortor both for external appications and for internal uses.
they are correct in that lime does have movement as it needs to breathe and obiously if you directly sand cement directly over it it doesnt allow for any expansion,it may shrink but you can add hydrated lime to your mix or various additives these days or fibres to allow for any expansion,if you are plastering directly over it.
Theres nothing wrong with boarding it out using a thermal plasterboard and treated timber or metal stud but there are better alternatives.

no problem, im off with flu at moment hence why im on here in the middle of the day

laxeylady

Owls - hope you're feeling better? We have been looking at the system you mentioned and had a query - does the membrane have insulating properties? (the one we saw was like eggbox almost so assumed the blebs would have some insulating qualities??).