Damp in a (solid) wall of a 400yr old house

[BritinFrance]

Can anyone help out there?
I have a solid wall (530mm) made from local stone with lime mortar. The exterior is faced with a rendering, which I suspect is a cement rendering put on with a tyrolean and not a lime based product which would allow the wall to 'breath' (But not positive.)
The base of the wall, to a height of approx 760mm/30" is rendered with a cement decorative rendering.

Inside the same wall to chest height is plastered "Aquaboard" or French equivalent. Above which is plaster (possibly lime based)

While this type of wall has to retain some degree of moisture, what we have is capillery action damp. Some so called experts recommended chemical injection, but I've heard from other sources that in this type of wall, it is unlikely to form a solid membrane.

Sorry its so long to get to the point, which is, If I remove the lower cement rendering on the outside, to be replaced by new lime mortar, then rip out the aquaboard and make good with a lime plaster (pig to work with) do I have a good chance of profiding sufficient 'breathing' for the moisture to despell and thus solving the problem?

Phew, it would have been an easier explanation if you could have seen my arms waving about!

Seriously any advice is most welcome.

Regards

Jim

 

[stuart45]

Lime mortar will help the walls breathe. On the exterior its best to use a hydraulic lime as this is more resistant to the weather.
Some companies in Somerset are now using lime on the exterior and sand/cement render with added waterproofer on the interior. The idea of this is to keep the damp away from the inside and let it come out on the exterior.

 

[wavetrain]

Considering you are in france, I am surprised that 'french drains' not been recomened since AFAIK this is the treatment of choice for this type od building.

http://en.wikipedia.org/wiki/French_drain

But if you wish to/also consider chemical methods, you should use a gravity method with silicon fluid where you allow the liquid to soak the morta over 2 or more weeks. Injecting methods do not allow time for the liquid to soak all the morta resulting in a dissapointing final result.

If I was in your position I would do Stuarts method and digg a trench on outside anf fill with stones. It doesn't need to have a drainage pipes to have a usefull effect, the action of the stones is only a small amount of the wall a little below GL is wet, compared to soil which ensures the wall below GL is wet most of the year

 

[JohnD]

cement rendering at the base of the wall may be to prevent water splash, e.g. from absent or leaky gutters. Check and fix if you have these problems. Or it might be to hide blown stone from frost when wet.

 

[BritinFrance]

Thanks guys

(Stuart also sorted my lintel probs)

On the French drain front...... I'm sure this wasn't suggested because right round the house is a 4 - 5" thick concrete path.

Seems to me, if I cut of the decorative rendering (no tears shed over that), replace with hydraulic lime, then cut a 12" wide trench, do the gravel bit then cover it with a 2 inch thick mesh reinforced cast slabs. (To provide access on a just in case basis. If I really get clever, I'll fit then into a metal rebate.

That should give a b****y chance of eradicating (good word that) the problem........What do you reckon?

Cheers

Jim

 

[BritinFrance]

left out 'good' after the b****y ......

 

[alittlerespect]

You ideally need to have a 150-200mm (6-8") gap between the wall to the house and the path, having the path come up to the house will encourage moisture penetration - hence the reason for the perimeter french drain - any moisture/water is allowed to drain away or evaporate before it becomes a nuisance.

Whats happening to the interior of the walls is partly due to the issues to do with the path (at a low level), and the remainder is going to be related to either surface and/or interstitial condensation caused by warm air meeting a cold surface/element - warm air holds more moisture than cold air and when the warm air is cooled air reaches saturation point and moisture is deposited either as surface and/or interstitial condensation. The specialist plasters while being moisture resistant will not be vapour resistant and the vapour will penetrate into the structural wall and condensate when it meets a cold element of the structure (thermal bridging). The only long term solution to your problem is to introduce thermal insulation to the warm (interior side) of the external walls).

When it comes to installing the insulation you will need to keep a minimum 25mm (1") cavity between the insulation and the external wall, the easiest way of achieving this would be to stick 25mm bitumen impregnated board to the wall as small dabs - say 100 x 150 and then stick an insulated plasterboard to the dabs, if you use a PIR insulated plasterboard you will not need to worry about introducing a vapour barrier. A 50mm PIR board will give you a significant improvement in thermal insulation or if you wish to meet best practice go for an 80mm PIR board.

Regards

 

[BritinFrance]

Une mille mercis

Thanks so much for your detailed instructions. With so much on a long list of 'to-dos', not necessarily large projects, one gets to the point of no see the wood for trees. This has given me both a solution and focus.

Once again

Thanks

Jim Martyn