old house with damp porous bricks - solutions?

[riffraff]

Hi All,

My parents in law have an old house near the sea in France that seems to have been built with a porous kind of rock and mortar.
It apparently was a popular building material years ago.
We think that the walls draw moisture up from the ground or outside and as a result one of the walls at least suffers from damp/mold inside.
They have been told that there is one method for dealing with this that involves drilling a number of holes a certain distance apart and placing some kind of cannister inside that repels the damp or something.

I was wondering if anyone has heard of this or have any other suggestions as to how to deal with this? I have been reading up on general damp proofing concepts but i keep hearing conflicting advice.
In my completely novice mind i would have thought that if its drawing moisture from the ground one method would be to put in some sort of waterproof layer between the ground and the walls.
And if it is coming from outside then there must be a way of sealing the front of the walls with some chemical?

Any comments or suggestions very welcome!
Thanks in advance.

 

[Blagard]

Not one for the UK forum really. Different country, regulations, materials and climate. The French use some hollow blocks that may be what you are talking about. Get a picture uploaded so that at least there is a chance of identifying the material

Maybe even get a picture off Google Maps with a street view!

 

[RedHerring2]

As Blaggard suggested, you're best seeking local help 'cos they'll have more experience, but I'll give a bit of guidance, if it'll help.

Old houses in France are normally built of stone, (en pierre) using mud-like mortar, or built from cob, which is basically the mortar used soley as a building material. Cob is made from mud, cow poo and animal hair, much the same way as used in Devon, Cornwall, etc.
Obviously this cob is not very weather resistant. Cob walls need rendering to provide some weather resistance.
The walls rarely have any damp proof course. (dpc)
If built in stone pointing will help provide weather resistance.

The houses were used with plenty of ventilation, open fires to encourage that ventilation, so moisture/damp was dealt with by allowing the walls to breathe. This is achieved internally by the use of a permable plaster on the walls, sometimes a cob like substance, again.

Bearing in mind that often, the winters are shorter than the UK, and the summers drier and warmer, depending on the location, of course.

So you really have two choices, return to the traditional type of occupation and materials, or update to modern techniques and materials, e.g dry lining with vapour barriers, etc.

Another point to watch out for is that sometimes old houses do not have the internal finished floor (ffl) above the external ground level. This needs some consideration to reduce any penetrating or rising damp.

This is my current project, in France:
//www.diynot.com/forums/viewtopic.php?t=237971

In one corner the internal ffl was about 1 meter below external ground level. The terrasse took care of that and the little steam that used to come through the walls during rain.

 

[riffraff]

Thanks guys for your replies!
Very helpful as usual...

 

[mointainwalker]

This mention of canisters sounds very like a "Dutch sytem" that is peddled under various names - none of which currently occurs to me (or maybe Vranken ) and which have a very poor reputation -