Rising damp or condensation ?

[TR]

Hello

We have a problem with some of our internal walls. There is a line of salt deposits appearing which is causing the paint to bubble & plaster to crumble.

The walls previously had vinyl wallpaper which when stripped off had black mould underneath. The walls were unpainted bare plaster.

We cleaned off the mould with a bleach solution & painted with emulsion. Soon after the salt deposits appeared.

The problem areas (where we can see them) are the kitchen walls, the conservatory wall (adjoining the kitchen), toilet wall (adjoining the kitchen) & dining room wall (adjoining the toilet).

It seems like rising damp but we're thinking it may be condensation because the affected areas are all hot/cold rooms.

We would be grateful for any information or experience anyone has.

Tony.

[Val_2]

Sounds like rising damp. In old houses around here,there are no dpc's and many have floors lower than the outside ground. I've seen many a property here in Brittany that is an uninhabited ruin with plenty of salt deposits on the internal walls and no way is that condensation when there is no glass in the windows and door in the hole and quite often the roof is only partly there as well. I suggest you get a professional artisan in to assess the trouble and treat accordingly as you will never get rid of the problem.

[TR]

Thanks for the quick reply.

The house is only 18 years old.

So if it is rising damp, it means either the house was built without a dpc or the the dpc has been damaged.

Should a house of this age have been built with a dpc by law ?

How can we check for a dpc ? The house is rendered on the outside. On our house in England you could see the black line a few bricks up.

Would rising damp affect walls that aren't outside walls ?

Who would be the best person to assess it ? I wouldn't want an assessment from someone who had something to gain from finding damp.

Thanks again to anyone who can help.

[Fontremy]

Hi - we have the same problem but it's a 16th century property. I'm interested to know if any of the damp injection solutions or dehumidifiers may work? May start another thread on this specifically.

[Weedon]

If it is rising damp and it is possible to do so can you not dig a trench outside the offending wall put in a land drain to take away the moisture and back fill with gravel.

I have done that and it worked for me.

On the inside wall if you clean off the old paint etc. then paint it with uni-bond or the local PVA then paint it with undercoat which covers up any staining and then emulsion. If you just emulsion it very often the staining still shows through.

Weedon(53)

[Teamedup]

Our house is 21 years old and we certainly don't have a damp proof course as we had in the UK. All it is is black stuff painted on the outside walls up to around 6 inches from the ground. It is visible and then the crepi starts. We were told not to cover this black stuff completely which we have not done. I have never seen dpc's here as in the UK.

[Dave&Olive]

are the offending walls plastered, if so they have been damp at some stage be it rising damp or penetrating damp.Even if you take away the source of the damp the plaster once affected with damp becomes anhydrase silica and will suck in water from the atmosphere and give off the efferfecence that you are getting that is why the building regs in blighty insist you take off 3ft of plaster when you install a new d.p.c. I am sorry but pva will not stop this,can you get your hands on a damp meeter? you need to find the where the problem is before you can find a cure . it could be something silly like a leaking drain or gutter  dripping water pipe ect hope this helps........ dave

efferfessencs efferfeccence must stop drinking this French wine ..

[Teamedup]

So what does a french DPC look like? I've never heard of other than what our builders have done and am very curious.

[Dave&Olive]

sorry do not know only ever looked at older properties in france but do know what a british one looks like sorry . what sort of guarantee is there on a new build in france ?? do a search 25years in blighty might help

[Teamedup]

The guarantees are shorter than 25 years in France, I know ours is well past now.

I really have never seen other than thick black gundge being painted on the lower bricks in France to act as a damp proofing.

Someone mentioned plastering, never seen that on the internal walls either, well not on new houses or in appts. Never thought about this before, but building methods are really quite different.

[Mysfloss]

dpc in new build ,usually done with an hydrofuge(in powder form) which is mixed in water and then added to the morter in the ciment mixer.This stops the cappillary action.Its good practice to do two courses below floor level and two above with hydrofuged morter.You cant see it either so you cant tell by just looking.