Causes of damp on internal walls

[NT]

Causes of damp on internal walls, in order of likelihood:

1. condensation. Cause: interior RH too high. Solution: find cause/s of high RH and fix em.

2. Faulty roof or rainwater goods dumping water onto the wall. Solution: clear gutters and hoppers, check rain drainage works ok, or fix roof.

3. Leaking plumbing

4. Salt contamination: this tends to happen to chimneys mostly, but can also result from iron pipe fixings or spillages. Solution: remove and replace plaster

5. Peeing: animal or small child peeing on wall. Solution: retrain.

6. Rising damp: it does exist but is rare. If every other cause has been ruled out, and every necessary measure taken, inserting a dpc just might work. Almost all rising damp diagnoses are false.


NT

ps please ignore the poll... couldnt help myself

 

[BMcD]

Cracked tiling and faulty grouting in shower rooms/cubicles will cause damp to appear on the other side of the wall

 

[Lime]

6. Rising damp: it does exist but is rare. If every other cause has been ruled out, and every necessary measure taken, inserting a dpc just might work. Almost all rising damp diagnoses are false.

I have seen more perfectly good slate damp proof courses damaged by drilling and chemicals inserted than I care to think about.

The usual cause of a lower section of wall being damp when a slate damp proof course is in place is bridging of the slate with earth outside or water entering, descending through the wall and stopping at the slate.

Mortgage lenders demand that a modern chemical damp proof course is added when surveyors or "damp experts" report any dampness. Hence they are responsible for damaging a huge proportion of older properties.

 

[worms]

NT, I feel the condensation issue is a bit more complex than

interior RH too high. Solution: find cause/s of high RH and fix em.

If you want the house to be warm enough to be habitable and the temperature outside is cold and you have an uninsulated surface, you are going to get condensation. So the solution for this would be to sort the insulation and/or the construction.

There will be other situations where the cold surface is caused by cold air-flow patterns in wall and roof spaces where cold air ponding causes a cold surface in a heated room.

I would reckon it is a better long-term solution to fix the insulation/air flow problems than reduce the household RH.

 

[Matt Green]

- Difference in ground (earth) levels on either side of the wall.

Solid one side and suspended timber the other. This happens all the time, especially in terraces where a kitchen extension has been put on the rear and has a solid floor.

- Plaster in contact with solid floor.

Occurs on a fairly routine basis.

- Solid floors covered/modified on one or both sides with an impervious barrier.

This situation promotes ground water evaporation from the base of the walls. common in toilets in period buioldings where thick vinyl floors with upstands have been fitted.


All of which are as common as condensation in my experience.



Matt Green