Wet wall

[EskimoJo]

We are having some trouble with damp on one of our kitchen walls. The wall is a large exterior gable which is very exposed to the weather. Being a 1950s house I thought at first that the damp course may have failed. After doing some research though I'm now not sure as most advice seems to be that rising damp only rises to a height of 1m or so? We actually found damp above the wall cabinets when decorating. Also a bedroom (directly above the kitchen) has fitted wardrobes and the walls there also seem damp (a little black mould and musty)

Also, yesterday I fitted an outside security light to the wall and noticed that when I was drilling, rather than the cement from the fixing hole being dusty and dry, it was wet and stuck to the drill bit rather like a paste. (The fixing holes were drilled into the mortar rather than the brick)

Any ideas what this might be? Is it possible that the brickwork is porous?

Any suggestion appreciated

 

[motorbiking]

What kind of wall is it? cavity, solid ? some pics would help. Is it worse when it rains, or cold?

 

[dishman]

There could be many causes.

Have you checked the roof? Gutters? Is there any drainage pipe work above?

We once had a mouse chew through a pipe in the cavity. So waste water was coming down the cavity and we were getting wet walls below. A very simple explanation.

Are the overflow pipes above this area? Is your house well insulated? Do you have enough ventilation?


Do not start jumping to conclusions as to the cause. The fact you seemed to think it was rising damp or the damp course had "failed" or that the brickwork is porus is concerning. These are all things that rogue and ill-informed damp specialists point the finger at and encourage you to spend large amounts of money on damp injections, tanking the walls etc or even painting the exterior of the property (big no no).

You have to look at everything objectively. How you live, the age of the building, have you used incorrect modern building practices i.e wrong type of plaster.

-----

Based on the locations you have mentioned, above cupboards on kitchens and in the bedroom above in or around fitted cupboards. This sounds like a simple case of not enough ventilation! This is just an initial hunch and something consider.

Warm air holds more moisture than cold air. So all the moist air produced in your kitchen circulates the room. As the air cools, it can no longer hold the water vapour and it can condensate on a cold surface. Areas especially prone to areas of poor air circulation (behind and above cupboards).

The solution? Especially when using the kitchen, do you have an extractor? Do you use it? Ideally you should have another fan with a humidistat which will automatically come on if the room is too humid.
Same for the bathroom.

The average household produces 15+ litres of water vapour per day. This water vapour has to go somewhere! If it is not dealt with via good controlled ventilation, it will end up as condensation on cold exterior walls. This ends up as a damp mould wall.

 

[EskimoJo]

Hi thanks for the replies

""What kind of wall is it? cavity, solid ? some pics would help. Is it worse when it rains, or cold?""

It's a cavity wall filled with wall insulation (the fibre type, installed around 20- years ago now). It appears to be no different whatever the weather as far as I can tell. I've been to have a closer look and some of the pointing higher up isn't great, in fact in some areas there is moss growing into the joints, I suppose this wont help.

""Have you checked the roof? Gutters? Is there any drainage pipe work above?

The roof seems ok as far as I can tell, there are no gutters on that side and no pipework visible (there is just a kitchen extractor outlet)

""Is your house well insulated? Do you have enough ventilation?""
The cavities are filled , its double glazed and has a loft extension with 100mm insulation between the roof joists etc.

I've never been sure whether its a damp or condensation problem however with the mortar between the external bricks seeming to be wet I wondered if there could be another reason altogether.

 

[dishman]

As I said, have you located all the pipework that runs through the cavity. Have you excluded any leaks? These could be tiny (a pin hole even) and it is tracking down the cavity. Have you given the loft a good inspection.

People often do not realise that the mortar in brickwork is designed to be expendable. A brick wall is designed to be able to breath. The mortar is meant to be the most porous part. The first thing to erode, should be the mortar. This in turn protects the brickwork. When an impermeable mortar is used or bricks are painted, you end up have bricks with spall (basically implode) as the moisture can't escape.

What kind of ventilation do you have in the bathroom and kitchen?

 

[vinn]

OP, are you still there?