Pigletjohn - a question about rising damp

[chunkiebride]

@PigletJohn

I know you are a crusader against damp / condensation caused by people drying washing indoors.

I wondered if you could give me your thoughts on rising damp?

I have one wall in my house that suffers for low down patchy damp areas. It’s creeped in slowly over the past 6 months.

I’ve had a few people come in telling me it’s rising damp.
One was a damp specialist so I ignored him, the other was a roofer who said that he has experienced similar and believes it to be rising damp.

I’ve always been a sceptic if rising damp having lived in many old properties without damp proof courses but wondering if it’s true and that I will have to succumb and get the damp proofed out?

Watching with interest as I have the same in my back room - slowly rising damp wall with no damp course (Victorian stone terrace, damp only recent).

Check - is the ground outside higher than the floor inside? Is there a flower bed or path that is raised up against the wall?
Is the guttering or a down pipe leaking and making the wall wet? Or a pipe in the wall? Or an overflow?
No signs of blocked airvents?
All these can cause damp.

I had this and it was a problem with inadequate subfloor ventilation. A few airbricks sorted it.

However, every property is different and obviously the cause of mine might not be the cause of yours!

How high is the damp patch on your wall? Are there any signs of mould? As another poster has said it may be that the ground outside is higher than the floor inside.
Have you looked at the cement between the exterior bricks?
Have you done any major work in your garden recently?
It wouldn't hurt to get a damp specialist in anyway, perhaps 2 and listen to what they have to say. You are under no obligation to commission them.

Outside ground is lower than inside
Drainage is clear
Guttering has been replaced and working
Roof has been checked for leaks
There is no Mould growth just mildly wet patches with flaky paint

What is your mortar like?

It’s in the one part of the house that has a concrete floor - no ventilation (unlike dry part of house which is floating wooden floor)

It’s only about 30cm of the floor is the highest point of the damp in this section.

It’s hardly damp enough to make the wall wet to the touch though, just enough to flake the paint

External mortaring is concealed by render.
All tender has been checked for any signs of cracking or holes and it’s all clear

concrete floor, you say.

Is it a kitchen?

About how old do you think this floor is?

And the rest of the house?

photos would be interesting.

Have you got a water meter?

Is there anything on the concrete, like vinyl flooring, or a mat?

Yes it’s a kitchen

Extension was built in 70’s, then further out in 80’s.

The flooring on top of concrete is engineered oak (on under lay)

No water meter.

There was a mains leak under said concrete floor earlier in year which was found and capped and then dried out for 3 weeks with industrial heaters

Rest of house built 1905.

I have photos which I can post up when I’m back home

External Render? Does that go to the ground? ..or are the bottom couple of courses of bricks showing?

External render and then it goes down to a black ridge before the ground. This is the same all the way around the house

"There was a mains leak under said concrete floor earlier in year which was found and capped and then dried out for 3 weeks with industrial heaters"

that's just the sort of thing I had in mind.

How do you know if the slab is now wet, or now dry? The heaters, fans and dehums would have been pointing at the walls.

How do you know that there is now no leak under the floor? l

We know there is no further leak as we actually re routed the mains from underneath the house to around the back of the house to ensure there was no possibility of it.

We were in a rush to get in, the heaters were pointed at the walls.

The place appeared dry after 3 weeks.

It’s very likely that it needed further drying but we needed to be in.

Could the residual moisture left in the floor still be coming out now and causing this?

The room in question has been left without heating since (until yesterday when a rad was installed)

Now a radiator will be keeping it warm and the dehumidifier working to remove moisture, I’m hoping we might see some improvement?

Yes, it's possible. If there is any part of the concrete floor that you can see, tape some plastic to it and see if damp forms underneath.

There could still be damp in a kitchen from leaks round the sink, washing machine, dishwasher, drains or radiators.

Pencil round your damp marks and photograph them, watch if they get bigger or smaller.

Post pics here please.

If you have a fan, point if at the damp patches and they will dry out faster. Heat not required. The windows will steam up from water vapour so turn your extractor on.

Can I jump in on this thread too please...

Any advise on if this is rising damp?

Thanks

looks like a water leak to me.

stand back and show the whole wall from the floor up, and put something in it for scale. A 50 piece or a CD case.

Is there a bathroom on the other side of that wall? Or a leaky drainpipe?

What's the floor made of?

How old is the house?