Possible rising damp

[miket1982]

Hi

Im after a bit of help. I've finally got around to pulling out a corner unit and can see possible rising damp. Last winter the wall was wet to touch, all the way up to above the concrete on the photo. Its on the start of an extension of a old detached house. Its obvious the previous owner has tried to do something to fix it or hide it

The damp in on the west wall. We had an old chimney removed last April from our south facing wall, we know this was leaking. I was hoping this was causing the damp problems and removing it would fix it.

The wall hasnt been wet this winter like last, but we've just pulled a unit out and wallpaper off and the very bottom of the wall is still wet. Its reading 33 on the moisture meter at the bottom of the wall and 17 were the wallpaper was wet historically.

Is this rising damp or could it be moisture from the chimney leak still in the wall nearly a year later? There wouldnt have been air circulating here because of the unit.

If it is rising damp is it worth installing dry rod?

Ive attached a photo for reference..... many thanks in advance

 

[Wayners]

Cavity wall?

 

[JohnD]

Is that a plumbing duct in the corner?

Is the floor concrete, or wood with a ventilated void beneath?

Is this a kitchen we're looking at? Does it contain a sink, pipes, taps, drains, washing machine? How close is the water to the damp?

 

[miket1982]

Thanks guys... im no expert so bare with me

Thats not a duct. Its solid, theres no plumbing work near that wall at all. That box is the end of the original building, the kitchen is extension. The original house is stone with dot and dab. This part is solid brick with plaster on top i think

 

[miket1982]

Should mention its pebble dashed out side so i cant actually see the wall

 

[miket1982]

Kitchen sink etc is the other side of room there no water sources near this. Its concrete flooring with tiles on top

 

[ree]

OP,
To give the wall & the masonry nib 25yrs to 30yrs damp free then hack off all the present plaster back to masonry - then render with a 3:1 sand & NH lime mix (use plastic corner beads).
Keep the render shy of contact with the FFL: ie stop it above the tiles.
As the gypsum plaster comes off maybe a soot contaminated background will be exposed?
It could be that theres no DPM (membrane) below the floor & flopping up the wall for 100mm?
Post pics if/or when you do remove all that plaster?

 

[miket1982]

OP,
To give the wall & the masonry nib 25yrs to 30yrs damp free then hack off all the present plaster back to masonry - then render with a 3:1 sand & NH lime mix (use plastic corner beads).
Keep the render shy of contact with the FFL: ie stop it above the tiles.
As the gypsum plaster comes off maybe a soot contaminated background will be exposed?
It could be that theres no DPM (membrane) below the floor & flopping up the wall for 100mm?
Post pics if/or when you do remove all that plaster?

Thank you, Im guessing you think its rising damp. What happens if there is no membrane?

 

[ree]

OP,
Nothing unless you want to dig out the present Floor & pour a new one..
Rising damp can be seen - the remains of the redundant flue is perhaps contaminating the gypsum plaster.

Dry Rods will do nothing for your difficulties.

 

[JohnD]

I wonder where the water is coming from

Might be rain, might be a broken drain, might be a leaking pipe.

Kitchens commonly have pipes under the floor. Water can spread under the tiles before finding its way out.

Before deciding on a cure, you ought to find out the cause.

Covering it up will not repair the fault.

 

[ree]

There is no fault - unless water in the ground, aka ground water, is claimed as a fault.
Covering up ground water would be a bit difficult.
All water on earth is rainwater.
Kitchens do not "commonly have pipes under the floor".

 

[mrrusty]

So what do we know - solid wall to outside, no air circulation in that space, in a kitchen where humidity is likely to be fairly high. My guess - at night, when the heating is off, that wall temperature drops below the dewpoint, and gets a bit of condensation. With no air circulation, it doesn't subsequently evaporate so stays as a little bit of liquid water in the wall. Following night, rinse and repeat.

It doesn't matter whether you use cement plaster, lime plaster, plasterboard, if the wall temp is below the dew point of the room air, it will condense, and without air circulation will not re-evaporate. For info, dew point of air at 20 degrees 60%RH is about 12 degrees, so not that cold. The dew point may be just inside the wall fabric, not on the surface, because if it is colder outside than in, there is a temperature gradient between inside and outside, through the wall, and at the dewpoint, water vapour condenses to liquid water.

We also know the outside is pebbledash rendered, so any interstitial (inside the wall) condensation can't evaporate outwards through the impermeable render.

The complication is that if there is a breach or absence of DPC in the wall, or the wall is very wet outside due to poor guttering, poor surface drainage, there may be a little damp coming from elsewhere, which does make that bit of wall a bit cooler, exacerbating condensation risk - so it may not be a single reason.

 

[miket1982]

Thanks for everyones thoughts

That corner has had nothing there for years except for a unit. It is away from all the plumbing and electricals, its a really big space.

We pulled the unit away last night and it seems a bit drier this morning so it maybe is condensation... but there again it hasnt rained in the last 24 hours.

 

[Ivor Windybottom]

A photo of the outside of this patch of wall would be useful.

 

[miket1982]

Ill try its the neighbours garden and I dont have access