Damp in corner of living room - please help

[chillybilly99]

Hi all,

I've got a long standing problem in the bottom corner of my living room which i'm hoping to get some ideas on.

The property is a bungalow and externally the corner is hit by driving rain. There is a down pipe from a gutter quite close to the area in question and this goes down into the tarmaced drive. The property was built in the 60's and the mortar is a very sandy mix.

This is what the corner looks like now that i've removed some plaster, and some skirting which was rotten towards the corner:

As you can see, the damp and black mould extends up around 12-18 inches in the corner but then there is an affected area along the wall for 10 foot or so, along the skirting:

A close up of the corner on the left:

and on the right:

The hole to the right in a mortar join was from a chunk of wood used to nail the old skirting into. It wasn't rotten.

I've used the gap to gain access to the cavity and see if there's soggy cavity wall insulation in there. I pulled a bit of the blown insulation out and it seemed dry - when pressed against toilet paper there was no dampness. There didn't seem to be very much insulation in that area.

I've had a damp company surveyor out who saw this before I stripped it down and suggested that the plaster was probably in contact with the floor/concrete and therefore wicking up moisture - this seems unlikely given the gap between the concrete on the internal wall.

Another damp company suggested it was entirely condensation related. Whilst there was condensation in the area, partly due to poor circulation and blocking furniture this could be the only cause as the corner of internal wall is 10C below the room temperature (8c versus the 18C in most of the room today) - with a 10C difference this corner will always be below the dewpoint for the room, so I know i have a coldspot problem and or damp problem, presumably related.

I've also noticed a difference between the 2 close up pictures. the felt/rubber damp proof course is below the mortar course to the left of the corner, whilst to the right the damp proof course is above the mortar course meaning that the damp proof course to the right is above floor level by half an inch or so. Could it be that plaster on top of that damp mortar was allowing moisture to wick up the wall and extend outwards?

I've also looked outside and the damp proof course on the outside has been repointed. The drainpipe doesn't appear to be blocked. The driveway is about 5 inches below the level of the damp proof course.

Any ideas as to what the likely cause of this is and how to remedy. I'm looking to eliminate the damp and raise the thermal properties so that condensation isn't an issue.

ps. can a kindly mod please get the pics into a sensible size? Edit: Sorted now, thanks.

 

[jeds]

It's unlikely to be moisture rising up through the masonry unless it really is sat in a lake. That would take something like a damaged drain or water pipe. Mould growth is certainly caused by condensation. Minerals and salts from the ground inhibit the growth of mould. You mention insulation, which presumably was injected. Gaps in the insulation will cause a concentrated cold spot, which in turn will promote condensation. The type of plaster on your walls is the worst for damp conditions. My advice is hack off half a metre or so of plaster - above the dew point line. Check the cavity for rubbish and eliminate any gaps in the insulation. Re-plaster with a renovating plaster - limelights or similar.

 

[ban-all-sheds]

ps. can a kindly mod please get the pics into a sensible size?

Hard to see how they could do that, when the pictures are on your PC, to which they do not have access.

You need to make them smaller, re-upload them, and edit your post with the new links.

Or use thumbnails. I've never used tinypic. but I'd be pretty surprised if it didn't give you thumbnail links, already wrapped with the correct URL syntax to copy & paste into your post.

 

[carpentrycardiff]

Its probably one of two things, either the dpc has failed or the cavity is bridged above dpc level.

 

[chillybilly99]

It's unlikely to be moisture rising up through the masonry unless it really is sat in a lake. That would take something like a damaged drain or water pipe. Mould growth is certainly caused by condensation. Minerals and salts from the ground inhibit the growth of mould. You mention insulation, which presumably was injected. Gaps in the insulation will cause a concentrated cold spot, which in turn will promote condensation. The type of plaster on your walls is the worst for damp conditions. My advice is hack off half a metre or so of plaster - above the dew point line. Check the cavity for rubbish and eliminate any gaps in the insulation. Re-plaster with a renovating plaster - limelights or similar.

Thanks. I'll be getting the plaster redone with renovation plaster. With the cavity, I haven't had a good look yet and I guess I'll be best off removing one brick for this, but if the cavity is looking bare of the injection wooly type stuff then what would the recommendation be for a remedy, what type of material?

 

[chillybilly99]

I've also noticed a difference between the 2 close up pictures. the felt/rubber damp proof course is below the mortar course to the left of the corner, whilst to the right the damp proof course is above the mortar course meaning that the damp proof course to the right is above floor level by half an inch or so. Could it be that plaster on top of that damp mortar was allowing moisture to wick up the wall and extend outwards?

After having this exposed now for 48 hours it is striking how the mortar course on the left which is above the DPC is nice and dry, whilst the mortar course on the right which was laid below the DPC is still very much damp. Seems to suggest to me that the DPC is working, in which case couldn't it be that the damp mortar course being in contact with the bottom of the plasterwork is to blame?

Any ideas what to do about the gap between the concrete floor and the inner leaf of bricks? Should it be there, should I insulate it somehow and should I extend the DPC over the gap with damp proof paint to seal it off?

 

[chillybilly99]

I've taken a couple of bricks out on the inside wall. There are definite gaps in the insulation and there is quite an amount of rubble at the base of the cavity around the DPC - the limited amount of insulation which sat on this rubble was moist. There doesn't appear to be water on the inside faces of the brickwork or in the cavity generally. I'm guessing that dampness is just bridging through via the rubble which combined with moist insulation is cooling the inner wall below the rooms dewpoint, causing condensation.

Does this seem right to the knowledgeable people on here, and apart from clearing the rubble as best I can, how should I proceed?

 

[ban-all-sheds]

how should I proceed?

Not like this:

//www.diynot.com/forums/viewtopic.php?p=1264814#1264814

 

[chillybilly99]

how should I proceed?

Not like this:

//www.diynot.com/forums/viewtopic.php?p=1264814#1264814[/QUOTE]

Thanks for that Hopefully I'll be alright just taking out a couple of bricks width, enough to be able to get my arm in.

I've found loads of rubble around 2-3 courses above the DPC. Here's a pic of some of it:

This rubble has also contributed to the insulation not filling down to floor level.

I'm having trouble clearing the cavity much more than 2 inches below DPC level. Hopefully this will at least be an improvement on the current situation where damp crap (uncertain as to correct technical term!) is up to and above the DPC.

 

[jeds]

Take out two bricks next to each other. A length of rebar with a hook on the end is a good tool. Rake as much rubbish out as you can then get a good look along the cavity. A digi camera can be good - point it along the cavity and take a snap. If you need to, take a couple more bricks out further along. Then fill the voids with mineral wool but make sure it is proper cavity batt - don't use ordinary loft roll. You can break it into small pieces and push it into the cavity but don't ram it in too hard.