Internal wall Damp

[billm]

I had a damp patch on an internal single brick wall between the lounge and the hallway. When it was damp outside the damp would be more apparent upto 18" or so from the floorboards.

A few weeks ago I lifted up the boards on both sides of the wall and installed a new plastic DPC under each brick working along the wall brick by brick. The joists were originally packed underneath with tiles/slates etc to make them level (as opposed to them sitting on the old DPC) so I did the same and made them all tight. Although the joists looked a bit damp at the ends I thought they would be passable, cleaned all the rubbish out of the floor cavity and nailed the floorboards back down.

The walls still showed the damp but I was expecting that to gradually dry out after a few weeks as the new DPC took effect.

But now several weeks later the damp is still there on the walls and seems to get worse when its raining outside. So today I lifted up the boards in the lounge and knocked off the plaster on both sides of the wall to check the bricks. They all looked dry to me (see photos)

I have checked the DPC I installed and its OK, nothing is straddling it so it should be stopping the damp rising and the bricks below it do look damp, above it they look dry.

So my question is: does 1930's plaster hold the damp once wet and hence why I should have knocked it off in the first place, are the bricks damp and will take time to dry out (if at all)

Should I knock the bricks out and put new dry ones in or could it be that the damp is coming along the joists from under the hallway and thus is above the new DPC (I haven't lifted all the boards from the hallway) but the ends going into the brick wall look dry on top to me.

I had planned on putting plaster board over the bricks and then skimming them to get the finish as an easier way than doing Browning and then thistle.

Have I done anything wrong or missed anything ? Do I need to remedy anything else first before doing the plasterboard ?

thanks

(you can see there is a radiator pipe sticking up in the hallway photo but I checked underneath and as far as I can see it hasn't leaked and caused the damp)




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[hotrod]

If the wall was damp I would have removed the plaster in the first place. Leave it for a few days to dry out and re plaster with dri coat and then use a skim coat as normal.

http://www.british-gypsum.com/produ...stle_undercoat_plasters/thistle_dri-coat.aspx

It's not cheap but you've only got a small area so 1 bag should see it off.

I would also of wrapped the joist ends in DPC whilst I was at it but if they were damp anyway, that would solve more problems than it it cured, and is an aside from your initial query....

 

[billm]

OK, thanks for that, I'll get some of that Dri Coat and sort the wall out next week after giving it a few days to dry off from both sides.

cheers

Update
the 2 builders merchants in my town don't stock Dri Coat and have never heard of it. As its cement based I assume all the builders around here render the wall in a 4:1 sand/cement mix instead and then skim with multi-finish ?

Would that work or is it better to travel and go get the Dri Coat from out of town ?

 

[foxhole]

Whats at the top of the house directly above the damp?

 

[billm]

Its a 30's semi house and this is a single brick wall all the way to the roof space and plastered on both sides

 

[foxhole]

Have you checked for leaks in loft, roof, they can travel down and then exit at base of wall.

 

[Alastairreid]

Update
the 2 builders merchants in my town don't stock Dri Coat and have never heard of it. As its cement based I assume all the builders around here render the wall in a 4:1 sand/cement mix instead and then skim with multi-finish ?

Dont forget to add waterproofer.

 

[hotrod]

As its cement based I assume all the builders around here render the wall in a 4:1 sand/cement mix instead and then skim with multi-finish ?

Would that work or is it better to travel and go get the Dri Coat from out of town ?

You can use a 4:1 render but as alastair has pointed out, don't forget to add a splash of waterproofer to your mix.

 

[billm]

I found some FebProof+ in my garage that should do the job. The instructions on the tub are not very helpful: 1-2 lt per 100Kg of Mix

How much do I put in a watering can .. a cap full ?

 

[tim00]

I'd think that your damp issues are, as has been suggested, penetrating damp from above or some kind of leakage. Examine the exterior esp. flashings. The joists would show fungal damage if it was "rising damp", and it's doubtful that any damp could rise thro the lower brickwork - you must remedy that with laid brick, and properly infill the higgle-piggle of masonry.

You should remove all cellulose debris from the sub-area, it attracts fungal spores

Snap lines above the ragged knock-off, undercut with a knife , hack off to the lines and work to a clean undercut edge.

2 caps per bucket.