Damp, Black mould on an external wall.

[jon ccc]

Hello,
I want to stop suspected rain water entering through the exterior wall of my house, and causing damp in a downstairs room.
The house is an edwardian house [1920s build, single brick wall, lime plaster. outside rendering looks about 1970s.]

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The room is downstairs with one exterior wall, and a cellar underneath.
I have black mould in the room, the greatest concentration is near the ground [see pic: damp1.jpeg].
The damp proof control [dpc] appears to be slate. The paving slabs outside next to the exterior wall are above the dpc. The slabs were lifted and earth unsettled 6 months, as I was unsuccessfully trying to find the drain man hole cover.
The room has 1970/80s plaster on the wall, so probably not breathable.

Looking at the layout [pics: water2] and seeing the green on the ext wall photo [pics: wall1,2,3], and that the underside of the floorboard nearest the exterior wall, is wet. Im assuming the rain n damp is coming in thru the brickwork, where it meets the paving slabs. All the ext wall is wet but the great area of wetness is under the airbrick area.
And With nonbreathable rendering and plaster, the moisture in the brickwork is not able to escape, so causing damp.


This is what Im planning to do:
1. add an extra air brick [9x3inch] in the cellar, there is only current one edwarian tiny one.

2. create a 'french drain' [see pic: french drain.jpeg] infront of the exterior wall to drain the water away. Put a DPM plastic sheet or bitumen against the exterior wall [15cm above ground, 30cm below ground]. Seal the DPM with sealant.
or
3. Put a DPM plastic sheet or bitumen flush against the exterior wall [15cm above ground, 30cm below ground]. Seal the DPM with sealant. [see pic: flush.jpeg]
or
4. remove 40cm deep of earth from the exterior wall [see pic: slab.jpeg]

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I wanted to check I was doing the right thing putting a DPM infront of the exterior wall. It would trap the current brick moisture in, but Im hoping that would be released by the extra ventilation from the additional air-brick

Yr thoughts, Other options?
Thanks

 

[^woody^]

It looks like you have a condensation probelm and not penetrating damp

 

[vinn]

The external render needs cutting back at least 50mm above ground contact - the render looks to be in poor shape.
Is there a throating below the window sill?

Is there splash coming down from the gutters?

Do you have a cavity in the wall?

What is happening to the wall below the floor in the cellar - does dampnes show?
Presumably, the floor joists are running into that wall?

Your proposals are a bit confusing for me - maybe hold off doing anything until you have more certainty as to whats happening?

Could you perhaps post more focused pics of the interior wall/floor junction?

 

[endecotp]

I agree with Woody that the internal symptoms look more like condensation rather than damp from outside.
Do you see condensation on the inside of that window?

What is the construction of the wall? If you don't know, look at the pattern of bricks (e.g. if it's exposed in the cellar) and measure the exact thickness at the window.