Damp Puzzle

[davey76]

Hi Detectives

We have a mysterious damp issue in our downstairs WC - any tips or pointers would be most welcome.

The most relevant fact may be that it gets worse after heavy rain ....

The wall has recently been 'injected' and replastered etc.

Its a Victorian house (approx 1900)

This image shows where the damp occurs (in blue area) - Its probably below the boxing in as well but I haven't checked

The red area on the floor is a line of grout that gets visibly damp after heavy rain

I have taken out the toilet and it doesn't seem to be a leak from there

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• davey76
• 20 Feb 2013
• 1

This pic is the outside - the damp area is roughly under the hose-reel

Note the downpipe nearby - and the water butt - that seems OK

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• davey76
• 20 Feb 2013
• 1

This is a close up of the outside where the damp occurs

The blue line is approx interior floor level - I have dug out a trench along the wall - approx 30cm below that

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• davey76
• 20 Feb 2013
• 1

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I don't think its the toilet or the water butt

Any ideas ? Could it be a cracked / blocked drain that leaks when it rains ? Should I rent a CCTV camera ?

Thanks

 

[luisdesign]

Have you had a DPC specialist in to check things?

Also, that downpipe goes into the ground... where does it go from there? I mean, is it connected to a waste system or does it literally spew out into the ground?

 

[davey76]

Hi - yeah the company that did the injection came back to have a look but wasn't particularly helpful - his view was that the problem was something 'fundamental' - and re-injecting probably wouldn't help (he did offer to reinject)

Never investigated the downpipe - what's the best way to do that ? There is a patio right next to it

Thanks

 

[davey76]

Should also mention there is a pipe running under the floor up to the toilet - not sure if this would get any worse with rain though ?

 

[freddiemercurystwin]

What is the floor construction?

 

[garyo]

Can you get a phone camera with a flash behind that boxing to take photo inside?

 

[dann09]

1. Block and screen the soil pipe opening, light and cooking odours will attract rats.

2. What pipe runs thro the concrete (?) floor - The soil or c/w supply?
Is the white pipe running below the boxing an o/flow pipe from the WC?
Is that waste solvent (?) pipe running from the boxing?

3. Check if the RWP discharges into a manhole.

4. Is the brick course below the blue line the drilled DPC course?
Why was a DPC installed?
Note that the patio surface is higher than the trench. Does the DPC go behind the butt platform and then step up?
Can you show where the bathroom FFL is on the brickwork?

5. Is there a membrane under the concrete?

6. The soil clinging to the brickwork is v. wet and mossy - is the guttering leaking? Will you trench below the water butt?

 

[davey76]

Thanks all

It is a concrete, plastic DPM, screed floor

Answers to Dannos questions...

1) Thanks
2) Definitely the CW supply to the WC. Not sure which direction the soil pipe goes. The white pipe is the kitchen sink waste pipe - it runds around the boxing and out into an outside drain
3) Whats the best way to check ? Dig down and follow the pipe ??
4) yeah roughly - it was done from inside. That area of the house has been 'damp' since we moved in (4 years) so our builder suggested and arranged the injection etc...
5) I think so - there definitely is at the other end of the WC room
6) Don't think the gutters leak - will check next time it rains. No room to trench behind the water butt

Thanks

 

[dann09]

1. the white pipe i'm referring to runs from left behind the soil pipe stub to right into the boxing area - it's a 3/4" plastic o/flow perhaps, or a painted copper pipe?

2. Dont do any interior digging.

3. Where is the soil stack location - is it "round the corner" to the right, in the pics?

4. Seen from outside, i still dont know where the FFL is?

5. Are you certain that no drilling took place on the external bricks? Unless more was known about the construction of the slab, i dont see what purpose injecting inside would achieve.
If he double-drilled from inside perhaps it would work?

6. Removing part or all of the boxing for pics would be helpful, as suggested above.

7. Clean all soil/moss from the brickwork.
If you dont continue your trench behind the butt, then you compromise the penetrating damp remedy.
However, maybe the raised height of the patio is already compromising any DPC?

 

[davey76]

Hi again

1) The white pipe is a cold water main 22mm

2) OK

3) Soil stack is about 20 feet away - I don't think this WC is connected to that. There is a drain about 10 feet away from the house so I think it connects to that somehow ??

4) I've remeasured and the finished floor level is about 3 bricks up from the mossy area as here ...

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• davey76
• 24 Feb 2013
• 1

5) Yeah he definitely did it from inside - he said he drilled into the mortar not the actual bricks

6) Photo from behind the boxing in is below - pipes are waste from kitchen, 22mm cold main and 15 mm cold feed to dishwasher

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• davey76
• 24 Feb 2013
• 1

Thanks

 

[joe-90]

You need to look for a leak in the vicinity of the phosphorescence.
(That white fluffy stuff).

 

[davey76]

Thanks Joe - it definitely gets 'wet' in that area - the floor tile grout on the other side gets damp and changes colour. The weird thing is that it only happens after heavyish rain ....

 

[joe-90]

When it is dry the leak soaks away into the soil. With heavy rain that doesn't happen and you get damp creeping up the wall. The white fluffy stuff shows that the water wicks up and then dries leaving the limescale behind.

 

[gregers]

You need to look for a leak in the vicinity of the phosphorescence.
(That white fluffy stuff).

er dont you mean,
efflorescence.

 

[joe-90]

I effing well do. Worra plonka.