Ok, bit of an odd one. Ive been trying to diagnose source of damp at bottom of bay window at concrete floor level. Dpc is approx one course of brick above concrete floor.

I watch it like a hawk. Damp patches and wet bricks comes and goes without pattern.

This morning was bone dry. Its been v hot and no rain last few days. Today no showers bath, dishwaher etc were used.

I last checked at mid day and was dry, then checked again few moments ago and is soaking.

The ONLY significaNt water usage today was me washing the conservatory roof at rear of building, 50 feet from the damp patch. All drains are sound.

The ground level at rear of building is approx one brick higher than at front.

Could this really be the cause? Would the water travel 50ft in a few hours and appear on interior brickwork? Exterior is dry btw.

Cant see what else it could be?

Ps building is dormer bungalow. Rear half built 1994 front half 1930s. All walls are cavity walls.

Thinking cap on!..

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By eck! ©

Try simulating the conservatory roof washing (like chucking a few buckets of water down) and see if the damp reappears a few hours later.

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By eck! ©

Thanks. Will try that if the damp dries before the rain comes!

What if it does though? Can the water travel under foundations?

I could try dye or uv dye too i guess. Really odd though been racking my noggin

Not sure if dye will show in this situation, but it's worth a try.

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By eck! ©

Ok was dry again this morning so i connected hose into drain and ran for a while. If damp returns the drain is bust underground. If no damp, will run hose on rear patio/ground and see if that makes it come back.

Just checked and the damp is back - thats with most of the water running directly into the drain. Odd.

Guess this means the drain is leaking underground?

How does it end up on the base of the internal wall? I have a piece of plastic sheet shoved down about 2.5 inches down the gap between the brick wall and concrete floor - the gap thats about 2mm max in most places. The sheet has droplets on it. It didn't earlier this morning when i checked.

Any ideas please? Does this mean the water is travelling under the foundations?

EDIT: I realise droplets may sound like condensation but this is below the top of the concrete floor level and the droplets are on the brick side. This is definately moisture occurring from the brick. This is also all below DPC btw, but as mentioned the top of the concrete floor is about 2 inches or so below the DPC. I know that damp below the DPC is "normal" but the moisture levels do vary a lot.. and I now know (i guess) that this is due to water fall at the back of the house... if my analysis is correct

Hi Mike,

The pipe (possibly clay and cracked), could well run under the house, can you trace it to a manhole or gully? Might be worth getting a CCTV survey!

SSM

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Measure twice, cut once!

thanks.

According to architectural plans from 1994 that drain should go to a soakaway located approx 20ft further back again. However the same is true for the drain opposite side of house but that actually goes to sewer. Im pretty sure thid drain in question therefore runs alongside house and out past front of house to street. There are three drains alongside this side of house and ive lifted inspection covers in past and it all seems ok to me.

However looking more closely this evening st suspect drain, the gulley is not well sealed in cement and its v possible some water is escaping down side of house. I have no damp problems at this corner of house however.

Tonight i installed a water butt at that drain in an attempt to divert the rain which is forecast. Be interesting to see if this has any positive effect...

Hi Mike,

Let us know how it's going, expecting some damp weather over the next few days so a good time to test.

SSM

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Measure twice, cut once!

Hi, thanks for your interest!! :)

Tonight i applied quick drying waterproof cement around the plastic bottle gully as there was a large gap between the gully and wall of the house. Gap went down several inches but hopefully thats the extent and it hasnt undermined the house lol.

Interestingly the outlet for this gully does indeed head north away from the house and into the garden, so it must presumably be connected to the soakaway mentioned on the plans. The garden is up hill slightly of the back of the house and a good bit higher than ground level around front of the house.

I know from removing a pond last year the ground is clay down about .5 metre.

Not sure if im getting anywhere but wall is dry at moment and butt is half full from the rain today. Thinking about it, there is quite a lot of roof draining into this gully/soakaway. I may redivert down sewer as rest of downipes do.

Just to update.. I currently have a hose connected to the waterbutt which is running at a trickle down a nearby drain which outflows via the sewer (all the other gutters drain to sewer btw - this gully is the only one on the house which goes to a soakaway).

We had so much rainfall in the last couple of days the water butt actually filled, then overflowed back into the soakaway. Having a hose connected to the outlet tap and trickle draining it is relieving the soakaway and also not wasting too much captured rainwater.

The back of the plastic has not been wet in days. The brick work in that area also seems to be drying out, though im not counting my chickens just yet.

What I dont understand is what is going on here. The soakaway is in the garden, probably 70 feet away from where the damp is appearing (house length approx 50 feet then another 20 to soakaway according to plans, from the drain point).

My guess is that the positioning of this downpipe is not ideal as it takes potentially 50% of a large roof, and half a conservatory roof, and judging by the waterbutt being filled so quickly this is a large volume of water. Perhaps the soakaway is clogged up, and the volume of water is raising the water table in the immediate area?? The ground where there soakaway is (assumed to be anyway) is higher than the front of the house by quite a bit.

If the soakaway is choked i guess i need to either dig another, or, given that the ground is a lot of clay content i would prefer run a underground pipe from the gully to run to sewer rather than soakaway, in keeping with rest of downpipe outlets.

Cheers.

Any thoughts Simon ? Appeciate any thoughts you might have..

You know its not allowed to divert a soak away into the sewer right?
Officially you may not increase the ammount of surface (including roof run off) water entering the sewer without informing your water company (and when you do they will put your bill up - if they allow it) first.
Have to say thats what I would do though (without informing them). Silt washed down drains soon blocks soakaways. I'd say the typical functional life of a typical soakaway is only 20 to 30 years before they are silted up and useless.
If you are sure that that drain is connected to your damp problem then you need to dig a new soakaway or divert the drain into the sewer. A bit of exploritory digging or tracer dye in the water may be the only way to proove it though.
I think if it was me I'd be getting on with diverting the drain or building the new soakaway and see if that cures the problem.
If you are doing the work yourself it will cost you more in time and effort than money so may as well get on with it and know that the problem is fixed or lies elsewhere.

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Mike

Hi - thanks for the reply.

Thanks - yeah I am sure the water company would not be too happy with that - any excuse to charge more i am sure. Although, the 5 remaining downpipes are already dumping their rainwater into the sewer, so I can't see that one more would really make much difference.. rather than go to the effort of changing the underground pipework, I was going to change the slope on the gutter slightly so it favours the middle of the 3 on this side of the building (which goes to sewer) and then capture any additional in waterbutts. In fact i'll probably place additional waterbutts elsewhere along that side so if anything there will probably be less going to sewer overall, though any overflow from the butt capturing from the soakaway drain i'll run via a discrete hosepipe into the sewer near middle downpipe (approx 20 feet or so). At the moment the slope on the gutter is toward number 3 so im sure the soakaway has been getting more than its fair share.

I have my eye on a 1200 litre water container and as the downstairs bathroom is on that side it seems an easy tasks to get at least the loo flushing off rainwater.

Still dont fully understand how the soakaway 70 feet from the front of my house can cause damp inside the building at the front bays and nowhere else. The brickwork is dryer than it was though still the concrete floor edges look damp... i guess the watertable must be high relative to the floor level, and the soakaway just tips it over the edge?