Moisture seeping from under bricks on top of raft !

evo111 · 4 Jan 2010

Hi
I am hoping that someone may be able to advise or re-assure me!!

A couple of days ago I noticed a damp mark along the mortar between my brick course and the raft foundation. I didnt think much of it considering all the icy and damp weather we have had lately.

The following day the damp mark had formed a small puddle that has seeped out (I have included some photos).

My question is where could this moisture be coming from?? It is not a large quantity but enough to concern me.

My house is twenty years old built on a raft foundation. I have not noticed this type of thing before and the rest of the brickwork and raft appears to be normal.
I don't have any leaks (that I know of) inside the house , and my mains water pressure is as good as ever.

I am really confused to what this could be. Somebody has told me that it could simply be condensation that has formed between the raft slab and dpm and that it is just seeping out - this is what I hope it is and nothing more sinister!!

If anybody has any suggestions or advice I would be extremely grateful.

Regards

Simon

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evo111
2 Jan 2010
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evo111
2 Jan 2010
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WabbitPoo · 4 Jan 2010

i am mno expert but I doubt it'd be condensate - too much there for that. Are you sure your central heating pipes arent leaking? check the pressure on your boiler.

evo111 · 4 Jan 2010

Thanks for that - dont really know how to check the pressure on my boiler. It a gravity fed sytem (oil-fired) - no pressure warning lights.

I would have assumed that any leaking radiator pipes would have caused dampness within the house??

I will try and investigate a little more.

hotrod · 5 Jan 2010

evo111 said:
Somebody has told me that it could simply be condensation that has formed between the raft slab and dpm and that it is just seeping out

Hi evo, there's too much moisture there for that to be condensation and the strange thing is the moisture halts one course below DPC. If anything you would expect it to stop at DPC. I've highlighted DPC in red here:-

And there is 1 brick shown that is perfectly dry and then another one further along (shown in another pic) - very odd. Does the liquid smell?

evo111 · 5 Jan 2010

Thanks for your reply
There is no smell to the liquid and it is clear.

I have my suspicion that it my be a leaking radiator pipe under the floor. I have ceramic tiles downstairs so damp is not really that obvious to spot. I have just noticed a little bit of skirting board that has ever so slightly come away from the wall (1-2mm) which would indicate moisture under the tiles and in the wall.

There is two radiators in very close proximity to the wet patch outside and I am quite sure that the brick where there is no dampness (highlighted on the photo) is where the internal wall is (load-bearing wall).

Think I may have to get plumbers out to investigate an claim on my house insurance!! Unfortunately they are going to have to smash up my tiled floors !!!

Thanks for your feedback

hotrod · 5 Jan 2010

evo111 said:
I have my suspicion that it my be a leaking radiator pipe under the floor. I have ceramic tiles downstairs so damp is not really that obvious to spot. I have just noticed a little bit of skirting board that has ever so slightly come away from the wall (1-2mm) which would indicate moisture under the tiles and in the wall.

I would question, how the moisture has managed to track across the cavity, and in such quantity. To do that, saturate the external leaf, and then pool on the path would require an awful lot of water. Are there no signs of dampness internally? Has the boiler lost any pressure? I wouldn't want you to destroy your floor to find there's no leak

noseall · 5 Jan 2010

Is the subsoil clay in your area?

jm2000 · 5 Jan 2010

Yeah i agree with noseall...and this is a strange one...one id like you to post the answer to, when you find out.

Your dpm, is your basically your floor, and for this amount of water to be coming from your cavity sounds very strange.

Can you drill through one of the mortar joints at the damp level....it may give you an indication to just how much water is in the cavity.

If your radiator pipe is leaking you would know by bleeding the rads. and seeing how much air you got. That much water coming out would leave a lot of air in your system.

Do you have any space under the tiled floor...it may be that water is trapped beneath the house and has begun to find a way out.....I say this because of an elderly lady that i went to see had a strange smell in the house. After much head scratching we took up a floor board under her kitchen unit _where the smell seemed worst- and found the whole 18 inches under the house to be full of water, the waste pipe from her sink had come apart and all the water and waste was going behind the unit straight down under the floor.

noseall · 5 Jan 2010

It may be cavity related - above the dpc. Is it a gable end?

Can you post a piccie of the entire wall.

evo111 · 6 Jan 2010

Hi
Thanks for all your replies.

There is no sign of moisture inside the house. The fact that all the moisture is below the dpm level makes me suspect that the heating pipes are fine and the moisture is coming up from underneath ???????

In reply to noseall question about subsoil clay - well I live in West Norfolk where I think there is a lot of clay in the soil - hence the houses in my area all being built on raft foundations - what is the significance of this ????

It is not a gable end - above the dmap puddle on the photo is a dining room and the front door is to the right of the damp patch. The whole area is actually sheltered under a porch.

Interestingly - the seeping seems to have stopped in the last day and the damp patch is drying out - so now I am even more confused !!

Ideas welcome

Thanks to all

Richard C · 6 Jan 2010

I lived on Canvey Island in Essex for many years, probably where reinforced raft building was invented, I think they were hoping they would just float away when the next flood came

What you have there is either a serious leak or water ingress under the floor my friend, looks around 2-3 inches; incoming water main would be the obvious suspect but if nothing else is obvious it could be one of the foul drain outlets; lift the easiest bit of floorboards you can find & have a look.

evo111 · 18 Jan 2010

Thanks for everybody's input.

I have investigated this problem further. Had a company in today to check for leaks. They checked the mains water pipe from the meter to the house and there was no sign of a leak - they also turned my water back on and watched the mains meter and there was no evidence of any water leaking from any household pipes either.

Although I am extremely relieved at this it still does not explain the puddle outside my wall!!

Interestingly in the summer of 2009 I had four very large poplar trees removed from outside my house (council removed them). Does anybody think that I may have developed a drainage problem ??? Is it at all possible that a great deal of moisture is now sitting under my land and seeping up through a small crack in the concrete foundation ????

Any further opinion greatfully received.

Thermo · 18 Jan 2010

if you are on clay could well be a ground spring. the water table is extremly high in many areas at the moment.

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Moisture seeping from under bricks on top of raft !

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