Dealing with damp in Victorian Terrace

[longdogs]

Hi all

I have recently moved into a Victorian terrace, fully aware that there was a damp problem in the lobby. I want to get this problem sorted before decorating and ultimately to lay new floor tiles.

This is a pic of the damp floor (the dark patches) this damp 'pattern' doesn't really change whether the weather is dry or wet.

I have lifted one of the floorboards adjacent to the tiles. See below:

I have inserted a long screwdriver through one of the mortar holes and behind the brick foundation it appears to be hollow or maybe sand? There is a concrete layer under the tiles.

At the bottom of the foundation, there is a steel water main entering the house. The pipes is damp where it goes through the bricks but nowhere else.

I am not sure whether the damp is coming from the pipe on the other side of the wall or elsewhere.

I have been told to dig up the tiles and lay a dpm but I am not sure that is the correct thing to do in a house this old as the damp could just be forced elsewhere. I was wondering about removing one of the bricks to see if it will dry out naturally. Airflow under the rest of the house is good.

What would be the best way to proceed - starting with the least disruption first.

Below is a pic of the outside where the pipe meets the main stop valve. If the whole floor has to come up, I would like to replace the steel pipe with plastic but not sure how I would be able to connect without also disturbing the tiles outside. See pic:

Just cautiously looking for advice and ideas at the moment so any help would be much appreciated.

Many thanks.

 

[endecotp]

Turn off the water at that outside stopcock and wait for a couple of months to see if it dries up

 

[JohnD]

the probable cause is easy to see.

Have you got a water meter?

And, if you are "halls adjoining," has your neighbour?

 

[ree]

The tile staining indicates water penetration from below - there's almost certainly no DPM below the concrete or whatever that the tiles are laid on - the whole area below the "concrete" is probably solid with an infill of earth/rubble (IOW's its not a suspended floor).
Are there any signs of damp in the hall flanking walls or skirting?

The steel supply pipe: you might have to dig out at the "main stop valve" on the side away from the house (& the red and black tile) exposing the stop-valve and its connection to the steel pipe.

Check the material of the pipe coming from the street mains. Is there another kerb or street stop-valve?

You could then use a large pipe wrench to constantly turn and pull the disconnected steel pipe back into the sub-area. When the tunnelled hole is clear you could snake a length of MDPE out to the stop-valve.
FWIW: you should have an accessible internal "main stop-valve".

The odds are that both joists & plate in pics 2.& 3. have hidden rot.
Have you crawled the property and examined all joists and plates in contact with brick or stonework?
Do you have adequate air bricks and thro ventilation?

Lifting the tiles and laying a DPM is problematic: the tiles were possibly laid into wet concrete and will not release and lift easily - ie. no adhesive would have been used. However, maybe the "concrete" has degraded and crumbled a little due to the moisture contact?

What do you mean by "removing one of the bricks" etc?
Actually, it would do no harm to remove a couple of bricks near the pipe to see exactly whats behind the brickwork.

How come this wasn't red flagged on any kind of survey at the house sale?

 

[longdogs]

the probable cause is easy to see.

Have you got a water meter?

And, if you are "halls adjoining," has your neighbour?

Hi
We do not have a water meter. We do have a modern plastic stop valve in the street. Our neighbour has exactly the same hall but has no obvious signs of damp.

 

[longdogs]

The tile staining indicates water penetration from below - there's almost certainly no DPM below the concrete or whatever that the tiles are laid on - the whole area below the "concrete" is probably solid with an infill of earth/rubble (IOW's its not a suspended floor).
Are there any signs of damp in the hall flanking walls or skirting?

The steel supply pipe: you might have to dig out at the "main stop valve" on the side away from the house (& the red and black tile) exposing the stop-valve and its connection to the steel pipe.

Check the material of the pipe coming from the street mains. Is there another kerb or street stop-valve?

You could then use a large pipe wrench to constantly turn and pull the disconnected steel pipe back into the sub-area. When the tunnelled hole is clear you could snake a length of MDPE out to the stop-valve.
FWIW: you should have an accessible internal "main stop-valve".

The odds are that both joists & plate in pics 2.& 3. have hidden rot.
Have you crawled the property and examined all joists and plates in contact with brick or stonework?
Do you have adequate air bricks and thro ventilation?


Lifting the tiles and laying a DPM is problematic: the tiles were possibly laid into wet concrete and will not release and lift easily - ie. no adhesive would have been used. However, maybe the "concrete" has degraded and crumbled a little due to the moisture contact?

What do you mean by "removing one of the bricks" etc?
Actually, it would do no harm to remove a couple of bricks near the pipe to see exactly whats behind the brickwork.

How come this wasn't red flagged on any kind of survey at the house sale?

Hi Ree

It was brought up on the survey but the price was right as a renovation project, so I knew it would have to be done. There is no obvious damp on the skirting although the moisture content is a little high. There is good ventilation under the property and there are are few other smaller damp issues that need addressing but this is the worst one.

I was thinking of removing one of the bricks, possibly around the pipe to see if the increased air flow would naturally dry the floor.

I do have an internal stop valve. One extra problem is that the external one serves my neighbour as well.

if it all has to come up then so be it but was initially looking for a more sympathetic solution. I know these are old properties are susceptible to damp and that it's all about the building 'breathing.'

Additionally, there were a few cracks at the front of the house where the tiles met the house and rain water was entering but this has now been remedied.

 

[JohnD]

it is very likely that the damp is because the steel pipe is leaking under that tiled floor. It might be at a joint, or it might be that being in damp rubble for 100 years has rusted it. With no water meter it is less easy to detect a leak. If you can get a young person with good hearing to sit in the silent hall while you turn the outside stopcock on and off, he might notice a sound stopping and starting. You only notice the sound of a small leak when it stops.

It is also possible to detect it with a glass at the kitchen tap, but your leak might be very small.

Have a look in the stopcock pit and see if it is damp. I'd put 50p on it.

Also post a pic of the outside in case there is a drain, gulley or rainwater pipe that might be interesting.

 

[ree]

Remove some bricks to see whats there not for the possibility of air flow.

The rim joist in pic 2. should come out - dropping the bricks below it would help. Do you have a Reciprocating Saw?

Lifting the tiles is a last resort and other approaches should be tried first.

If you and your neighbour are on a common supply then the Utility might be willing to split you for free - to do that they would have to dig out the stop-cock in pic 4. thereby providing access to the connections for your project.

Thing is to do a proper job will take a bit of time, effort and maybe expense. - first things first would be to replace the steel supply pipe.

 

[spudsbit]

Another suggestion is to insulate the pipe - it may be due to warm air condensing on the cold pipe = water droplets. Further suggest you increase the air-flow under the floor.

Angela

 

[longdogs]

If you and your neighbour are on a common supply then the Utility might be willing to split you for free - to do that they would have to dig out the stop-cock in pic 4. thereby providing access to the connections for your project.

Ooh. Worth looking into.

 

[Joe Malone]

Firstly, simply locate your internal stop cock and if it connected to an incoming polyethylene pipe then you've probably nothing to worry about. I know you show a steel entering the house but just double check in case this is an old redundant pipe.Steel pipe can corrode very quickly when laid in aggressive soils without suitable protection. If it isn't Polyethylene then carry out a back siphon test. I'm sure I've posted on here before how to do that but simply turn off the external stop tap. Hold a glass of water under the neck of a tap and open up the tap. If the incoming main is leaking then it will siphon water from the glass. If not then no problem.
Do not under any circumstances consider installing a DPM under the encaustic tiles floor in the hall, they are meant to breathe and act as a giant buffer for damp. Installing a DPM would simply push damp up the walls and cause a wall base damp problem.
You would also need to check that you have no foul drainage leaks by inserting a drain bung into the outgoing waste at the inspection chamber, then try to fill up a sink. If the sink doesn't fill, or fills but doesn't hold its level then you have a foul drainage leak. I use pneumatic bungs but cheap rubber bungs are available.
Finally, how much sub-floor ventilation do you actually have? The general rule of thumb is that an air brick is required every 2 linear meters but I double this requirement for terraced properties since only the front and rear walls are available to install them. Having them on one elevation is no good since you need a good crossflow of air. If you've proven to have no no sub floor leaks then this is simply about installing adequate sub-floor ventilation.
You will never completely stop moisture evaporation through the tiled floors, nor should you attempt to.