Historically we've had a leak from our shower in our bathroom which has leaked into the neighbour below's bathroom and kitchen (this has gone though the bathroom wall to the kitchen which is adjacent). This caused staining on the ceiling and dividing wall of the neighbours kitchen / bathroom.
Was fixed in Feb this year and the neighbour reported no further problems. We decided to wait a long time for everything to dry out – the building is an old 120 year old tenement flat with a large amount of deadening material (soil, rubble, stone, sand) between the floors so a lot of water could be absorbed and need time to dry out.
About mid July this year we had a leak from our kitchen sink into our neighbour kitchen. This found a path through the interfloor material quite quickly so we are not sure how much water was absorbed. I'm told it leaked through the ceiling although I suspect water would have been absorbed everywhere behind the ceiling plaster, including going down the wall against the brickwork. Anyway, leak fixed.
Now neighbour is telling me that they are getting further marks / stains on their walls and wants me to take down my shower and pull up my kitchen floor to investigate. They have been away for three weeks so I am not sure how much of this has suddenly appeared and how much of this happened while they were on holiday.
To make matters worse, I am away from home at the moment and have let my flat out. I won't be back for about 7 weeks without making an unplanned flight home.
I think this might be residual marking as the wall dries out / water comes to the surface – plaster on these walls is about 30-50mm thick, but I'm no expert. I'm not able to actually see any of this other than some photos so it's difficult to tell if this is actually a further leak.
We've contacted a firm who say they can do a thermal image of the wall to show the temperature differences along with actual damp meter readings which will indicate how damp the wall is (cost ~£100).
We could buy one of these Damp Test Meters, or Non-contact Moisture Meters from Amazon.
Anyone have any suggestions? Are stains appearing 2 months after the initial escape likely to be the wall drying out?
Any suggestions on ways to find the leak if there is one?
(sorry for the long explanation and perhaps incorrect keywords – there's no "damp" keyword)
Best Answer
We had a leak going into our ceiling. Luckily, as a wood turner, I already own a moisture meter. This can test the moisture content of wood (but other similar density substances too) merely by pressing a button. That meter worked very well for my problem. Of course, if you do buy one, I don't expect you will find many other uses for it than catching an occasional leak, but it can still be cheaper to buy one than to pay someone to make a simple reading for you. Just store the meter after you are done with it with the battery removed.
It will take several weeks or even months for a ceiling to dry out. This depends on how enclosed the area is, and whether there is still water getting in. Readings made over time should be decreasing. If not, there is still a problem. The moisture content of even dry wood will be around 8%. Check other walls in your house, because this number will vary by where you live, and what time of year it is.
There are several styles of moisture meters. One relies on pins that must be inserted into the material, testing electrical conductivity between the points. As such, it will leave small holes. Better are the styles that do not leave a hole, but they are more expensive. Note that the cheaper models use a probe. This probe will have pins to stick in the wood.
By the way, while the ceiling is still damp, stains WILL continue to spread by capillary action. The water will continue to wick the stain further away. 2 months later is a long time for new stains to appear, however, old stains can bleed through new paint. You may wish to use a product like Kilz to seal in those stains. But wait until it is surely dry before you paint. This is where the meter will help you out.