Oh dear, what’s wrong with my bricks...pic attached.

[LoveGigi]

I’ve been insulating under my suspended timber floor today. 95% of the sub floor is bone dry and in good condition. However at the front of the house in the corner of the living room near where my lead water pipe and gas supply is coming in there’s is a white and yellow growth on the bricks and mortar. This area is mildly damp, cold rather than wet. There are no obvious leaks. In the past we have also had slugs coming in through the floor boards in this area too. I know all signs are pointing to some form of damp. The area in question is also about a meter away from the front gutter. I’m a bit scared to find out what the problem is, I might favour burying my head in the sand! Anyone had anything similar?

Is it crystals? It's probably just the salts in the brick and mortar leaching out and reforming.
Nothing to worry about, just a natural process.

Hi thanks for your reply, it isn’t crystal like in texture. it is soft and crumbly. Not efflorescence unfortunately.

Seen a lot worse! It just looks like brickwork which has suffered years of cold and damp and not anything serious but if you’re worried I’d get it checked out.

Are those bricks below the damp proof course (below the ground level outside)?

If so, damp is normal below ground level.

If above ground level and it's a cold external wall then it's likely condensation will form here- ventilation and heating is the remedy.

Check the guttering and down pipe for leaks next time it rains, see if any of the rain is pooling down the walls. Also check the drains for splash back- this is the type of thing that usually cause damp and are easily remedied.

Is it an old house?

It’s a Victorian house 1890. The area is below ground level but the substance is only in this area. One of the joists is also suffering. I am hoping to upgrade my lead pipe to plastic soonish so if there is a leak from this pipe somewhere that I can’t see then that will help obvs. The rest of the external wall below ground is dry. I will check the exterior wall the next time it rains. There is no apparent damp anywhere above floor level.

Can you see the timber damage?

Is there a drain near the outside of that wall?

The gutter drain is about 1 meter away from that mouldy corner. the hall is between the living room mould and the gutter. I don’t know which way the drain runs under the ground. There is also another gutter drain about 3 meters away in the other direction. No signs of problems in that corner. I do plan to go under he hall floor boards soon so that will allow me to see what is going on on the other side of that mouldy wall.

The look of the wet makes me think of an incoming water pipe. If so, changing that to blue plastic (what size are you getting?) will fix it, as long as it is all the way from the pavement stopcock to the above-ground internal stopcock. Have you got a water meter and a torch?

However, you probably have clay sewage and drain pipes in the ground, and yard gullies made of clay. If you are in London, or any town or city that was industrialised prior to 1945, or on a clay soil, they are pretty sure to be cracked and broken. A builder can dig them out and replace with plastic, but the socket (at least) on the first pipe that connects to them, and the first underground bend, may also be cracked and leaking. This sort of leak usually shows itself by a cavity in the ground, leading to concrete yards and paths close to the drains sinking and being repaired.

Meanwhile, pull away your insulation from the damp area, and clean out the airbricks to encourage draughts and airflow that will help the water dry out. You need enough airflow to dry it out at least as quickly as it is getting wet.

You will need to replace the timber that has been wet, and possibly nearby floorboards.

Thanks Pigletjohn, we have had a water meter recently installed and are soon to have a loft conversion. I will look to upgrade the water pipe and get Thames water to connect it up when we are doing the loft. Once they are digging around I suspect the source will become clear.

have a look at the water meter. You may find a glass window with an air bubble in it. All the time water is flowing, the bubble turns.

Turn off your indoor stopcock and see if the bubble stops.

this is a much better indicator than watching the numbers (unless you have a huge leak)

That’s a great tip, I’ll have a look and see what I can see.

Also, if bricks are left wet for too long, they eventually get porous and then the frost makes them crumbly.
You may want to check if the mortar between the bricks is still hard, and if not, have it repointed. Also check that the soil level outside the house isn’t touching the wall above the damp course.
It’s all fairly normal for old houses.