Help! Weird band of damp suddenly appeared

[buckleberrybinn]

Calling Piglet John and all other kindly knowledgeable people! 3 weeks ago I painted in the living room - 2 days later noticed this band of damp that has appeared just over half way up my living room wall, next to the front bay window frame. It goes back along the wall and round the corner wall too. Under this band there is a semi-circle of damp at the window frame edge. Long drip stains have now appeared in the wallpaper too. Cannot understand it at all as it was not there prior to painting.

Outside the pebbledash and the window seal seem fine to my untrained eye. I have looked at the guttering in pouring rain, doesn't seem to be spilling over. Upstairs radiator not leaking. Victorian semi.

Have had 2 builders round - first suggested checking out the guttering. Second said it was probably condensation and to put in trickle vents (really not sure on that one...) Have another coming on Friday. But am very worried that no one will work out where it is coming from. Ideas welcomed. Thank you.

Could you have a leak in the brickwork somewhere or what about pipes under bath/shower?

Blodss - I have no bathroom upstairs, only radiator in room above, outside is all pebbledash with no obvious crack visible. I did have the front of the house painted in May so currently it looks in good condition.

Is the bay only on the ground floor? Could it be the bay window roof or a gap around the window? Sometimes water finds its way out some distance from a leak and a little bit of damp looks a lot on a wall.

If water is getting behind the pebbledash from above (e.g leaky gutter leaky roof dripping on a hairline crack in the pebble dash higher up) the water will seep down with gravity until it hits an obstruction (eg a solid mass of concrete stuck to the wall at a certain level. It will then pool in the wall and soak inwards. Pebbledash put on with cement is impermeable so will soak inwards as it has nowhere else to go.

I say all this with the experience of living in a 1920 cement rendered house with a huge damp patch on a bedroom wall caused by exactly this problem. We mended the roof and the gutters and the problems disappeared.

I now live in Georgian house rendered with lime based stucco plaster. In the past the previous owners repaired the stucco with ordinary grey Portland cement that caused damp patches. The cement is impermeable to water but stucco breathes.

Cement render on a wall is sure fire way of getting damp. It sounds to me like someone repaired the pebbledash at some point in the past possibly from ground level up to a certain level on the wall and that impermeable line is where the damp is appearing.

All house walls have damp in them and they need to breath as the seasons change. Now autumn is with us your damp has appeared. Our remaining small damp patches also appear as if by magic near a bay window if it rains heavily or the air is damp in Spring and Autumn. In Summer and Winter when the air is dry they disappear.

Apart from checking gutters and roof to make sure nothing is coming in from above I suggest you tae a careful look at your pebbledash as I think that is the problem. It may be worth paying a surveyor but don't get some sort of damp proofing firm in they will just tell you it is rising damp and sell you some expensive solution that wont work. You need to understand why it is happening - not just hope to cover it up or inject something into the wall.

Could the radiator in room above have a leak

freeworker sounds right. I think rain is getting in and running along a crack.

I don't believe it's condensation. Tape a piece of clear plastic or clingfilm tightly to the wall. Observe if water droplets form on the room side or the wall side of the plastic.

Thank you Freeworker - I can now have a very sensible conversation with the builder when he comes on Friday! Agreement from Piglet John too seals it. I need to find a builder or surveyor willing to help me find the cause, not just do any old quick fix, though I really want it fixed now, so worried about the water coming in. (Will do the taped plastic to wall though, just to check). Thank you all.

JT05 - the square bay extends up the whole of front of the house to roof. Will get someone to check guttering closely and for any cracks in pebbledash around the top.

Have you checked all the silicone sealant joints round the window frame where it
meets the wall? Water can get through tiny gaps where the silicone has shrunk and dried out.

We have patches like this in our house. We knew the render was in a poor state when we bought so luckily we expected it but don't be fooled by how small the damage on the outside can be and still cause a problem.

Window sealant is a possible suspect - need to have another good inspection in daylight. The render/pebbledash is now my prime suspect though! It's dark when I get home in evening so have to wait till Friday when I'm off to go out again and inspect.

the stain looks like it slopes downward from right to left, so I would suspect water entry in the right corner. I would look for a cracked downpipe outside, or damage where the pipe clamp had been spiked to the wall, or loose render.

I had this. In my case the drainpipe was overflowing because three pipes were collected into one. It would overflow and water would run down the side of the house.

The exterior had to be redone meaning the stucco was scrapped and redone before being painted and new pipes were put up. Cured it but cost about £15k in 2004 to do because of scaffolding for 5 stories. I also didn't go with PVC pipes due to the character of the property. I went with copper pipes I purchased from a house down the road being renovated. I matched what the salvage yard was going to pay so saved an awful lot.

Also if your windows are wooden framed check their condition on the exterior. Hopefully the damage isn't long term as if so you may need to replace the frame. I just sanded down the frames and repainted.

My big worry is that pebbledash has to come off but the cost of yours Want2!! My house is very small but hoping it doesn't come to that.
PJ - there is no downpipe that side of house, my short bit of guttering joins to neighbour who has downpipe beside his bay. My downpipe is other, far side of my bay window. But guttering and fixings need to be looked at.

Hate to break it to you but if I were to do the work today using a third party contractor it would probably cost me at least GBP50k. I had my Dads team do the work so I paid cost and they stayed with me as all are from the north and the place was in central London. We had to rent the scaffolding which was about GBP5k back then.

It sounds to me like you have bad guttering plus you probably have leaves etc in the gutter making them less efficient. I had major arguments with the council regarding roof access because the only way to safely clean the gutters was to get onto the roof (which was flat). They thought I wanted a roof deck or something when I wanted to install stairs. I just didn't like climbing down a ladder twice a week in the autumn with a heavy bucket full of smelly gunk from the gutters!

Pebbledash is usually easier to remove than stucco making it much cheaper. Worst case they can apply a very thick layer of paint over the top of the pebbledash which should give you a couple of years to save up to fix the exterior properly. The exposure of the facade to the sun has the biggest effect on the paint lasting. My place faced the sun and the road was like a wind tunnel so I had to paint the front every 3 years. The back was painted every 10 years.

Upvc windows here. I'm telling myself that it won't get to the point of re-doing front of house.

Just to update after seeing builder today. I am going to eliminate my windows first of all. The surround and sealant is old and poor, although not obviously defective. I am getting all of the indoor surround plastic (which is quite wide) removed, check inside for leaks, then replace and reseal. Also getting outside window edges resealed too. Rain water could be pooling on window sill and seeping inside (will look when next rains). I'm also shortly getting someone to check all the guttering at front of house, and clear it, if necessary and to check for cracks in pebbledash at the top that we can't see. Also, will try to get up one small bit of laminate in upstairs bedroom, under the radiator to see if any leak. Have family help for most of this, so hoping won't cost too much at this stage. If we don't find cause will then have to get professional in to look more closely into the pebbledash. Hope to get these first bits done within the next two weeks. Really need to find the problem. Thanks for all advice.

I noticed the post about it possibly being the radiator leaking. Hope that is it as could be the easiest to fix

'mmm

has your boiler got a pressure gauge?

Have you got a water meter?

What does it mean if the plastic sheet taped to the wall has condensation on the wall side or outside?

on the room side, it is condensation from humid air in the room.

On the wall side, it is from a damp wall.

Piglet - no water meter and no pressure gauge. Old boiler (11 years) - v basic model but works fine. I have taped cling film to wall - no water on it yet.

I still think the source is rainwater, most likely from the roof and gutter, showing through a crack in the wall, but a radiator pipe leak can easily be confirmed.

With a sealed system, loss of water would show as a pressure drop on the gauge. An open vented system will have a small feed and expansion tank in the loft, about 18"x12"x12". In it is a ball cock like in an old WC cistern. Tie the float up (you may find a piece of string and a nail in the roof timbers from last time this was done (which will prevent it from being topped up). Observe the water level (there will be a tidemark). Leave it for a day or so. Look again in a day or so. If there is a leak, the water level will have dropped. Remove the piece of string after this test, but leave it handy for next time. The F&E should have a close-fitting lid to keep dirt and wildlife out. There may be a layer of mud at the bottom which you can deal with another day. Don't stir it up.

Ok Piglet - will get up in loft shortly to check and try what you suggest. Really appreciate your advice.