condensation between windows

[captaincaveman]

i've read a lot of posts re. condensation and can't find an answer to curing my problem.

i have a damp patch in my bedroom about the size of a dinner plate. Its on the wall between two large sash windows, between the windows sills.

My house is circa 1900, the outside bedroom wall is north facing and the room doesn't get much light, the bedroom always feels cold. there is always condensation on the windows during cold spells, but the sills never feel wet.

I have resealed window frames, sills, cleared out cavity wall and still have the problem. i don't dry clothes in there, is there something else i can do other than stop breathing!!?
please help!

 

[^woody^]

A brown damp patch that comes and goes after rain, or a patch of black mould that's always there?

What sort of external cills are fitted, and is it really a cavity wall from that time?

 

[captaincaveman]

A brown damp patch that comes and goes after rain, or a patch of black mould that's always there?

What sort of external cills are fitted, and is it really a cavity wall from that time?

Hi Woody,
theres no black mould, just discolouration of the paint where its damp. I've taken a bit of the plaster off, and theres concrete/cement render underneath. I guess it is worse after rain, however always seems to be there.

the external cills are rounded dark grey blocks, there wasn't a significant mortar joint between each block so i removed one from the cill and respaced the blocks.

when i had removed the cill i was able to reach down into a cavity, underneath the window frames, and managed to clear some rubble, i think the cavity only goes down as far as a course of dark grey bricks running the length of the outside wall about 12 inches or so underneath the windows.The walls at the bottom are probably at least a foot and a half thick. I'm not sure whether theres a damp course, however one of the windows used to be a door, and i remember there was a plastic sheet running down inside the cavity underneath the window. hope this is not too much info, regards nick.

 

[captaincaveman]

Hi Woody,
theres no black mould, just discolouration of the paint where its damp. I've taken a bit of the plaster off, and theres concrete/cement render underneath. I guess it is worse after rain, however always seems to be there.

the external cills are rounded dark grey blocks, there wasn't a significant mortar joint between each block so i removed one from the cill and respaced the blocks.

when i had removed the cill i was able to reach down into a cavity, underneath the window frames, and managed to clear some rubble, i think the cavity only goes down as far as a course of dark grey bricks running the length of the outside wall about 12 inches or so underneath the windows.The walls at the bottom are probably at least a foot and a half thick. I'm not sure whether theres a damp course, however one of the windows used to be a door, and i remember there was a plastic sheet running down inside the cavity underneath the window. hope this is not too much info, regards nick.

 

[^woody^]

It seems more like penetrating moisture, rather than condensation.

In which case check external wall immediately outside the damp spot or above for anything obvious. If it is a cavity, then moisture will only get across is there is a bridge across the cavity.

Alternatively, it may be a cold spot casual by the render or a solid bit of wall or suchlike, and his could be being made colder by rain, without penetrating, but cold enough to cause local condensation.

 

[JohnD]

tape a piece of clear plastic tightly to the wall. If water forms on the room side of the plastic, it is condensation. If it forms on the wall side, it is wet wall.

Near a window it is often water coming in where the frame meets the wall. It may run down a crack and across a tie and show, nowhere near the point of penetration.

You can try getting someone to squirt a hose at the wall while you watch, in a dry spell.

 

[captaincaveman]

many thanks gents for your comments, i have re-mortared, resealed, and redecorated the window frames outside, i was contemplating removing a brick from the area of the damp patch, inside, maybe that will shed some light on the problem!? i will persevere