Help with condensation in my 1930s semi

[Jaygray9093]

Hello

I recently moved into a semi detached 1930s property in East London.

Survey said it possibly had damp issues.

One wall in particular, seems to be the problem. Particularly under the suspended floor.

Solid wall construction.

The wall is an external gable end. Facing the shared alleyway between me and the neighbour.

The brickwork below the suspended floor is covered in condensation. It's rotted out multiple joists closest to the wall.

I've checked for leaks. No issue there.

Patches of mould all over the wall in different rooms. However the worst part in under the suspended floor, in between two airbricks. Roughly 2.5m to the closest one.

I'm thinking it needs better airflow. The rotting and soggy sand/cement needs to come out.
But is that enough?

 

[Jaygray9093]

Condensation above dpc

 

[Cubist]

Hi There and Welcome,
The only way for condensation to form in that location is for warm air from elsewhere in, or under, the house to come into contact with that cold brick wall. Warm air from any/all domestic heating systems will rise and draw cold air from this void making condensation highly unlikely. I've never seen this phenomena personally but I believe what you are seeing here is rainwater from outdoors bleeding through porous bricks. If I'm right then the problem will have to be addressed outdoors.

Hopefully other members with more relevant knowledge and experience will be along soon to offer alternate ideas of the cause and treatment.

Cheers for now,
Cubist

 

[Stevers]

It's worth monitoring as that amount of condensation could be from wet and 'warm' (for time of year) weather following a cold spell. The sort of weather pattern that causes condensation on the outside of windows!

 

[fernicarry]

@Cubist could be right about the source of the moisture but I'd add that with the temperature bouncing up and down every few days at the moment things that are usually dry have become soaking wet after the temperature drops suddenly. My garage where the power tools live is a prime example. Some mornings the metal surfaces are soaking wet. Its not heated or attached to anything heated. I'd monitor the wall for a while to see if there is a pattern to when it gets wet.

What is the rotten joist sitting on? It needs some sort of DPC between it and the sleeper wall. Also doesn't look like its in contact with the wall so the condensation won't matter to it.

Is the pink stuff in the distance squirty foam? That could be bridging moisture in the wall onto the ends of the floor boards so causing more harm than good. Won't necessarily be the cause of the joist rot but you could have a range of things going on under there.

 

[Cubist]

Thanks @Stevers and @fernicarry I hadn't considered the external temperature bouncing up and down as it has been as a means to precipitate condensation on the inner face of the bricks but, as the air temperature in the floor void must be warmer, theres no reason why it shouldn't. Good catch fellas.

 

[Jaygray9093]

It's worth monitoring as that amount of condensation could be from wet and 'warm' (for time of year) weather following a cold spell. The sort of weather pattern that causes condensation on the outside of windows!

Thanks Steve, I'll monitor and report back once I have a pattern..

 

[Jaygray9093]

@Cubist could be right about the source of the moisture but I'd add that with the temperature bouncing up and down every few days at the moment things that are usually dry have become soaking wet after the temperature drops suddenly. My garage where the power tools live is a prime example. Some mornings the metal surfaces are soaking wet. Its not heated or attached to anything heated. I'd monitor the wall for a while to see if there is a pattern to when it gets wet.

What is the rotten joist sitting on? It needs some sort of DPC between it and the sleeper wall. Also doesn't look like its in contact with the wall so the condensation won't matter to it.

Is the pink stuff in the distance squirty foam? That could be bridging moisture in the wall onto the ends of the floor boards so causing more harm than good. Won't necessarily be the cause of the joist rot but you could have a range of things going on under there.

The sleeper is sitting on brick. No dpc or slate. It is touching the external brick, which is where it's most rotten.

The pink think is insulated tile backer as that area sits under of a newly installed showee tray. No leak from the shower/ it's only been in a week so woukdnt of caused the rot.

How do I know if my dpc is working? Does condensation have anything to do with DPC?

 

[Lacan07]

The sleeper is sitting on brick. No dpc or slate. It is touching the external brick, which is where it's most rotten.

The pink think is insulated tile backer as that area sits under of a newly installed showee tray. No leak from the shower/ it's only been in a week so woukdnt of caused the rot.

How do I know if my dpc is working? Does condensation have anything to do with DPC?

they never used to bother wth a slate dpc on sleeper walls I believe, mine never had any. The only rotten plates I had were in the corners of rooms adjacent to external walls where high external ground was causing damp issues. makes you wonder about the validity of rising damp really.

i wouldn't have thought your condensation has much to do with the dpc

 

[stuart45]

They were supposed to put a slate DPC on sleeper walls, depending on the age of the build. A lot depends on the water table. Often the ground inside the footprint is dry, so you don't get a problem.