Why is this wall damp?

[JRJ]

The easiest way would probably be to remove the upper trim panel outside, hopefully without damaging it

Does it get worse in certain weather conditions? for example rain and high winds but not rain only, could be a bit of a wind tunnel down the side of the house and driving rain against the frame.

 

[GeX]

Ta, I'll see what I can get to.

The only time I really notice anything get worse is when it's humid.

tbh, I think the whole internal side of that wall could do with the plaster coming off, DPC doing and then anything else fixing at the same time before new plaster goes on. There are too many parts that are having issues, indicating multiple issues that need addressing.

 

[DXP55]

My old house was built just before WW2 and was according to council planning one of the first cavity wall houses in Shropshire - We had no problems but when a new neighbour moved in (semi) and had been there for a while he came round and asked if we had water in front room on floor.
We hadn't so he ripped floor up and concreted it which cured it but only because the plastic sheet under concrete finished above the damp proof course.
When we did our extension and knocked a wall through we found that the base bricks under damp course were solid and damp proof course was pitch/tar spread across surface of bricks and then cavity was built above.
Next door in his hast to start converting removed gutters from front door porch and his tarmac drive sloped right up to front door - The rain water coming off porch roof just hit tarmac and splashed up outside of wall then just ran across damp course and came out the other side.
This long reply really means you might have a solid DPM

 

[GeX]

I can see the cavity is full of debris. I should have remembered this when doing the fibre as the loads of debris that's come down.

Blue = outer course
Red = inner course
Orange = bricks the joists are sat on

Can see the fibre goes up to the vent

Then looking from there down to the corner that is damp. (can see pipework for the rad)

 

[fastwunz]

Perfectly normal to have cavity houses of this age. Plenty of them.

Get yourself an endoscope off of Amazon

 

[JRJ]

I can see the cavity is full of debris. I should have remembered this when doing the fibre as the loads of debris that's come down.

Blue = outer course
Red = inner course
Orange = bricks the joists are sat on

Can see the fibre goes up to the vent

Then looking from there down to the corner that is damp. (can see pipework for the rad)

As @fastwunz said grab an endoscope and take a look inside, you'll likely find that that cavity is a sealed section only to the external vent and not the main wall.

Is the cable through the vent causing rain water to track inside and then during humid weather its not able to escape, part of me is thinking that this maybe a ventilation issue if its during humid weather and not heavy rain.

 

[GeX]

No, the cable is not related. It’s no where near any damp bits and the damp bits have been there long before the cable. It’s just that I can easily lift the floor there and see the construction of the wall as the external vent is there but also a gap in the inner course to allow the sub floor to ventilate

 

[-Ad-]

Endoscope is a good idea for a look around.

It doesn't look damp under the house, looks really dry actually.

I would be investigating more around the top of the window.

 

[Ogoshi]

I'd have a very good look at the guttering for any blockages or cracks, but also any internal pipework.
I found a trickle leak from a pipe in our loft last week which had tracked down a vertical pipe to the ground floor ceiling before soaking the ground floor chimney breast.

 

[Ogoshi]

Also from your picture the base of the external wall where the downpipe meets the drain cover looks wet - could be related?