Damp Wall - Advice needed

[fonzee]

Evening Gents,

Hopefully some of you have some experience with controlling/dealing with damp issues.

The property in question is a mid-terraced cottage roughly 100 years old, renovated 3-4 years ago by the previous owner, including a new roof.

Basically the damp is bad in one of the walls/ends in the loft and is now showing in the master bedroom beneath.

One side is stone (possibly original?) and one side is partitioned with insulation/plasterboard etc (neighbours that side went up into the loft).

The stone side is the problem side.

Here is the stone side:

I have been reading the damp values of this wall and generally the red area is reading 27-33% (high), yellow 20-26% (medium to high).

^ That reading was taken just above the beam low down on the wall, the master bedroom side.


And just to give a full picture of the loft, here is the opposite end, the boarded side:

Generally the damp readings on this are far lower (10-19%) except the main wooden strut in the centre, which is also reading high at around 25-30%. This side generally doesn't concern me as we have no real issues below on this side of the house.

Going back to the stone wall...

Now I noticed the previous owner has shoved insulation down the side gap between the last beam and the wall itself. I have started removing half of it (highlighted in red) to have a closer look.

I was thinking maybe too much insulation is being used as air still needs to be ventilated in the loft?

And finally here is the damp patch showing in the master bedroom below:

Generally wall reads at 10-12% until it shoots up to a 24-26% on the damp area.


My question is what is the most likely cause of this?

Too much insulation used? Leaking roof?

I can find no actual water presence/wetness anywhere. No other areas are affected. Lower rooms/ground floor is fine.

Anyone had similar before?

Any advice appreciated.

edit: added to description, house is a mid-terrace, so this wall is not external.

 

[fonzee]

From what I can tell from looking through the ground floor vents the walls have a gap between the wall and the celetex/plasterboard.

So it goes Wall > Gap > Celetex > Plasterboard...

And both gaps feed up into the loft space front and back I believe.

However there is no vent to outside anywhere... None on ground floor and none in roof space. Only internal as it were if that makes sense?

So basically black is main structure/walls, red is plasterboard on studwork and green bits are the ground floor vents. There are no vents on first floor.

 

[fonzee]

Thanks for the feedback guys. House is a mid-terrace, so no, not an end wall.

I believe that wall is original so possibly lime like you say. I'll take a closer look tonight.

As you can see the previous owner has rendered over some parts too. I noticed this render is starting to fall apart/come away already I assume because of the damp.

So basically for plan of action:

1. Add more ventilation in general
Should I add a vent to the outside wall somewhere on the ground floor to get some fresh air flowing through the walls? As far as I can tell there is no external input currently. And as for adding ventilation in the roof area itself, the roof has no overhang/soffit so I can't add the circular downfacing vents, so I guess I only have slate vent options?

2. Remove cement render and replace with something more permeable?
I assume it would be best to add a more permeable render after a few months once the wall has dried out?

 

[fonzee]

I assume it's there for a reason. I'll remove and see what I find/post up pics.

Any thoughts on adding an external input at ground floor level?

 

[fonzee]

OK I've been looking into this again tonight.

Removed some of the cement render, lots of eroding lime behind it, not surprised! So all this render will have to come off at some point.



Then had a closer look at the eaves.

You can see where I have pulled back one length of insulation, the neighbouring piece shows you where he placed it.

I assume this is far too close? Thoughts?


I then pulled the rest of the insulation in that section back. There is no ventilation what so ever.

Went back next to the wall to check for water getting in again under the ridge with proper light. Found this:

That is at the stone wall/chimney end. The circled areas are wet to touch.

The strut below was also very damp as shown.

And these struts below that were damp on the outer edge too.

The rest of the rafters in the loft were dry, it's just this area/end.




Onto the outside...

Here's the front, best picture I could get as I don't have a tall enough ladder to get me up there:

That vent on the right hand side is the bathroom extractor fan so separate ventilation from the attic itself.


Onto the rear, was able to get up on the extension roof and get some better pictures:

You can see what a mess he made of the neighbours side.


Zoomed in a bit to the offending area here:

So what do we reckon? Ridge tile cracked/pointing knackered?

I can't believe it was done 3 years ago :/