Damp wall : Not quite sure how its supposed to stay dry ?

bob_a_builder

Firstly , despite the user name I am NOT a builder just a DIYer 

We have a problem with a damp wall, but looking at the construction of the area I'm not quite sure how its meant to remain dry 
Below is a rough plan of the area - the numbers refer to some photos in the shared google drive folder for reference
The main house itself s 1830s with solid walls, although its not clear when the annexe was added - 60s maybe, just a guess

Link to photos
https://drive.google.com/drive/folders/1Xm59n4MTgAIC-841SlFI3ljUXyNItclO?usp=share_link

The obvious case would be something wrong or broken in the external downpipe and gutter in the area,  but it does't seem to be the case 

Wall A is the damp wall, on both faces


I have highlight below the points I am have difficulty understanding in relation to keeping Wall A dry - As much discussion points as specific questions realy

Wall A is and has been severely damp for quite a long period judging by the rusting plaster corner bars - apparently towards the top half of the wall
This wall is a painted brick front with internal breeze block wall , a damp course can been seen from the outside of annexe, below the paint line

Wall B, I assume has to be a double skin wall, brick to the garage side and presumably breeze block to the annexe, hence the render
But can see that wall is rendered to the right of wall A  - that render is not attached very well to that wall nearer the annexe - sounds hollow as you tap it in that area
Q1: The render goes right up to the brick face of wall A, so there seems plenty of possibility to transfer damp there ?
Q2 : Wall B seems to be both an internal (beside stairs) and external wall ( to right of wall A) - How can it be both ?
Q3:  Is there / should there be some break in (the internal part of)  that wall to align with the cavity in Wall A ?


Wall B is capped by some ridge tiles 
Q4: Is there possibility there for the capping to bridge the cavity which I assume must exist in wall B

On the garage roof you can see some weeds and budlia have gained a foothold, which no doubt accounts for the damp on the garage internal wall, although this looks to be closer to the front of the garage than the problem point Wall A joins Wall B
Q5: Could that have breeched the cavity in wall B - if the beam holding garage roof was too long

I already asked question here about the plastic material seen in the hole opened in the small box section which has been opened up in the area (picture 3)
https://forums.moneysavingexpert.com/discussion/6440477/what-the-purpose-of-this-material
This does seem to imply there was an expectation of damp in this area ?

So just looking for some help/knowledge/thoughts on how Wall A is meant to be kept dry ?
And how you might tackle the problem

Thanks for reading this far and I hope the drawing and photos give you some idea what I'm talking about 

stuart45

When a cavity wall joins another wall at right angles there's allows a chance of moisture getting through in the corner. That's why if the existing is a cavity wall a new cavity is cut into the existing, or a cut and vertical DPC installed. If it's a solid wall you can't do this.

twopenny

Does the sun ever get into that stairwell? It does, from the drawing, seem like it could be a shady cold area.

bob_a_builder

twopenny said:

Does the sun ever get into that stairwell? It does, from the drawing, seem like it could be a shady cold area.

Not very much, just 1st thing in morning if lucky - Wall A faces east.

The annexe is only really used for letting in the summer, and or family visitors so not really heated most of the time

Sarahspangles

I’ve heard an architect who worked with vernacular listed buildings say that many were never designed to stay dry by preventing water getting in.  The fact there were fires on hearths as the main method of cooking, heating and heating water, plus reasonable ventilation from every leaky window and the eaves, kept them dry in winter.  Then it was a bonus if there were cold places in summer as your milk might not curdle by teatime.

stuart45

I'd look at the areas where the moisture looks like it's getting in. Around the end of the gutter looks a damp place, and below the timber cladding are a few courses of exposed brickwork.

markin

The plants want removing and repointing done, The is no over hang on the ridge tiles, I think i would remove them and have lead flashing put on it.

External insulation probably all you can do, if the was a good roof overhang a new wall to make it a double brick cavity wall could have been built.