Bedroom wall stain mystery..

Joined
28 Jan 2004
Messages
14
Reaction score
1
Location
Surrey
Country
United Kingdom
I've been trying to get to the bottom of this problem for years - and hoping someone might be able to throw some light.
We have a damp /stained patch about 1m sq in an upstairs bedroom that starts just above the skirting. Its a solid external wall with painted pebble dash rendering externally. I figured possible cuplrits are:
1) Flashing where garage flat roof joins the same exetrnal wall at about the right height. However the patch is random in shape and not consistent with position or run of flashing.
2) External boiler flue chimney. This is not used and is now open at the top (although not open to weather) and capped at the bottom (in kitchen). Its position does overlap some of the damp / stains but again does not follow a consistent position. I am pretty certain the flue is dry as there is no evidence of damp where it is capped at the bottom.
3) Moisture trapped behind the external render.
3) Ventilation issues.

I have attached a rough sketch.

4 years ago the problem was mostly at the top in the corner of the room so I was blaming leaking roof / gutter / flue chimney flashing. I removed chimney & extended tiles, checked gutters etc. Not the slightest bit of difference (although it didnt seem to get worse after rain anyway).
So I hacked the internal render & plaster back to the brickwork and applied a solution to neutralise possible salts resulting from flue. Waited 6 months. Had wall re rendered (with sand & cement & waterproof agent) & plastered.
Top corner is now dry - and problem has now moved to lower area as per diagram.
I have used stain blockers of every type and they just bubble up & stain comes right through.
I am left with a few possible next steps.
Remove & replace external pebbledash render in case damp trapped behind - but reluctant as no apparent damp source...
Put airbrick in redundant flue in case condensation tracking into wall - but frankly as long shot in my view.

I'd appreciate any thoughts!

Damp patch.jpg
Sketch.jpg
IMG_20220627_090708.jpg
 
Sponsored Links
Joined
30 Jun 2021
Messages
680
Reaction score
129
Country
United Kingdom
At the moment you are moving the damp penetration from place to place.

Looking for damp signs, have you carefully examined the ceiling and wall in the room directly below?
Can you pic the fireplace in the ground floor kitchen?
Why not show a pic of the outside of the wall - pic the flat roof abutment with the external wall - a pic of the external chimney breast - and pics of the flashing and flaunching/capping of the chimney terminal?

Presuming that this is a gable wall, can you access the loft to examine the pike/triangle of brickwork?
 
Sponsored Links
Joined
28 Jan 2004
Messages
14
Reaction score
1
Location
Surrey
Country
United Kingdom
I have attached a few more pics. They do seem to point to the flue chimney as being the culprit. I am 99.9% sure water is not getting into the chimney but have had my suspicions it could be condensation as it is only open at the top (inside roof). It was capped at the base 20 years ago at ceiling height (as per pic). Perhaps an air brick at low level in the chimney might help - or else complete removal...?
Exterior wall.jpg


Flashing cu.jpg

Top of flue.jpg

Damp with dims.jpg
capped flue text.jpg
 
Joined
30 Jun 2021
Messages
680
Reaction score
129
Country
United Kingdom
Thanks for the new pics.
1. its not condensation.
2. it seems the kitchen previously probably had a solid fuel fireplace.
3. why they left that remainder of capped flue chimney breast "hanging" below the ceiling i dont know?
4. In the long run (or whenever you decide) it would be best to remove the whole of the old chimney breast from kitchen ceiling to eaves soffit.
5. Hygroscopic salts from the abandoned and partially vented flue are probably penetrating the solid wall.
6. you could hack off all plaster on the affected wall, & the return wall to a min 300mm beyond staining.
7. use a 3:1 sand and lime render mix to make good the walls. dont use any gypsum.
8. standing on the flat roof with a selfie camera & stick you could pic the gutter and first course of tiles?

If you decide to remove the chimney breast then you an always come back here to get advice for how to safely do it.
 
Joined
28 Jan 2004
Messages
14
Reaction score
1
Location
Surrey
Country
United Kingdom
Thanks for your thoughts. Extra pics below. Re:
3) We had the kitchen wall removed to enlarge kitchen. Yes we should have had the chimney breast removed at the time but it wasnt in budget - hence just capping it at the base.
5/6/7) I had the plaster & render comletely hacked off a few years ago and treated the wall with netralising solution as there was obviously a salt issue. Gypsum wasnt used but its still come back.
8) The grey plastic diverter is inserted between 1st & 2nd row of all tiles. (I have done this for the whole house as roof didnt extend far enough into some gutters). Coupl eof extra pics showing chimney breast running up between roof timbers.

Do you think worth trying setting a low level air brick in the chimney breast is worth a go? Give it a year and if no improvement then I'll go for removal.

IMG_20220630_100835.jpg

Exterior wall brick.jpg

IMG_20220630_101041.jpg

IMG_20220630_101049.jpg
 
Joined
30 Jun 2021
Messages
680
Reaction score
129
Country
United Kingdom
Yes, thats the position for an air brick.
The roof felt is supposed to go over the "plastic diverter" (AKA a felt supporter) & discharge any moisture into the gutter.
Your gutter is 1/2 full with debris.
By "gypsum" i mean any gypsum based powder plaster. If you didn't use any gypsum then what did you use?
"neutralising solutions" & similar are a waste of money - they mislead, they dont work. Render works.
 
Joined
28 Jun 2005
Messages
21,665
Reaction score
2,014
Country
United Kingdom
Have I missed a picture - I see no debris in the gutter ?
 
Joined
28 Jan 2004
Messages
14
Reaction score
1
Location
Surrey
Country
United Kingdom
Render layer was a cement / sand mix (not sure exactly what he used) with a waterproofing additive. Top coat was standard plaster - so presumably gypsum based.
Re gutter - its just a thin layer of dust washed off the roof - although agree might look a bit deeper. FYI the roof has no felt - its tiled directly onto timber slats. Makes for a dirty loft...
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Top