A dark patch in the Paint

[Roger111]

Hi All

Im looking for a little learned input. ive patched some lime plastr in my attic room, filled it in, all with lime products. I have a section of wall near the top of the room just below ceiling. I didnt need to patch plaster on this wall as was solid. When we painted (Using Earthborn Clay) the room looks great but this one area about 2ft by 3 ft appears darker.

It almost looks damp, but doesnt feel damp. Its about 3ft away from chimney breast (All of which looks fine).

Any ideas? Should I paint again, Get a moisture meter on it etc.

Would really appreciate any advice?

Also as a second questions, in lower rooms ive got gorgeous old skirting boards 12 inches high and about 2 inches thick. Im told oak. They have oodles of old paint on them. Is it ok to just sand? Ive tried it in places (using safety gear) and it looks ok, but coming from modern houses im used to Barrat style smooth wood.

Am I letting the side down and should i strip it all, or is it part of the character

Thanks again all, This forum has kept me sane!

 

[Surveyorman]

Hi Roger,

Regarding the first part of your post:

Any chance of a photo of this area? Alarm bells ring when mysterious damp patches appear near chimneys as these are areas that are often heavily contaminated with salts from the historic burning of fossil fuels. These salts are hygroscopic and can draw moisture from the air so sometimes these “mysterious” damp patches appear, dry out and disappear only to reappear again when the Internal atmosphere changes. Be careful of using a moisture meter near a chimney as these will give back erroneous readings if they come into contact with salts.

Another consideration is that the chimney stack itself is usually situated directly above the attic space. Have you had a look at the stack for areas of potential moisture ingress? Check flashing, flaunching, pointing. What are the gutters, soffits and fascias like adjacent to the chimney and in the corresponding area of where you are noticing this damp patch?

If you’re able to send a photo I will tell you whether or not it is worth investing in a moisture meter to take a reading...

 

[Flyfisher]

Regarding the skirting, it sounds wonderful but whether or not to strip off all the paint will depend on the rest of the decor. Personally, I think layers and layers of paint add something to such things and when ‘cleaned up’ they can look too new, probably because the paint layers add a ‘rounding’ effect to sharp edges and mouldings. But that’s just a personal preference. Of course, with intricate mouldings or carvings, layers of paint can be detrimental so it’s all a question of balance.

Assuming you want to repaint, a light sanding to provide a key for another layer seems fine to me. Just beware that old paint is likely to contain lead so the usual dust precautions apply, though it sounds like you’re already on top of that. Incidentally, lead testing ‘pens’ are available for a few pounds if you really want to be sure. I used one once but now just assume that all our old paint is lead-based.

 

[CliffordPope]

I've got these odd patches in places, nowhere near chimneys, that have no apparent relation to water ingress. They come and go with the humidity, and I think are caused by hygroscopic salts present in some stone. It's impractical to think of excavating into the walls to remove and stonework, so the only solution seems to be to locally mask them with impervious paint, or stick on a patch of special wall paper.
I've even resorted to sticking an impervious backing onto a picture and hanging it over the patch.

It's a similar sort of problem to wood that has ancient oils or tars deep inside, and no matter how much one cleans and paints, eventually the colour gets drawn to the surface and causes unsightly stains in light paintwork.

 

[TheForge]

Shellac primer may mask the discolouration. Zinssers BIN applied by aerosol will give the thinnest possible coat or you can dissolve your own shellac flakes in alcohol. Permeable distemper will readily adhere over it (although the shellac will be relatively impervious).

 

[CliffordPope]

But you want the paint to be impermeable at that point, surely? It's because the surface is permeable that the discolouration comes through?

 

[TheForge]

Yes, the point being the shellac provides the barrier and the same permeable paint as the rest of the room can be used to cover the shellac maintaining the same finish and colour.

 

[Roger111]

Hi All

Apologies for the lack of reply. Thanks again for all the inputs. Its really appreciated

One last question.

Ive got all my breathable paint. Earthborn ready for painting. The decorator, who has a great reputation is stating we could have bought Matt Trade as its also breathable? I was led to believe this isnt the case hence buying Earthborn.? Any ideas.

Im still confused re breahthaility, Im a middle terrace and whilst lime plaster, stairs and landing have been gypsum skimmed many years ago with no negative affect ?

Best

 

[Feltwell]

Im still confused re breahthaility, Im a middle terrace and whilst lime plaster, stairs and landing have been gypsum skimmed many years ago with no negative affect ?

Breathability is a funny old thing. Firstly, it only matters on external walls, I presume quite a few of those are internal. Secondly, lack of breathability *can* lead to problems, not *will* - you can have an external wall covered in gypsum and emulsion that is never a problem, you can have another that has a problem, there is sometimes no obvious reason why! Of course the outside of the wall makes a difference as well, if that's breathable, does it get the weather on it, is the pointing / render in good order, etc etc

 

[Roger111]

Thanks Feltwell. Much appreciated!

 

[Abi Cott]

There are different levels of breathability, and the vapour permeability is not easy to compare between paints because companies don't always publish the figures.

Trade Matt (non vinyl) paint is breathable, you can use a mist coat of it over recently applied gypsum plaster and the plaster will continue to dry, albeit somewhat slower. However it is not as breathable as Earthborn paint. If a manufacturer doesn't tell you exactly how breathable it is, assume it isn't enough is my rule of thumb.

 

[Roger111]

Thanks Abi

Much apprecaited!