Strange Circular Damp Stains? - Used Zinsser bin.... returned in 3 days

[RussB32]

As you can see in the photo, I have 2 circular stains, and some further staining down at the bottom of the wall behind the skirting.
These have been present for several years, so I decided to tackle them. As intructed on the Zinsser BIN tin, I painted straight onto the wall onto the existing paint and stain. I applied two good coats with a couple hours dry time in between (it was touch dry within 20 mins). I then repainted over the Zinsser BIN with the same Deluxe paint as when we decorated the room originally.

Within 3 (dry) days the stains have returned, and are as seen in the photo.

What's my next plan of attack?

For more info.... 1930's solid brick house. Outside walls are sound with no obvious brick defects or holes. Potential damp/rising damp issue that I'm still working on solving.

 

[JohnD]

The marks look like spot damp. If there is, for example, a metal object or a defect in the brickwork, it might be condensation.

If there is a defect in the brickwork, and a source of water on the outside, such as a leaking gutter, it might be penetration.

If there is a pipe buried in the wall, it might be a leak.

It does not look like "rising damp" because damp does not leap up from below the ground up to two spots part way up the wall.

The person best placed to look at your house and investigate the source of water is yourself.

Why is there a pipe sticking out of your skirting board?

 

[RussB32]

The pipe is a door stop. Does look like a pipe from the photo!

I think it could be a brick defect then. There is no immediate water source on the outside of the wall. The drain pipe from the roof is 6 feet away on the corner of the house. There is no pipework in the wall, only a radiator pipe that runs under the floor. But I think id be aware if my heating system was leaking substantially.

 

[opps]

That is odd. The shellac based version of BIN should stop any water stains bleeding through. Did you use the shellac based version or the newer waterbased version- I have not used the latter.

It might indeed be condensation hitting cold spots. Try aiming a fan heater at it and see if it disappears. Alternatively, tape some aluminium foil to the area for a few days. If moisture from the wall, you will see evidence of moisture on the side facing the wall. If the foil is tight enough to the wall, if condensation, you may see moisture on the room side of the foil.

 

[RussB32]

See a pic of the tin.

I 'knocked' around at the wall at the weekend. A lot of the wall sounds very hollow, apart from the damp circles which make a dull thud. I'm not entirely sure if the wall has been plaster boarded, and the circles could be Dot/Dab ?

The cold is potentially bridging across this point on the wall, as it is in contact with the cold outside bricks.

If this is the case, and the condensation is forming from within the house, how do I solve this?

I have 3 dehumidifiers in the house and try to maintain a reasonable humidity level

 

[foxhole]

How about some pics of the other side?

 

[opps]

Not really sure what you can do until you deal with the rising damp.

You could use thermal lining paper, eg https://www.toolstation.com/wallrock-thermal-liner/p43007

Although I am a decorator, I have never used the stuff and cannot say if it really works. @Wayners have used it.

The fact that you have 3 dehumidifiers suggests that you know that you have a condensation problem.

It might be worthwhile waiting a while for responses and then if still no joy, ask the Mods to move it to the general subforum.

Over the years, I have had customers with 9" walls, first floor so not rising damp, 3 external walls, the advice was to dot and dab insulated plasterboard and then fit an air brick.

I don't know how sound the advice was, but it seemed to work.

 

[RussB32]

Photos of the house. I have highlighted in a red circle roughly where the damp spots correspond to the outside wall.

Further house history.... To ensure no opportunity for rising damp. I dug out a 2 foot ish wide trench, right down to the concrete footing off the house. I think dug another inch or 2 below the footing top. I then back filled with trench with old brick/rock/coarse gravel and then finish gravel on the top. My theory is water cannot be 'trapped' against the brick now, and there is a small amount of air flow available down to the footing. I have current done from the left hedge to the front door. I plan to do the same from the front door, to the right down to the back gate this winter.

When we first moved in, the house didn't have a bathroom or kitchen extractor, so condensation and humidity was a big problem initially. I have since fitted good quality bathroom and kitchen extractors which have greatly improved the internal air quality. I still use the 3 dehumidifiers (1 on each floor, we have a loft conversion) as an extra form of humidity management.