Bubbling paint due to reoccurring damp problem, what cause?

[Barzin]

I have a problem with bubbling paint work on the ground floor of my house beneath a living room window and to either side underneath the window. The bubbling typically occurs around 6-12 inches above the skirting but also higher up, with clear 'lines' of damp stretching upwards in places. The wall is an outside wall, and I have concrete floors.

The problem does actually extend to a corner where the exterior wall meets an interior partition, and the problem does stretch a few inches along the partition also. On the other side of the partition is the kitchen, but I've not had any major problems showing in there because there are cupboards/tiles on the other side. However, I did notice some low level condensation on the tiles in winter - whether this is related in any way I don't know. I've not seen any signs of condensation on the living-room side of the partition.

I've checked the wall outside and there is no sign of cracking/damage (was rendered a few years ago), there's no sign of potential water ingress around the window itself, and the guttering was replaced in the last 12 months. The problem has been ongoing for just over 2 years and shows up every few months, at which point I strip and re-paint the affected areas. The last time I tried damp sealant paint but (predictably) it didn't really help much.

Cavity wall insulation was installed in 2002 (I moved in in 2006), but I don't know whether this is related. There is an air vent on the outside of the house around the point of the interior partition, but this looks to be free of any blockage.

Photos attached below showing bubbling and areas where bubbling paintwork has been removed. Can anyone help shed some light on what might be causing the problem, before I contact the cavity insulation installers for assistance?

Untitled

• Barzin
• 23 Mar 2009
• 1

Untitled

• Barzin
• 23 Mar 2009
• 1

Untitled

• Barzin
• 23 Mar 2009
• 1

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[mac3]

I once had similar problems and found it to be a failed seal on the glass unit in the frame. the water was running down the glass and through the upvc frame and into the wall causing localised damp around the corner of my window sill.

 

[Barzin]

mac3, I did wonder that at one point as there seems to be a path from the side of the window frame down, but I'm guessing it was clear that the glass had failed in your case? I can't see any sign of where water would get in to the glass or frame.

 

[hotrod]

Hi Barzin, How old is the property? The skim finish under the window looks relatively new but I suspect the house is not? Do you know if the property has an effective damp proof course?

From what you have said and the pictures I would either agree with mac3 that moisture is getting in via a failed window unit or it could be hygroscopic salts

To be honest it does look suspiciously like hygroscopic salts but it's difficult to tell from your photos. See what Nose et al think later

 

[^woody^]

The images are unclear if there is associated brown staining which would indicate penetrating damp.

There may be cold spots causing some condensation, but the pattern does not seem like rising or penetrating, but thats not to say it is not happening as all the details are not available. But condensation does seem unlikely in that area

Another possibility is a salt reaction between the plaster and paint - possibly from past dampness. If this is the case, then paint will keep peeling in the exact same places, and the plaster will have to be renewed

 

[Barzin]

I think the house is 1950s - I couldn't say for sure about the damp proof course, but I assume it has (is there actually any easy way to check??). I actually took back a lot more of the paintwork last time I repainted, and I seem to recall there was a difference in the colour of the plaster behind the bubbling and non-bubbling areas (brown versus white), but to be honest I'm not sure if the difference is that pronounced this time.

I don't know for sure, but the plasterwork does seem relatively new compared to some of the other plasterwork in the house (as in few years as opposed to 10s of years). I don't know much about hygroscopic salts, but from a quick read on the subject there is an implication that it applies more around chimney breasts and the like (which, as an aside, is a different reoccurring problem I'm having in the upstairs bedroom!!)

 

[noseall]

It could be a debris filled cavity.

If it were a chimney breast then i would always suspect hygroscopic salts, if other obvious causes are not evident. This is an unlikely location for salts migration, though i would expect a bit of efflorescence when the wall does dry out.

The wall does look very wet though........

 

[^woody^]

More likely gypsum salts or other sulphates which will be drawn out of the plaster while damp evaporates.

Best thing to do is remove all the paint and observe the bare plaster over a few weeks to see if white salts emerge or if the colour changes. Draw on it with a pencil if need be to mark areas.

Look after periods of heavy rain, at times early in the morning and late a night (or when your heating comes on and off), and at times when it is cold outside.

You will then see if damp is penetrating or if condensation is occurring.

Also check outside under the cill to see if water is dripping or tracking back onto the brickwork after periods of rain

 

[mac3]

Hi, mine wasnt the glass that failed it was the seal between the outer glass face and the upvc frame. it would then run inside the frame and track back on a poorly fitted sill into the wall. I ran silcone around the edges as a test to prove it and then replaced the seal and fixed the sill.