Damp spots symmetrically positioned (pics inc.)

Aka Ishur

Hi all,

I have damp spots in my extension (kitchen downstairs, bathroom upstairs.) They are very symmetrically positioned as you will see in the photos. Anyone know what would be the cause?

Edit - the spots are actually tough to see unless you have a good monitor but they are about 2-3 inches in diameter at regular intervals (between 1 and 3 feet apart) from each other in lines parallel to the ceiling

sarkozy

I don't know anything about this, but, if these are external walls, could it be that the builders mechanically fixed internal insulation using metal fixtures, causing a cold bridging effect and causing condensation dampness to collect around those spots?

sydthebeat

Did you get your walls pumped recently?

Do the spots appear regularly vertically as well as horizontally?

How old is the house and do you know the exact wall make up?

foxy farmer

Aka Ishur wrote: »

Hi all,

I have damp spots in my extension (kitchen downstairs, bathroom upstairs.) They are very symmetrically positioned as you will see in the photos. Anyone know what would be the cause?

Edit - the spots are actually tough to see unless you have a good monitor but they are about 2-3 inches in diameter at regular intervals (between 1 and 3 feet apart) from each other in lines parallel to the ceiling

Could be dampness crossing the cavity wall ties if its an external wall due to mortar lodging on them during building. Drywall fixings could stain through paint as well.

Aka Ishur

Hi all, i dont know the exact makeup of the walls as it is a rental property, but the extension was done two years ago. I highly doubt there is internal insulation as the two rooms are absolutely freezing. And to sydthebeat yes they do appear vertically also.

foxy farmer

foxy farmer wrote: »

Drywall fixings could stain through paint as well.

My sister in laws house had the exact same problem and it was the fixings that stained the paint, a second coat of paint resolved it.

Gumbo

Seen this recently and it was in the locations where the plasterer placed the blobs for the fixings of the plaster board. A couple of coats of paint sorted it out too.

Aka Ishur

The spots only appear on colder days tho. Paint staining wouldnt do that no?

mylesm

Definitely looks like fixings to me very round doubt blobs of adhevise would be so even

On cold days the temp of the fixing might be low enough to cause condensation ie damp on the head of the fixing

PROJECT K

Hi Aka,

As stated above, most likely is condensation forming on metal fixing heads - particularly if the walls were drylined internally. Alternatively, if there is no cavity or cavity blocks were used or cavity was pumped recently then water ingress via the fixings is possible (these fixings are generally hollow and if water can penetrate the cavity it can make its way in quite easily). Worst case scenario, combination of both but i would be very confident its the former issue.

If condensation is the reason, make sure there is adequate ventilation in the building and limit the amount of water vapour production (i.e. no drying clothes internally, open windows when showering etc etc). How long ago did this manifest itself - this may be have occured as the building was 'drying out' and once remediated with a coat of paint may not reoccur (at least to the same extent)

If water ingress then you will need to inspect the quality of the render externally, and check building details like gutters, downspouts, window/door heads/cills/jambs for evidence of weaknesses.

Hope that helps

PK

kkelliher

stain block and then paint and you should not see it again. Its very common from the use of the metal mushroom fixings for the plaster slabs. The manufacturers have now introduced a plastic cap for the head to prevent this but up to now it was common for this to happen

neilthefunkeone

mylesm wrote: »

Definitely looks like fixings to me very round doubt blobs of adhevise would be so even

On cold days the temp of the fixing might be low enough to cause condensation ie damp on the head of the fixing

We have the same.. Metal fixings holding the plaster board on and skimmed over!

Glad to see we are not the only ones..

EugenesDIYDen

kkelliher wrote: »

stain block and then paint and you should not see it again. Its very common from the use of the metal mushroom fixings for the plaster slabs. The manufacturers have now introduced a plastic cap for the head to prevent this but up to now it was common for this to happen

I'm using these fixings for slabs. A plasterer suggests filling the hollow fixing with expanding foam to stop dampness on the fill. He seemed to think that it would stop thermal bridging, but its the shell of the fixing that cools the head, so filling wouldn't prevent that, but it would stop damp air coming through from the cavity block behind. He also suggested painting the head with a primer which would eliminate a reaction between paint and the metal of the head which I've seen discussed elsewhere may produce an oxide and cause staining.
Is there an insulating filler that can be used to fill the depression over the mushroom head? That would help stop condensation.