DIY Doctor UK DIY Forums

Hi

I had a DPC done in 2003 and all was okay. Last year I decorated my front room which consists of plastered walls. The alcoves either side of the chimney breast and the breast itself suddenly started having dark patches randomly appear. Similar to a patch of emulsion that hasn't dried out so is darker than surrounding.
It is is worse in one corner about 5 ft, 8" up the wall. It's a localised patch and felt crunchy so I hacked it to brick and it's all salty, now it seems to be spreading a bit higher and round onto the next wall.
DPC was injection, tanking, sand & cement render then skim finish. It is just this one damn wall I have a problem with.

Any ideas please.

Thanks

It could be coming from above, has the chimney been capped off?

Hi - may i ask if the alcoves form part of the chimney itself? ie. do they link in with the continuation of the chimney breast in other rooms upstairs?

If so, one possibility is that the problem you are having may be down to deposits of hygroscopic salts that collect in the chimney from years of burning coal and wood. These draw the moisture from the air and discolour the plaster and permeate the brick. We've got the same problem in our bedroom and its been recommended that we have the chimney swept, hack the plaster back and replaster using a salt resistant additive. A more extreme recommendation was to have that section it rebuilt!

Hope this helps!

Dan the man wrote:It could be coming from above, has the chimney been capped off?

Apparently yes.

acidburn110 wrote:Hi - may i ask if the alcoves form part of the chimney itself? ie. do they link in with the continuation of the chimney breast in other rooms upstairs?

If so, one possibility is that the problem you are having may be down to deposits of hygroscopic salts that collect in the chimney from years of burning coal and wood. These draw the moisture from the air and discolour the plaster and permeate the brick. We've got the same problem in our bedroom and its been recommended that we have the chimney swept, hack the plaster back and replaster using a salt resistant additive. A more extreme recommendation was to have that section it rebuilt!

Hope this helps!

Yes they do, it's weird that is just a patch 2ft x 3ft and only in an isolated clump.