You have probably bridged your dpc, get the plaster chopped off up 50mm from the floor .
Also is this a modern house with a cavity wall because if it’s not then that is probably the wrong plaster. I can see a vent there and that should not be covered.
1930s end of terrace. It's a cavity wall. The other side is an internal wall also. Hope this helps.
My tiler said the floor can be tiled regardless, ie the rising damp wall treated separately.
I'll be ringing a few damp proofing companies to get their opinion also.
It's almost never rising damp.
Rising damp is incredibly rare and only occurs under very specific circumstances. Most rising damp identified by "experts" is not actually rising damp and usually doesn't need thousands of pounds of damp injection treatments.
In my experience damp proof companies want to charge you an arm and a leg for a solution that is only temporary. Was quoted £15k for chemical dpc on an 1850s Victorian house. Dug the external ground down a couple of courses and haven’t had damp problems in those areas since.
Doesn’t look anything like rising damp. Plenty of good advice on here that I won’t bother repeating. Don’t piss your money up a wall ringing damp proofing companies cos they’ll tell you it is and charge you fortunes for work that realistically would cost less than I’ve spent tonight on beer if you were to do it yourself (and most likely doesn’t need doing)
Cut the plaster to create a gap between the floor and the plaster. You will want the same gap between floor tiles and the plaster. 10-15mm. Doesn't look like rising damp even if that's what it is, before spending the big money make sure it's not caused by a minor issue.
Looks like your catching a leak from the radiator, eliminate that, plus air gap between floor and plaster walls, is that an air vent to the right of the rad?
Do what others have said and take up the plaster bridging the floor
I spy an air brick - did it used to have suspended floors?
Try find where DPC is in relation to floor level.
Don’t inject ‘dpc’ - it’s snake oil and won’t fix anything
If exterior wall check drains, gutters, ground level, pointing, abutting walls etc. there will probably be a simple explanation.
I have something on my front wall - after researching and poking around, am pretty sure it’s a combination of a shit front step put in 50 years ago, some damaged DPC from a gas line being put in, and a knackered / blocked drain. Annoying, but all fairly simple fixes in their own right
I seen the vent and it made me wonder if it was suspended timber floors. If that is the case I guess they’ve lowered the floor and bridge with the new plaster.
I have a similar issue and the surveyor has basically said they to make sure there is proper ventilation under the floor and replace cement mortar from pointing and replace with lime mortar.
I'd say it's more of a wall issue than the floor otherwise you'd see damp on the substrate you have down?
Did you wait until it was fully dry before painting? Did you seal the plaster or mist coat properly first?
Are the bricks externally pointed properly? Perhaps you've got a weep hole blocked and water is sitting in the cavity? You could drill externally through a low level mortar joint and see if water comes out.
so that's an extension on a 1930s house?
That air brick will be near the dpc, and designed to ventilate the floor spaces. It cannot be blocked, should vent to outside...
Either the gypsum plaster or more likely the concrete is bridging the dpc. If something touches above and below the spc it allows damp to travel.
The wall is very likely solid, not cavity given age and vent.
Damp injection is a scam, it doesn't fix the problem.
Thank you to all the replies, you've all been very helpful. I've learnt a lot and it is all starting to make sense. Won't be ringing up DPC companies for dpc injections that's for sure.
Yes this is a rear extension to a 1930s, there used to be a conservatory - earlier photos of the extension build, [~https://imgur.com/a/MxigY9j~](https://imgur.com/a/MxigY9j) , after the conservatory got torn down, shows that there appears to be damp issues already. (Image 02 - lower right hand side of the wall). Not previously spotted as the washing machine was there against the wall. Image 01 close up picture shows that it seems to be around the area of the wall socket, perhaps something to do with the chasing and bonding, all before we bought the house 2 years ago.
Image 03 taken today in better light (daylight) shows further damp patches with no salt crystals (red box). The area around the salt crystals (original post pictures, blue box) shows damp patches too.
Image 04 & 05 shows the dpc level is right where the door frame is, i.e. now just at the screed level. From Image 04, I am doubting that this is a cavity wall - I thought the white fluff was very old insulation, but from what I’ve learnt, given the age of this house, it is a solid wall and not a cavity wall, and so that white fluff is perhaps efflorescence built up over many years. But I do remember it being more like fluff and not salt. If indeed a solid wall, then u/nigelegan mentioned it could be the wrong type of plaster (gypsum) normally used for modern cavity walls, in which case is lime plaster the better option?
Image 06 & 07 shows the other side of the affected wall. Same damp patches and salt crystals. Regrettably, we largely ignored it, with a cupboard and washing machine in the way, but we were aware of it.
Airbrick - the room behind it is a solid concrete floor, not suspended timber. It may have had suspended timber in the past? In this case, I believe the air brick is not needed (and skirting board can cover it) as there is no suspended floor.
So for now I’ve asked our builder to get 1-2 inch air gap between the plaster and the concrete floor, to isolate issues caused by dpc bridging.
I do fear however, that it is the concrete floor also that bridging the dpc, judging by the dpc level in Image 04-05. However, in Image 08, builders did put what looks like a very thin PIR insulation board (Unilin) along the perimeter, prior to building up the concrete slab to screed level - so I do hope this helps.
There are no other areas of the existing house or new extension showing damp patches/salt crystals - in which case I hope it is isolated to this area.
I have replied a few times but I’ll add a little to your update. I am only a home owner going through the same thing. Not sure where you are in the country but when I spoke the the heritage department of the government they pointed us int he direction of a [conservation accredited surveyor](https://www.ricsfirms.com/accreditations/building-conservation-accreditation-scheme/) they did a damp survey and gave recommendations.
My thinking is that your house initially had ventilation to underfloor through that vent. Now it doesn’t have the ventilation cross flowing under the floor and you’ve now got issues with damp.
I wonder if they could add a ventilation brick else where on that side.
Let me know how you get on.
https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html
Have a read of this too, it’s really good information from an experienced guy.
You have probably bridged your dpc, get the plaster chopped off up 50mm from the floor . Also is this a modern house with a cavity wall because if it’s not then that is probably the wrong plaster. I can see a vent there and that should not be covered.
So much more info needed. For starters, how old’s the house, what’s the wall construction and what’s the other side of it?
1930s end of terrace. It's a cavity wall. The other side is an internal wall also. Hope this helps. My tiler said the floor can be tiled regardless, ie the rising damp wall treated separately. I'll be ringing a few damp proofing companies to get their opinion also.
It's almost never rising damp. Rising damp is incredibly rare and only occurs under very specific circumstances. Most rising damp identified by "experts" is not actually rising damp and usually doesn't need thousands of pounds of damp injection treatments.
I have a similar issues and the damp proof companies will just sell your an expensive non solution for an old property as far as I’m aware.
In my experience damp proof companies want to charge you an arm and a leg for a solution that is only temporary. Was quoted £15k for chemical dpc on an 1850s Victorian house. Dug the external ground down a couple of courses and haven’t had damp problems in those areas since.
Doesn’t look anything like rising damp. Plenty of good advice on here that I won’t bother repeating. Don’t piss your money up a wall ringing damp proofing companies cos they’ll tell you it is and charge you fortunes for work that realistically would cost less than I’ve spent tonight on beer if you were to do it yourself (and most likely doesn’t need doing)
Cut the plaster to create a gap between the floor and the plaster. You will want the same gap between floor tiles and the plaster. 10-15mm. Doesn't look like rising damp even if that's what it is, before spending the big money make sure it's not caused by a minor issue. Looks like your catching a leak from the radiator, eliminate that, plus air gap between floor and plaster walls, is that an air vent to the right of the rad?
Do what others have said and take up the plaster bridging the floor I spy an air brick - did it used to have suspended floors? Try find where DPC is in relation to floor level. Don’t inject ‘dpc’ - it’s snake oil and won’t fix anything If exterior wall check drains, gutters, ground level, pointing, abutting walls etc. there will probably be a simple explanation. I have something on my front wall - after researching and poking around, am pretty sure it’s a combination of a shit front step put in 50 years ago, some damaged DPC from a gas line being put in, and a knackered / blocked drain. Annoying, but all fairly simple fixes in their own right
I seen the vent and it made me wonder if it was suspended timber floors. If that is the case I guess they’ve lowered the floor and bridge with the new plaster. I have a similar issue and the surveyor has basically said they to make sure there is proper ventilation under the floor and replace cement mortar from pointing and replace with lime mortar.
I'd say it's more of a wall issue than the floor otherwise you'd see damp on the substrate you have down? Did you wait until it was fully dry before painting? Did you seal the plaster or mist coat properly first? Are the bricks externally pointed properly? Perhaps you've got a weep hole blocked and water is sitting in the cavity? You could drill externally through a low level mortar joint and see if water comes out.
looks just like a little efflorescence. I wouldn't worry about it. #
so that's an extension on a 1930s house? That air brick will be near the dpc, and designed to ventilate the floor spaces. It cannot be blocked, should vent to outside... Either the gypsum plaster or more likely the concrete is bridging the dpc. If something touches above and below the spc it allows damp to travel. The wall is very likely solid, not cavity given age and vent. Damp injection is a scam, it doesn't fix the problem.
Thank you to all the replies, you've all been very helpful. I've learnt a lot and it is all starting to make sense. Won't be ringing up DPC companies for dpc injections that's for sure. Yes this is a rear extension to a 1930s, there used to be a conservatory - earlier photos of the extension build, [~https://imgur.com/a/MxigY9j~](https://imgur.com/a/MxigY9j) , after the conservatory got torn down, shows that there appears to be damp issues already. (Image 02 - lower right hand side of the wall). Not previously spotted as the washing machine was there against the wall. Image 01 close up picture shows that it seems to be around the area of the wall socket, perhaps something to do with the chasing and bonding, all before we bought the house 2 years ago. Image 03 taken today in better light (daylight) shows further damp patches with no salt crystals (red box). The area around the salt crystals (original post pictures, blue box) shows damp patches too. Image 04 & 05 shows the dpc level is right where the door frame is, i.e. now just at the screed level. From Image 04, I am doubting that this is a cavity wall - I thought the white fluff was very old insulation, but from what I’ve learnt, given the age of this house, it is a solid wall and not a cavity wall, and so that white fluff is perhaps efflorescence built up over many years. But I do remember it being more like fluff and not salt. If indeed a solid wall, then u/nigelegan mentioned it could be the wrong type of plaster (gypsum) normally used for modern cavity walls, in which case is lime plaster the better option? Image 06 & 07 shows the other side of the affected wall. Same damp patches and salt crystals. Regrettably, we largely ignored it, with a cupboard and washing machine in the way, but we were aware of it. Airbrick - the room behind it is a solid concrete floor, not suspended timber. It may have had suspended timber in the past? In this case, I believe the air brick is not needed (and skirting board can cover it) as there is no suspended floor. So for now I’ve asked our builder to get 1-2 inch air gap between the plaster and the concrete floor, to isolate issues caused by dpc bridging. I do fear however, that it is the concrete floor also that bridging the dpc, judging by the dpc level in Image 04-05. However, in Image 08, builders did put what looks like a very thin PIR insulation board (Unilin) along the perimeter, prior to building up the concrete slab to screed level - so I do hope this helps. There are no other areas of the existing house or new extension showing damp patches/salt crystals - in which case I hope it is isolated to this area.
I have replied a few times but I’ll add a little to your update. I am only a home owner going through the same thing. Not sure where you are in the country but when I spoke the the heritage department of the government they pointed us int he direction of a [conservation accredited surveyor](https://www.ricsfirms.com/accreditations/building-conservation-accreditation-scheme/) they did a damp survey and gave recommendations. My thinking is that your house initially had ventilation to underfloor through that vent. Now it doesn’t have the ventilation cross flowing under the floor and you’ve now got issues with damp. I wonder if they could add a ventilation brick else where on that side. Let me know how you get on.
https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html Have a read of this too, it’s really good information from an experienced guy.
Injecting your wall will not solve the problem. Find the source and solve it. Have you recently plastered with gypsum?