Is this 'rising damp'? And if not, what?

battenburg88

The attached photos show the base of a wall in the living room in my Victorian terrace. It's the remaining 'stub' of what was the dividing wall between the living and dining rooms which was knocked through before I lived here. What looks like damp has very slowly grown over the past couple of years. It doesn't appear on the other side of the wall in the hallway (although oddly, as shown in one of the photos, it does appear on that side of the wall where its within the living room).

I had a damp proofing person out who suggested the standard approach: hack off the existing plaster, inject a chemical damp proof course and reapply a waterproof plaster. All sounded very straightforward, but I'd also been doing a bit of reading that suggested rising damp doesn't actually exist and the standard approach is just damaging the fabric of the building. It seems like there are conflicting opinions on the matter! So, I'd found myself in a quandary and have ended up doing nothing as yet.

As a layperson, this seems visually to be very much what I would expect damp rising up through the brickwork to look like. So the 'standard' approach seems to make sense, but obviously I don't really want to pay out for the damp proof course if it isn't really tackling the source or isn't the right solution. Would an alternative be to apply lime plaster so that dampness could evaporate away? Or something else?

My other thoughts were whether there could be a leak. But, the mains water supply would come in through the hallway (and no dampness is showing on the hallway side). There is a radiator in the living room just to the left but a plumber suggested that, if that was leaking, then the heating system would be losing pressure and that isn't the case. 

Any suggestions would be appreciated! Taking up the floorboards is a bit awkward although I know it is a good starting point. I'm not sure what I would be looking for though, even if I did, so some pointers would be very helpful.

Apodemus

Doesn’t look like rising damp to me!  And is that not a damp line on the carpet?  

battenburg88

Apodemus said:

And is that not a damp line on the carpet?  

If you mean the first image just infront of the door, then no. The floor is a bit uneven and the door gets wedged on the carpet so if we're talking about the same thing then what you can see is the line where the door hits the carpet and stops. Another thing on my list to sort out, but a bit further down the list!

lesalanos

What's above that? 
Possibly something leaking down the cavity and sitting at the bottom.  I had issues where a roof on an extension was leaking, running down the wall and damp at the bottom 

battenburg88

lesalanos said:

What's above that? 
Possibly something leaking down the cavity and sitting at the bottom.  I had issues where a roof on an extension was leaking, running down the wall and damp at the bottom

Its an internal wall so above it is a bedroom wall. There is a radiator not too far along on that wall upstairs so I suppose there could be heating pipes in the general vicinity of the floor above. But, I don't think it would be a cavity wall, just based on the age of the house and that its internal (I'm not an expert though!). You've made me think out of the box a little bit though - the one floorboard that I have managed to life elsewhere in the room showed that there is a big pile of what looks like builders rubble under the joists, which I suspect is from where the internal wall was knocked through and they didn't bother to remove it. I wonder if that could also be around the base of this wall and causing some kind of moisture bridging.

Apodemus said:

Doesn’t look like rising damp to me! 

Sorry, I didn't ask this originally - is there a reason that you say that? Some kind of telltale pattern of the damp that suggests it has some other source?

Doozergirl

If you have floorboards then it's time to get them up and have a look.   

Are there plenty of airbricks underneath, allowing cross ventilation under the floor?  

It's going to be something relatively simple if you have suspended floors. 

FreeBear

battenburg88 said: - the one floorboard that I have managed to lift elsewhere in the room showed that there is a big pile of what looks like builders rubble under the joists, which I suspect is from where the internal wall was knocked through and they didn't bother to remove it. I wonder if that could also be around the base of this wall and causing some kind of moisture bridging.

Sounds a bit like the place that Jack bought - https://jack-kelly.com/insulating_our_victorian_living_room - Quite a horror story there...

If there is a pile of rubble under your floor, it will interfere with ventilation, and quite possible that it is bridging the DPC. Lifting boards in the general area is going to be your first job. Hopefully, they are not tongue & groove boards, so lifting shouldn't be too difficult. If you are lucky, they may even be screwed down which would make things even easier.

battenburg88

Thanks for the link. A very interesting read (albeit it has made me a bit nervous of what's under there!). I've known that I should look under the floorboards, but I'm not particularly DIY-minded and therefore feel like I might be a bit overwhelmed with what to do whatever I find.  Which has probably led to me not doing it.

Doozergirl said:

If you have floorboards then it's time to get them up and have a look.   

Are there plenty of airbricks underneath, allowing cross ventilation under the floor?  

Good point, and probably not. There is one air brick in the centre of the bay window at the front and only one other at the back. This was visible from the one floorboard that I lifted and so isn't blocked by the rubble but air isn't exactly going to be freeflowing.

As a general thing then, how might I approach any possible fixes like this with a tradesperson? As in, I could probably lift the floorboards and have a bit of a look, but realistically I won't really know what I'm looking at beyond "that doesn't seem quite right". So do I ask a general builder to come and have a look too....do I pay them a few hours of investigation time whilst they lift floorboards and clear some of the rubble? Not quite sure how best to approach it. 

Doozergirl said:

It's going to be something relatively simple if you have suspended floors. 

I like this optimism!