Part concrete floor - rising damp

[wuptdo]

Here's a picture from outside that wall. Nothing immediately obvious aside from the boiler overflow / vent and the brick 'lip'. Oh and the poor pointing.

 

[wuptdo]

Good Afternoon,

I got a pca-type surveyor in for damp/moisture diagnosis and a wall tie check, but taking the proposed solutions on the damp side with a pinch of salt. I’d like a few extra thoughts if possible please.

House background:
~1930’s semi, cavity wall construction, built with no DPC, ~50mm cavity, insulated with blown fibre. Insulation (from wall tie check) appears bone dry. In my personal opinion, if it’s useful to know, the house also potentially has externally applied (StormDry like) masonry cream. The house floor sits ~1m above ground level on all sides – aside from party wall. A previous owner has applied a (waste of time most likely) retrospective chemical dpc externally around the floor level of the house. The rear wall of the house is quite exposed.

View attachment 274786

The moisture/damp appears to be around the perimeter of the concrete floor. It is causing noticeable staining/damage to the side elevation. Going by what the damp surveyor has said and my own reading, I suspect the solid floor base material is wicking up moisture which is travelling through the concrete floor. It then hits the asphalt layer and is pushed sideways and comes up the plaster in the walls. Although, feel free to tell me that moisture is unlikely to be wicked up that far and the moisture is coming from elsewhere.

The damp surveyor has initially proposed extending the asphalt dpm with a plastic dpm part way up the walls and replastering. However I feel this may just mask the problem and the moisture still travels up the walls (potentialy wetting the CWI). I can think of two other possibilities that don’t just cover up the damp:
1-Remove the asphalt layer and allow the concrete to breathe naturally rather than pushing the moisture out into the walls. Or will it be far too wet? If I do this, how do I handle reflooring?
2-Dig up the floor and reconcrete with a plastic DPM? (use the occasion to insulate and install UFH)? How do you prevent the moisture travelling up the wall here/'lap into the DPC' (as there is no DPC in the walls)? Or can you retrospectively insert a plastic DPC / apply chemical DPC cream?

Thanks for any thoughts in advance!

Thanks for all the help thus far. The investigation continues...the damp/moisture definitely seems to be rain reactive. Whether that's from drainage or otherwise is TBD. Whilst I have initially been concentrating my focus on the room with the very visible staining and feels moist up to 1m (the room with the boiler in). This has potentially original cement/concrete like plaster on the wall.

I decided to pop into the 'top left' room on the initial floor plan I have quoted above. The wall which has had insulated plasterboard applied doesn't have significant visible staining but it feels moist/damp to the touch to a very high level (~2m above the floor / ~3m above outside ground level).

Here's my question - even if there is moisture coming from the drainage / water inlet into the concrete floor, can plasterboard (skimmed with gypsum) and brick really carry moisture/damp to this height? (i.e. failed CWI / rubbish bridging the cavity in the corner where we didn't invasively check the wall ties or water entering between the brick lip and the render)

 

[wuptdo]

A bit more info. I decided to rip the damp plasterboard off the side elevation in that room. Turns out it wasn't insulated just plasterboarded.

The plasterboard had some black mould on the back. The dot and dab adhesive and the plasterboard paper lining were moist to the point where it pretty much fell off readily. In comparison to the boiler room where the cement render feels like it's bonded to the brick so I'm making slow progress in there.

They have installed yet another chemical dpc internally here. In the bottom half layer of exposed bricks above the asphalt or modern equivalent replacement.

I think the plasterboard was carrying most of the moisture. As the bricks mostly appear dry. Although the chemical dpc'd bricks seem quite wet.

Another couple of notes -
(1) this DPM appears to be more plastic like and possibly could be a modern replacement as you mentioned previously instead of the asphalt that's seen in the boiler room.

(2) the felt like dpc is nowhere to be seen - I expect it sits 0.5-1.5 courses below the top of the floor level.

 

[JohnD]

Here's a picture from outside that wall. Nothing immediately obvious aside from the boiler overflow / vent and the brick 'lip'. Oh and the poor pointing.

View attachment 275559

Where is "internal floor level" on that wet wall?

 

[wuptdo]

Where is "internal floor level" on that wet wall?

Just done a quick measurement assuming the overflow runs in/out of the same height/course of bricks.

The internal floor level is mid way through the brick below that external chemical dpc.

So we have 3 dpc's it seems:

The felt internal leaf dpc sat 1.5-0.5 course of bricks below the internal floor.

The chemical internal dpc sat 0 - 0.5 course of bricks above the internal floor. (The dot and dab/plasterboard may have been bridging this - although I'm not sure how the chemical dpc works - is the entire brick now dpc or is it a band in the middle?)

The chemical external dpc sat ~1 course above the internal floor.

(And possibly an old external leaf felt one which has been covered by mortar or it was built without one?)

 

[JohnD]

Let's suppose the solid floor was very wet

The wall would look like that

Let's suppose there was a leaking pipe in the floor

It would make the floor very wet.

 

[wuptdo]

Let's suppose the solid floor was very wet

The wall would look like that

Let's suppose there was a leaking pipe in the floor

It would make the floor very wet.

Thanks. Will arrange a drainage survey / check (access is poor) and do a thorough listen with a helper on the water inlet.

 

[wuptdo]

Coming back to this thread some time later...

I had a drain survey done - the access was poor but the main lateral appeared in good condition. To permit a survey of the soil stack / down pipe and to improve future maintenance - I am having a small inspection chamber put in a couple of weeks. I was doing some test digging ahead of this to work out where pipes ran and ended up coming across a surprise pipe...

I posted about it on here - https://www.diynot.com/diy/threads/pipe-bingo-whats-what.607239/ - the consensus appears to be that it may be the original lead water main. Subsequently there's potential that it still runs into the solid floor and was 'capped off' (and is inevitably leaking...)

On the 'symptoms' front. The walls are much damper in winter (I suppose there's less chance for the floor/walls to dry out if it's raining/cold).

The following image is taken from an external wall in the 'small room' as originally described. The door is always closed and there's nothing else in there so I'd expect it to be cold, but also have minimal moisture content. I have left the window closed in here though, so there wouldn't be any ventilation either...

Is this water likely to be from the leak directly and moving up the wall? or is it likely to be condensation caused by the cooling effect on the building by the leak? (note the house themostat is maintained at a minimum 13C at all times (I expect this room to be cooler than that though as it doesn't have heating and half of the plaster is missing)

Will update this thread with any further details later.

 

[Koolpc]

That looks like condensation. I may be wrong.

Trying a dehumidifier may help in the short term.

 

[wuptdo]

Hmm - possibly. A dehumidifier is currently ran throughout all non-sleeping hours in the remainder of the house.

 

[JohnD]

It does look like intense condensation, but of course the water is coming from somewhere.

A dehumidifier will not repair the source of water.

It is consistent with water coming from a leaking pipe in the ground