External Concrete Plinth - Should I Remove?

[bobasd]

"tanking is a last resort, and usually the worst and incorrect solution. it creates cold surfaces and stops the natural escape of moisture"
I wonder who said that?

 

[dontbelieveawordofit]

i did but the alternative in a room with 60% humidity isn’t lime render .

 

[dontbelieveawordofit]

"tanking is a last resort, and usually the worst and incorrect solution. it creates cold surfaces and stops the natural escape of moisture"
I wonder who said that?

thanks ! didn’t see that coming. you walked straight into it lolololololol

 

[dontbelieveawordofit]

they may as well call this the lime render club! some people think the answer for absolutely every thing is lime render or the lack of!

 

[Nige F]

they may as well call this the lime render club! some people think the answer for absolutely every thing is lime render or the lack of!

Benny , I think of the late great Benny Hill. When he did "the chase" every episode... builders running around the site . Who will be the slaphead guy

 

[dontbelieveawordofit]

Benny , I think of the late great Benny Hill. When he did "the chase" every episode... builders running around the site . Who will be the slaphead guy

let me think

 

[HandSlander]

Well here is the update;

1) I'm not convinced the clay gulley is refilling itself from a crack after all. I think it may have rained a little overnight previously.
2) I conducted an amateur drain survey... refer to my very professional drawings below

Key:
Blue= Rainwater downpipes from roof guttering. Main roof & bay downpipe join before entering a clay gulley. Extension roof downpipe enters a new plastic hopper, but a little unclear from there.
Brown = Cast Iron SVP
Green = Wastewater from sinks/boilers etc.
Red = Drain with manhole near the large glass door

Findings

1. Manhole inspection indicates no blockages with water flowing freely.
2. All drain outlets in manhole appear to be original clay
3. Drain Rod inspection from manhole along red line drain provided almost no resistance until reaching about the point of the old extension (end of balcony). At which point the drain rod would go no further and when prodded some muddy water and loose rocks could be seen coming down the manhole. Upon retraction drain rod showed sign of mud at the far end. Clearly some issue there... but the humidity issue pre-dates the extension.
4. I placed a mains pressure hose in both blue gulleys and water was free flowing in both cases with no overflow..

What are my next steps?

 

[HandSlander]

OP,
your original complaint was roughly about humidity its causes and consequences.
You mentioned previous work by a D&T company, and the possible humidity consequences of the sand & cement plinth.


To first get the plinth issue out of the way: the plinth is not a cause of your humidity. Cut the plinth off by 40mm to 50mm from ground contact
and then leave it alone.

The D&T claim of installing a "full length vertical DPC" means what?
You have solid walls - so was a horizontal chemical DPC line installed anywhere on that elevation?
What kind of tanking was installed?
Are the installed air bricks telescopic?
Site inspection might be needed to determine if your re-pointing is adequate? Its, perhaps, sand & cement over an original sand & lime beds and perps? It should be raked out to a min of 20mm.

Condensation creates mould and mould is bad for health esp a child's health. Humidity can damage interior fabric.
You should have a permanent air brick high level vent in the bed room.
Trickle heat & trickle venting often help with condensation.
Timber frames provide better leakage ventilation than PVC windows.

AAMOI: wood frames & chimney stacks (period details) often add value to a property.

A site call: could be its time to remove the tanking back to brick, and then render with a sand & lime render?
Any joist tails landing on that wall are at risk of fungal damage, & need inspecting - maybe use your Endoscope?

Thanks, very helpful response.

As I said it was a previous owner that did the 2010 damp proofing... here is all I have, hopefully all should be clear from my previous photos.

 

[bobasd]

Thank you for the D&T survey plan.

The items below are for your reference:
"walls to be treated" - how, with what?
Does "treated" mean installing a DPC from the interior only because i dont see signs of an external DPC from 10 yrs ago?
The only wall "treated" on both sides is the wall between the bedroom & kitchen.
The mix used for re-plastering should have been specified.
The hallway is a very vulnerable area & should have been inspected. (maybe use your endoscope?)
Which areas were treated for woodworm?
No mention of Telescopic air bricks.

 

[dontbelieveawordofit]

There’s clearly a historic issue with underfloor ventilation and the failure or absence of a dpc. the red line shows where the walls were internally injected with chemical dpc. the bay in the bedroom was tanked most likely because it’s a single skin. and the mix would have been 4:1 sand cement render 1m high with waterproofer/salt inhibitor. the diagram tells you everything you need to know. woodworm treatment needn’t be a localised thing. as a rule when the sort of works outlined on the survey are being conducted the whole lot under the floor, or at least everything thats sprayable gets sprayed. the diagram is fairly self explanatory.

 

[HandSlander]

No idea is the answer to most of @bobasd 's questions unfortunately. I simply don't have any more information other than the D&T survey plan in regards to the works done. On the plus side there is no longer any visible or touch damp on walls internally or externally whatsoever. On the minus side clearly there is still excess moisture attributable to very high and persistent humidity levels, causing persistent condensation and mould growth, and that needs to be addressed. I don't believe any of the walls are single skin, the rear structural wall is ~450mm thick at ground floor level and other walls are > 300m thick. The installed air bricks are definitely NOT telescopic and are modern clay/ceramic style.

A few other factoids;

• The ground floor stopcock is at the end of the entrance hallway accessible from what is currently the bathroom (probably originally Victorian kitchen). No visible damp or leakage in the wall void.
• The large aluminium glass door is a recent addition, and I can share the following WIP shot that shows what looks like a DPM under the floorboards.... really not sure what to make of that.

 

[bobasd]

OP,
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

1."the red line shows ... injected with a chemical dpc" - the red line shows nothing of the sort - where exactly does it say that on the plan?
There's a multitude of ways to install a DPC or treat a damp surface.

2."single skin" - rubbish, utter nonsense. Stop doing this kind of thing to OP's.

3."the mix would have been ... inhibitor" - nonsense, more mystic meg invention, where precisely does it describe the mix on the plan?

4. Your comment about "woodworm treatment" is in barely understandable English, and totally wrong technically.

xxxxxxxxxxxxxxxxxxxxxx

 

[dontbelieveawordofit]

op. contact the original installer of your damp preventitive measures and the author of the plan. They will tell you more or less exactly what’s in my post above.

 

[dontbelieveawordofit]

No idea is the answer to most of @bobasd 's questions unfortunately. I simply don't have any more information other than the D&T survey plan in regards to the works done. On the plus side there is no longer any visible or touch damp on walls internally or externally whatsoever. On the minus side clearly there is still excess moisture attributable to very high and persistent humidity levels, causing persistent condensation and mould growth, and that needs to be addressed. I don't believe any of the walls are single skin, the rear structural wall is ~450mm thick at ground floor level and other walls are > 300m thick. The installed air bricks are definitely NOT telescopic and are modern clay/ceramic style.

A few other factoids;

• The ground floor stopcock is at the end of the entrance hallway accessible from what is currently the bathroom (probably originally Victorian kitchen). No visible damp or leakage in the wall void.
• The large aluminium glass door is a recent addition, and I can share the following WIP shot that shows what looks like a DPM under the floorboards.... really not sure what to make of that.

thats a dpc , it’s there to protect the underfloor joists from the elements . given the close proximity and damp ground level of the air bricks. it’s as it should be.

 

[dontbelieveawordofit]

your property seems to have been damp proofed and repaired to a high standard.
however you must realise that the whole level of the ground outside is too high in relation to the floor ,dpc ,and sub floor inside.
moisture and possible water leakage is entering the sub floor faster than the installed air bricks is drying it. it’s really not rocket science.
and fyi . I have a strong notion that the brickwork under the bedroom bay is a single skin , and the timber bay was letting damp in relentlessly, hence the tanking.