What to do with this very tall concrete plinth?

[madcadiyt]

Hello,

About to exchange on a property and the damp survey has suggested removal and replacement of the damp proof course that goes around the house.
It is a solid brick wall and it is assumed there is a slate DPC hiding under there.

Now from my research most people say to remove it but its not clear what I replace it with. Would the bricks under it not be significantly damaged and I wouldnt be able to replace a whole row of bricks.

Its also VERY high, well above the suspended concrete floor ? There also seems to be a layer of concrete around the base of the plinth in some areas.

Any ideas?

Thanks in advance

 

[martygturner]

Is there an issues with damp in the house ?....I would suspect that the only reason why there is a replace damp course note was because the damp course could not be seen due to the capping.......typical cover my arse bloocks from a surveyor...

 

[madcadiyt]

There is any issue with damp in part of the house where the paint is also blistering.

They didnt actually say the replace the DPC but felt the concrete plinth could be bridging it.

Ideally I would like to leave as is but we will also be replastering so that further increases the risk AFAIK

 

[Notch7]

Ideally I would like to leave as is but we will also be replastering so that further increases the risk AFAIK

I would say when you do replastering, take the opportunity to do a damp proofing system.

look at a membrane system like Oldroyd or an damp proofing application like drybase

personally I would try and leave the rendered plinth, you risk creating an awful mess by removing it

Oldroyd Xp Plaster Membranes

Studded cavity drainage membrane incorporating a mesh welded to one side - providing a key for plaster.

safeguardstore.co.uk

Drybase Liquid-Applied DPM - Protects against damp, vapour, and gases

Liquid-applied DPM. Applied by brush, roller, or spray. Use as a DPM on floors and wall-floor junction.

www.safeguardeurope.com

 

[JohnD]

These plinths are usually applied to hide (they do not cure) damp at the foot of a wall instead of finding and correcting the cause of damp.

Looking at your house, it's likely that it was originally built with a slate DPC. Slate lasts at least 400 million years so is probably not defective. The plinth is very likely bridging it and allowing damp to rise into the brickwork.

It would be very informative to investigate a sample part of the wall by taking off the plinth and looking for tbe DPC. It might possibly be at or below the level of the concrete paving which is a common cause of damp. You might be able to see the DPC inside the house, beside a doorway, or under a doorstep. It is possible to groove out a plinth to prevent it bridging the DPC once you know where it is. IME this does not look good. I think you have soft red bricks that will be damaged by removing the plinth. I don't know a good solution. Exposing the bricks will allow water to evaporate off them, making the wall drier.

Looking at your iron soil pipes, it would be common to find they have cracks or breaks below the surface, resulting in leaks that are a common cause of damp. Often there will be signs where the concrete paving sounds hollow, or has cracked or been patched.

Are the internal floors solid? (Concrete, terrazo, tiles)?

Most importantly, do not allow anybody who sells silicone injections near your house.

 

[mikeey84]

Most importantly, do not allow anybody who sells silicone injections near your house

This.

If you are worried, find a specialist damp surveyor you pay (typically a couple of hundred quid) rather than a "free" survey that recommends £5ks worth of useless injections

 

[madcadiyt]

IME this does not look good. I think you have soft red bricks that will be damaged by removing the plinth. I don't know a good solution. Exposing the bricks will allow water to evaporate off them, making the wall drier. This is my main concern. Would a lime plinth be ok? The plinth is definitely above where the DPC would be as its shin high even for the internal floors.

Looking at your iron soil pipes, it would be common to find they have cracks or breaks below the surface, resulting in leaks that are a common cause of damp. Often there will be signs where the concrete paving sounds hollow, or has cracked or been patched.

Are the internal floors solid? (Concrete, terrazo, tiles)? concrete

Most importantly, do not allow anybody who sells silicone injections near your house.

 

[JohnD]

The water might be coming from a leak in or under the floor. Do the floors have damp patches? Near the kitchen?

Or it might be coming from a drain leak or water lying on the paving. Maybe you just live in area of high water table (this would affect all your neighbours though), But the plinth is probably allowing it to rise up the wall and bridge the DPC, so you need to expose the DPC anyway.

While working you may discover, of at least find clues to the source of water. Don't worry about reinstating the plinth for now.

 

[theflyingpig]

How about chopping the concrete path back from the wall and putting gravel in there, a so called 'french drain'... You wouldn't have anything to lose....

 

[JohnD]

How about chopping the concrete path back from the wall and putting gravel in there, a so called 'french drain'... You wouldn't have anything to lose....

This may well be necessary, if, when you find the DPC, it is below, or close to, the level of the paving.

But you need to find the DPC first.

 

[robinbanks]

do not allow anybody who sells silicone injections near your house

Indeed, pumping silicone into anything that wasn't originally supplied with it can turn out to be a horrendously expensive affair!