DPC bridged by render and raised ground (ed.)

[Rageyboy91]

Hey guys,

I'm new too the forum, been finding these tips really handy, I've been reading through alot of threads with similar issues too my problem and learnt alot but could do with some broad guidance. I've listed the problems below and I've tried to come up with solutions, just hypothetically would they work?

I'm buying a 1930 mid terrace house it has damp (rics survey) the owners have tried to fix it internally but I have not yet had the information on what works were done, but it's clear that the external render is bridging the dpc, it's a classic case of the driveway being built highier than the dpc as the original houses has a step too the front door.

The air brick is also part blocked by render, there is a drain at the front door and at the driveway under the front window, with around 40cm gravel soakway between the drive and house, the gravel is touching the airbrick and the render goes all the way too the gravel.

Solution: chop back the render at the front above the dpc. Lower gravel level and Clear airbrick. Check drains etc, add another air brick for added flow too help dry out areas.

The tricky bit..

Theres a front porch extention running along the same wall hitting the neighbours boundary, both drives are level with their front door recessed by the side of the porch extention wall which is rendered to their driveway floor with no channel or drain. I can only hope they added a new dpc level when they built the porch side wall but regardless it's still being bridged by the render.

I can imagine they wouldn't be happy with me exposing the brick dpc or cutting a channel in there drive so...

solution: check drains nearby. Check dpc level if too low Add a chemical dpc then a render plinth with a bell cast dpc (stopping splash back from rain) and blend the render in above, making the wall like the original.

I'm trying to think of practical solutions but wanted to hear from professionals or possible ideas. I dont think these will cost too much? the rest of the house is nice and dry it's just the front wall and porch.

If you guys have any tips it would be most appreciated. I dont want to add any pics because I havnt completed the purchase yet, hopefully I've described it enough.

Thanks guys.

**solid wall brick and the porch is unknown (built in the 80s).

Damphouse

• Rageyboy91
• 16 Dec 2020

 

[Bonni]

Is it a solid wall house or cavity?

 

[Rageyboy91]

Ah knew I'd forget something, solid wall. The porch could be cavity as its newer built in the 80s. Cheers.

 

[Bonni]

Ok. Solid walls need to breathe, many people get obsessed trying to seal solid walls. First things is, the ground level outside is too high, people just lay new paths onto old etc.. So the outside ground level should be at least 6" below DPC.

Second thing is, any render MUST be lime render, if it's sand and cement, moisture cannot escape.

If brick, the joints must be lime mortar, again no cement mortar and never paint the brickwork.

Inside should be plastered with lime plaster and were originally painted with clay paints which are still available.

Draughty windows and doors used to keep solid wall buildings aired, but with modern materials, moisture build up causes problems. Moisture gets into the bricks and stone and breathes out the joints. Seal the inside with none breathable paints and plaster, and render or paint or cement mortar the outside does not allow the wall to breathe.

All the house in the UK suffering from damp, 90% would be sorted overnight by lowering the outside ground.

NEVER use products such as Thompson Water Seal on a solid wall.

https://www.celticsustainables.co.uk/earthborn-claypaint/?msclkid=a527f77baf2f172b1acea885b57f937a&utm_source=bing&utm_medium=cpc&utm_campaign=Claypaint&utm_term=buy earthborn paint&utm_content=Claypaint

 

[Rageyboy91]

Thanks for the reply this is pretty much what I had come to aswell. It's going to be a nightmare fixing the porch wall as it's the neighbours driveway thats too high and butted against it but hopefully they'll be understanding. Thanks again, I'll post back if I ever fix it, got to move in first

 

[foxhole]

Agree with Bonni, many 30s built properties, mine among them were thrown up and the render tends to hold everything together and hide the poor brickwork.

 

[Rageyboy91]

That's reassuring lol. Crazy the difference in house prices and how far the money goes, not very haha. Im pretty confident most of the issues is due too a lot of the issues bonnie mentioned, just too much moisture hopfully the air brick being cleared, using the correct breathable materials and chopping off the bridging cement render will fix the damage done, been hearing horror stories about new builds being completly sealed and unable to breath.

 

[Bonni]

That's reassuring lol. Crazy the difference in house prices and how far the money goes, not very haha. Im pretty confident most of the issues is due too a lot of the issues bonnie mentioned, just too much moisture hopfully the air brick being cleared, using the correct breathable materials and chopping off the bridging cement render will fix the damage done, been hearing horror stories about new builds being completly sealed and unable to breath.

The only ventilation on a new house are the trickle vents on windows.

When I get to build, it'll be a passive house so the ventilation controls the temperature from the ground heat source pump.

 

[Rageyboy91]

I was thinking over the porch side damp, and theres a drain on the far side wall of the porch that has a square cut out from it for a downpipe and looks like that area is thinner than the rest of the external wall rendered in concrete.

Its unlikly I can remove the concrete as it's on my neighbours side, but I was wondering if I could isulate from the inside or any other solutions too warm that wall internally. It would need to be thin though and I dont want to trap damp. I guess my question is if I lime plastered the interior the moisture would still be drawn too the cold external wall where itll be trapped by the concrete, so I'm worried this wont work and I'm struggling how this is fixable, wondered if anyone had any ideas?

 

[StephenStephen]

If I were looking to thermally insulate the inside, I'd either use lime hemp from Ty Mawr, or lime cork from Mike Wye.
But neither would be a thin layer, or address the cause...

 

[Rageyboy91]

Cheers might be abit thick but it's an option, need too see how damp it is, not sure you can use the hemp with a damp wall I wonder if theres a RH moisture limit.

 

[Rageyboy91]

This stuff sounds really cool, breathable plasterboard. Not that it helps me in anyway...lol

https://www.mikewye.co.uk/product/savolit-plus-wood-wool-board/

 

[Rageyboy91]

I found out the interior walls were cream injected and had damp proof plaster. Without the company doing anything about the bridging render or drive levels... actually quite disgusting these companies get away with this.


Does anybody know if you could render lime internally and keep concrete render exterior. And also is it possible to line render a lower exterior wall while retaining the concrete at highier levels. I'm trying to think of way of saving money. And I'm.hoping the walls will breath and I can monitor humidity levels from inside.

Only issue I can foresee is the cold exterior drawing the warn air moisture from the house then being trapped behind the concrete exterior render, rather than the lime pulling the cold air towards the warm interior air sucking out moisture into the house, which is what I want because I have no other option. How would it work? Cheers