Where is my DPC?!?

[Emilie99]

Hello all,

Am new here but for the past couple of weeks have been finding this place the most helpful regarding answers to my renovation.

I bought my first house in the middle of June, 1884 build Victorian semi detached. I knew it was gonna be a bit of a renovation project, but I did not anticipate the extent of which was going to suddenly come to light. Partly because the sellers had hidden everything so well even the L3 survey didn’t pick it up. I have since heard from my lovely neighbours the extent to which they were doing this right up until I moved in.

The one thing the survey did pick up was the concrete render over he DPC and how this needed removing and the ground lowering as the ground was half way up the outside vents.

I’ve removed the concrete, I’ve lowered the ground to below the vents.

In a couple of areas I could see slate along the walls so I could figure out that was the DPC. However this doesn’t line up with the vents. And the vents are slate lined and go down way under the sub base. Under my floorboards there is maybe two inches and then concrete. And apart from around the concrete that is dry, the water is coming in from the sides. The two walls where I have removed the concrete the water ingress is visibly less despite me having not fixed the brickwork fully or rendered ( a week of rain prevented this but I had it covered up with waterproof tarp.)

Now it’s sunny I’ve started to fill in the brick work and doing to begin the rendering in lime mortar.

However, I am now lost as to where to start and finish this. Due to time and weather I stopped smashing down the ground level and chipping off the concrete a couple of inches below the vents. But today I noticed the rendering goes down far far further.

Do I need to go down in my removal right to where the current rendering stops? What is down there? This is well below the base under my floorboards and I don’t know if damp is coming into whatever is under there? How do I find out.

Pictures attached so the above makes a bit of sense.

Appreciate any advice as this is urgent for a variety of reasons. Mostly because the guarantee I get with the de-moulding is void if I don’t stop the damp. And I have 11 days…..

First photo is where I have started filling in gaps in mortar so I can render.

Second photo is a close up of the existing render I had removed but it goes so far down. What do I do here? It is well below the slate lined vents.

Third photo is of the wall I am still working on lowering the ground. But same applies to where is the dpc and do I remove the rendering regardless of how deep it goes?

Related but different question. The worst damp is coming into from around my fireplace. I’ve removed concrete and floorboards and found there is no sub base surrounding the chimney. Does anyone know why this might be? Can I just create one via plaster sheeting and cement that matches the height of the rest of my flooring?

Am doing all of this entirely by myself and the research alone is taking up so much time so I’ve truly appreciated everything in this website as it has solved a lot of questions the rest of the internet couldn’t!

 

[a twig]

Difficult to see in the photos but peering at them it looks like your slate DPC could be in the mortar two courses above the vents.

To “unbridge” the DPC you just need to remove the render that overlaps the DPC, in my case I went 1 and a bit courses above the DPC and removed the render from there on down, made a bell mouth to tidy up the render and the walls dried out and resolved the issues:

A

Thread 'Hotel Dampifornia'

Aug 12, 2023

You can check out but you’ll never leave!

So, sadly had to sell our forever home in Somerset - moved to a newer house supposedly with no problems. Didn’t bother with a survey as have got bored of paying for ever more inventive works of fiction and so moved in to inevitably find daaaamp in the old section of the house that dates back to 1860…

The previous owners were kind enough to share the survey they had done when they purchased which said there was no DPC in the original building and also there was no asbestos anywhere in the building.

Having found asbestos in the building not long...

• a twig
• Replies: 23
• Forum: Projects

• 

It sounds like the subfloor in your house might have been backfilled with concrete in an attempt to “cure” the damp which likely means the vents won’t be doing much.

If that is the case I would worry too much about the vents for now as a priority, you could look at cutting back concrete in the future if sorting the render and ground levels hasn’t addressed the issues.

 

[a twig]

Re how deep to go, for what you are trying to achieve for now one course below the vents should be fine, just need to make sure all the gutters etc are working as you won’t want water coming back in the vents.

Easy to say but I wouldn’t worry too much about the demoulding guarantee, if you get the walls dried out, and the house warm and dry the mould will take care of itself

Coming back to the gutters - make sure they are all unblocked and draining away properly to where they should, probably 2/3rds of the damp issues I’ve faced in my time have been due to blocked gutters and downpipes causing water to sheet down the walls, and broken gulleys dumping rainwater into the base of the walls

 

[Emilie99]

Difficult to see in the photos but peering at them it looks like your slate DPC could be in the mortar two courses above the vents.

To “unbridge” the DPC you just need to remove the render that overlaps the DPC, in my case I went 1 and a bit courses above the DPC and removed the render from there on down, made a bell mouth to tidy up the render and the walls dried out and resolved the issues:

A

Thread 'Hotel Dampifornia'

Aug 12, 2023

You can check out but you’ll never leave!

So, sadly had to sell our forever home in Somerset - moved to a newer house supposedly with no problems. Didn’t bother with a survey as have got bored of paying for ever more inventive works of fiction and so moved in to inevitably find daaaamp in the old section of the house that dates back to 1860…

The previous owners were kind enough to share the survey they had done when they purchased which said there was no DPC in the original building and also there was no asbestos anywhere in the building.

Having found asbestos in the building not long...

• a twig
• Replies: 23
• Forum: Projects

• 

It sounds like the subfloor in your house might have been backfilled with concrete in an attempt to “cure” the damp which likely means the vents won’t be doing much.

If that is the case I would worry too much about the vents for now as a priority, you could look at cutting back concrete in the future if sorting the render and ground levels hasn’t addressed the issues.

Thank you. So essentially if I render from say an inch below the vents to just above what looks like the slate dpc and keep the ground level low enough with a lil soakaway trench and drip beads out of the render do you think it’s ok to not go down as deep as whatever that existing render is?

 

[Emilie99]

Would love the mould to take care of itself but it’s so bad the attic is basically one giant spore. It’s coated the insulation because there was no ventilation as they had plastered up every single vent and the shower vents into the attic but not outside. I have zero allergies or health issues and even in a full hazmat and respiratory mask I can’t do more than half an hour in the attic removing the insulation without feeling burning and itching and brain going weird. I don’t think that level of mould will casually go away. In the house maybe, but the concentration in the attic is filtering down through the ceilings and walls, you can see it in some corners

 

[a twig]

Thank you. So essentially if I render from say an inch below the vents to just above what looks like the slate dpc and keep the ground level low enough with a lil soakaway trench and drip beads out of the render do you think it’s ok to not go down as deep as whatever that existing render is?

Sorry I might have been a bit unclear in my ramblings, you don’t want to render over the DPC as that bridges it and is the cause of a lot of the issues, I was attempting to use my previous efforts as an example to say basically as a minimum you don’t want any render from the course above the DPC downwards, and that render free area should go down to at least one, maybe two courses below the vents.

The posts in my thread might have been confusing as your walls aren’t rendered so the bell mouth bit isn’t really relevant to you - sorry.

 

[a twig]

Would love the mould to take care of itself but it’s so bad the attic is basically one giant spore. It’s coated the insulation because there was no ventilation as they had plastered up every single vent and the shower vents into the attic but not outside. I have zero allergies or health issues and even in a full hazmat and respiratory mask I can’t do more than half an hour in the attic removing the insulation without feeling burning and itching and brain going weird. I don’t think that level of mould will casually go away. In the house maybe, but the concentration in the attic is filtering down through the ceilings and walls, you can see it in some corners

Sounds horrendous - sorry to hear that. The point I was trying to make is that once you have restored ventilation and dried everything out the mould won’t be able to grow so then once it has been removed it won’t grow back, so the guarantee is somewhat irrelevant if they are saying it doesn’t apply to damp / wet walls.

At the risk of sounding very depressing if everything is really wet it is nigh on impossible that you will get everything dry in 11 days even with an army of dehumidifiers etc, walls just don’t dry out that quickly.

Depending on the wall construction and how wet it is, it can take 2-4 weeks per inch of wall thickness for a wall to fully dry out