Is this slate DPC? 1901?

11 Nov 2021
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United Kingdom
Hi all,

I am currently renovating a 1901 Victorian terrace house. It has all the classic problems with a property of this age such as damp in rooms etc. The front bay is particularly bad with damp.

The soil level was extremely high at the front of the house (bay) when we moved in. The soil was even a little over the airbricks.

I have dug down to see if I can find the old DPC (if it even has one!) and definitely have found what appears to be a black horizontal line going across the brickwork.

Question / Advice
Can anyone confirm if this is indeed slate DPC? I believe a house a this time would have used slate.

The Plan

If this is the DPC, my plan is dig a channel (150mm away from the house) and at least 150mm below the DPC (general building guidlines). Line the channel with a geomembrane and re-fill with pea shingle (to stop splashing of the rain and help with drainage). I will then slope the rest of the front garden away from the house.

Any thoughts, advice would be most appreciated :)

Nice one!


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It looks like the fillet of mortar on top of the brick plinth is what you call the dpc, so you could chip away at that to reveal the slate dpc, if there is one, and then decide how to reinstate (150mm depth as you say). The fillet was likely added to throw rain off the brick, or as a feature before someone decided to build up the soil. Is the floor inside solid or suspended? If the former there may well be damp coming up from the ground if it was not protected by a membrane. If the latter, there might be rot in the floor joists and beyond. Just some pointers….

That's super useful, thanks @blup.

The floor is suspended, and in good condition. We took up all the carpets in the house and all the timber was in pretty good nick. Definitely worried about the possible rotting of the joists, but it does make sense as joists in a house this old are embedded into the bricks which can be half sized therefore probably have gotten wet.

I am a bit of a novice. But would you recommend to just fill the soil back in and leave it till we do a larger project when the weather is better next spring? We do plan on sorting the whole thing out (replacing stone, sandblasting paint back to red brick etc).

I guess my question is, is the plan I suggested going to make things worse? Or will it remain the same or help? If my plan to dig a channel and re-fill etc isn't going to make things better then I may as well stop for now.

Any advice or help would be great.
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Hello Andy

The ground level (ideally) wants to be two courses of brick lower than the dpc.

Your images don’t show any dpc, you may have to inspect the mortar fillet to see if you can see slate or probably bitumen For that year.

As for the trench you are suggesting, it won’t hurt, just don’t fill it in with pea shingle, it’s too small and in a year or two will be solid again.
Use large pebbles, not 20mm gravel either.

what’s the ventilation like under your floor? Is there any rot/worm to have to sort out?
Hi @Mr Chibs

Thanks for your reply.

I have inspected the mortar fillet and it's pretty tough. It looks like and feels like coal or asphalt (which makes sense as I am in Bristol in a coal mining area). How would I tell if it bitumen??

Ok, noted about the pea shingle and depth of two bricks. Should I be concerned that exposing old bricks may lead to further water ingress? I am not skilled in pointing and hadn't planned to repoint bricks etc.

Regarding ventilation, I haven't dared take up the floorboards yet. There is evidence of worm on a couple of floorboards downstairs (but no present evidence) looks like they had an issue and had it resolved. The airbricks are most likely in need of clearing out on both sides of the house.

Any other help or suggestions?
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@Mr Chibs

On further inspection, I think it is Bitumen. Mainly as it looks like its been layered on like a liquid... still unsure how I can be certain that is the dpc :/
Yes, think You’ve found it. Sounds like mine, 1900’s.

Don’t worry about unearthing the bricks.

The air bricks want attending to, as does lifting a floorboard to see what’s what.
Worm can be treated, rot, not so much.

I’ve just been doing the same a couple of weeks ago.
Hi @mrchibs,

Thanks for your help here. I will continue doing what I'm doing.

Air bricks definitely need to be replaced. I'm thinking of adding a couple extra as well to help with ventilation.

I will pull up a couple of floorboards to see what's what under there. Wish me luck!

With regard to the air bricks make sure they are below internal floor level. It sounds odd but occasionally they don’t line up

Six days later, did you go under the floor, did you chip away the filett and confirm a DPC?
Hi all @tell80 @blup,


1. I can confirm that Bitumen was definitely used as the DPC, I chipped away at it, I also confirmed with builder who was walking by and worked on houses of a similar age (I also confirmed once I lifted the floorboards)
2. Lifted the floorboards around the bay, the previous owners stuffed insulation (non-breathable) on all the air bricks from the inside (no wonder there was damp inside!) so no air was finding it’s way to the sub floor
3. I’ve cleared out the air bricks, the air is flowing loads into the sub floor now
4. Plan is lower the soil level still and lay some slate tiles sloping down away from the house
5. I’m going to replace the air bricks wi the modern styles that allow more air to pass through (I may even fit a telescopic one to ensure air makes it right under the sub floor void

I’ll keep you all posted on my progress :) thanks for all your help everyone!!
Hi @tell80

Another question. Would the bitumen that’s been used be effective still? I assume it doesn’t have a long shelf life?
Thanks for that update. What ccondition were the joists in under the bay? Is the ventilation through ventilation to the back of the house air bricks?
The bitumen DPC is probly in good condition but its maybe being bypassed by capillary action on the outside wall surface.
The fillet might need removing or renewing. can you pic where you've chiselled it away. Pic to show the bitumen and any brick ledge that the fillet sits on?
The plinth was installed to help prevent rising damp - plinths cause problems with damp not solve them.
Can you post pics of the whole bay at ground level and the bay at floor level inside the house?

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