Patio level with DPC

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luke seall

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We had a conservatory removed at the back of our house and are planning on replacing it with a patio. However, the concrete slab that was under the conservatory is only about 75mm below the DPC, so by the time we put the paving on it and factor in a fall away from the house, the ground level will end up at best level with the DPC. I know building regs require 150mm below DPC etc, and I've read lots of posts about similar situations but I have several questions if you don't mind.

1. We are planning on installing an ACO drain along the wall of the house. Does it matter if the top of the ACO is only a few mm below the DPC? I'm sure in an ideal world it should be 150mm below. Is there any benefit to installing it lower and then filling in with gravel on top so that it is level with the paving?

2. If we install the ACO, can the paving be higher that both the top of the ACO and the DPC? Need to make sure we have enough height for the fall away from house

3. Is there a machine that could lower the height of the concrete slab by perhaps 20mm in places? It is very uneven and bumpy. Something like one of these? https://www.hss.com/hire/p/htc-gl450-grinder, https://www.hss.com/hire/p/surface-scaler-starwheelelec

Thanks in advance
 
Thanks for input lonner. Can you elaborate on why you think we need to do this?

As I said, I know building regs specify 150mm below DPC but that is not always possible, and plenty of properties now have a level threshold with patio doors without a drop. Removing the Base is not really an option to be honest.
 
150mm isnt critical you can go a bit higher but 125mm should be max and then a small step ect.
The base won't be very thick .
If the base is a standard 4x3 m you will struggle to get a fall.
I know it's a pain removing the base but its going to cause more trouble keeping it.

Another option may be to pave the base and the step down from that to the new level.

You could cut 100mm of the base away at the house,this will allow the wall to breathe and avoid any damp issues.

Are you using a thin slab like a textured slab 32mm? Or something thicker 40-50 mm
 
If that is the case how do people achieve a flush threshold with patio and doors? I've read on lots of forums that using an ACO drain against the side of the house is an acceptable alternative. I just want to know where the ACO should sit in relation to the DPC.

Slabs are 20mm sandstone.
 
luke seall said:
If that is the case how do people achieve a flush threshold with patio and doors? I've read on lots of forums that using an ACO drain against the side of the house is an acceptable alternative. I just want to know where the ACO should sit in relation to the DPC.

Slabs are 20mm sandstone.
Click to expand...


That's when you use big bi- folding doors and glass.
Different to what your asking.

Do what you want it's your property.
I'm only advising from a contractor point of view.
I wouldn't do what your asking for a customer unless they asked in writing.
 
wouldn't the conservatory base have a damp membrane already, making a stepped damp course?
 
As I understand it, the issue is the splash-back of rain that bounces off the ground and hits the brickwork, which can lead to damp/damage. In the case of a door threshold with a bottom-sill, there is no risk of this absorption as there's no exposed brickwork, but a clark drain can still cause the "bounce-splash" (albeit a bit less when the rain hits a slot), and even if slabbing is laid with a fall away from the wall (so no puddling), the splash-back can lead to damage - hence the 150mm recomendation
 
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