Patio extension advice

[Mark975]

After some advice for our patio extension on how to install slabs next to neighbors garage. The finished slabs have to be 150mm under dpc, but i can’t see the dpc!
As you can see in the pictures the garden slopes down, presumably by the developers to stop the damp being an issue.
After being quoted £6600 to do the job we’ve decided to undertake it ourselves. One of the quotes said he’d put a retaining wall 300mm from the garage but then we are left with a ridiculous area, ideally we’d like to patio all the way up to the wall. Thought about using an aco drain channel and connect it to one of our down pipes?
The other quoted tradesman said to wall straight across so I’m at a bit of a loss where to go.
Any advice would be appreciated. Have attached some photos to help

https://imgur.com/gallery/qLlcYCs

Thanks in advance

 

[Thecaferacer]

Your DPC will generally be what the door/patio sits on. That's your line.

Unless you are liable to very heavy rainfall, the risk of damp is low with modern houses. After all thats what the DPC is about. Patio slabs on top of MOT type 1 will drain exactly the same as you have at the moment.


My best advice is give building regs a call and for a low call out fee they'll advise the best course of action. A channel in-between the patio and wall, connected to the soakaway will be a nice touch for the "just in case" but not essential. A French drain is also an option and cheaper.

Personally I'd two step the patio. One row iniline with your neighbours DPC. The next raised up in line with your using a line of concrete blocks or a concrete trench pour.

 

[Maccapacca]

You'll need a little retaining wall up against the adjoining property, make sure your patio falls away from their property and forward towards the garden and you haven't made anything worse.

Worse case bring it back a bit and finished patio sooner with a handrail.