Patio drains at damp proof course urgent!

IvyFlood

I am in the process of having a new patio laid (work started today).

The damp proof course is very low and the plan is to have an aco drain running alongside the house and some in the middle. They’ve laid the ones in the middle but it’s practically sitting on the damp proof course and although the water will drain down lower than the DPC and not touch the house it still makes me feel uncomfortable/nervous.

I would have preferred it lower and that was the plan however once they’ve got there they’ve noticed some pipes which means they can’t lay it any lower. They said they could make the middle ones lower but this would mean a gravel border running alongside the house which I didn’t want really.

Unsure of what to do! I’ve attached some pictures for reference.

Boohoo

It could just be me but if this stays as it is I think in a few months you could have a lot of damp problems as it looks to high next to the dpc.

stuart45

The damp course isn't low, it's the ground level that's too high. What's the pipe for that they say is causing the issue? The top of the gully look s to be 2 courses below the DPC, which was the original ground level.

IvyFlood

https://forums.moneysavingexpert.com/discussion/comment/82060894#Comment_82060894

Not sure, but its a very old ceramic/clay pipe running under where my patio doors are.

Boohoo

https://forums.moneysavingexpert.com/discussion/comment/82061450#Comment_82061450

How old is the house?

Didn't think clay pipes have been used for decades.

stuart45

It looks like a 60's or 70's build to me, especially as it seems to have retro cavity wall insulation. At that time clay was still quite popular.

Alderbank

Vitrified clay sewer pipes should be at least 600mm deep to protect them from frost. It doesn't sound as though this one is.

Albermarle

https://forums.moneysavingexpert.com/discussion/comment/82061635#Comment_82061635

Hepworth Clay | Clay Drainage & Terracotta Products | UK Manufacturer

FreeBear

Hard paving should be 150mm below the DPC - If these contractors knew their stuff, they should be aware of BS7533.

If they continue to lay paving right up to the wall, and level with the DPC, you will end up with damp problems internally. You need to tell them to dig down deeper and do a "proper job". If there is a pipe too close to the surface, then it needs to be moved. A couple of questions to ask of them -

How thick is the MOT1/hardcore ?

It should be at least 75mm for a light duty path or patio.

How do they intend to lay the slabs ?

If they say five dollops of mortar, tell them to collect their tools and leave. Slabs should be bedded down on a full bed of mortar or well compacted sharp sand. The five blobs method will result in slabs cracking and provide an ideal home for ants, slugs, and other insects.

Oh, and hard paving should not go right up to a wall except for doorways. Leaving a gravel filled border helps to reduce splash back when it rains.