Patio and dpc

bouicca21

I've had several quotes for laying a patio. They vary enormously. I think I've finally worked out why. The cheaper ones intend to lay the patio so that it is one brick below the dpc. This is actually roughly the existing patio level.

To me 'excavate to correct levels' implies two bricks below the dpc, but I had a long conversation with one contractor who insisted this is totally unnecessary. He said that if the freeholder insisted on this it would be unreasonable. But as far as I can see this goes against standard advice ...

There is a terrific difference in cost. What's the risk?

Furts

There will be exceptions to any rule, but in general any contractor telling you it does not matter about levels and distance below dpc is a cowboy.

The accepted rule is 150mm below which is a minimum depth - it could be more. Damp penetration, mould, algae and frost attack are the risks if you do not abide by the rules. Plus questions raised by a surveyor when you wish to sell your home.

SJshah

Funnily enough, we are in the same situation and have been getting the same "advice" by the contractors/builders/tradesmen. All the cowboys want to lay the new patio at about 50mm below the DPC because this means its an easier job.

The patio should actually be layed 150mm below the DPC to prevent damp. If that means digging up the existing concrete, so be it. You would rather pay extra to get it done properly than have a rising/penetrating damp issue due to the patio being layed to high and moisture entering.

There are ways around it like havig a gap (being 150mm below DPC) between the patio and the house and filling it with shingle or slate chips. Depends how much you have to spend in it.

Read through this website before getting anyone to work on your patio: http://www.pavingexpert.com/dpc01.htm

bouicca21

Thank you both. I note that that website suggests that a contractor not laying a patio to 150mm should give a written warning about possible consequences.

So I'm not crazy for thinking that the extra money - it's £2.5k - would be worth it? Excavation to the correct levels would be a much bigger job. Mr Expensive was also the only contractor to send a copy of T&Cs, and the only one to mention constraints of building regs in relation to a possible soakaway.

As it happens Mr Expensive laid the patio at my first house some 30 years ago when he was first starting out. And that patio was excavated to correct depth and drained perfectly.

System

are any of the others proposing a linear drain or similar?
tbh it's not worth doing if it has potential for problems in the long term, if you can get to 150mm below the dpc then do so, could you not ask the others for their quotes to include that - it's just a basic bit of excavation so shouldn't be a problem, just time.
I think the 2.5k is high for that cost, is his bill itemised?

bouicca21

I've reworked the figures allowing for VAT, and it works out as a little over £1800.

Mr Cheapest isn't replying to questions, and may not be cheapest as makes no mention of VAT. Mr Middling, he who says 150mm not necessary and made it clear he wouldn't consider doing that, said no drain necessary as run off would go to the lawn. I very much doubt that would work, given the levels. No itemisation.

Mr Expensive has not itemised other than for different types of stone. He has however included a soakaway 5 metres from the building which is probably not necessary as the freeholder says run off can go to the existing rainwater drain.

System

get another quote saying what you want - if the guy won't consider doing the job you want then it's pointless going any further with him.
If the expensive guy doesn't do the soakaway then surely that would drop his price a fair bit?

Furts

bouicca21 wrote: »

I've reworked the figures allowing for VAT, and it works out as a little over £1800.

Mr Cheapest isn't replying to questions, and may not be cheapest as makes no mention of VAT. Mr Middling, he who says 150mm not necessary and made it clear he wouldn't consider doing that, said no drain necessary as run off would go to the lawn. I very much doubt that would work, given the levels. No itemisation.

Mr Expensive has not itemised other than for different types of stone. He has however included a soakaway 5 metres from the building which is probably not necessary as the freeholder says run off can go to the existing rainwater drain.

It depends on the paved area, but typical patios drain into the garden and to the gap between them and the house - this would be a margin of pipe bedding or small pebbles.

A soakaway would add significantly to the cost. It is unlikely to be done well and will be pointless if you are in a clay area - and many people are.

An unofficial way would be to drain into the pipe bedding surrounding any drains.

Or build the patio as a porous construction. This is easiest by leaving small gaps between the slabs.

robertkbrown1984

Patio and dpc are both important factors when it comes to placement. If the proper standards are not considered, your whole setup will fail. One of my friend did a fixed window installation from Landmark Home Solutions in Toronto, which provides lifetime warranty. There are some sort of certifications for the products and also for the person who comes for the installation. The procedure and methods used for installation shall vary with each individual. But I would recommend you call some experienced person for such installations.