Block paving - draining...?

[paddytt]

We want to sort a damp problem around the side of the house and the back door. Currently the area is concreted, which we are keen to remove as the inside floor level is lower than the concrete outside, and we were thinking of putting a grating / grille (with an "e", before Penners gets me...) to allow the wall to breathe. But there are a couple of drains in the way, and the grating solution looks expensive.

Would block paving on sand with a french drain under it be suitable? We can connect into the main drains so no problem getting rid of the water.

Or any other suggestions?

cheers

TT

 

[Zebra]

I would think that you were rather the French drain expert now, looking at what you've just constructed round your house!
In my own limited experience, I would have to say no, I don't think that would work, or at least only to a limited extent depending on the amount of water there is. If you can't lower the external ground level because of the drains, if I've understood correctly, then a French drain would help to remove excess water but I don't think that the wall will breathe through block paving. It could be made to be very free draining, but won't allow the wall to dry. But it depends on the amount of water we're talking about.
My own first attempt at a french drain, backfilled with gravel, did not work because there was enough water retained in the gravel to keep the wall damp. It drained but it didn't breathe.
Could you take a two-stage approach, or tackle it in several stages? First, get rid of the concrete, just take it back to bare earth and dig it down as far as you can. In my sideway this was enough to solve the problem. Perhaps install your French drain and just backfill with gravel for now? Gravel's pretty cheap, and if you managed to solve the damp problem, you could think about paving later?

 

[Feltwell]

Would block paving on sand with a french drain under it be suitable? We can connect into the main drains so no problem getting rid of the water.

Not convinced at all on that one. Plus, if Building Regs are to be involved, I don't think you'll be able to connect into to your main drain - if that goes to a public sewer. You'd need to have a soakaway, which can of course be some distance from the house.

 

[AMc]

IMHO I think the grating is a much better idea even if it's a bit more complicated and expensive. The drainage through block paving or surface water is going to be far slower and it will offer no real opportunity for moisture to move upwards.

Again IMHO connecting surface water drainage to the main sewer isn't a great idea - if your sewer backs up it's easier to deal with a bath full or a few flushes than a sustained rainstorm flooding mixed fould water over your back door.
It's more generally frowned upon because surface water in the sewage system can overwhelm the treatment plants which has forced them to dump raw sewage into the rivers and sea during sustained heavy rain fall. I read an article about the increase garden paving, esp. in London which had resulted in huge increases in problems with flash flooding and sewage overflows - not good and the reason the latest regs insist on permeable paving and soak aways.

 

[paddytt]

Thanks for all the replies.

Does anyone have any experience of the Marshalls block paving that allows free drainage?

http://www.marshalls.co.uk/transform/Products/Driveway/driveways/range/driveline-priora/

It's built on a bed of 20mm and 6mm stone chips, so would be similar to having a stone filled channel next to a wall, and can incorporate a drain that looks like a french drain!

I'm thinking of giving it a go...

Regards

TT

 

[Feltwell]

PaddyTT (is that because you're Irish and like road racing by the way? If so shouldn't it be "PaddyNorthWest200" then? )

Have you looked at the Paving Expert website? Lots of good info on there, and there's a forum who were of help to me with a past paving-related query.

http://www.pavingexpert.com/