Drainage for New Drive

[hermes]

We are having our driveway block-paved, it will be finished tomorrow. The whole of the front is being done, which slopes down towards the house. When the guy came to quote he said he would put in one of those drains (with the metal grille on top) across the full width of the house (close to the house wall) and also continuing past the edge of the house on one side up to the boundary wall. What he has done today is to put in a gulley, a sort of row of concave bricks, across the front of the house, but not across the bay window and not across the path at the side of the house. He said he has done this because the drain that we had put in several months ago was not compatible with the type of drainage we originally agreed on. He said it would be ok because the blocks absorb 40% of the rainwater and the gully should take care of the rest. My concern is that in heavy rain the water will run down the drive and overflow the gully, which is quite shallow, and lap against the house. Does anyone have any experience of this type of thing?

 

[PFE]

without knowing the exact details it is difficult to say.

There are ways of calculating the capacity of gullies, but i am not that familar with them so couldn't advise. In practice its not likley to be a problem unless your drive is enormous. The statment that the blocks will 'absorb' 40% of the rainwater doesn't sound correct though - how is it supposed to do that?
I have a similar situation (although I have 2 gullies, most of the runoff goes to one) with a tarmac drive area and have never had a problem with the gullies over topping even in very heavy rain. How big is your gully and its outlet pipe?

Two things to check:-
Will the rain water all fall to the gully, if its not raining get a hospipe out to check.
Make sure you keep the trap (if there is one) and grille to your gully clean and clear of leaves and debris.

Plent of advice on this sort of thing on www.pavingexpert.com

 

[masona]

My concern is that in heavy rain the water will run down the drive and overflow the gully, which is quite shallow, and lap against the house.

A lot depends where the gulley goes to and the fall ratio for draining.

 

[2scoops0406]

The blocks soaking up 40% of the moisture sounds at best dubious. If you agreed that linear drains should have been installed then that's what should have happened, how is the linear drain incompatible with your current drainage system. I would suspect that he can't be ar5ed to do it 'cos linear drains can cost a fair bit, depending on the category.

As has been said previously, whether or not the gully can take a serious downpour depends on the depth of the gully, and the fall of the drive, which is supposed to be about 5 degrees.

If it was me, I'd have words with your paving contractor !!

 

[Thermo]

soaking up 40% is pie in the sky. Unless he knows the exact properties of the sub base and whats underneath it, as well as the water table and the exact amount of rain then hes talking waffle. The block paving will act as a hard surface and carry the water in which ever way its sloping, with only a small amount going through the gaps in the blocks. After a few years the sand between them will become almost impenatrable and so it will just head on down hill.

In short i agree with Eddie!