Need Drain for Patio?

[slowginjoe]

I removed an old concrete patio between the house and the garage. The surface water drained off of this patio into a carport adjacent to the garage. Now I plan on building a paver patio, with the same outline and drainage as the old one, directing surface water to the carport entry way. My question is how much of the surface water can I expect to seep into the ground beneath the patio? Enough so that I need to install a land drain to prevent water pooling up or will most of it travel over the pavers and out the carport? I plan to use 100mm of sub-base material.

thanks!

[slowginjoe]

Okay, after 4 hours of reading this superbly done website, I think I found the answer to my own question:

"There's a study been done by the TRL (IIRC) and they calculate that 98% of the water that lands on a flexible block pavement will run-off - only 2% finds its way via the joints to the laying course and sub-base."

So a land drain is not needed afterall! (but please let me know if I'm wrong!) :D

[84-1093879891]

As long as there is somewhere for the water to go once it hits the car-port area, you should be ok.

It's a common misconception that, becaus ethe joints in a brick pavement are filled with sand, any surface water will just disappear into the ground beneath. There are pavers and paver systems where this would be true, but, for most 'typical' block pavements, you might as well treat the surface water as 100% run-off, so some provision for drainage must be made.

If the water can get away from the car-port and isn't going to 'pond' there or cause any problems, then that will be ok, but, if there's any doubt at all, it's much easier to put in a gully or linear drain at this stage than have to do it 3 months down the line because you can't get into the car without wearing your wellies.

[slowginjoe]

Yep, the old concrete patio I removed drained out the carport as well, and the carport drains onto the public road. Thanks!