Forum: Drainage
Topic: How to drain this garden? with pic
started by: PaveMeHappy

Posted by PaveMeHappy on 13 June 2019,19:18


Iíve got a long garden that steps down towards the house. The top of the garden is 7-8m above the bottom so lots of ground to drain and the ground is clay. How would you guys plan the drainage for the area shown in the pic? I want to pave the lot with a sleeper wall at the back of the top level and a sleeper bed along the back wall on the lower level. I thought for the top level a land drain behind the sleeper wall draining into a down pipe to the bottom level where it could be connected to the existing drain and a slot drain along the front wall also going into that down pipe. For the lower level though Iím a bit unsure. Could I do another land drain in front of the sleeper bed, then along the side wall to the front of the house where it can go into an existing drain there? I wanted something a bit more discreet but I think with a linear channel only the water will be under the subbase and wonít be able to drain away? If I go with the land drain how does that work with a compacted †subbase right up next to it or does the subbase go over the drain? I hope that makes sense? Thanks!

Posted by PaveMeHappy on 17 June 2019,18:41


Iím hoping two land drains as shown, one behind retaining wall on upper patio and one in front of sleeper bed on lower patio, will be enough to drain the water coming off the garden. The one on the lower level Iíd like to also use to drain the surface water coming off that patio. Is it ok to have the sub base (grey in the diagram) on top of the drain and stop the slabs before they touch the sleeper bed? Will the water drain through the sub base? Or do I need to create an edge like a flag on edge between the drain and the sub base?
Thanks!

Posted by Tony McC on 20 June 2019,17:59
I'd have an < interceptor drain > behind the riser of every step on the terracing, then have the paved area falling *away* from the house with a dev=cently deep linear channel or slot drain at the base of that final/first riser.
Posted by PaveMeHappy on 27 June 2019,07:33
Thanks Tony! Iíve been busy digging the interceptor drain behind the first riser as you suggested. Can you take a look at the following diagram and tell me if it looks right please? I can compact the sub base up against the geotextile of the drain without damaging it? I want to keep the drain as narrow as possible at the top. Cheers!


Posted by Tony McC on 27 June 2019,08:54
Yes - that's fine!

In practice, I'd probably fold over the geo-textile at the level of the base of the sub-base, place sub-base agg all over, compact, and then dig out a channel in the sub-base to extend the interceptor upwards, unfold the geotextile, top-up the interceptor, and then dress it.

Which raises the question: what will you use at the top of the interceptor?

Posted by PaveMeHappy on 27 June 2019,12:41
Top man! I intend to use slate chippings at the top of the interceptor drain.
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