Drainage for sleeper wall

[chilluk]

Just in the process of landscaping my garden. Plan is to have patio outside back door, sleeper wall approx 500mm high (with integral steps) up to raised lawn area.

Patio is already laid. Luckily I put hardcore base down last Bank Holiday and resulting monsoon highlighted some "issues" with drainage. Have now laid strip drainage (not sure of proper name but drains with metal covers) all along edge of patio and connected into existing SW drains. All good (although not yet tested by rain of course!!). Patio was put down this weekend just past and has pretty good run off angle.

The shallow "trench" where the wall will go pretty much filled with 2 inches of water - although we had 5 days solid heavy rain, and at that point it was the lowest part of the garden, which currently has no greenery at all to soak anything up.

Next up is treated new softwood sleeper wall. Now wondering what to do with drainage for that.

The garden is weird in that it's pretty heavy clay lower down (at depth of patio) yet pretty good up top - we are surrounded by Oaks which usually drink loads - we get quite bad cracks in lawn in very dry weather!!

The wall will go immediately adjacent to the strip drain so was wondering if just backing up with some shingle and leaving some weep holes (or even drilling some holes and putting some pipes through?) would work, as in theory water should go into the drain?

However doing research (ignorance is bliss isn't it) makes me wonder about geotextiles and perforated pipes now. I guess with a bit of work I could almost connect a perf pipe into the pipe that takes the water from the patio drain to the SW system.

Also should I be protecting back / underside of wood with anything - some sort of bitumen paint, or membrane?

Was planning on bedding wall on semi-dry sand/cement mix to get levels - is that the best way?

Will be laying the sleepers flat and screwing together with timberlok - there will be some 90 degree angles in it so it'll almost stand up by itself I think. It'll comprise 25 or so sleepers and so will be pretty heavy.

It's only going to be 450-500mm high so not masses of weight to hold up.

Any advice massively appreciated.

Chris.

[lutonlagerlout]

seek and ye shall find
LLL 5:06

[chilluk]

I have had a good look through the site - I was after advice related to my specific situation - bearing in mind the existing drainage I have just added etc.

Also if anyone has any answers to treatment of timber first or not that would be good.

I wasn't being lazy just sometimes there is too much useful info and pinning down what applies or not can be tricky for the novices.

Cheers.

[lutonlagerlout]

well obviously any timber in or around ground level should be tanalised
shingle on its own will silt up eventually a land drain is always better
hope this helps ya
LLL