Water build up against wall

[Lyrik]

I'm currently having a retaining wall built to form a garden patio and started to fill and compact MOT1. On top of this I am likely to lay 100mm fibre enriched C25 concrete and then eventually (next year) lay a resin finish.

My question is relating to drainage as the fall will be away from the house and cause build up of rainwater against the retaining wall. Normally I would just install acco type drainage channels but the wall is curved so I am a bit stuck.

Someone suggested I use some flexible shuttering 10cm inside the retaining wall, pour the concrete and once cured I should then pull back the top layer of MOT1 and lay a perforated land drain. Which should then be covered on top with a DPM and backfilled with pea gravel. Finally I should drill weep holes at 900mm lengths at the bottom of the retaining wall.

I follow the weep holes. I'm not sure if the perforated land drain is a good way to go about this and don't follow use of a DPM above at all.

I could install water collection gullys every few metres along the wall but don't think this will get the water off quick enough and it would still sit on the wall until it reached the gully. So prefer a form of linear yet low cost drainage along the wall to be collected before it actually hits the wall.

Firstly does the perforated land drain idea sound a good one?

Secondly has anyone got any other suggestions?

Appreciated,

Richard

[seanandruby]

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