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How to add drainage behind a wooden retaining wall?

I have an old wooden retaining wall. The previous owners did not put down shingle and drainage pipe behind the fence. Now the hill side is cracking with water fissures. Fissures in the lawn, pressure on the wooden retaining wall I can lay shingle and pipe but I need to know the best way for the water to flow out at the lower end. There are makeshift steps at the lower end, do I just exit the water straight over them? Those steps are close to the neighbours. There’s a lot of work to do in this sub tropical garden, but sorting the drainage may be a priority.

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Comments

EricL

Hello @Margs

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about drainpipes.

In this particular instance, I suggest engaging the services of a landscaping specialist or plumber who has superior knowledge in regards to garden drainage. There is no doubt that a Vinidex 100mm x 20m Socked Slotted Draincoil will need to be installed, but whether a French drain will be needed as well will need to be determined. If a great deal of rainwater is being diverted towards that section a second or third drain might be needed to prevent the ground from being saturated with rainwater.

In regards to where the water will flow out, I suggest diverting it into the storm water pipe if possible. This is to prevent the excess water from pooling further on down the lower end. Please note that connecting to your storm water pipe must be carried out by a licensed plumber for safety and compliance.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

Eric

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/49250#Comment_49250

Good Evening @Margs

Its a little hard to visulize the slope and run off areas. Is there a chance of a few more photos showing the cracks and where the water now flows?

If you draw out a top down sketch of your yard as is, draw in the lumps of any hills and the existing retaining wall plus other hard objects (trees, paths, washing line) You should end up with a page of probarly some elongated blobs and some contour lines.

Now comes the fun part, grab a blue pencil or texta and draw flow lines on the page following where the water now goes. You said your steps are close to your neigbours, is the retaining wall also? The aim is to move the water away from areas such as your neighbours and towards a stormwater pipe. You can either conside a french drain, ag pipe or a dish drain. I like the idea of a dish drain as its the easiest and also something that is used rarely. You are just channeling the water at this point. With the retaining wall I suggest a gabion wall as it handles water passing through it without an issue. No real drainage needed for a low wall.

With your steps that are near the neighbours, is there a way to funnel the water away?

Looking at the photo I am wondering how much soil that retainig wall holds back? From the angle of the photo it does not appear to be high. Would it be possible to smooth the fall of the slope so it dosnt need a retaing wall?

Dave

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