How to build a low retaining wall along fenceline?

BriggsyNZ

Hey guys!

Love reading through these forums so thought I'd put something up in hope of some direction on a low retaining wall project.

Our yard is slightly sloped (500mm drop) at the moment and the plan will be to terrace the top 3m or so and then drop down to a low level deck (more questions on that to come)

I have a few main questions which are below.

1. As we will need to build up the soil at the top of the yard, we will need a way to retaining it on the fence lines either side. Would the easiest way to do this be digging out a small trench and @dropping treated sleepers in which are pegged into the ground? I wouldn't expect it to be more than 200-300mm at the max drop however am trying to figure out how to build it up as close to the fence line boundry as possible without impacting the fence itself?

2. For the side walls, do they need to have drainage/backfill or will it be okay as the water will naturally flow downhill?

3. Everything I have seen shows retaining walls with sleepers on the external face (to take the weight of the wall + soil behind it). In our case as the wall is quite low (roughly 500mm), is there a way of the vertical support posts being on the inside face so that they don't stick out on to the deck or will they need to be on the outer face?

Sorry about the poor plans/ layouts, if anyone has a suggestion on software to use to help plan too, that would be appreciated.

MitchellMc

Hi @BriggsyNZ,

These Retain-It upright joiners should make your life easy and don't protrude on either face of the sleepers, only on their thickness. 

You'll likely need to do some investigating to find out the regulations in your area surrounding retaining walls close to boundaries fences. Employing the services of an engineer to design the retaining walls would likely fast track any application process. Retaining walls built within a certain proximity to boundary fences will quite possibly need to be engineered and an application submitted to council for them. This is due to the likelihood of adverse effects being seen on the adjoining property. Failing having the wall engineered and an application approved, you'll be liable for any rectification works deemed necessary to put right any damages to the neighbouring property. This could be anything from installation of drainage systems on their property to divert runoff or notices to remove all works and restore the property to the former layout.

The drainage installation and consideration of where runoff will flow would be critical factors in getting a submission approved. Due to it being so low, you might find that council doesn't need an application for its construction. However, engineered plans and council approval are reasonable assurances that you won't run into roadblocks.

Please let me know if you have any questions.

Mitchell