What drainage for retaining wall along fence?

[paula24]

Hi

I am wanting to level block in backyard.  Putting 2 sleepers high retaining wall 400 high along fence line. 

Do I need to worry about drainage or what type of rocks can I put in between retaing wall and fence. Gap will be aprox 250 to 300

 

 

[MitchellMc]

Welcome to the Bunnings Workshop community @paula24. It's brilliant to have you join us, and many thanks for your question about building a retaining wall.

When it comes to building a retaining wall close to a boundary, there are usually regulations you need to follow. Drainage is often a requirement to prevent water pressure building up behind the wall, but the rules can vary depending on your location. I’d encourage you to check with your local council to see what’s required for retaining walls near boundary lines in your area.

Regarding the 250–300 mm gap between the wall and the fence, ideally, you shouldn’t be filling that space. Adding rocks or other fill could place extra weight on the fence, which it isn’t designed to take. A better approach is to leave the void and, if you want a finished look, cap off the top of your retaining wall with horizontal sleepers to bridge the gap between the wall and the fence. This keeps the wall strong, avoids loading the fence, and still gives a neat finish.
 

You might like to check out our range of sleepers, posts and this helpful guide: How to build a retaining wall.

Please let me know if you have any questions.

Mitchell
 

[paula24]

thank you Mitchell for your respond.

I have had quotes from landscapers and they haven't said anything about approval from oouncil. I am confused as to why i would need approval.

i didn't think it is required since its not very high its only 2 sleepers high and its used to level the block to the concrete. i am too scared to call haha.

putting sleepers on top might be difficult since the gap is not very wide and also you would create like seating area which is added cost. 

I didn't think it would get this confusing. I did upload pictures for you to look at:)

[JacobZ]

Hi @paula24,

It's unlikely that the height of the retaining wall will matter, but its proximity to the boundary can sometimes be significant. The rules around building retaining walls at close proximity to the boundary are usually in place to limit the potential for disputes with neighbours around drainage issues and the future maintenance of the retaining wall. If you look up "retaining wall boundary setback" and your local council's name, there will likely be some information.

As Mitchell mentioned, filling the space with stones is not usually recommended as it will place pressure on the fence and can cause premature rotting of the timber. When you know what requirements you have in terms of setback from the boundary, you can work out what to do with the space. 

Planting some screening plants, such as Lilly Pillies or Japanese Buxus, can help to fill the space. You could also add some decorative pots with medium to large plants if the ground is not suitable for direct planting.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[paula24]

Thank you for your response. I had look on website. I appears it needs council approval.

we decided not to put plants because the plants would look low comapred to the height of the soil on the other side of the retaining wall plus added soil.

we could maybe put crushed small rocks and not build them up too much next to the fence.

i am surprised landscaper hasn't said anything about permit. they just want to come and do job and leave and you are left with headache

[JacobZ]

Hi @paula24,

Rules can differ from council area to council area, so your landscaper may just be unaware. That's why it's always important to check.

If you are set on using stones, then I'd suggest something lightweight like scoria.

Let me know if you have any further questions.

Jacob

[paula24]

One last question please.  Landscaper is putting that black plastic to protect sleeper.  Is that good idea ?

Paula

[JacobZ]

Hi @paula24,

The plastic is fine. It will help prevent water or eroded soil from travelling through any gaps in the retaining wall.

Assuming there is drainage in the form of gravel and an agi pipe being installed behind the wall, it will hit the plastic barrier, fall down into the gravel and then find its way to the agi pipe to be carried away.

Let me know if you have any further questions.

Jacob

[paula24]

I think plastic will be facing outside not inside of the retaining wall.

We might just put scoria rather than aging pipe for drainage.  

[JacobZ]

Hi @paula24,

On the back of the retaining wall, where it will be covered by soil, it makes sense. On the outside, not so much. I don't see why your landscaper would do that.

Has your landscaper indicated that they would be putting drainage behind this retaining wall? 

There's no problem using scoria as a drainage material, but including an agi pipe inside the drainage will collect and move the water to a defined location. It is certainly worth considering.

Jacob