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How to build a base for retaining wall?

Kvic
Having an Impact

How to build a base for retaining wall?

I have a ambitious goal to change this part of the yard into a separate entertainment area.

 

IMG20230317092410.jpg

 

The pit with gravel is the drainage channel and where I am going to place a Besser block wall along.

 

So the first step is to determine the height and design of the wall which will be determine by a mockup.

 

IMG20230626073051.jpg

 

and create a design like this

 

Grey-Block-Rendered-Finish-Raidsed-Garden-Bed-and-Built-In-Seat-562x350.jpg

 

My first step to creating this starts with the base for the blocks and I understand the base must be square and level otherwise the finished wall will be uneven.

 

I would like some advise on the type of base and thickness I should start with, like a compacted crushed pebble with a piping frame sitting on top to run along the pit for leveling and the thickness of concrete base on top.  

 

 

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Backyard Project

Hi @Kvic,

 

Adding a concrete foundation under the wall would be a good idea to ensure it doesn't subside and shift over time. Depending on the height of the wall and the nature of the ground beneath, you might be able to compact it and then add crushed rock and compact it again. We hire compactors that will make your life easier. You really want to thoroughly go over the area to ensure the ground is compacted.

 

Besser Block retaining walls are mortared together. The blocks need to be core-filled with grout and reinforced with steel for engineered and load-bearing walls. It's best to check with your local council to determine whether your wall requires engineering. 

 

Having the wall on top of the existing crushed rock and drainage likely wouldn't be a good option as it will prevent surface water from falling down into your Agi-line. I would suggest building the wall on the lower side of the slope to the drainage line so the water flows down, hits the wall, and then falls into the drainage.

 

Whether you're constructing a concrete foundation or laying crushed rock foundation, you'd have those around 100-150mm in depth. Here's a helpful step-by-step guide: How to pour a concrete slab.

 

Please let me know if you have any questions.

 

Mitchell

 

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Re: Backyard Project

Hi Mitchell

The wall will be free standing and I feel the height will be cap around 6 blocks above ground with drainage running along both walls.

 

I sat on a wall with a height of 2.5 - 3 blocks and the knees and hip was inline and comfortable IMG20230626101124.jpg

 

Not going to disturb the surrounding area and place the first layer below ground as the compactor is 420mm wide and 68 kg I will have one end of the ditch at ground height as the ground level is lower that the picture above so the wall will rapidly decline.

 

Will need Steel reinforcement to be placed in the concrete, does Bunnings have them?

 

Step 1. Dig trench 500mm wide by 650 mm

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Backyard Project

Will the wall be six blocks high, and will it retain any soil @Kvic? Either way, you'll likely need to speak with your local council to see if engineering and approval with be required. A Besser block wall that high is a sizable structure and, if it's not designed and constructed correctly, could cause significant damage if it were to collapse. You're also building it on a slope which adds to the complexities.

 

A six-block high wall would require reo bars inserted into it for stability.

 

Mitchell

 

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