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Hi @AJ-DIYer,
I don't believe garden beds with four sides are governed by the same regulations as retaining walls. Retaining walls hold back tremendous weight and need to be capable of not being pushed over. A garden bed doesn't need to cope with such stress, as the boxed sides retain the soil within it. If you were thinking of doing a combination, where part of your garden bed acts as a retaining wall, then you'd need to follow height restrictions in your state or have it engineered.
Construction materials are up to you, but if you're planning on rendering the outside, it might be best to use Besser blocks so you can waterproof the inside walls. If you don't stop water from penetrating the inside walls, then the moisture will discolour the render on the outside. The cheaper option would most likely be using timber sleepers.
You can either work with the elevated gound or cut into it to create a flat base. The gradient of the slope would likely dictate your decision. Would you be able to post some images of the area and show us how you will be placing the garden bed?
Here's a helpful step-by-step guide: How to build a raised garden bed.
Please let me know if you have any questions.
Mitchell
Thanks @MitchellMc
I have attached some photos here, the rectangle pink border is where I am planning to build the garden bed. As you can see the ground is high to low from right to left, to give you a better pic, the top of the cinder block is where the surface of the ground will be later on the right side where I am planning to put pavers on as a seat area.
I dont know how high I should go, any suggestions?
Still not sure whether to go with timbre or besser blocks for a pleasant look.
If I go as high as 800 mm, that would be 4 x 200mm sleepers on top of each other, do I need to add a single post inside each corner for that high to maintain the structure?Do they need to go into the ground?
Would it work that I go up to 4 sleepers high from the wall half way and then go up to 3 sleepers high the rest? Or should I level up that section like you suggested to go 4 sleepers high all around?
will it be better to render over cement sheet set on timbre frame or paint over it using textured paint?
As a different option, we had the initial idea to set up the garden bed at the of back of the seat area (inside the right box) rather than outside on the left. Is this a better looking option?
Hello @AJ-DIYer
Allow me to try and answer some of your questions. Having the garden bed a t a lower height will obviously save you a bit as you won't have to spend on extra material.
To get a visual idea of how high 600mm and 800mm are, I suggest getting your tape measure and locating the aforementioned heights. Place the extended tape measure and place it beside you. This will indicate to you how high the garden bed will be.
A Besser block bed gives off an industrial look, it is a solid base material that stands out in a sea of greenery it makes for an interesting contrast if that is the look you are after. Timber sleepers on the other hand are natural products and they tend to be softer on the eyes as they blend in with the other timber materials in your garden.
In regards to the timber construction, I highly recommend having a look at this guide - How to build a raised garden bed by @Adam_W. It will give you a good visual idea of how to build the raised garden bed. But to answer your question, yes, the timber post must be placed in the corners and anchoring it to the ground will make it very safe.
If the soil is on a slope, you can either build to the slope which means that the garden bed will also be on a slope or dig into the slope or modify the posts so that the garden bed is straight and level.
If you want to put cement sheeting in front in order to render it, I suggest painting the back with Gripset Betta 1L Waterproofing Membrane Bitumen Rubber. This will prevent water from passing through the cement sheet and damaging your render.
My best advice for the location of the seat is to place it where you can have the best views possible and access to it is easy.
If you have any other questions we can help with, please let us know.
Eric
Hi @AJ-DIYer,
Adding a concrete foundation under the walls would be a good idea to ensure they 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, add crushed rock, and compact it again. We hire compactors that will make your life easier. You want to thoroughly go over the area to ensure the ground is compacted.
Either constructing a concrete foundation or laying crushed rock foundation are options. Here's a helpful step-by-step guide: How to pour a concrete slab.
Besser Blocks are mortared together and come in various sizes to suit your needs. Rendering can be applied over their front face. Here's another guide: How to render. There's no need to render the internal wall, but I would be painting it with a waterproofing membrane.
The location of the garden bed is really up to your preference. Remember to consider accessibility and exposure to sunlight.
Please let me know if you have any questions.
Mitchell
Hello @AJ-DIYer
I suggest having a look at this discussion - Hugelkultur raised garden bed using Colorbond fencing by @Aussie-Garden. There are some excellent suggestions on what organic matter you can put at the bottom of your raised garden. You can put leaves, bark, tree offcuts, cardboard and horse manure.
If you need further assistance, please let us know.
Eric
Hi @AJ-DIYer,
Just thought I'd add to Eric's reply that the wonderful @Noelle created a guide How to fill a raised garden bed that you should find very useful.
Jason
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