How to build a robust footing for garden?

[CarlL]

Good morning all,

I am gonna build a garden (roughly 5m long) along timber fence with Brighton Masonry Eziwall Lite Block. It's a 3-half circular wall design with 1 course. Will bury half a block in the ground. Please refer to images attached, the garden is highlighted in blue on the plan.

So, here is my question - what should I use to build the footing/foundation?

Have done some research online. Some use compacted road base and damp sand and cement mix over it while others use mortor, tooth paste consistency.

Which method will give me a stronger and more robust foundation? I dont expect lots of traffic on the garden. However, walking/stepping occasionally on the wall block is inevitable. Also thinking to plant some Lilly Pilly Resilience or Ficus Hillii Flash inside the garden, both of which will grow an massive root system.

TIA

[JacobZ · Accepted solution]

Hi @CarlL,

Sand and cement, and mortar are more or less the same things; the main difference between having a lightly damp mix and a toothpaste consistency mix is how clean it is and how easy it is to level. 

With a mixed mortar, it is soft and malleable, and your level can be adjusted by tapping the blocks with your trowel or a rubber mallet. With a damp sand and cement mix, you'd have to shift the blocks back and forth to work them into the mix and seat them at their correct level.

In terms of compressive strength, either option will be relatively similar once dry.

Realistically, if the road base layer is around 100mm thick and well compressed, it will create most of the compressive strength, and the mortar or dampened sand and cement are just there to hold the block in place and offer a levelling material. I have a preference for mixed mortar because it is easier to level things on the fly, but you really could use either.

If you were really concerned, my suggestion would be to have your layer of compacted road base, then pour a concrete strip footing over the top and then bed your blocks on mortar. This layer of concrete will offer much more compressive strength than either mortar or a sand and cement mix. 

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

Jacob

[CarlL]

Thank you @JacobZ so much for the tips and advice.

How thick of the concrete strip footing shoud be?

Thanks

[EricL]

Hello @CarlL 

I propose doing a conservative footing of 100mm in thickness. My best advice is to use a builder's line as a guide for the concrete strip footing.

If you need further assistance, please let us know.

Eric