Grant Steven explaining site preparation while holding a Mattock
Before constructing the walls we need to do a little site preparation, this usually only involves giving the lawn a good hard mowing to get the grass as low as possible. If you have rank tall grass it might be best to use the Scrub Bar and also it is possible to scalp the grass right down to the dirt, both where the walls are going to go and on the inside of the bed and the pathways. If you can`t get hold of a Scrub Bar then try to buy a Chinese Mattock which is like a big heavy Grubber with a much wider blade. This is a very powerful tool and is ideal for knocking Kikuyu down and scalping it`s root system out of the ground. You can buy the blades for about $20 from Mitre 10 or sometimes the Warehouse, it comes in several different sizes and weights depending on the job you want it to do and your own size and strength
I`m a little casual about completely eliminating Kikuyu as I believe my method severely suppresses Kikuyu and if maintained and not neglected then eventually all kikuyu will dieout. Kikuyu doen`t like growing under the walls because underneath the walls is cold, wet and dark. Also the media in the beds is very deep and the surface is constantly mulched so any kikuyu is buried deep and has little chance to see sunlight. On the pathways the soil is heavily mulched with sawdust and regularly weeded with the Push hoe or Mattock. So in most cases it should not be necessary to resort to Roundup and if the other methods fail then maybe a little use of Roundup, at a later date, can always be applied at much lower rates.
If there are any big bumps or big holes then level them out but it is possible to build walls with these moulds on surprisingly rough land as the mould just rides over the surface and the concrete is rammed into the uneven patches. It is totally unnecessary to dig and lay foundations as the low centre of gravity and wide base of the wall makes it`s own foundation and this is reinforced by filling in the beds and mulching the paths so that the walls are naturally embedded on both sides. In fact it is possible to dig the pathways slightly below the bottom of the walls as long as you are careful not to undermine the walls. This allows you to apply a thicker layer of mulch on the paths with out reducing the height of the beds too much, it also gives you more material from the pathways to fill the beds with.
I have never used reinforcing iron and don`t think it is needed. It just makes the process more expensive and complicated.
So in conclusion it can be said that these walls are highly stable, have never fallen over and are only prone to cracking a little bit but this can easily be fixed with a little plastering.
If you want to build the beds on an existing garden site or you don`t have the means to fill the beds with customised soil then you will have to dig the pathways out by shovelling the soil onto to where the beds will be. This will need to be wide enough for both the path and the wall as the wall needs to be built on a firm foundation of subsoil. I believe in making wide paths as this allows easy access to the garden and makes it easier to work and push wheelbarrows around. It also means you have plenty of soil to fill your beds up with if you can`t afford to buy a lot of things in and it gives you a large area to cover with mulch on the pathways which will eventually break down and be shoveled onto the beds, this could be said to be a form of in-situ composting. So I recommend you make your pathways 90cm wide.
The other problem with narrow paths is that at least in my opinion it creates too higher density of concrete if the walls are too close, this is a another reason I like to have a wide bed width and we have settled on 1.4 metres as the width of the beds from the inside of the walls. This is an important number to remember when building the walls as the End Assembly Mould as been standardised to this width and won`t fit properly if you go wider or narrower. Many Raised bed Gardening Systems recommend 1.2m but these methods don`t have walls you can sit on and the beds are not normally 1 foot high, as in this system, so it is not as easy to reach in into the middle of the bed and the bed has to be narrower. But the narrower you make your beds the more walls and paths you have compared to the area of garden beds, so you loose productive capacity.
If you can not afford or don`t want all your beds to be walled-up, then you can form raised bed gardens without walls but I would recommend you stick to the same spacings as you would use for the walled beds. This will allow you to wall them up in the future, but if you do not, I think it is a good spacing to work with anyway and is very similar to the Whole Systems Method of John Warner and the Synergistic Garden of Emelia Hazelip [See handouts on those Raised Bed Garden Systems at back of folder]