Hi, I’d like to pour some concrete garden planter boxes. I will be making two boxes, so will need to reuse my forms. The boxes are 12′ x 5′ on the outside dimensions. I’m open to advice on the wall thickness, as I’m no expert on strength of concrete, but I’m thinking 2.5″.
As for height of the boxes, it varies since they’re on a mild-to-moderate slope. On the lowest grade side, the walls will need to be roughly 27″ high. On the other side, they’d be 13″ approximately.
I’m looking for advice on how to create the forms. Mainly, what type of wood would you recommend (plywood?), how to reinforce the forms for the pour, and whether rebar/mesh is required for this application. I have chain link fence material lying around; would that work as remesh?
I’m not sure how to calculate or know what to expect as far as soil pressure forces on the low grade wall, so any advice there is appreciated as well.
Replies
That is a pretty large job for a first concrete project.
You need to understand the frost depth where you live, and make sure to get the walls below that depth. otherwise your hard work will be moved and cracked by the forces of nature.
You are better off making the bottom and top level, which means digging a trench where the walls will be.
You might want to look into renting forms for this job.
Rental place can help with rebar and mix specification.
Thinking "outside of the box" -
How about building the box as a kit of parts, each part being a side or floor of the box?
This way you can pour them flat, much easier, and tip into position. The top/ dressed side or the form side can be the outside face, if exposed.
Slab should have a key-way to accept the side panels. Side panels can have a diagonal brace to lock them square.
Frankie