I had three reasons to undertake this project. Firstly, I wanted to get some plants growing, and had left it far too late into spring to construct the raised beds I wanted. Secondly, I like the idea of growing plants on steps to utilize vertical space and make existing buildings blend into the natural environment. Thirdly, and most importantly, I was keen to start another wood working project.
Amongst other articles I found this example of a DIY planter, which has been used to support deep trays, not small plots. This example is great, but I wanted to make a full A-frame construction, and give lots of lateral stiffness. As far as possible I also wanted to avoid killing the grass under the planter and get to it with the lawn mower.
I managed to find some reasonably priced planting trays 600mm long 300mm wide and 240mm deep. I designed the structure around 3 columns and 3 rows of these.
- 1.8 m long
- 1.2 m high
- 0.6 m depth
- Step supports: 215mmx20mmx1.4m (or 1' by 9' by 4.6ft) planed pine x 3 lengths
- Step platforms: planed pine 215mmx20mmx1.8m (or 1' by 9' by 5.9ft) x 3 lengths
- Frame verticals: 38mmx38mmx1.2m (or 2' by 2' by 3.9ft) x 3 lengths of treated pine
- Frame back angle piece: at least 19mmx19mm (or 1' by 1') in cross section and at least 2.16m long x 1 length
- Frame horizontals: 38mmx38mmx1.8m (or 2' by 2' by 5.9ft) x 4 lengths of treated pine
- Frame feet: 38mmx38mmx0.6m (or 2' by 2' by 2ft) x 3 lengths of treated pine
- Feet blocks: 19mmx19mm (or 1' by 1') treated pine approximately 215mm long x 3.
- Right angle brackets x 6
- Long coach bolts at least 76mm long x 4
- Exterior wood paint or sealant
- Assortment of screws and nails
Step 1: Making the Step Supports
Take the 3 step support sections, which have been cut to 140mm long. These need to be marked up according to the dimensions of the pots that you intend to store on the shelves. The depth of the planter is 600mm I set the height of each of my shelf sections to be 450mm.
If you look at the final construction, the shelf platforms themselves extend forward of these step supports. It is most important not to take too much material away from these supports as they are load bearing. Better to extend the shelves outwards rather than cut too far into these timbers. From the marking up images you'll see that I cut approximately half way into these timbers, but not much further.
Once I was satisfied with my design, I cut the the waste away from the marked up section. I then used this as a template to mark-up the other two. These where also cut using a jigsaw before cutting those.
Step 2: Making the Back
This part of the instructable will be made a lot easier if you have a flat surface to work on.
Take one of the frame horizontals and all three of the vertical frame supports. These will be assembled to form the frame back as the first image shows. So that the timbers lock together, mark them up and cut them so that they fit together in the rebated fashion shown in the images. After cutting the timbers, I applied a coat of the wood sealant to the inside of the joints and let it dry over night.
Take the frame back angle piece. Place it diagonally along the back of the frame. It can be trimmed to an exact length later. Now ensure that the top and the bottom of the frame measure exactly 1.8m (i.e. the frame is square). Now screw the angle piece directly onto the back of the frame to prevent any skew.
Screws can now be driven into the rebated joints.
I used some of the offcuts from cutting the step supports to further sure-up the centre of the frame and prevent skew.
Step 3: Making the Feet
Take the feet 2' by 2' sections and attach the 1' by 1' blocks to one end. The blocks should sit flush with one side of the foot timbers. The space left is where the hypotenuse sections of the A-frame will sit.
I drilled pilot holes before nailing with 3 long screws in each. Screws would also do the job nicely.
Step 4: Fixing the A-Frames
Feet to Vertical Frame
Drill holes through both the vertical supports and the feet. The wooden blocks we nailed on to the feet in the previous step should be on the opposite sides of the feet from the sides we are drilling the holes on, and the blocks should be facing skywards. See the second image of this step which has some additional notes. Now pass through the coach bolts and slide the nuts on. You will need to do this for each of the 3 pairs of vertical and feet frame items.
Completing the A-Frame
It is important that you verify that you are forming right-angles between the feet and the vertical sections before you tighten the coach bolts. I used a flat surface and an external wall as a guide before tightening. I strongly suggest pinning the step support planks in place and verifying that you've formed a 90 degree angle before screwing the A-frame tight. Now tighten the bolts on the feet.
This frame is designed to take a heavy load of soil. The horizontal 2' by 2' supports should ensure that the load is distributed across the whole structure and will help prevent lateral movement. Fix brackets to the underside of each horizontal support, as the image shows.
I used some light weight timber to prevent pots from sliding backwards. You can see in the image the lower supports. The timber used here was approximately 1' by 1/4' in cross section and 1.8m long. 3 pieces were used.
Step 5: Attach the Platforms
Screw the platforms into the horizontal supports using 50mm screws. I also screwed through the back supports into each platform to prevent twist.
Step 6: Seal It
This planter is going to live outdoors with no roof, so will be very vulnerable to the elements. By sealing the timbers we can help keep water out of the wood itself and extend the lifetime of our structure. I suggest applying at least two coats of sealant using a small brush to coat every surface. It can take some time to do this properly and you'll have to lean the structure onto it's front to get to the underneath.
Step 7: Plant It
You should find that your A-frame is very strong and can bear a large load. Mine has survived a few storms and it seems to easily bear it's full set of trays.