Metal roofing raised beds

 Here at DIGS, we need to rebuild and replace some of our raised beds, and since the lumber we used to use (4" x 4" yellow cedar) has become prohibitively expensive at approximately $500 for a 24 foot by 4 foot garden bed, we took a look at two local designs that utilize a timber frame mounted with corrugated metal roofing.

 Firstly, a brief field trip to the Co-Op Greenhouse at Beban Rec. center gave us a good look at their use of horizontal metal roofing (click on photos to enlarge):

The design requires plenty of costly 2x4" wood, and the Co-Op volunteers showed us how the longest pieces of wood do warp, bend and bow over distances, which looks slightly irregular. Also the flaw in this particular build was that the wood is exposed to the wet soil where it would rot and need replacing at the corners. The above beds were obviously also too tall for our uses at DIGS (they filled the height of the beds utlizing "hugelkulture" to save on the amount of soil required) so we'd need to re-think the design for our own uses.

On the other hand, utilizing the metal roofing vertically, as our P.I. neighbour Gordon did in his garden on Pirates' allows perfectly strong and stable beds of any length, and have no wood exposure to wet soil at all. Just brilliant. The cost is approximately $140 worth of metal for a 24 foot by 4 foot garden bed (we still have to price the lightweight lumber). Plus we have the nearby expertise of the inventor himself, who has built several, to show us the easiest way to put them together. What a win all around!

click on photos to enlarge

Note that all the roofing comes pre-cut from the store, and has standard nut fasteners that affix it to the lightweight wood.

Note too that in the preferred second design, with the metal used vertically, there are no corner posts at all. The strength of the product is in its vertical positioning.

Jim Harris has asked that we take more DIGS garden measurements and really sort out how many beds will fit. Our priority is to plan on the maximum grow area for the left front of the garden where the beds will be replaced first (the clematis and rose trellis area will be replaced with public and possibly some allotment veggie beds). All of this will be voted on and planned as we go.

We can put the new beds closer together than lawn-mower-width, Jim suggests, and use mulch on the paths instead of lawn, as long as the paths are wide enough for wheelbarrows. So this could be fun to work out using graph paper and little paper pieces, if folks are into it.

We should also decide on whether, over time, all the rotten timber should be replaced with vertical metal roofing in this new design. They should last for decades without the need for further investment. The Zinc coating is foodsafe and does not break down over time, and the 1"x3" trim will be Yellow Cedar. (Red Cedar suffers from a powder beetle problem).

So this is part of the success of our tiny field trip this week, as well as finding the structural engineer who will help us build a healthy/organic footing for the greenhouse (timber, gravel, rebar anchors etc.).

All the news, now for some measuring and planning!

Jen (for Jim Harris) (who doesn't use computer)