Raised garden beds from reused roofing

      Comments Off on Raised garden beds from reused roofing

Raised bed gardening does have some advantages over the traditional row method. They require less “good” soil and less tilling. They are spatially more efficient, in that they take up much less space than rows. And they need less maintenance, as there is a smaller area requiring weeding. But these advantages carry over from the Square Foot Garden technique, made famous by Mel Bartholomew. There are however added advantages of building up. In fact, in the All New Square Foot Gardening book Mel now recommends raised box constructions over in ground beds.

Why raise up?

  • Height provides an additional barrier against short garden pests
  • They protect your good soil from washing away during heavy rains
  • Raised soil warms earlier in the spring, allowing earlier planting

Hugelkultur? I hardly know her!

Raised beds are also great for Hugelkultur, a gardening technique involving the burial of decomposing logs beneath the beds, to serve as a continually renewing source of humus and as a means of retaining moisture for the plants above.

The Project:

Over the years as our garden has expanded, I built new beds post-hoc, without any particular consideration for how the garden worked as a whole. But last year we came up with a master plan to replace the varied assortment of existing beds with a standardized design. Read on, and I’ll tell you all about our new beds.

Reuse existing materials

Reuse of old materials is very important to me, and this time I wanted to see just how far I could take that. I had a lot of old rusted sheet metal that I saved after repairing our shed roof. I knew I wanted to incorporate that metal into the design. I chose to make simple panel, using reclaimed lumber to provide structural support to the metal sheeting. These could be constructed in my work shop and then later assembled in place within our garden.


Use what’s available: Second Chance, my source for reclaimed lumber always seems to have plenty of 2X6 boards.

  • I built the frames of the first two beds last year entirely from reclaimed 2X6 boards, which cost about $75 total.
  • This year I discovered that Second Chance sometimes puts lumber in a free pile in their parking lot. For the new beds about half of the lumber came from the free pile and I purchased the rest.
  • I used an online cut list calculator to figure out exactly how much lumber I needed. With CutList Workbench, you can even enter the available lengths and prices and it will figure out which lengths are the best value for your project.

Save a tree: A 12 foot 2X6 reclaimed board costs $5.41 at Second Chance. New ones from Lowes are about $12.

Building the frames

Our raised beds are L-shaped, each consists of 6 panels. I started the project by cutting to length all the wood that I would need to build the frames for the panels. I then drilled the holes for the fasteners to join the frames, applied wood sealer, and assembled the frames



I prefer to use pocket hole screws when constructing joints on large casework like this. The Kreg Pocket Hole Jig is a good investment and easy to use. I purchased pocket screws made for outdoor use, but I’ve found that the regular ones typically outlive most outdoor projects.


Wood sealer

You would think that applying a finish is the last step, but doing it prior to assembly ensures that all surfaces get coverage. I’d like for these to last a while, so I applied a couple coats of wood sealer. The Susquehanna branch Habitat for Humanity’s Restore had new unopened cans for $1 (Cost about $30 a gallon elsewhere).



I lay everything out on a flat surface. Clamping isn’t really necessary with pocket hole fasteners. Just line up the boards and apply some light pressure to hold them in place and the pocket hole screws will draw the joint closed.



Here are several of the panels, stacked and set aside and ready for the next step.

Adding the metal panels

What initially inspired this project was my unwillingness to discard the well used sheet metal that I took from my shed’s roof during repairs. Although they were no longer suitable for roofing, they were still very strong. I eventually ran out of roofing metal. The remaining sheet metal came from a discarded washing machine.


Cutting to length

I used tin snips to cut the sheets. Even after > 50 years exposed to the elements, this metal took a lot of work to cut. I used a lumber crayon to mark my line. Heavy gloves are a must when cutting rusty metal.



The metal looked good as is, but since we will be brushing up against the raised bed when we’re tending to the garden, I decided to clean all the loose bits of rust off and add a clear coat of finish.



I used self drilling sheet metal screws to secure the sheet metal to the frames. Most of these came off of an old washing machine that I dismantled.


Completed panels

The panels stacked and ready for assembly into raised beds.

Assembling the Beds

In the construction of the panels, I used pocket hole screws to join the frames. Joining the panels required something more substantial. I used 4 inch long stainless steel lag bolts. Galvanized bolts are fine too. Either one will outlast the wood. Bolts and most other hardware items are cheaper if you buy by the pound.



This cart is on it’s fourth reincarnation. Every few years the wood rots away and I reuse the wheels and hardware to build a new one.


Bolting the panels together

I used a couple of clamps to hold the panels together while I drilled pilot holes for the lag bolts.


Leveling the beds

Our garden isn’t on the most level of surfaces. This had the effect of making the first two raised beds look slightly uneven. I tried to correct this problem while assembling the new beds by placing rocks and old landscaping timbers beneath the lower ends


Completed assembly

Just a few more things to be done before this last one is ready to fill with soil.

Adding a layer of decomposing wood

As I mentioned before, this is known as Hugelkultur. I didn’t actually know that when I started this project. Mel Bartholomew, who literally wrote the book that inspired the modern home gardening movement maintains that you only need about 6 inches of good soil in raised beds. My beds are well over 2 feet tall. It would be a terrible waste to fill these entirely with good soil. Mel suggests filling the void with sand, but sand is heavy and I don’t have any. I do however have plenty of rotting wood and I was overjoyed to learn that this was not only an acceptable solution but also could serve a beneficial role in our garden. The wood retains moisture, reducing the need for watering and as it gradually breaks down it will replenish the soil nutrients.


Rotting logs

This red oak fell long before we purchased our home. It was joined by a few maples and poplars that came down in the wooded part of our property during some heavy wind.


Barrier between structure and soil

I lined the beds with plastic sheeting. I had a roll of vapor barrier which I used on the first two beds. I still had more than enough to line the second two beds, but I decided instead to reuse some plastic sheeting that was previously used to wrap wood pellets. It’s nice thick plastic, that usually goes straight into the land fill after a single use.

What about soil?

If you dig anywhere on our property, you will hit clay pretty fast. Plus, who knows what else is in there? We live in a very old school house, so there’s probably plenty of lead paint. Then there’s a cemetery only fifty or so feet away from the garden. So it’s not the best soil for gardening. Better to start fresh. Mel Bartholomew (creator of Square Foot Gardening) says that soil is the last thing you want to skimp on. He recommends that you start your beds with a mix of equal parts: mixed compost, peat moss, and vermiculite.

  • Compost is the easiest element of the mix for me to find. The county I live in has a composting facility, and will fill a truck bed for a mere $10.
  • Peat and vermiculite are a bit harder to find. I get the impression that big box home centers don’t want us to mix our own gardening soil, because I almost never see either of them on the shelves. Instead they have lots of bagged ready mixed soil. Pessimistically, I assume this is a profit maximizing strategy.

So that’s about it. Last summer we grew peppers, soy beans, and tomatillos in the first two of the new raised beds. This year the tomatoes, okra, squash and what ever else we grow will get planted in the recently completed beds. I may need to get out the ladder when we harvest okra.