Recently I put together my newest raised bed. I was inspired by some pictures I’ve seen lately where metal roofing materials were used for the sides. It was a very cool look that I wanted to see if I could replicate for my garden. Plus metal materials last longer than lumber for raised beds.
I went to the store and gathered 9 2×4’s, 3 steel roofing panels, and a box of deck screws. The total material cost for this raised bed is around $100 but you could greatly diminish that if you could find old metal roofing from a barn or a shed. The metal roofing panels were $15 each which adds up to almost half the project.
Building a Metal Raised Bed from Roofing Materials
I built the side frames for the raised beds first. The 8′ sides used full length 2x4s with 3 21 1/4 inch vertical pieces as supports on the sides and the middle. The 4′ sides only used 2 supports per side which made for a total of 10 vertical support pieces. I cut one roofing panel into two 45″ pieces and used the full length of the other two panels. The sides are set at 48″ but I needed a gap on either end of the 48″ sides for the wood corners to contact each other for a smooth connection.
The construction of this bed is pretty simple but it does take more time to build than a typical wooden raised bed where you simply screw the corners of the wood together. The metal sided raised bed is very tall at around 28 inches but is a good height for anyone who may have health issues that prevent them from bending over to do garden work. At this height you can do all the maintenance from a standing position.
The big challenge will be filling the bed. I’ll begin with a layer of straw bales in the bottom and layer with compost, newspapers, leaves, grass clippings, soil, and any other organic material I can find!
Filling a Raised Bed with Hügelkultur
You could also fill up a raised bed like a hugelkultur garden. Hugelkultur uses large logs as a base organic material that can hold water then adds material to the top of the logs. You layer the garden bed with branches going from large in size to smaller then cover with other faster to decompose materials like grass clippings and leaves. Then cover with soil. The organic matter breaks down over time to become a rich compost. The branches also create air pockets which aids in the breakdown of the materials. Microbes need oxygen to survive and thrive.
How I Built the Metal Raised Beds
Here’s a video on the construction of this metal raised bed. I hope it’s helpful!
For some tips on raised beds check out my post on 11 Things to Think About When Designing a Raised Bed Vegetable Garden Layout.
Updated 12/22/2024
The biggest issue with raised beds like this is the amount of material needed to fill them. Volume in this raised bed if filled all the way is about 64 cubic feet. That comes to about 2.37 yards of compost/soil. The hügelkultur method mentioned previously works well to fill raised beds up fairly cheaply. You will still want the top 8-12 inches to be a layer of good rich compost and soil. My advice would be to stock up on organic matter and build lots and lots of compost.
What I noticed is that no matter how full I filled this raised bed the soil level composted and sunk. It was very tough to keep it full. I nicknamed it the “monster” since it was big and seemed to eat everything I gave it! If I were to build this again I would opt for a shorter raised bed that didn’t require quite as much material to fill. You can make twice the amount of raised beds and have more growing area for your plants.
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Dave, I really like this and now I have questions!
1) Were you screwing in your deck screws at an angle? Any special tools needed?
2) What did you use to cut your metal? AND
3) Do you think using painted roofing will mitigate the reaction between the metal and the treated wood? (I have lots from prev. proj.)
4) Do you think that much straw bale on the bottom will rob your fruits and veg of nitrogen, and if so, what will you supplement with?
This project really looks awesome! Thank you for your answers to my questions. ~Lynda
Great tutorial on the monster raised bed! Look out Bob Vila, there is a new guy in town…
Planning on putting up some raised beds this summer so they are ready for next season…I know..kinda late. This is good info and I will definitely be considering it as part of my options.
Thanks!
Dave,
My husband and I constructed very similar raised beds several years ago and have been very pleased. Although we chose to rip our roofing leaving our overall height at around 13' you could make the bed at any height you desired. To conquer the problem of bending over to tend the beds, we use a wooded "seat" that rests on the rails of two beds. I can slide the seat from one end to the other or completely remove it. Our oldest beds are about 5yrs old and still going er… I mean growing strong!
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I didn't know how to add a pic here so I added a picture to your FB page so that you could get an idea of what our beds look like. Although you can't see the bottom of the bed in the pic, I wanted to note that we did not use any lumber along the bottom edge so we have had no rot. We also don't have wood in our corners, we used aluminum flashing that we bent to a 90* angle there instead of wood. We have had no issues with stability because the rebar is driven close to 24" into the ground. I'll try to dig up a better pic and add that to FB as well.
Angela
Hi Dave,
My wife and I are both retired now and very much interested in building raised bed gardens. As any couple that's been married for 45 years, we don' always agree on everything. I want to use some 4×4 posts that I've had to build the frame and the legs to be able to adjust the overall height suited to our needs. The center line of the posts would make a 4'x8' opening for the bed. Then use 2"x12" beams sitting on top of the outside edge of the posts, leaving a 2" ledge on the inside of the posts. Then use some 1"x2"x4' boards for bracing across the length of the bed. This is where my wife and I disagree. I would then put a 4'x8' length of roofing sheet metal secured to the bracing and with holes drilled into it to allow for drainage, and then put the soil directly on top of that. My wife thinks that it would be dangerous to have the soil in direct contact with the sheet metal, causing some kind of toxic reaction with the soil and absorbed into the veggies, etc. I honestly don't know, but if it didn't it should by far outlast the wood in the frame. What do you think? I don't want to start until I have some guidance…thanks.
Bill and Shirley