Building Raised Beds

This post is part of a series called Roof Garden Rookies, which explores my attempt, as an amateur gardener, to grow a garden on the rooftop of my building in lower Manhattan.

For the past two weeks, some of the building’s residents and myself have been on the roof non-stop, getting the garden ready for its debut this weekend at our annual shareholder’s meeting. We hauled lumber, soil, plants and other materials, up 6 flights of stairs (no elevator!), to create a living space on our brand-spanking new roof. First thing was first, we needed to build the raised beds.

We chose cedar for its ability to withstand rot for longer than other woods, and because we found a deal on 1″ x 8″ planks upstate, 1/3 of the price of the cedar in the city. We had considered plastic planters, but it seemed the potential to leech chemicals was too great, and besides, they weren’t as nice looking.

A little bit of math, and I figured out how many boards we’d need. Luckily, Lowe’s made cuts for us, saving us time and a sawdust sandwich. In addition to 1″ x 1″ posts for mending the corners of the bed together, we also picked up some hardware: 1 5/8 inch stainless steel square head deck screws, which will not rust outside and go into the wood like butter!

With these boards, we built 16 ” high rectangular beds. For the bases of the beds, we were fortunate to have kept slats from our roof deck in a woodpile in the backyard. We pillaged that pile (simultaneously destroying a pigeon brothel that had formed over the year), cut the lengths we needed and connected the cedar boxes we’d made to their bases.

Our plan was to build fifteen beds, six large planters at 6 ft x 2 ft, three smaller planters at 4 ft x 2 ft, and six even smaller planters, which ended up being window boxes at 8″ x 5 ft. In order to distribute their weight on the roof (an engineer assessed our weight allowance at 60 lbs/square foot) we placed the beds in a “u” shape around the perimeter, and the window boxes would follow formation, hanging from the parapet.

beds3

Our next challenge was to prepare the main beds for soil. Essential to this process is creating drainage in the bottom of the bed so that heavy rains can easily find their way out of the planters. We started by placing screens over the widely spaced bottom slats (also notice the metal mending brackets, used to prevent bowing), and then filling the beds with drainage material: packing peanuts.

On the ground, most beds would use rocks for drainage. But since weight was an issue for our beds on the roof, Kerry Trueman, expert from Retrovore who has been helping us on all aspects of the garden, suggested using packing peanuts. And why not? they won’t be touching the soil or plant roots, so no possibility for leeching. They are 95% air, and would otherwise end up in a land fill. Sounded perfect. Only problem was, I didn’t want to buy them new.

beds4

Luckily, I reached out to my network of New York friends (Thank you Kerry, Janine, Jenni, Leah, Erin and Yann!) and was able to mobilize peanuts, mostly from their various workplaces, which I want to name check here because they do great work: Eat Well Guide, Recycle the City, and The Mill.

Following the peanuts, a quick addition of landscape barrier fabric helped to keep them from flying away (so did the addition of bamboo fencing, which serves as a great wind break), all stapled into place and ready for soil. Look out next week for my planting report, and more photos of what is growing up on the roof!

12 thoughts on “Building Raised Beds

  1. hey paula
    great work! Am sure you won’t have trouble with slugs up high, but if you do, copper tape around the edge of the planters is the way to go.
    Our garden and allotment is blooming. Hope yours will soon be too.xx

  2. Any thoughts on a good stain or paint to use that will not toxify my soil or food plants? I want to keep the wood as long as possible while facing the elements but am very concerned about leeching of coverings.

  3. This is great! I’m excited to see how it all works out. Have you looked into sub-irrigated planters (SIPs) otherwise known commercially as Earthboxes? There is a great blog (Green Roof Growers) that details the efforts of some Chicago residents to build their own planters and grow on their roofs. I took a tour of their gardens last summer and it was amazing. Some of the healthiest and most productive plants I’ve ever seen.

    Sasha

  4. This is strange.

    Someone else, Sasha @ comment #6, plugging our blog, @ #4.

    Anyway, I’m still curious about the growing medium. What are you using?

  5. I too am an urban gardener and excited to see your column. As Sasha mentioned above, Earthboxes are a great way to grow plants in urban area, I have several on my deck. They are also cheap to build and the yields are amazing. Because you can fill them up with water and leave them, it’s no problem if you go away for a few days and the sun gets hot. I would highly suggest you try one and see how it compares to the raised beds. I would be interested to know the results.

  6. What a pleasure to see your story and photo in the NY Times this a.m. Can’t wait to hear more about the crop.

  7. where did you find the windowbox brackets that fit over the parapet? I’ve been looking for some time both online and in stores without any luck. Saw the nytimes.com article . . . looks great!

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