The plan at a glance
This U is three narrow beds around a path: a back bed 96 × 24 inches and two arms 72 × 24 inches, one down each side from it, on a patch 8 × 8 feet. Walk into the 4-ft path between the arms and every plant is in reach: each bed is 21 inches across inside, within the 24-inch reach from one side that the width and reach guide explains, and the arms can be worked from outside as well.
Each bed is a box of its own, built the way every board plan here is: 2 × 6 boards on edge, 11 inches tall, the long boards running the full length of the box, the end boards between them, and a 4 × 4 post inside each corner and in the middle of each long side. Built as three boxes, the U has no inside corners to join, and you can build the back bed first and add the arms later.
Cut list and materials
A 2 × 6 board is 1½ × 5½ inches when you buy it dry, and a 4 × 4 is 3½ × 3½ inches, the dressed sizes the American Wood Council lists. The lengths below use those sizes and allow ⅛ inch for each saw cut. Cut together, the three beds take 13 boards 8 ft long: an arm board cut to 72 inches leaves 23⅞ inches, enough for one 21-inch end board, so eight of the twelve end boards come from offcuts.
| Part | Cut from | Length | Pieces |
|---|---|---|---|
| Back bed, long boards | 2 × 6 × 8 ft, used whole | 96 in | 4 |
| Arms, long boards | 2 × 6 × 8 ft, one from each board | 72 in | 8 |
| End boards | one from each arm board’s offcut, four more from one 2 × 6 × 8 ft board | 21 in | 12 (8 from offcuts, 4 from 1 board) |
| Corner and middle posts | 4 × 4, three lengths of at least 6 ft, six posts from each | 11 in | 18 |
| Stainless steel exterior screws | 3 in | 120 (40 a bed) |
13 boards in all: 4 for the back bed’s long sides, 8 for the arms and 1 for end boards.
Build it
- Choose a level patch 8 × 8 feet and mark it out: the back bed along one side, 96 × 24 inches, and an arm 24 inches wide and 72 inches long down each side from it, leaving a path 48 inches wide between them. Put the open end where you will walk in.
- Cut eight boards to 72 inches for the arms, and a 21-inch end board from each offcut. Cut four more 21-inch end boards from one board, and cut each 4 × 4 into six 11-inch posts. Check each cut with the square.
- Build the back bed: lay two 96-inch boards flat, edge to edge, place a post on them 1½ inches in from each end and one centered at 48 inches, and drive two screws through each board into each post, 12 screws a side. Make the other long side the same and stand both up, posts facing in, 21 inches apart on the inside.
- Fit two 21-inch end boards at each end, between the long boards and against the corner posts, with two screws through each end of each board into the post. Measure both diagonals on the outside: they should both be about 99 inches. Push the frame until they match, then check it is level.
- Build the two arms the same way from the 72-inch boards, each long side with a post 1½ inches in from each end and one centered at 36 inches. An arm’s diagonals should both be about 76 inches.
- Set an arm against the front of the back bed at each end, at right angles to it and flush with its end. The path between the arms should measure 48 inches at the back and at the open end. Each bed stands on its own, so the arms need no fixing to the back bed.
- If gophers or voles dig in your garden, fasten hardware cloth across the bottom before you set the bed down. UC IPM advises hardware cloth or ¾-inch mesh poultry wire under raised beds for gophers; Colorado State University Extension gives ¼-inch hardware cloth for voles and pocket gophers.
- Fill the three beds.
How much soil it takes
Filled 10 inches deep, with the posts taken out, the back bed takes 10.9 cubic feet of soil and each arm 8.0: 26.8 cubic feet in all. Bought for the three together that is 18 bags of 1.5 cubic feet, sharing the part bags between the beds; bed by bed it rounds up to 20 (8 for the back bed, 6 for each arm). An inch is left at the top of the 11-inch walls for mulch.
26.8 cubic feet is 0.99 cubic yard, so one cubic yard of bulk soil fills all three with almost nothing over. Whether a delivered yard costs less than 18 bags depends on the supplier’s minimum load and delivery charge: the bagged vs bulk soil calculator compares your two quotes.
Open the back bed in the soil calculator to change the depth; an arm is 69 × 21 inches inside. The calculator counts the inside with the posts left in, so it shows a little more.
Bagged vs bulk soil calculator
Open the calculatorThe path, and what goes where
The path is 4 feet wide, the room the University of Georgia Extension allows between beds for carts, wheelbarrows and wheelchairs. It ends at the back bed 6 feet in, so a barrow goes in forward and comes out backward; the path guide explains how to check the turns for your own barrow or chair.
If you can, set the back bed along the north side. University of Maryland Extension puts taller crops on the north and west sides of a bed so they do not shade the shorter ones: tomatoes or beans on a trellis in the back bed, then lettuce, herbs and roots in the arms, where the sun reaches them. The trellis plan fits the back bed as it fits a 4 × 8: the back bed has the same 96-inch side, 11 inches tall and filled 10 inches deep, with a post inside each corner, so the uprights, the rail and the net are the same.
Three beds also means three to water. The irrigation kit fit checker takes the number of beds and their size and says which kits are stated to cover them and what else to buy; the drip irrigation guide goes through the parts from the faucet to the beds.
Wood and screws
Use cedar heartwood and stainless steel screws, as in the 4 × 8 cedar plan, which gives the reasons; the best wood guide compares the other choices.
What this plan does not cover
This is a plan for beds on open ground. It is not an engineered design and makes no load rating. For a bed on a patio, deck or roof, read the hard-surface guide and have the surface assessed for the filled weight first. Vego, Vegega and Greenes Fence sell U-shaped beds as kits; the L- and U-shaped beds we list give each one’s sizes and the soil it takes.
Try it with your numbers
Open the raised bed soil calculator with this guide’s bed filled in, then change any figure to match yours.
Open the raised bed soil calculatorReferences
- Raised Garden Bed Dimensions (Circular 1027-4), University of Georgia Cooperative Extension.
- Span Tables for Joists and Rafters, 2024 Edition, American Wood Council.
- 2018 NDS Supplement, Table 1B, American Wood Council.
- Wood Handbook: Wood as an Engineering Material (FPL-GTR-282), chapter 14: Biodeterioration of Wood, USDA Forest Products Laboratory.
- Raised Beds: Will They Benefit Your Vegetable Garden? (FS075E), Washington State University Extension.
- Fasteners for Outdoor Projects, Western Red Cedar Lumber Association.
- Pocket Gophers (Pest Notes), UC Statewide IPM Program.
- Vegetable Gardening in the Mountains, Colorado State University Extension.
- Planning a Vegetable Garden, University of Maryland Extension.