The Well Kept Garden

Menu

How to build a 4x4 raised garden bed

A 4 × 4 ft raised bed from four 8-foot 2 × 6 boards, a 4-foot 4 × 4 post and 32 screws: the cut list, the steps, and the 8 bags of soil it takes 10 inches deep.

The plan at a glance

This square bed measures 48 × 48 inches on the outside and stands 11 inches tall: two 2 × 6 boards high on every side. Two sides use 48-inch boards, the other two use 45-inch boards that fit between them, and a 4 × 4 post sits inside each corner. The inside is 45 × 45 inches.

Each 8-foot board gives one 48-inch and one 45-inch piece, so four boards make the whole frame. A 4-foot side needs no middle post: the corner posts are already less than 4 feet apart, the support spacing the University of Georgia Extension asks for on boards only 1 inch thick, and these boards are 1½ inches.

48 in outside45 × 45 in inside
From above, drawn to scale: long boards whole, end boards between them, posts inside.

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 list for the 4 × 4 ft bed
PartCut fromLengthPieces
Side boards2 × 6 × 8 ft, one from each board48 in4
End boardsthe rest of the same four boards45 in4
Corner posts4 × 4, at least 4 ft11 in4
ScrewsStainless steel exterior screws, 3 in32

Build it

48 in
1. Each long side: 2 boards of 48 in, 2 posts, the end ones 1½ in in from the ends.
45 in end boards
2. Stand the sides up and fit the 45-inch end boards between them, into the corner posts.
48 × 48 in outside, 11 in tall
3. Square it, set it level and fill 10 in deep: 11.4 ft³, 8 bags of 1.5 ft³.
  1. Choose a level spot and mark a 48-inch square. Leave a path on at least two opposite sides: from both, the middle is 2 feet away.
  2. Cut each of the four boards into one 48-inch and one 45-inch piece, and cut the 4 × 4 into four 11-inch posts. Check each cut with the square.
  3. Build two sides: lay two 48-inch boards flat, edge to edge, and place a post on them 1½ inches in from each end, leaving room for the end boards. Drive two screws through each board into each post, 8 screws per side.
  4. Stand the two sides up, posts facing in, so the boards are 45 inches apart on the inside.
  5. Fit two 45-inch boards at each open end, between the side boards and against the posts. Drive two screws through each end of each board into the post, 16 screws in all.
  6. Measure both diagonals from corner to corner on the outside. They should both be about 67.9 inches; push the frame until they match, then check it is level.
  7. 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.
  8. Set the bed in place and fill it.

How much soil it takes

Filled 10 inches deep, the depth UGA gives as the minimum for most crops, the inside of this bed takes 11.4 cubic feet of soil once the posts are taken out: 0.42 cubic yards, or 8 bags of 1.5 cubic feet. That leaves an inch at the top of the 11-inch walls for mulch.

Open this bed in the soil calculator to change the depth or split the soil into a mix.

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 a bed 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.

References