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How to build a stone raised garden bed

Pavestone’s plan for a 98 × 49 in stone-look raised bed of RumbleStone blocks, 10½ in tall: the 142 stones course by course, no cuts, and the 12 bags of soil.

8 ft 2 in × 4 ft 1 in outside
The finished bed, drawn to scale: 8 ft 2 in × 4 ft 1 in outside and 10½ in tall, from above and beside an adult 5 ft 6 in tall.

How much the stones weigh

Pavestone’s cut sheets give a pallet of RumbleStone as 1,976 lb, whether it holds 96 Large, 144 Medium or 576 Mini, so a Large weighs about 20½ lb, a Medium about 13¾ lb and a Mini about 3½ lb. The 142 stones for this bed come to about 1,560 lb; the Medium bed’s come to about 1,240 lb and the Small’s to about 990 lb. Pavestone calls its weights approximate.

Plan the trip home before you reach the store. What a car or pickup may carry is on the label on the driver’s door pillar, and it counts everyone aboard: the federal rule’s own example label allows 1,400 lb, which leaves 1,250 lb after a 150 lb driver, so in that vehicle the stones for this bed take two trips. Otherwise ask the store to deliver. The weight guide shows how to read the label, and the 12 bags of soil add their own weight.

Build it

Course 1
1. Course 1: lay each 49-in end wall, then the long walls between them, 84 in each.
Course 2
2. Glue on course 2, turned at the corners: the long walls run the full 98 in, the ends fit between them.
Course 3
3. Glue on course 3, laid as course 1.
10½ in tall, 10 in of soil
4. Every joint sits over a stone below. Fill 10 in deep: 17 ft³, 12 bags of 1.5 ft³.
  1. Choose a sunny, level spot and mark a rectangle 98 by 49 inches. Clear or smother the grass first: the site guide shows how.
  2. Pavestone’s sheet asks for a stable, level area. Level a strip under each wall, a little wider than the stones’ 7 inches: scrape off the high spots and tamp the soil firm, checking with the level on a straight board. Every course sits on the first, so take this step slowly.
  3. If gophers or voles dig in your garden, lay hardware cloth over the levelled ground now, cut to 98 by 49 inches, so the first course sits on its edges and no gap is left under the walls. UC IPM advises hardware cloth or ¾-inch mesh poultry wire under raised beds for gophers, and screening a bed’s sides as well as its bottom; Colorado State University Extension gives ¼-inch hardware cloth for voles and pocket gophers.
  4. Lay course 1 dry. Each end wall runs the full 49 inches: Large, 2 Minis, Large, Large, 2 Minis, Large, the Minis on edge. Each long wall fits between the end walls, 84 inches: Large, 2 Minis, Large, 2 Minis, Large, Medium, Large, 2 Minis, Large, 2 Minis, Large.
  5. Measure both diagonals on the outside: each should be about 9 ft 1⅝ in. Nudge the walls until they match, and check the inside is 84 by 35 inches.
  6. Course 2 turns the corners. Run construction adhesive along the top of course 1, then lay each long wall the full 98 inches: Large, 2 Minis, Large, 2 Minis, Large, 2 Minis, 2 Mediums, 2 Minis, Large, 2 Minis, Large, 2 Minis, Large. Fit each end between them, 35 inches: Large, Mini, Large, Mini, Large. Every joint now sits over a stone below.
  7. Glue course 3 down the same way and lay it exactly as course 1.
  8. Let the adhesive cure as its label says, then fill the bed 10 inches deep, half an inch under the top.

How much soil it takes

Filled 10 inches deep, half an inch under the top of the stones, the inside takes 17 cubic feet of soil: 0.63 cubic yards, or 12 bags of 1.5 cubic feet. Ten inches is the least the University of Georgia Extension gives for most garden crops; where the ground under the bed is poor, loosen it so the roots can go deeper.

Open this bed in the soil calculator to change the depth or split the soil into a mix. At the same depth the Medium takes 8 bags and the Small 5.

Reaching the middle

All three sizes are 35 inches wide inside, so the middle of the soil is 17½ inches from the inside of either long wall and 24½ inches from its outside: about the 24 inches across the walls of a 4 × 8 board bed. Check it against your own comfortable reach (the width guide shows how to measure it). The flat 7-inch top makes a ledge for a trowel or a seed tray.

Are concrete stones safe for growing food?

RumbleStone is concrete. University of Maryland Extension says cement, cinder and concrete blocks are all made with cement and fine aggregates, that labels do not say what aggregate a block contains, and that there is little research on the question. It leaves the choice to you; if you are concerned, it suggests sealing the blocks with polymer paint or choosing another material. The concrete block plan lists the other concerns Ohio State University names, among them lime leaching into the soil.

What this plan does not cover

This is Pavestone’s low garden bed, three courses on open ground. It is not an engineered wall and makes no load rating: for a taller bed, or one that holds back a slope, follow the block maker’s or a mason’s guidance. For a bed on a patio or deck, read the hard-surface guide first.

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 calculator

References