Composite raised garden beds

Composite raised beds, made of plastic mixed with wood fiber, compared by the sizes, heights and soil figures their makers publish.

Frame It All’s composite boards slot into corner brackets, and another level of boards and brackets stacks the bed higher.

Why composite

GardenBLOX builds up in 5.5-inch levels to 22 inches, so you stop at the height you need.
Frame It All gives a limited lifetime warranty if you register the bed, five years if you do not.

Watch for

Composite names a mixture, not one specification: compare each maker’s own figures.
No extension service we cite gives composite a lifespan, so the warranty is the figure to compare.
Gardener’s Supply’s guarantee is paid as store credit.

The beds

All raised beds

9 beds from 2 makers · 33 sizes and layouts · 5.5 to 22 in tall · 1.8 to 117.3 ft³ stated

For a composite garden bed

Gardener’s Supply Sustainable raised bed

10.5 in tall · 7.8 to 15.8 ft³ · 2 sizes and layouts

Composite · Bed on the ground · Lifetime warranty (store credit)

Choose a composite bed made with recycled plastic and reclaimed sawdust, held by aluminum corners. Two footprints provide a low, open-bottom growing space.

10.5 inHeight, below the knee on an adult

10.5 inPlanting depth

7.8 to 15.8 ft³Stated soil capacity

Bed on the groundCompositeLifetime warranty (store credit)2 sizes and layouts

The bottom is open to the soil below. Choose a ground location with drainage, or use a contained planter for a patio.

For a small herb or flower box you can build up in stages

Frame It All GardenBLOX 2 × 2 ft composite box

5.5 to 22 in tall · 1.8 to 7.3 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 2 × 2 ft composite box, four 2-ft boards to a level, that stacks from one to four levels. Each level adds 5.5 inches of height and 1.83 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

1.8 to 7.3 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

Frame It All suggests it for herbs or flowers. Two levels, 11 inches, take 3.66 cubic feet: 3 bags of 1.5 ft³. It can grow later: stack another level on top, or swing one side board out and add boards to make it longer, without moving the soil.

For a narrow starter bed, 11 to 22 inches tall

Frame It All GardenBLOX 2 × 4 ft composite bed

11 to 22 in tall · 7.3 to 14.7 ft³ · 3 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 2 × 4 ft composite bed, sold two to four levels high: 11, 16.5 or 22 inches. Each level adds 3.67 cubic feet of soil, by the maker’s figures.

11 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

7.3 to 14.7 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered3 sizes and layouts

At 2 ft wide you reach across it from one side, so it can stand against a fence or wall. Two levels, 11 inches, take 7.34 cubic feet: 5 bags of 1.5 ft³.

For a narrow bed against a fence or wall

Frame It All GardenBLOX 2 × 6 ft composite bed

5.5 to 22 in tall · 5.5 to 22 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 2 × 6 ft composite bed of 2-ft boards that stacks from one to four levels. Each level adds 5.5 inches of height and 5.5 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

5.5 to 22 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

From two levels up, two boards cross the bed, so it reads as three 2 × 2 ft squares. At 2 ft wide you reach across it from one side, so it can stand against a fence or wall.

For a long, narrow bed you work from one side

Frame It All GardenBLOX 2 × 8 ft composite bed

5.5 to 22 in tall · 7.3 to 29.3 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 2 × 8 ft composite bed of 2-ft boards that stacks from one to four levels. Each level adds 5.5 inches of height and 7.33 cubic feet of soil, by Frame It All’s soil calculator.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

7.3 to 29.3 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

Order by Frame It All’s soil calculator, not the product page. For three and four levels the page prints 18.5 and 26 cubic feet; the calculator gives 21.99 and 29.32, what a 2 × 8 ft bed holds at 16.5 and 22 inches. The page’s figures leave you 2 bags short. From two levels up, three boards cross the bed, so it reads as four 2 × 2 ft squares, and at 2 ft wide you reach across it from one side.

For a square bed you can build up in stages

Frame It All GardenBLOX 4 × 4 ft composite bed

5.5 to 22 in tall · 7.3 to 29.3 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 4 × 4 ft composite bed that stacks from one to four levels. Each level adds 5.5 inches of height and 7.33 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

7.3 to 29.3 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

Stack only the levels you need: the soil figure rises by 7.33 cubic feet with each one. The 4 × 4 ft size is nominal, so measure inside after assembly.

For the usual 4 × 8 bed, built up in stages

Frame It All GardenBLOX 4 × 8 ft composite bed

5.5 to 22 in tall · 14.7 to 58.7 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 4 × 8 ft composite bed that stacks from one to four levels. Each level adds 5.5 inches of height and 14.67 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

14.7 to 58.7 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

From two levels up, a board runs across the middle of the top level, so the bed reads as two 4 × 4 ft squares. The 4 × 8 ft size is nominal, so measure inside after assembly.

For a long 4 ft bed in three square sections

Frame It All GardenBLOX 4 × 12 ft composite bed

5.5 to 22 in tall · 22 to 88 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

A 4 × 12 ft composite bed that stacks from one to four levels. Each level adds 5.5 inches of height and 22 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

22 to 88 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

From two levels up, two boards cross the bed and divide it into three 4 × 4 ft squares. At 4 ft wide it is at the limit Frame It All gives for a bed you reach from both sides, so leave a path along each long side. For four levels the product page prints 88.88 cubic feet; the soil calculator gives 88, four times the one-level 22: 59 bags, not 60.

For a large square bed you can build up in stages

Frame It All GardenBLOX 8 × 8 ft composite bed

5.5 to 22 in tall · 29.3 to 117.3 ft³ · 4 sizes and layouts

Composite · Open-bottom bed · 10-year warranty if registered

An 8 × 8 ft composite bed, two boards to a side, that stacks from one to four levels. Each level adds 5.5 inches of height and 29.33 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight, up to mid-thigh on an adult

CompositeWarranty: 10 years if registered

29.3 to 117.3 ft³Stated soil capacity

Open-bottom bedComposite10-year warranty if registered4 sizes and layouts

The middle is about 4 ft from every side, and Frame It All itself gives 4 ft as the widest bed you can reach from both sides: plan how you will reach the middle before you fill it. The 8 × 8 ft size is nominal, so measure inside after assembly.

What composite is made of

Composite boards mix plastic with wood. Frame It All states 38% HDPE plastic and 62% wood fibers for its GardenBLOX boards, and Gardener’s Supply describes its Sustainable beds as recycled plastic and reclaimed sawdust with aluminum corners. Composite names a mixture, not one specification, so compare each maker’s own figures.

No extension service we cite publishes a lifespan for composite beds, so the warranty is the figure to compare. Frame It All gives a limited lifetime warranty if you register the bed, or five years if you do not; Gardener’s Supply’s store-wide guarantee is paid as store credit.

Build the height in stages

GardenBLOX stacks in 5.5-inch levels up to 22 inches. Each level adds 1.83 cubic feet of soil to the 2 × 2 ft bed, 3.67 to the 2 × 4, 5.5 to the 2 × 6, 7.33 to the 2 × 8 and the 4 × 4, 14.67 to the 4 × 8, 22 to the 4 × 12 and 29.33 to the 8 × 8, by Frame It All’s figures. The depth guide gives the soil depth most crops need, so you can stop at the height you need.

Composite or cedar?

The cedar and composite comparison sets the two side by side, and the materials guide adds metal and fabric.

References

4' x 4' Raised Garden Bed - GardenBLOX Classic, Frame It All.
4' x 8' Raised Garden Bed - GardenBLOX Classic, Frame It All.
8' x 8' Raised Garden Bed - GardenBLOX Classic, Frame It All.
2' x 2' Raised Garden Bed - GardenBLOX Classic, Frame It All.
2' x 4' Raised Garden Bed - GardenBLOX Classic, Frame It All.
2’ x 6’ Raised Garden Bed Planters - GardenBLOX Classic, Frame It All.
2' x 8' Raised Garden Bed - GardenBLOX Classic, Frame It All.
4' x 12' Raised Garden Bed - GardenBLOX Classic, Frame It All.
Raised Garden Bed Soil Calculator, Frame It All.
Sustainable Raised Beds, Gardener's Supply.
Our Guarantee, Gardener's Supply.