DIY Composite Lumber Raised Bed: Rot-Proof Triangular Planter from Trex Decking

DIY Composite Lumber Raised Bed: Rot-Proof Triangular Planter from Trex Decking

Composite lumber (Trex—recycled plastic bags and wood fibers) makes rot-proof raised beds. This triangular design uses 52-inch 4×4 posts and 2×6 sides/tops. Rectangular planters can be modified from this design.

Composite Lumber Tips

• Heavy—build in sections to assemble on-site.
• If ≤3 boards high (~16 inches) on flat site, posts can rest on ground (longer posts for in-ground).
• Use self-drilling deck screws (Fastap Poly²) or pre-drill for standard screws.

Specs

• Time: One day
• Cost: ~$160
• Materials: Three 52-inch Trex 4×4s; three 10-ft Trex 2×6s; one 14-ft Trex 2×6; 100 3-inch deck screws; one 9-inch step bracket; twelve 1¼-inch machine screws.

Tools

Tape measure, pencil, circular saw, combination square, framing square, electric drill

Directions (Summary)

1. Cut seven 16½-inch posts from 4×4s.
2. Cut side boards with 45° miters: from each 10-ft 2×6, one 48½-inch (A) and two 32½-inch (B). From 14-ft piece, one 67½-inch (C) and two 39¾-inch (D) top pieces.
3. Mark alignment lines 3 inches from ends of A and B.
4. Assemble sides on posts; check square; screw.
5. Stand B sides upright; join mitered ends with step bracket inside.
6. Butt A side against B ends; screw.
7. Place top boards flat; secure with screws.