Building a Raised Bed Against a Fence Without Rot

A 90-inch-wide strip between a driveway and a 4-foot post-and-rail fence will become a 45–50-inch-wide raised bed with a mortared stone front wall. The back, against the fence, needs a practical soil barrier that won't rot the fence.

Barrier Options

• EPDM rubber sheeting: Roofing-grade, fastened to fence face with stainless/galvanized fasteners, sealed at top edge. Pool liner works too.
• Plastic roof flashing: Rigid, durable, same fastening rules.
• Critical: No aluminum fasteners or flashing with modern copper-treated (ACQ/CA) lumber—causes galvanic corrosion. Use stainless or hot-dipped galvanized only.

Superior Design: Raise the Fence

Shorten fence boards and perch them on the back wall of the raised bed. Wrap concrete collars around posts where they meet soil. This eliminates wood-soil contact entirely and looks intentional.

— Mark Harshman, MAH Drafting