Installing a Fence on a Unistone Block Retaining Wall

A homeowner wants to mount a chain-link fence atop a 60-foot Unistone block retaining wall that drops about three feet. Contractors have warned that drilling post holes into the blocks will lead to cracking from water infiltration over time.

The Solution: Flashing the Post Penetrations

Think of your retaining wall like a roof. Where plumbing vents and chimneys penetrate a roof, flashing prevents leaks. The same principle applies here. Visit your local home improvement center and explain the project—they can recommend appropriate flashing materials for your climate and block type. Properly flashed post holes will keep water out of the block cores, preventing freeze-thaw damage and cracking.

— Russel