Build a Simple Garden Bench That Lasts Twenty Years

Outdoor furniture fails in two places: where end grain drinks water, and where timber touches the ground. Get those right and even cheap timber lasts decades.

Materials

• Seat and rails: 45 x 145 mm treated softwood, or larch/oak if the budget allows.
• Legs: 70 x 70 mm treated posts.
• Fixings: M10 galvanised or stainless coach bolts with washers. Not screws, and never plain steel — plain steel bleeds black stains down the timber within a season.

For a 1500 mm bench you need roughly 5 m of the 145 mm and 2 m of post.

The build

Make two identical leg frames: two legs, a cross rail bolted between them near the top, and a shorter foot rail. Bolt, do not screw — bolts through both members are what stop a bench racking after a few winters.

Bolt long side rails between the two frames. Then lay three or four seat boards across the top, spaced with a 8 mm gap between them so water drains and debris falls through. Fix seat boards from underneath if you want a clean top surface, or countersink deeply and plug from above.

Seat height 430 to 450 mm. Depth 400 to 450 mm. Add a 5 degree backwards slope to the seat if you want it comfortable for more than ten minutes.

The two details that decide its lifespan

End grain. Every cut end is an open straw. Treat all cut ends with end-grain preservative before assembly — especially the tops of the legs and the ends of the seat boards. This is a ten-minute job that doubles the life of the bench.

Ground contact. Never stand timber legs directly on soil or grass. Either bolt the legs to small galvanised feet, or stand the bench on slabs or gravel so the base can dry after rain. If the legs must go into the ground, use posts rated for ground contact and set them in gravel rather than concrete, so water drains away instead of pooling around them.

Finishing

Leave it to weather to silver, or use a penetrating oil rather than a film-forming varnish. Film finishes crack and peel outdoors, and then you are sanding. Oil just needs a fresh coat every couple of years.

Build it in a morning. Sit on it for twenty years.