The lone voice of horticultural reason

Don’t build a stone, boulder, concrete or timber retaining wall on a slope without building it level.

Don’t build a stone, boulder, concrete or timber retaining wall on a slope without building it level.

Top terrace is semi-correct, but it appears the homeowner lost enthusiasm during installation of the middle and bottom walls. Is this photo taken after a mudslide?

Minnesota wisely passed a No Texting While Driving law, with which I concur, but probably should pass some law aimed directly at me, along the lines of, “Don’t drive with your head on a swivel checking out every house you pass for a photo op to add to your ‘Don’t DO That’ feature.” Perhaps legislators could shorten it to, “Don cannot have a camera in his truck while driving.” One of these days I’ll rear-end somebody.

But this is a beaut, and a mistake I see homeowners commit in all parts of the country and Canada. You want to terrace a slope with walls, or run a stone wall alongside a sloping driveway, so without thinking it through, you lay the wallstone (or concrete block, or, egads, timbers) flat on the ground, letting the slope dictate their angle.

Nope. Think of a fence that runs up and down a hilly area. Every eight feet, is each fence post at a different angle, perpendicular to the slope as it changes, or are they all perfectly vertical, regardless of grade of slope? Or a house built into a hill; the walls are perfectly vertical, the lines in the brick or lap siding perfectly horizontal, the same with the gutters and top roof line.

Retaining walls need always be based on what is true level, regardless of degree of slope.

This is not only essential from an aesthetic standpoint, but from an engineering standpoint. A wallstone, concrete block, or boulder retaining wall of anything more than a few feet that is not built level, into the slope, greatly diminishes the wall’s ability to retain soil and remain standing in periods of heavy rain.

Buy a level. Run strings, or use a laser level. Yes, you have to dig in the foundation for the wall flat (level) as you work up the hill. Otherwise, you could wind up on some anal jerk’s international website.

Don Engebretson
The Renegade Gardener