A Home for Your Gnome

Gardening Advice from a Fan of Fun!

Navigating a Slippery Slope

January 13, 2024 | Design

The Search for the Elusive Level Plot of Land

Slopes are great for skiing and sledding but dealing with grade change in gardening can be a challenge.

For anyone who has snow skied or hopped on a sled, we know that mild slope equals mild fun. And it was here where I was going to make a joke about how it never snows anymore in Knoxville but a dicey forecast says I should probably keep quiet.

OK, on to our topic of topography. The human eye is easily tricked when we view a piece of ground and assume it is fairly level. I often tell clients, “Whatever slope you think exists on their property, multiply that x 2.” Before the excavator arrives to begin construction on a new home, we’re often fooled into thinking that not much soil will have to be moved. But once the stakes are set and grading begins, the property owner’s eyes are opened wide. A hoped-for gently sloping driveway often turns into a test plot for 4-wheel drive vehicles.

Look closely near the base of the garage and you’ll notice a little extra help was required to get that vehicle into the garage. Not a home for those with accessibility challenges.

I once had a client call and ask about designing a pool. “We don’t think this will be too expensive since our backyard is pretty level.” I looked at the site and explained where there would have to be a low retaining wall to hold back the grade. They thought otherwise until grading began. Sure enough, we wound up with a 3’ wall. And anytime retaining walls come into the picture, dollars fly out of the wallet.

In East Tennessee level land can be as rare as a politician with a conscience. A visitor to our home recently commented on our prime location in the neighborhood. “Pretty much every kid around has learned to ride their bike right in front of our house”, I joked. We are pretty lucky in that regard. But neither do we have a mountain view. Sometimes with topography, there is a trade-off.

I think it is human nature to want to claim the highest point around. For those lucky enough to own a mountain, I say good for you. It’s hard to match seeing a beautiful sunrise over the horizon. But most properties I’ve dealt with who have such an opportunity usually don’t have enough real estate to also have a level chunk of ground to do much but just look over the next ridge. Plus, they always insist on their house being located at the absolute highest point. There was a renowned landscape architect in the mid-20th century, Thomas Church who wrote in his book Gardens Are for People that it is better to locate a structure on what is known as the military crest. This would likely be just south of the pinnacle for those wanting to capture some passive solar benefits (in the northern hemisphere. Locating a house in this fashion may also protect it slightly from high winds.

Sure, they may have a decent view but this is not the property you want if you’re a garden lover.

Okay. So, most of us don’t have the bucks to buy a mountain and maybe think a bit smaller in scale regarding some garden enhancement. Most outdoor living requires at least a little bit of hardscape (patios, terraces, and such) on which to relax or entertain. As I mentioned earlier, even the most modestly sloped backyard usually requires some planning when carving out a couple hundred square foot patio. There are usually three choices one has when doing this: cutting into a slope, bringing in fill (expensive and always requiring a wall), or creating a level patch by both cutting and filling (check out my illustrations since that may be as clear as mud).

Creating a level area via 100% cut typically requires a retaining wall on the uphill side. On top of this, you will need to decide what to do with the excavated soil. If it’s good stuff, I’ll take it. But I’m guessing you’ll be able to use it to build some new raised beds. Walls can be pretty expensive and you better darn well make sure they are structurally sufficient. Anything over a certain height (3-4’, depending on your local codes) may require a structural engineer’s involvement. As I try to keep these posts fairly short, I won’t jump into the retaining wall discussion in detail but look to a future post for more about that.

If you decide to do no excavation and build a patio or terrace on 100% fill of course you’ll need a good source of that fill and access to some equipment to bring that material on site. If this is the choice, you will want to be sure to hire someone who knows about soil compaction as you don’t want this beautiful new terrace to settle and crack over time. Again, depending on the existing slope you will likely need a wall to hold the fill back, or if done without a wall, make sure the fill of the resulting slope is compacted sufficiently (which can make planting in that area unfun).

The best approach to creating a level terrace or patio is to balance any cut with the fill. This means the final elevation of the level pad will be right at the contour that falls across the middle of that area. For a case such as this, costs may usually be controlled as you do not have to move soil very far and you won’t be carrying it off-site nor having to bring in material/fill.

A – 100% fill, B – 100% cut, C – Cut & Fill balanced

So, I’ve rambled all this time and have yet to mention perhaps the most important thing to consider when creating a level space. Drainage! If you asked me a couple of months ago about this, I may have snarkily replied, “Don’t worry. It’ll never rain again.” But thankfully, the faucet has been turned back on and we’re getting some much-needed and appreciated rain.

When designing any outdoor living space, you MUST think about how water will flow. Uphill from any retaining wall make sure you have a small swale (shallow ditch) for the water to drain to either side before meeting the wall. On the patio or hardscape itself, while it may be tempting to try to make this tabletop level, you really would like just a small slope towards the downhill side. This can be as little as .5%. If you’ve ever been on any sports field, you might have noticed a slight crown to the playing area. Same with a very flat road. The folks who design these also know the importance of moving water off the surface. Even treads on any set of outdoor steps (but not decks) need to have a slight pitch to move water. Otherwise, any settled liquid may turn to ice and place a few uninvited lawyers at your door after someone bites the dust.

What seemed like a level spot at my daughter’s home turned out to be just a tad more sloped than I thought. The far side of this new patio is about 14” higher than the grade.

Well, as tempting as it is for me to keep writing on this chilly day, I do hope I’ve offered a small bit of guidance for anyone thinking about creating a level space. Until another random thought of garden advice enters this brain….

Stay level and happy planning!