[Garden Variety]

I'm currently designing two whole-yard landscapes for new homes. Both have exposed basements in back--one fully exposed and one half exposed. Both have level front yards; one has a sloping back yard. My question relates to the side yards.

For each project, I'd like to have turf in one of the side yards for ease of maintenance access. What's the steepest advisable "mowable slope?" (The steeper of the two is at 61%.) At what point is it best to design steps & retaining features instead?

FYI, we have heavy clay soil around here, and of course both lots are full of disturbed post-construction soil.

Thank in advance.

[schleng]

I don't go over 3:1 or 33%. Anything above that calls for retaining walls. I try not to evenly divide the area with a retaining wall. Plantings at top and bottom of walls are nice, if you feel the budget allows. Plants at top will provide protection from falling over.
Susan

[Dale Wiley]

Lets be realistic here... to safely and efficently mow a slope it should be no more than 23 degrees. I would not even consider installing or maintaining grass on more than a 23 degree slope. Safely issue for employees - liability issue for the company.

More than 23 degrees it needs to be some type of other surface than grass... maybe a wild lawn mix, ground cover or something that does not require weekly mowing and associated activities.

As far as retaining structures go, thats really up to the designer....

[Paul]

A 2 to 1 slope is mowable but not comfortable. (1 foot rise over 2 feet)

[GLAN]

Originally posted by Paul
A 2 to 1 slope is mowable but not comfortable. (1 foot rise over 2 feet)

Realy?


Have you tried?

With what machines?............or perhaps not any machine at all and that they were goats.



From what is being described....

Terrace and steps........or a ground cover

[Garden Variety]

Safety first, of course. I see some crazy steep lawns around here, both with new construction and in some of the old neighborhoods. Just because it's done doesn't mean it's right.

I've found some nice examples of terraces and steps since posting. Will continue along this tack.

Thanks.

[Stonehenge]

If you check the manuals of the typical homeowner riding mower, they don't recommend over 10-15 degrees of slope. I know a 30% slope just about saw me make in my pants driving a skidsteer up and down it, so I have to imagine that'd be too steep for mowing, too.

What about no-mow grass?

[Paul]

A 2 to 1 slope is 27 degrees, a 3 to 1 slope is 18 degrees.

There is a big difference in % slopes and degree slopes

[Paul]

here's something from the web.

Finally, you mention 5, 25, and 45 degrees as decision points. I definitely would not operate a tractor on a 45 degree slope (one foot of elevation change for every foot of distance traveled). Also remember that slope as a percent, and slope as a ratio can be confusing. Many people talk about slope as percent slope, while others talk about it as degrees as you do. These are very different numbers. For example, the 45 degree slope you mention would be a 100 percent slope. The 5 degree slope you mention would be an 8.7 percent slope. For comparison, the maximum slope you would find on a mountain highway would probably be 10 percent or less, which is about 5.8 degrees. Service roads and fire roads in the forest are commonly 15 percent or less, which would be 8.5 degrees. A 30 degree slope would have a change of elevation of 1 foot in every 1.73 foot of horizontal distance, which would be a steep slope indeed. A change of 1 foot elevation for every 4 feet traveled, or a 25 percent slope would still be a pretty steep slope, but would only be 14 degrees. I have summarized these for you below: You can play around with a yardstick and create some of these "slopes" yourself to get a feel for what they look like, or alternatively, actually measure a few on your own property.

Distance traveled per foot of elevation change

5 degree of slope, 8.7 percent slope = 11.5 feet

7.5 degree of slope, 13.2 percent slope = 7.6 feet

10 degree of slope, 17.6 percent slope = 5.7 feet

12 5 degree of slop, 22.2 percent slope = 4.5 feet

15 degree of slope, 26.8 percent slope = 3.7 feet

17 degree of slope, 31.5 percent slope = 3.2 feet

20 degree of slope, 36.4 percent slope = 2.7 feet

[cutntrim]

You know what, forget percentages and degrees. If you think it might be too steep (and you're not even the one who'll be cutting it) then it is.

I wish every landscaper/designer had to apprentice as a maintenance contractor first, then we wouldn't have to deal with so many pretty, but non-functional landscapes at customer's houses.

[Greensmith]

Hehe, my old design teacher said until you mow fancy beds with a zero turn you can't design beds right.

[Garden Variety]

Thanks, folks, for all of the helpful responses. As a designer who's never worked out in the field, it's my hope to avoid ill-conceived designs by researching possibilities and potential problems and discussing them with installers first.

[Dale Wiley]

Originally posted by Stonehenge
If you check the manuals of the typical homeowner riding mower, they don't recommend over 10-15 degrees of slope. I know a 30% slope just about saw me make in my pants driving a skidsteer up and down it, so I have to imagine that'd be too steep for mowing, too.

What about no-mow grass?

And most manufactuers ratings are about 30% under what the machine actually will do, so that 23% I threw out seems to be pretty consistent with that...

but then again I was in on a few tests back in the day and know about the under rating thing.....