How Much Slope Does a Yard Need to Drain?

Key takeaways

The common code standard is 6 inches of fall in the first 10 feet away from a foundation, about a 5 percent slope.
Away from the house, lawns need at least about 1 percent (1 foot per 100 feet) to keep water moving; paving needs about 0.5 percent.
Too steep causes problems too: University Park caps side-yard grade at 5 percent.
A string line, line level and tape measure tell you the slope of your yard in a few minutes.

A yard needs about 6 inches of fall in the first 10 feet away from the house, roughly a 5 percent slope, and at least about 1 percent (1 foot per 100 feet) across the rest of the lawn so water keeps moving to an outlet. Paving can drain at about half that. Rein Irving Drainage Company measures these grades before choosing any fix.

The numbers that matter

Area	Common target	Source
First 10 ft from the foundation	6 in of fall (about 5%)	Common residential code standard
Lawn, swale or other earthen surface	At least 1%	Grand Prairie drainage design manual minimum
Driveway, patio or other paving	At least 0.5%	Grand Prairie drainage design manual minimum
Side yards in University Park	No steeper than 5%	University Park amended residential code

The 6 inches in 10 feet near the house exists to get water away from the slab quickly. On Irving’s expansive clay, water that sits against a foundation soaks in on one side and not the other, which feeds uneven movement. The foundation drainage page explains that link.

The 1 percent minimum farther out is about keeping water moving at all. Below that, small bumps and low spots in a lawn are bigger than the overall fall, so water collects in them. Older lawns often drift below 1 percent as sod is laid over sod, beds are built up and swales fill in.

The 5 percent side-yard cap in University Park is a reminder that more is not always better. A steep chute between two houses can scour soil and deliver all of both roofs’ water to the front in one rush.

Converting percent to inches

Slope in percent is fall divided by distance. These are the conversions most useful in a yard:

Slope	Fall per 10 ft	Fall per 100 ft
0.5%	0.6 in	6 in
1%	1.2 in	12 in
2%	2.4 in	24 in
3%	3.6 in	36 in
5%	6 in	60 in

To go the other way, divide the fall in inches by the distance in inches and multiply by 100. A drop of 3 inches over 25 feet is 3 divided by 300, times 100, which is 1 percent.

How to measure your yard with a string line

You need two stakes, mason’s string, a line level (a small level that hangs on a string), and a tape measure.

Drive a stake next to the foundation where water should leave the house, and a second stake 10 feet out (or farther, along the path water takes).
Tie the string to the house stake at a convenient height, say 12 inches above the ground.
Run it to the far stake, hang the line level in the middle and adjust the far end until the bubble is centered. The string is now level.
Measure from the string down to the ground at each stake.
Subtract. If it is 12 inches at the house and 18 inches at the far stake, the ground falls 6 inches over 10 feet: about 5 percent, which meets the common standard.

If the far measurement is smaller than the near one, the ground slopes back toward the house. Repeat along each side and across the lawn toward where water should leave the lot. For long runs, measure in 10 foot or 25 foot steps so you can see where a low spot interrupts the fall.

A laser level or builder’s level does the same thing faster and over longer distances, which is how elevations are shot for a regrading plan.

What the measurements tell you

Ground falls toward the house. Regrading the first 10 feet is usually the first fix, and often the cheapest. Pull mulch and soil back from the slab, keep the finished grade below the weep holes, and restore fall.
Lawn is below 1 percent overall. Water will sit in the low spots. Options are regrading to restore fall, or a catch basin at the low point piped to an outlet.
The yard is flat with no lower outlet. Grading alone cannot make water flow uphill. A sump or a long pipe run to the curb may be needed.
Slope is fine but the lawn stays soft. That is often water perched on clay below sandy topsoil, which slope does not fix. A shallow French drain may.

The standing water page helps sort out which of these you have.

Slope, permits and neighbors

Reshaping a yard can change where its water goes. Grand Prairie requires an earthwork permit when the grade or drainage pattern changes from the subdivision plan, and state law bars diverting water so it damages a neighbor. See the permits guide and neighbor water runoff in Texas before moving much soil. For Irving addresses we confirm the rule per address.

What regrading costs

Regrading has no honest single price range: it depends on how much soil moves, whether soil is brought in or hauled away, access for equipment, and how much sod and sprinkler work follows. The regrading cost guide explains each driver.

Next step

Measure the first 10 feet on each side of the house. If any side falls toward the slab or is close to flat, send photos and your measurements, or start with the drainage assessment.

Questions people ask

Is 2 percent slope enough for a lawn?

Yes, for open lawn away from the house. Two percent is about 2.4 inches of fall in 10 feet, double Grand Prairie's 1 percent minimum for earthen surfaces. Next to the foundation, aim for the steeper 6 inches in the first 10 feet.

Can a yard have too much slope?

Yes. Steep slopes move water fast enough to wash out soil and mulch, and a steep side yard between houses can dump water at the front all at once. University Park caps side-yard grade at 5 percent for that reason.

Why does my yard hold water even though it looks sloped?

The eye is poor at judging small grades, and a single low spot along an otherwise sloped run will hold water. Measure along the actual path the water takes, not just from the house to the fence.

How much slope does a yard need for drainage?