How to Level Ground for a Patio (and Keep the Right Slope)
Setting string lines, building in a drainage slope, digging to depth and compacting, so a patio base comes out flat and sheds water.
“Level” is a slightly misleading word for patios. A patio that’s perfectly level holds puddles. What you want is a surface that’s flat (no dips or bumps) with a gentle, even slope away from the house.
How much slope?
A common target is about ¼” of fall per foot, running away from the house. That’s barely visible but enough for rain to run off.
| Patio depth (away from house) | Total fall at ¼” per foot |
|---|---|
| 8 ft | 2" |
| 10 ft | 2.5" |
| 12 ft | 3" |
| 14 ft | 3.5" |
| 16 ft | 4" |
| 20 ft | 5" |
The finished patio surface should also sit below any door threshold and well below siding. Check how much room you have before you start, especially next to a back door.
What you need
Stakes, mason’s string, a line level or a long spirit level, a tape measure, a flat shovel and a garden rake, a straight 2×4 or aluminum screed board, and a plate compactor (rentable). A laser or water level is a bonus on large patios.
1. Mark out and set string lines
Drive stakes a foot or so outside each corner. Tie strings between them at the height of the finished patio surface. Square the corners by checking that the diagonals are equal.
Level the strings along the house first. Then set the strings running away from the house to drop by your fall, for example 3” over 12 ft. Every depth you dig is measured down from these strings.
Call 811 (in the US) a few days before digging.
2. Dig to depth
Your dig depth below the strings is the base, the 1” sand layer and the paver thickness added together. With standard 2⅜” pavers:
| Base | Dig depth below finished surface |
|---|---|
| 4" base | about 7 3/8" |
| 6" base | about 9 3/8" |
| 8" base | about 11 3/8" |
Measure down from the strings every few feet as you dig. The bottom of the hole should follow the same slope as the strings. Remove sod, roots and soft, dark topsoil, even if that means going deeper; fill the extra with base gravel, not soil.
See Paver Patio Base Depth for which base to use on your soil.
3. Compact the ground
Run the plate compactor over the bottom of the hole, two passes in different directions. Soft spots that pump or squish need digging out and filling with gravel.
4. Build the base in thin layers
Spread crushed base 2–3” at a time, rake it to the slope, dampen it lightly and compact it. Check against the strings after each layer. Fill low spots with more base and scrape high spots down; aim for no gaps bigger than about ⅜” under a straight edge.
5. Screed the sand
Lay two 1” pipes on the base, parallel to the slope, and drag the screed board across them to leave an even 1” bed of sand. The sand only fills small differences; it can’t fix a wavy base.
Common mistakes
- Using sand or soil to level the ground. Both settle. Only compacted crushed stone belongs under the sand bed.
- Sloping toward the house. Double-check the direction of fall before you dig.
- Compacting in one thick layer. The bottom stays loose and settles later.
- Not checking the strings again after they’ve been bumped. Re-check them every morning.
The Paver Patio Planner works out your dig depth and base tonnage for any size and soil.