Paver patio slope calculator

How the slope calculator works

Example: a patio running 12 ft out from the house at ¼ in per foot falls 12 × 0.25 = 3 in. The slope is 0.25 ÷ 12 × 100 = 2.08%.

The “run” is the distance the water travels: from the house wall to the low edge. On a patio that slopes along its length rather than away from the house, use that length instead. The width across the slope doesn’t change the fall; every point along the high edge is at the same height.

Fall by patio size

Choosing a slope

• ¼ in per foot (about 2%) is the common target for patios and walks. Water moves off briskly and tables still feel level.
• ⅛ in per foot (about 1%) is a minimum. On pavers with textured or tumbled surfaces, water can sit in low spots at this slope.
• ⅜ to ½ in per foot (3–4%) drains fast but starts to feel tilted under chairs and tables. It suits walkways and driveways more than patios.
• Walkways usually get a cross slope of about ¼ in per foot to one side, or a slight crown in the middle.

Keep the finished paver surface below the door threshold and below any weep holes or siding at the bottom of the house wall, and make sure the low edge drains somewhere: a lawn, a garden bed or a drain, not toward a neighbor or back toward the house.

Setting the slope with a string line

1. Drive stakes at the house end and the far end of the patio, on both sides.
2. Tie a string between the stakes at the house end height of the finished surface, and level it with a line level.
3. Lower the far end of the string by the total fall from the calculator. On a 12 ft run at ¼ in per foot, drop it 3 in.
4. Measure down from the string as you build: to the top of the compacted base, the depth is the same everywhere (paver thickness + 1 in of sand), so the base follows the string’s slope.
5. Check with a level. On a 4 ft level, the downhill end should sit 1 in low at ¼ in per foot. A 1 in shim under that end should center the bubble.

The slip also lists marks every 4 ft along the run, handy for setting screed pipes at the right height in the sand.

Slope the base, not the sand

The bedding sand must be an even 1 in everywhere. If the base is flat and the sand is used to create the fall, the sand ends up 1 in deep at one end and 4 in at the other, and the deep end settles unevenly. Shape the subgrade to the slope, then lay and compact the base to the same slope. The paver base calculator and the paver sand calculator explain both layers.

Slopes and edge restraint

Pavers on any slope tend to creep downhill, especially on walkways and driveways. A firm edge restraint on the low edge stops it. See the edge restraint calculator.

Check any local rules that apply to grading near your house's foundation and to where you can send runoff. They take priority over general guidance.