Patio Slope & Drainage Calculator
Why is Patio Slope Critical?
When building a patio, proper drainage is the most important structural consideration. Without a correct slope (also known as "pitch"), rainwater will pool on the surface of your pavers or concrete. This can lead to several serious issues:
- Foundation Damage: If the patio slopes toward your house, water will collect against the foundation, potentially causing basement leaks or structural cracking.
- Surface Staining: Standing water promotes the growth of algae, moss, and mildew, which can permanently stain and degrade stone or brick surfaces.
- Freeze-Thaw Damage: In colder climates, trapped water in the joints of your patio can freeze and expand, causing pavers to heave and crack.
Standard Patio Slope Guidelines
The industry standard for patio drainage is a 1/8 inch to 1/4 inch drop for every one linear foot of distance. This ensures that water moves quickly enough to avoid pooling but not so steeply that the furniture feels tilted or the slope is visible to the naked eye.
- 1/8″ per foot: Best for smooth surfaces like large pavers or poured concrete where water flows easily.
- 1/4″ per foot: Recommended for textured surfaces like natural stone or cobblestone where friction might slow water movement.
How to Calculate Patio Pitch Manually
The formula used by our calculator is straightforward: Length (ft) × Slope Rate (inches/ft) = Total Drop (inches).
Example: If you are building a patio that is 16 feet long and you want a standard 1/8″ slope:
- 16 feet × 0.125 inches = 2 inches.
- Your patio should be exactly 2 inches lower at the far end than it is at the house wall.
Practical Tips for Grading
To ensure your slope is accurate during construction, use the "string line" method. Drive stakes into the ground at both ends of your planned patio. Tie a string between them and use a line level to make the string perfectly horizontal. Then, measure down from the string at the far end to the distance calculated by our tool. This identifies exactly where your finished grade should be.