What Is the Minimum Fall for a Patio? (With Gradient Examples)

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Patio Gradient Examples (mm per metre, % and Degrees)

Fall (mm per metre) Percent (%) Degrees Notes
10mm per metre 1% ~0.57° Absolute minimum — only suitable on ultra-smooth slabs or under covers
15mm per metre 1.5% ~0.86° Most common UK patio fall — works well for general paving and drainage
20mm per metre 2% ~1.15° Recommended for larger patios or areas prone to heavy rain
25mm per metre 2.5% ~1.43° Ideal for patios near walls or tight drainage spots

Why Patios Need Fall

  • ✔ Prevents standing water and puddles

    A gentle fall stops rainwater from pooling on the surface, keeping your patio dry and slip-free after heavy weather.
  • ✔ Reduces frost damage in winter

    If water sits on the surface and freezes, it can damage the joints or crack slabs. A proper fall helps shed that water before it becomes a problem.
  • ✔ Stops algae, moss and staining

    Flat, damp areas are ideal for algae and grime buildup. Good drainage keeps your paving cleaner and easier to maintain long term.
  • ✔ Helps slabs stay level and supported

    Waterlogged bedding can weaken over time and cause dips or movement. A proper fall keeps the base drier and more stable.
  • ✔ Keeps patios low maintenance

    Less standing water means fewer weeds, stains, and pressure washes. A well-drained patio stays looking fresh with minimal effort.

Flat Patio

  • Neat, clean visual lines — especially against modern buildings.
  • Easier to build in tight or confined spaces.
  • No visible slope makes it ideal for decorative or tiled surfaces.

Flat Patio

  • Poor drainage — water can pool and cause staining or algae.
  • Higher risk of frost damage and surface wear over time.
  • More maintenance needed to keep the surface clean and safe.

Sloped Patio (With Fall)

  • Excellent drainage — water runs off efficiently and quickly.
  • Reduces risk of weed growth, staining, and slippery surfaces.
  • Improves slab longevity by keeping bedding layers drier.

Sloped Patio (With Fall)

  • Needs careful planning to get the slope consistent and subtle.
  • May require slight step-downs or edging adjustments near doors.
  • Can look slightly uneven if not installed with precision.
🔹 What is the minimum fall for a patio in the UK?
The minimum fall for a patio in the UK is typically 1:80 — that’s about 12.5mm of drop per metre. However, 1:60 (around 15–17mm per metre) is more commonly used to ensure reliable drainage, especially in wetter areas or on textured paving slabs.
🔹 Does every patio need a slope?
Yes — almost all patios need some form of slope (fall) to prevent standing water. Even small outdoor spaces should direct rainwater away from buildings and toward a drainage point or soft area like a lawn or gravel border.
🔹 Where should the water drain to?
Ideally, a patio should drain away from the property and toward a soakaway, garden border, lawn, or external drain. Never let water run toward the house — it can cause damp issues or pooling near walls.
🔹 Can I make a patio look flat but still have fall?
Yes — with good planning and subtle adjustments, you can create a patio that looks flat while still shedding water. Use laser levels or string lines to create a gradual fall that’s barely noticeable but still effective.
🔹 What happens if my patio has no fall?
Without proper fall, water will pool on the surface, leading to staining, moss, algae, and potential frost damage in winter. It can also weaken the bedding layer over time and lead to slab movement or dips.