Slip and trip hazards on driveways and patios: causes and how to reduce them

This guide provides general safety information about reducing slip and trip risk on outdoor paving. It is not a substitute for a professional risk assessment, particularly for a commercial property or a household with specific mobility needs.

A driveway or patio that looks fine on a dry summer afternoon can turn into a genuine hazard the moment it rains, frosts over, or grows a film of moss in a shaded corner. Most falls on paved surfaces come down to a small number of predictable causes, and most of them are fixable without starting from scratch.

What actually causes slips

• Surface finish. Smooth, sawn, or highly polished stone finishes look sharp but grip far less well underfoot when wet than a riven (textured, split) finish or a surface with visible aggregate texture. This is measured formally as a slip resistance or PTV rating, but in practical terms, texture is what matters.
• Moss and algae. Shaded, damp corners of a garden are prime conditions for a slick green film to build up, often gradually enough that it’s not noticed until someone slips. This is one of the most common and most overlooked causes of a fall.
• Standing water. A surface without proper falls (the slight gradient that sheds rainwater) collects puddles, and pooled water both increases slip risk directly and accelerates moss growth in the same spot over time.
• Ice. Any wet patio or driveway can freeze in cold weather, and shaded areas that don’t get direct sun stay icy longer than the rest of the surface, creating an inconsistent hazard across the same area.

What causes trips

• Uneven settling. A gradual, small dip is usually cosmetic. A sharp height difference between adjoining slabs or blocks, often from an isolated area of sub-base failure, is a genuine trip hazard and worth fixing rather than monitoring.
• Raised tree roots or ground movement pushing up individual slabs or sections of block paving.
• Loose or missing edge restraints that let paving units shift out of alignment at the boundary of a path or patio.

Comparing common surface types for grip

Surface	Typical grip when wet	Notes
Riven natural stone	Good	Textured finish sheds a thin water film better than smooth stone
Sawn or honed natural stone	Lower	Smoother finish, better suited to covered or less exposed areas
Textured block paving	Good	Grip depends on finish; heavily worn or polished blocks lose texture over time
Smooth porcelain	Varies	Choose a porcelain product rated for outdoor, wet-area slip resistance specifically
Resin bound	Good	Aggregate texture provides consistent grip across the whole surface

Reducing risk without a full resurface

1. Clean moss and algae off regularly, particularly in shaded or north-facing areas, using a stiff brush or a proprietary outdoor cleaner rather than a pressure washer alone, which can loosen jointing.
2. Apply a slip-resistant sealant designed for outdoor paving if your existing surface has become smoother with age.
3. Improve drainage where water consistently pools, since standing water is often the root cause behind repeated moss growth in the same spot.
4. Address any sharp trip points promptly rather than waiting, particularly on a route used by older visitors or young children.
5. Consider the finish carefully if you’re resurfacing anyway, especially for a north-facing patio or a driveway on a slope, where risk is naturally higher.

When it’s worth professional attention

If a whole area has become consistently slick, if drainage is clearly failing across a wider section, or if you’re planning new paving for a household with reduced mobility, it’s worth getting a professional assessment rather than treating it as routine cleaning. Our patio and garden paving hub lists rated local contractors who can advise on surface choice for exactly this kind of situation, and our methodology page explains how those ratings are worked out. The full directory is available from the homepage.