Inputs
Adjust conditions to estimate traction and risk on garden surfaces.
Example data table
Sample comparisons using typical conditions.
| Surface | Condition | Slope | Estimated COF | Risk | Notes |
|---|---|---|---|---|---|
| Broomed concrete (medium) | Dry | 2% | 0.63 | Low | Good baseline traction. |
| Ceramic tile (smooth) | Wet | 3% | 0.22 | Very High | Consider anti-slip treatment. |
| Natural stone (rough) | Damp + algae | 6% | 0.29 | Very High | Clean growth and improve drainage. |
| Composite decking (anti-slip) | Wet | 5% | 0.46 | Moderate | Use routine cleaning and mats. |
Values are illustrative and depend on product and wear.
Formula used
The estimate combines a base traction value with site multipliers.
Risk bands
- Low: COF ≥ 0.60
- Moderate: 0.42 to 0.59
- High: 0.30 to 0.41
- Very High: COF < 0.30
How to use this calculator
- Choose the main surface material and texture.
- Select moisture and contamination to match conditions.
- Enter slope in percent or degrees, then add age.
- Set footwear, traffic, drainage, and maintenance frequency.
- Submit to view the estimate above the form.
- Download CSV or PDF for sharing and recordkeeping.
Understanding estimated COF values
The calculator reports an estimated coefficient of friction (COF) from 0.05 to 0.90. Many pedestrian surfaces target higher values because traction generally improves as COF rises. In this tool, risk bands use 0.60+ as Low, 0.42–0.59 as Moderate, 0.30–0.41 as High, and below 0.30 as Very High.
Moisture and contamination as primary drivers
Moisture commonly reduces traction by 10–45% depending on the surface texture. Damp conditions are treated as a moderate reduction, wet conditions as a stronger reduction, and oily or soapy films as the largest reduction. Organic growth such as algae can push the estimate down sharply, which is why routine removal and safe cleaning matter.
Slope, drainage, and standing water exposure
Slope increases slip demand because gravity adds a downhill component to foot forces. The calculator converts degrees to percent and applies a conservative reduction as slope rises. Poor drainage keeps surfaces wet longer, so a small design change—better fall, channels, or permeable joints—can raise traction in daily use.
Wear, traffic, and maintenance frequency
Higher traffic can polish some materials and track fine grit, while low traffic can allow biofilm to build up. The model reflects these patterns with modest multipliers, then adjusts again for maintenance frequency. Weekly cleaning typically outperforms monthly cleaning on shaded paths and near planters where moisture persists.
Interpreting results for practical decisions
Use the estimate to compare options: rougher finishes, anti-slip coatings, improved drainage, and targeted mats at entrances. If the result is High or Very High, prioritize remediation before peak wet seasons. For critical areas, confirm performance with field testing and document conditions when exporting CSV or PDF reports.
FAQs
1) Is this a replacement for slip testing?
No. It is a planning estimate for comparing surfaces and conditions. Use it to prioritize changes, then confirm critical areas with appropriate on-site testing and documented wet conditions.
2) Why does algae reduce the estimate so much?
Algae and moss create a thin, lubricating film that lowers traction, especially when wet. Removing growth and improving sunlight and drainage can meaningfully increase surface grip over time.
3) Should I enter average or worst conditions?
For safety planning, use the worst realistic condition (wet, shaded, debris present). Average inputs are useful for comparing routine maintenance schedules, but they can understate seasonal risks.
4) How is slope handled if I only know degrees?
Select “Degrees” and enter the value. The calculator converts it to percent grade internally, then applies a conservative traction reduction as the grade increases.
5) Do sealers always reduce slip resistance?
Not always, but smooth sealers can reduce texture and lower traction. If sealing is needed, consider products with anti-slip additives or coatings designed to preserve surface micro-texture.
6) What actions usually improve the score fastest?
Cleaning organic growth, improving drainage, and adding anti-slip treatments typically provide the quickest gains. Also address transitions, edges, and ramps where slip risk is concentrated.