Measuring Surface Hardness
🗝️ Surface firmness is one of the key Performance Quality Standards (PQS) measurements used in football (soccer) to ensure a pitch is safe, consistent, and fit for play. Below is a clear explanation of how surface firmness is assessed.
How Surface Hardness Is Assessed in Football PQS
💡 Surface hardness is normally measured using a Clegg Impact Hammer (also called a Clegg Hammer or Clegg Soil Impact Tester). It quantifies how hard or soft the playing surface is.
The Tool Used: Clegg Impact Hammer
A 2.25 kg or 0.5 kg hammer (dropping mass) is used, depending on the governing body’s standard.
The device is dropped down a guide tube from a fixed height.
A built-in accelerometer measures deceleration on impact.
What It Measures
📝 The reading is given in:
- CIV (Clegg Impact Value): This is the most common unit, with one CIV unit equalling 10 gravities.
- Gravities (Gm) : The original method measures the impact in units of gravity, which is an indication of soil strength.
Testing Procedure
🎯Sampling Pattern
Tests are taken across the pitch in a grid or set pattern.
Typical sampling points:
- Goal mouths
- Penalty areas
- Centre circle
- Wings
💡 Additional points depending on competition (e.g., Premier League, UEFA, etc.)
🎯 Drop Method
- Place the guide tube vertically on the surface.
- Drop the hammer from the set height.
- Take readings from the 2nd or 3rd drop, depending on the specification (to stabilise the surface after initial compaction).
- Record the value.
Typical PQS Target Ranges
(Note: exact values vary by competition, league, and governing body)
General guidelines:
60–120 g-max → Ideal playable range for natural turf
<60 g-max → Too soft; may cause instability and excessive wear
120–140 g-max → Too hard; increases injury risk
💡 Professional football may specify narrower ranges.
Why Surface Hardness Matters
Player safety
👉 Hard surfaces increase risk of:
- Joint stress
- Concussion (for turf-head interactions)
- Impact injuries
👉 Soft surfaces can cause:
- Muscle/ligament strain
- Foot instability
- Uneven traction
Ball behaviour
- Excessively firm → higher ball bounce & faster roll
- Too soft → inconsistent bounce & slower roll
