How to measure a bridge crossing

Why Accurate Measurements Matter

Incorrect bridge measurements can lead to:
> Inaccurate quotations
> unsuitable bridge designs
> installation delays
> additional site costs

Measuring the Bridge Span

Measure the bridge length from the edge of one bank to the edge of the opposite bank, adding a minimum of 2 metres.
This allowance provides approximately 1 metre of bridge length beyond each bank edge.
As Bison bridges are stocked in 1-metre increments, selecting the next standard size up, for example an 8m bridge instead of a bespoke 7.8m unit, is often the most cost-effective option.

Other Important Measurements

Bridge Width

Consider:

• wheelchair access
• maintenance access
• future route usage

Bank Levels

Record any height difference between each side of the crossing, as this affects:

• accessibility
• gradients
• ramp requirements
• installation complexity

Watercourse Conditions

For river or stream crossings, assess:

• erosion
• Flood risk
• debris movement

A crossing that looks straightforward in summer can behave very differently during winter conditions.

Site Access Considerations

Before specifying a bridge, consider:

• vehicle access
• crane positioning
• restricted countryside access
• overhead obstructions
• ground conditions

Installation access is often one of the biggest overlooked challenges on rural bridge projects.

Site Photographs Help

Clear photographs can significantly improve quotation accuracy.
Useful images include:

• both bridge approaches
• upstream and downstream views
• surrounding terrain access routes
• existing structures

Including a tape measure or person in photographs also helps provide scale.

Our team at Built by Bison are always willing to help with your project; please call 01530 242 405 if you like help specifying your bridge.