Level II timber bridge inspections go far beyond a visual walk-around. They require under-bridge access — often via snooper trucks, scaffolds, or boat access — to evaluate every structural element at close range. The inspection protocol follows the Ontario Structure Inspection Manual (OSIM) and Canadian timber bridge codes.
Access and setup
For each bridge, we establish safe access beneath the structure. This might mean positioning an under-bridge inspection unit on the deck, rigging scaffolding from the abutments, or in remote sites, using climbing access with a safety team. The goal is to get within arm's reach of every bearing, connection, pile cap, and timber stringer.
Condition assessment
Each element is rated on a 0–4 condition scale. For timber specifically, we look for:
- Decay and rot, especially at ground contact points and in areas with trapped moisture
- Mechanical damage from vehicle impact or ice loading
- Check development (seasoning checks, through-checks, and split evaluation)
- Fastener corrosion, especially at steel-to-timber connections
- Section loss from any cause
Moisture and decay sampling
Where surface indications suggest internal decay, we take increment core samples or use a resistograph to measure internal wood condition. Moisture content readings are taken at multiple locations — above the water table, at the ground line, and at bearing points. Readings above 20% moisture content trigger deeper investigation.
Documentation deliverables
Every inspection produces:
- Completed condition sheets per element
- Photographs keyed to element locations
- Damage sketches and dimensioned notes
- Priority-based repair recommendations
- Estimated remaining service life
The real value of a Level II inspection isn't the data collection — it's the translation of field findings into a maintenance plan that infrastructure owners can budget against.
A well-documented inspection directly guides which bridges need restoration drawings, which need monitoring, and which can be deferred.