Open end
Top and bottom chords run to the bearing with the web open. Bears on a wall plate or a ledger.
Floor trusses
Open-web floor trusses
Longer clear spans than dimensional joists, and an open chase for mechanical runs. No drilling, no notching, no field engineering to get a duct across a room.
The case for them
Why open-web instead of joists
A solid joist has to be drilled or notched for every pipe, duct and cable that crosses it, and every hole is governed by rules the framer has to get right on site. An open-web floor truss leaves the space between the chords open by design.
- Longer clear spans, so fewer bearing walls and beams below
- Full-depth chase for HVAC trunk lines, waste pipe and wiring
- Wider nailing surface at the top chord than a 2x joist
- Flatter, squeak-resistant floors with less shrinkage movement
- Ribbon or open ends to suit your bearing detail
Sizing
Depths and spans
The table below shows the depths we fabricate and the span range each one typically reaches at 19.2" and 24" on centre. Actual spans are set by the sealed truss design for your loads — treat these as planning figures, not permission to build.
| Nominal depth | Typical span @ 19.2" o.c. | Typical span @ 24" o.c. | Common use |
|---|---|---|---|
| 12" | up to 16 ft | up to 14 ft | Short spans, shallow floor systems |
| 14" | up to 19 ft | up to 17 ft | Residential rooms, light mechanical |
| 16" | up to 22 ft | up to 20 ft | The most common residential depth |
| 18" | up to 25 ft | up to 23 ft | Open plans, ducted chases |
| 20" | up to 28 ft | up to 26 ft | Long clear spans, multi-family |
| 24" | up to 32 ft | up to 30 ft | Commercial floors, large trunk ducts |
Spans assume 40 psf live load and 10 psf dead load with a L/480 live-load deflection limit. Heavier loads, tile finishes, or a stiffer deflection criterion shorten every figure above.
Details
End conditions and openings
Ribbon end
A continuous ribbon board ties the truss ends together, squaring the floor system and simplifying layout.
Bearing block
Vertical block at the bearing where reactions are high or the truss sits on a beam rather than a wall.
Stair openings
Trimmed and headed at the shop with the doubling shown on the placement plan — not cut in on site.
Duct chases
Tell us the trunk size and route and we design a clear opening on the run rather than a chase you have to fight.
Cantilevers
Balcony and bay cantilevers designed into the truss with the back-span and hold-down requirements stated.
