Removing or modifying bridges between truss or joists to make way for ducting

by David Scarlett   Last Updated October 20, 2019 03:21 AM - source

I want to run ducting for a kitchen extractor through the ground-floor ceiling of a two story building in order to get it to an external wall. The ducting would be running in the same direction as the ceiling truss/joists (or are they floor joists if there's another level above?), however in addition to the joists and truss, there are bridges joining them every couple of meters. (I say joists and truss because there are joists through most of the ceiling, but then open web truss in the vicinity of the kitchen, needed to allow for plumbing from a bathroom above.)

The red arrow in this image shows the desired direction of ducting travel, and the bridge that is blocking it.

Direction of ducting travel

Bridge detail

The truss/joist height is 280mm, and the ducting diameter is 200mm. That doesn't leave much room for anything to remain of the bridges.

My question: I'm assuming this is something I'll need to consult a structural engineer about, but generally speaking, how necessary are these bridges? Could they be removed, or replaced with something that would leave room for duct? Although with only 80mm available height remaining with the duct installed, maybe it'd need to be steel rather than wood?

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