I'm thinking of making a desk with a top made from engineered bamboo, and I'm wondering whether I need to follow expansion rules (e.g., breadboard ends) when building the tabletop. I'm unfamiliar with bamboo's tendency to expand based on environmental factors.

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    When you say engineered bamboo do you mean the same stuff that you would get for flooring? – Matt Sep 27 '15 at 0:01
  • This stuff: woodworkerssource.com/Bamboo.html -- I considered it engineered because it's not actually one big piece of bamboo but lots of glued-up pieces, which I assumed would change the behavior of the wood. – Peter Grace Sep 29 '15 at 15:49

Bamboo in general

Bamboo, like any woody material, does respond to changes in humidity and its dimensions do change as a result. This expansion and contraction, like with wood, takes place primary across the grain.

"Engineered bamboo"

This could be one of a number of things.

If the bamboo product is just a simple glue-up (like a "butcher block" countertop material on a smaller scale) then the grain orientation in each strand is important. If the bamboo is arranged face-up some expansion will occur; if so, best to treat as though it was wood and attach it accordingly. If on the other hand it's arranged edge-up you could probably safely ignore it; there will be some movement but it will be very small, small enough that at table sizes it is negligible.

If, however, the bamboo product is a layered material with strips running one way on the surface and cross-strands of bamboo underneath at 90° then it's like plywood, and just as with plywood you can safely ignore dimensional changes due to changes in moisture level. It might also have a bamboo surface, almost a veneer, with a composite layer as a core, and there too movement is not an issue.

I'm wondering whether I need to follow expansion rules (e.g., breadboard ends)

Breadboard ends aren't a requirement to deal with seasonal wood movement. They just need to be made/implemented correctly to allow for it.

These days breadboards are generally done just for appearances, but the practical purpose of breadboards was to help ensure tabletops stayed flat (didn't cup). This was much more of a problem historically because boards were generally much wider than today, at the extreme entire tabletops could be a single board. These can be more prone to bowing than the glued-up panels used almost invariably today.

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