I am installing a Central Vac system in mostly new work, adn I have to run 2" PVC all over the place. It will be a major pain-in-the-@#$%! to do this unless I can bore 2-1/2" holes through several 2x8 floor joists. (Solid, not wood I-beams). This is being done in new, or exposed old, work.

The general carpentry book I have warns that 2" dia. is the max in a 2x8, and that applies to a bore right in the middle, within the first 1/3 of the span.

Suppose I were to make a couple of scabs out of 2x6's (or even 2x8's) and surround the openings with these?

Any other suggestions would be most welcome! Thank you.

-DS