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I'm sure this topic has been beaten to death but...

Previous homeowner installed 3/4" x 2 1/4" oak hardwood parallel to joists in a my 12'x22' living room. I've done some remodeling and now am installing 3/4" x 5" Cumuru in my newly formed kitchen/dining room (16" x 22") on the opposite side of the house. The oak and the cumuru will meet in two places. My subfloor is 3/4" tounge in groove plywood on 2"x10" floor joists that are 16" OC.

Is it okay to run my new floor parallel to the joists like the previous owner did or do I need to run it perpendicular to the joists? If parallel do I need to add blocking in the basement or another layer of plywood first?

House was built in Massachusetts in 1994. Best guess is that existing oak floor was installed less than 5 years ago. Currently no know issues with previous install.

The guidelines say not to..

Adding blocking will save unwanted height build from an additional layer of plywood.

But honestly... Its your home.. You can install it parallel and never have an issue.

We have been in plenty of situations that called for us to install this way... Especially when new addition has joined old structure.... If you have 3/4substrate you should be ok...