I am installing HW flooring in my bedroom and have reached the entry to my walk-in closet. The current installation of HW runs across the floor joists. I have two options that I am considering.Make a trans. piece and turn the board opposite of the current pattern,then start laying the closet flooring with the joists. I could also put is the trans. piece and lay the closet flooring in the same direction as the room.Any suggestions on how the accomplish this?

If I rip a piece of HW to use as a termination in the doorway and butt both sides of the flooring tightly are there concerns regarding expansion?

Why do you think you need a transition across the closet doorway??

Usually the flooring is run through, without a transition, or header board, unless that is what is specified or requested.

Looking thru the doorway the tongue is on the right side of the board. The last board stops at the edge of the left side door jamb so the next board will be able to extend thru the doorway and connect to the flooring in the closet. The only way I see this happening is to make a dry run with the flooring starting on the left wall of the closet to the left edge of the doorway,mark the flooring on the underlayment,break the flooring apart and then staple the flooring.

My concern is getting the flooring of the room to align with the flooring of the closet after extending the flooring thru the closet door.

My goal is to not have a transition in the doorway.

Disclaimer - I'm a DIY guy, not a pro.

Here's what I'd do. Start in the room and build across the room like normal. When you get to the closet, extend into the closet through the doorway and keep building in the normal direction. Get to the other side of the doorway and continue as normal with the rest of the room. Then go back and finish the far side of the closet as normal. Then put a spline in and finish the near side of the closet with the tounges aimed the opposite direction of the room.

Where can I get this?

Get what? A spline? I just made mine. Piece of oak cut to the width of the groove and a bit less than 2X the depth.