I recently put in a bifold on a laundry/closet. The opening was exact = 36". It was pretty darn hard trying to get the bifold door to fit even though the directions called for that size. It was and is very tight. Now I'm ready to do the same thing on two recently built clothes closets. The openings at the moment are about 37.5" and I will size the opening to fit the 36" bifold..but my question on this is: Will it be OK to give myself an extra 1/2 so that putting the door in is not such a hassle? Will it look OK with a 36 1/2" opening? Would a professional give it a second thought?

Yes. I would make the framing slightly over size. However you should be aware that installing the framing square, level and plumb is just as important for a bi-fold as for any other type of door. That's why you see so many that look so bad and function so poorly. Some people think because the door it self can be adjusted you can compensate by adjusting the door. I like to install door stop material around bi-folds. It hides any differences in gap between the door and the frame. Granted the top piece only hides the track and not the gap but that's better than nothing.

I would also take your tight door and remove the one side, bring it to a cabinet shop and have them plane or jointer it down the outside edge a bit, even slant it if needs be.

Harold. I'm making sure the opening is level and plumb today. But have realized I have an additional problem. I know that we'll be installing carpeting. The instruction for the door say an 80" height. The carpeting and pad will be the last bit of flooring to go down. We have to refinish the hardwoods first but I want to get these bifold doors done now. Is there any rule of thumb for the additional carpeting and pad to tell me how much of an increase I should make in the height? Thanks for all help.

Allow about 1" for carpet and padding. Cut a wooden block about 3/4 X 3/4 by 3" and nail to floor where the pivot shoe will be. Cut padding around block, carpet over block then secure pivot shoe to block through carpet. That gives your pivot shoe something to be attached to with out sinking in carpet and pad. Check height of bi-fold doors. I believe they are 79" to allow for track. If that is correct the hieght of the present floor would be about 81" to allow for block. If you select raised panel bi-folds note that the inside is flat. You can make you own bi-fold by purchasing a regular door and riping down the middle, glue in a filler strip (no nails necessary) in each half and have raised panels on the inside. Purchase bi-fold door track and hardware kit separately. You can also use this option if bi-folds are not available in the size you want.

Thanks a million Harold. I'm still working on getting the two doorways level and plumb and redoing some patching on the sheetrock. You're help was brilliant. Very helpful now and down the road. I was wondering how deep that door would sit into the carpet. The wooden block makes it 'right' and I'm pretty sure the carpet installer will not have thought to do this.

If you are going to apply stops to hide the gaps between the bifold door and the jamb. You will need to set the track and pivot shoes back in to accommodate the stop width.