A common misconception is that closet door hardware, especially hardware for sliding closet doors, requires a bottom track. The belief is that the bottom track helps support the weight of the doors as well as keep the doors aligned.
The Johnson Hardware, that we supply with our closet doors, is actually designed the other way around. The top track rollers (shown at right) can support doors up to 200 lbs each for medium rated (3 wheels) and 400 lbs each for the heavy duty rated (4 wheels). This means that, since the top track supports all of the weight, the optional bottom track is used only to help guide your sliding closet doors and bifold doors.
When should I use a bottom track?
You really only need to use the bottom guide when there is a concern that the doors might be bumped hard enough to swing, front to back. Some good examples would be if the doors are being be used between rooms or if you have small children or large pets.
If you have only 2 rows of closet doors in the opening (1 or 2 doors in the front row and 1 or 2 doors in the back row) there is a simple floor guide (shown at left) that keeps the doors separated and from hitting each other. If you look closely at the top picture, you will see these guides where the front row doors overlap the back row doors. (a close-up is shown in the image to the right) 
If you have doors in 3 or more rows, then bottom guide tracks are required.
Are bottom tracks only for sliding closet doors?
No. Larger bi-fold doors are also good candidates for a bottom guide track. Follow the same rule as with your sliding closet doors. If you think your bi-fold doors are going to be bumped a lot then a bottom guide track might be helpful.
Do I need to cut into my floor to install the bottom track?
No. Since the bottom guide tracks do not support any weight they can be surface mounted to your floor. Wood strips can be placed on either side of the track to give the look of a finished threshold. If you have not installed your floor you can also use a bottom guide track. In this case you would simply install your flooring on either side of the bottom guide track. The nice thing about this method is that the track is submerged below the floor level so there is no concern about tripping.
So while a bottom track is not needed to support the weight or your doors, it can help to guide your doors.
*This post was updated on December 24th, 2019
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I want to replace bi-fold doors in the house we bought with sliding mirror closet doors. We want those fully guided and supported from the upper rail, and no lower rail, only that little part that keeps them from swinging. I know Stanley used to sell those through Lowes or such. Can you help, we ask.
Many thanks.
Hello Sergio,
I am not really familiar with Stanley sliding door hardware. We only use the heavier duty, commercial grade from Johnson Hardware. I do know that Home Depot sells some of the Johnson residential hardware but NOT the commercial grade.
The sliding door hardware we use is the johnson 138F series. It has only the track at the top that supports the full weight and then the little tab guide that at the bottom that just keeps the doors from swinging front to back. You can buy that from us or direct from Johnson Hardware – http://www.johnsonhardware.com/138f.htm .
I hope this helps. If you need anything else please let me know.
Jim