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Robin E. Snyder
Senior Member
Username: robin

Post Number: 764
Registered: 08-2004
Posted on Sunday, March 24, 2019 - 04:33 pm:   Edit PostDelete PostPrint Post

Masterspec has the following language: Where threshold is shown or scheduled, provide 1/4 inch (6.4 mm) from bottom of door to top of threshold unless otherwise indicated.

Can anyone clarify if this is intended for exterior thresholds only, maybe where there is a sweep? Or interior as well?
Guest (Unregistered Guest)
Unregistered guest
Posted on Sunday, March 24, 2019 - 09:12 pm:   Edit PostDelete PostPrint Post

After close reading of MasterSpec text, clearance depends on which door quality standard you reference. (old) AWI, WI(C), and WDMA; all cite difference dimensions (old AWI std also depends on which grade you specify).
I believe at the "end-of-the-day" the designer's detail should indicate?
Robin E. Snyder
Senior Member
Username: robin

Post Number: 765
Registered: 08-2004
Posted on Sunday, March 24, 2019 - 11:45 pm:   Edit PostDelete PostPrint Post

Designer's detail? I am lucky if I get a filled-in door schedule, much less a detail of the undercut of the door!
Ellis C. Whitby, PE, CSI, AIA, LEED
Senior Member
Username: ecwhitby

Post Number: 453
Registered: 03-2003
Posted on Monday, March 25, 2019 - 07:29 am:   Edit PostDelete PostPrint Post

Remember: Some mechanical designs rely on door undercut for some air flow. In commercial office design, 3/4" is no unusual.
James Sandoz, AIA, CSI, CCS, CCCA
Senior Member
Username: jsandoz

Post Number: 261
Registered: 06-2005


Posted on Monday, March 25, 2019 - 08:35 am:   Edit PostDelete PostPrint Post

Don't forget code requirements as well.
John Bunzick, CCS, CCCA, LEED AP
Senior Member
Username: bunzick

Post Number: 1773
Registered: 03-2002
Posted on Friday, April 12, 2019 - 04:19 pm:   Edit PostDelete PostPrint Post

Be careful not to conflate "clearance" with "undercut." The language that Robin cites is for clearances for job fitted doors. In this scenario, the door is being cut down on site to fit existing conditions. The threshold is probably in place, but if it's not, the same carpenter is likely installing it. Here, the dimension the carpenter will work with is the clearance. It wouldn't matter if it's interior or exterior. (As an aside, most wood door manufacturers will not provide a warranty on doors used in exterior locations.)

Undercut is the door-to-bottom-of-frame dimension, used in the door and hardware industry for shop-fabricated products. The undercut has to take into account the thickness of the threshold or finished floor, and the clearance. For a job-fit door, it's kind of irrelevant where the bottom of the frame is, if it's even visible.

Here's a simple explanation of the difference on the I Dig Hardware site: door clearance

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