Door Undercut dimension

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Author Message Bruce Konschuh Senior Member Username: brucek Post Number: 14 Registered: 08-2014 Posted on Friday, July 29, 2016 - 11:55 am:    an architect has asked me where our door undercut info is called out, and I told her that all our door spec sections reference NFPA 80 for this. Now I have a few questions: 1. where in NFPA 80 is this described? All I am finding is a definition for undercut. 2. I have seen door undercut dimensions(s) called for in door schedules, arch notes, arch door specs, mech specs, and mech drawings. Where do you spec this and why? J. Peter Jordan Senior Member Username: jpjordan Post Number: 904 Registered: 05-2004 Posted on Friday, July 29, 2016 - 12:07 pm:    Clearances for doors are typically shown in the specifications. If I understand "undercut" correctly, this usually refers to a condition where the space between the door and the floor is used for return air, typically in residential construction. If this is commercial construction, "clearance" is the term used and is determined by NFPA requirements (for fire-rated doors) or by industry standards (DHI, SDI, etc) for non-fire-rated openings. J. Peter Jordan, FCSI, AIA, CCS, LEED AP, SCIP Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1411 Registered: 03-2003 Posted on Friday, July 29, 2016 - 12:39 pm:    It is based on the tested assembly, but 3/4" is the maximum per NFPA 80 (2016), Section 4.8.4.1. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Elias Saltz, CSI, CCS, LEED AP Senior Member Username: elias_saltz Post Number: 16 Registered: 03-2009 Posted on Friday, July 29, 2016 - 01:13 pm:    NFPA 80 only applies to fire rated doors. For non-fire rated doors I reference AWI Section 9. AWI 9.6.4, under "Clearance" article states: Clearance ... at non rated doors shall be a minimum of 1/4 inch and a maximum of 5/8 inch measured from the bottom of the door to the highest point of the finish floor that the door swings over. For me, that 3/8" variation tolerance is generally acceptable (as long as each door is square to itself). I personally think that 1/4" clearance is a little low given that floors can be uneven. Bruce Konschuh Senior Member Username: brucek Post Number: 15 Registered: 08-2014 Posted on Friday, July 29, 2016 - 01:16 pm:    thank you both for your replies. A 3/4" gap is pretty large, and if it's a conditioned space (which 99.9% of instances are), I have rarely seen the mechanical engineer call for anything more that 1/2". thx again! Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1668 Registered: 05-2003 Posted on Friday, July 29, 2016 - 01:26 pm:    For hospitality work, we include the following in the Wood Door Spec Section under Fabrication: Undercut Requirements: Guestroom Entry Door = 1/4-in above threshold. Guestroom Connector = 1/2-in above threshold as coordinated with door bottom. Guest Bathroom Door = 3/8-in above threshold. Doors swinging over carpet = 3/4-in above top of subfloor. Michael Chusid, RA FCSI CCS Senior Member Username: michael_chusid Post Number: 187 Registered: 10-2003 Posted on Friday, July 29, 2016 - 01:26 pm:    Decades ago, in Wisconsin, I used to undercut doors by as much as two inches to allow for air return instead of using a door louver. And the undercut was called for on the door schedule. But that was long ago and far away. Michael Chusid, RA FCSI CCS www.chusid.com www.buildingproduct.guru 818-219-4937 Bruce Konschuh Senior Member Username: brucek Post Number: 16 Registered: 08-2014 Posted on Friday, July 29, 2016 - 01:40 pm:    Michael, good thing there aren't any varmints in Wisconsin. Guest (Unregistered Guest) Unregistered guest Posted on Friday, July 29, 2016 - 12:56 pm:    Industry standards for non-fire-rated HM doors (SDI and HMMA specifically) don't have an exact dimension that you could point to and say, "give me this." Rather, they give a range of not less than 1/8" and not greater than 3/4". I believe WDMA and AWS are similar in that they just specify a maximum of 3/4". NFPA has it in various places. For starters look at NFPA 80, 4.8.4 (max 3.4"). Also NFPA 252 (referenced in NFPA 80 explanatory material), 5.3 for what the testing requires (3/8"). Paul Sweet (Unregistered Guest) Unregistered guest Posted on Friday, July 29, 2016 - 12:31 pm:    I usually put it on the door schedule, since only some doors need a specific undercut for air circulation. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1669 Registered: 05-2003 Posted on Friday, July 29, 2016 - 02:16 pm:    Paul, I don't prepare the door schedule and if I recommend the undercuts be indicated on the door schedule, it doesn't mean they will, so I cover undercuts in the specs. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1684 Registered: 03-2002 Posted on Monday, August 01, 2016 - 03:42 pm:    It's important to point out that undercut is measured from the bottom of the door to the bottom of the frame. Normally, the frame sits on the finished floor, that is, without finishes. So if you call for an "undercut" to the top of the threshold, it is technically incorrect, even if it seems clear. "Clearance" is the term to use here. Check out HMMA 810 TN01 which illustrates this well.