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ADA threshold height, door bottoms, seals and astragals
An ADA threshold is no more than 1/2 inch high at a doorway, the limit in section 404.2.5 of the 2010 ADA Standards, and any part of its edge above 1/4 inch is beveled no steeper than 1:2.
A door threshold is also specified by the opening width, the height it has to bridge and the seal it works with. Gasketing and door bottoms are specified to the gap they close, and on a rated opening to the rating.
This answer was checked on against the sources listed on this page.
What decides the part number?
The opening width, the height to bridge, the seal type and any fire or smoke rating decide the part number.
How is a threshold sized?
Thresholds are cut to the opening width. A saddle threshold bridges a floor change with a bevel on each side, and a taller profile suits a larger gap under the door.How high can a threshold be on an accessible route?
Under the 2010 ADA Standards, a threshold at a doorway may be no more than 1/2 inch high (section 404.2.5). An existing or altered threshold may be up to 3/4 inch high if both edges are beveled no steeper than 1:2 (exception to 404.2.5). We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.Door sweep or automatic door bottom?
A sweep mounts on the face of the door. An automatic door bottom drops a seal when the door closes and lifts it when the door opens, which suits a floor with no threshold.What does perimeter gasketing do?
Perimeter gasketing seals the frame stop against drafts, light, sound or smoke. On a fire or smoke rated opening the gasketing has to be listed for that door. We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.What is the ADA threshold height limit?
This section and those after it, unless dated otherwise, were checked on against the sources listed on this page.
The ADA threshold height limit is 1/2 inch. Section 404.2.5 of the 2010 ADA Standards for Accessible Design caps a doorway threshold at 1/2 inch high, and section 303 sets the edge: the first 1/4 inch may be vertical, anything above it is beveled no steeper than 1:2, and a change in level over 1/2 inch has to be ramped.
| Rise | What the edge must be | Section |
|---|---|---|
| Up to 1/4 in | May be vertical | 303.2 |
| Over 1/4 in, up to 1/2 in | Beveled, no steeper than 1:2. The advisory note says 1/4 inch vertical plus 1/4 inch beveled is permitted, 1/2 inch in all | 303.3 and its advisory |
| Over 1/2 in | Ramped, to section 405 (ramps) or 406 (curb ramps); a ramp run no steeper than 1:12 | 303.4 and 405.2 |
| Existing or altered threshold, up to 3/4 in | Allowed with a beveled edge on each side, no steeper than 1:2 | Exception to 404.2.5 |
A 1:2 bevel needs 2 inches of run for every inch of rise, so an edge beveled over the full 1/2 inch needs at least 1 inch of run, and one that is 1/4 inch vertical plus 1/4 inch beveled needs at least 1/2 inch.
The same limit applies at automatic and power-assisted doors (404.3.3). Within the maneuvering clearance a door requires, changes in level are not permitted apart from slopes no steeper than 1:48 and a threshold that meets 404.2.5 (404.2.4.4).
We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.
Is a 3/4 inch threshold ADA compliant?
A 3/4 inch threshold meets the 2010 ADA Standards only where the threshold is existing or altered: the exception to section 404.2.5 allows up to 3/4 inch when both edges are beveled no steeper than 1:2. A new threshold is held to 1/2 inch, sliding doors included.
The 3/4 inch figure also comes from the 1991 ADA Standards, which allowed it at exterior sliding doors and held other doors to 1/2 inch (section 4.13.8). The 2010 text has no sliding door allowance, and the US Access Board’s guide says its threshold limits apply to all types of doors required to comply, including sliding doors.
The Department of Justice rules printed with the Standards make the 2010 edition mandatory for new construction and alterations from March 15, 2012, dated by the building permit application or the start of construction (28 CFR 36.406(a) and 35.151(c)).
For a step at a door in an existing building, section 405.2 allows a ramp steeper than 1:12 where space limitations make it necessary: up to 1:10 for a rise of up to 6 inches, up to 1:8 for a rise of up to 3 inches, and never steeper than 1:8 (Table 405.2).
We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.
What is an ADA ramp threshold?
An ADA ramp threshold is a ramped threshold for a floor that changes level by more than 1/2 inch at the door. Section 303.4 of the 2010 ADA Standards requires any change in level over 1/2 inch to be ramped, and section 405.2 limits a ramp run to 1:12, at least 12 inches of run for every inch of rise.
Pemko builds its modular ramp thresholds to that slope for floor offsets of 1/2 to 2-1/4 inches; each flush assembly is a little over 12 times as long as its offset is high (catalog page 125):
| Floor offset | Pemko assembly | Assembly length |
|---|---|---|
| 1/2 in | R.5F | 6-1/8 in |
| 3/4 in | R.75F | 9-1/4 in |
| 1 in | R1F | 12-3/8 in |
| 1-1/4 in | R1.25F | 15-1/2 in |
| 1-1/2 in | R1.5F | 18-5/8 in |
| 1-3/4 in | R1.75F | 21-3/4 in |
| 2 in | R2F | 24-7/8 in |
| 2-1/4 in | R2.25F | 28 in |
The part number reads R, then the offset, then F for flush, or OS or OSS for an up-and-over assembly with a 7 or 3-1/2 inch top plate. MR adds a pair of miter returns, and AK is PemKote, the skid-resistant finish Pemko recommends especially outside. Higher offsets take its RAMP13 and RAMP14 risers.
A ramp also needs the landings of section 405: at least 60 inches long at the top and bottom of each run (405.7 and 405.7.3), and a door’s maneuvering clearance may overlap a landing beside it (405.7.5). We quote Pemko modular ramps and saddle thresholds by opening width and floor offset.
We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.
How do you know if a threshold is ADA compliant?
Check the threshold as installed, not by its name: section 404.2.5 of the 2010 ADA Standards limits a doorway threshold to 1/2 inch high with edges that meet section 303. Even a maker’s barrier-free mark carries conditions. Pemko defines its symbol as an installed height difference of no more than 1/2 inch with allowable edge and slope conditions, and qualifies some products that carry it:
- The 2006 latching panic exit saddle is ADA compliant only when butted to 1/4 inch tile or other floor material (catalog page 99).
- Miter returns on the modular ramp thresholds are not ADA compliant (pages 125 to 127).
- The 257 and 259 ramp thresholds are not ADA compliant at a door opening, and the 257 is not when used alone (page 131).
On a specification, the fifth character of an ANSI/BHMA A156.21 threshold number carries the flag: 3 means barrier free, so J32130 reads aluminum (3), flat saddle (2), fluted (1), barrier free (3). Pemko reprints the 2019 designations on catalog page 16.
| Height | Pemko saddle series, with width |
|---|---|
| 3/16 in | 173 (2-1/4 in) |
| 1/4 in | 151 (3 in), 270 (4 in), 271 (5 in), 272 (6 in), 276 (7 in), 2748 and 274×4 (8 in), 2749 (9 in), 2750 (10 in), 2746×6 (12 in) |
| 5/16 in | 166 (2-1/2 in) |
| 1/2 in | 169 (3 in), 170 and 175 (4 in), 154, 171 and 1710 (5 in), 172 (6 in), 176 and 1547 (7 in), 2548 (8 in) |
The Pemko lines we quote are under commercial door thresholds and seals.
We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.
How do you seal the bottom of a door with a low threshold?
Seal the gap under the door rather than raising the threshold: a sweep fastened to the face of the door, a door shoe on its bottom edge, or an automatic door bottom, whose seal comes down only when the door shuts. Pemko’s automatic door bottoms close a gap of up to 3/4 inch, or 1/2 inch on its 420 model, provided the gap is the same across the whole door (catalog page 136, as are the points below).
- The drop bar is a straight aluminum extrusion, so a gap that starts under 3/4 inch and grows cannot be closed.
- The drop follows the plunger 1:1: another 1/4 inch of plunger extension lowers the bar 1/4 inch.
- The drop bar mechanism keeps the seal from skidding along the floor or threshold as the door closes.
- Sizes run from 12 to 72 inches; from 24 inches up they can be made with 2 inches for field trimming, while shorter sizes come at net length.
To build the seal into the threshold instead, Pemko’s 2005 latching panic exit saddle is 1/2 inch high and 5 inches wide with a replaceable seal insert, works with a surface vertical rod exit device or as a stop and seal, and Pemko says to allow 3/8 inch of door clearance (page 99).
The head and jambs take perimeter gasketing; the bottom takes automatic door bottoms or door sweeps.
What is an astragal on a door?
An astragal is the vertical strip mounted where the two leaves of a pair of doors meet, covering or sealing the gap between them against weather, smoke and sound. Security astragals also cover the gap between a door and its frame, on pairs and on single doors, against prying.
| Type | How it fits | Pemko series |
|---|---|---|
| Split | Two matching pieces, one on each leaf’s face, sealing against each other; ordered as a pair of door-height pieces (/2 on the part number) | 297, 303, 305, 29310 |
| Overlapping or T | One piece on the face of one leaf, lapping over the meeting edge of the other | 355, 356, 357, 359, 375 |
| Adjustable | Surface applied (the 351) or mortised for bullnose doors (the 354); used as split astragals, a pair takes two lengths, one per door | 351, 354 |
| Meeting stile seal | A seal on the meeting edge itself; Pemko says these do not work well on beveled-edge pairs | 300, 313, 314, 369 |
| Security | Covers the door-to-frame gap full height against prying (the 353 on outswing singles and pairs, the 3572 bar on single outswing doors) | 353 (PemGuard), 3572 |
| Locking | Weatherstripped, with slide bolts or locking spring bolts, for 1-3/4 inch inswing pairs | 3493 to 3498 |
Order by the pair: door height, the active leaf and its hand, square or beveled edges, the swing and any fire or smoke rating. Pemko hands a locking astragal by the active door, read from the position of its hinges viewed from the outside, the key side (see the door handing chart).
Pemko marks fire rated, listed astragals with its fire-rated symbol (UL 10B and 10C, catalog page 14), so tell us the rating of a rated pair before we quote. We quote Pemko astragals.
We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.
What do we confirm before it ships?
Before anything ships we confirm in writing: opening width, the gap or height to bridge, the floor, exterior or interior, and whether the opening is fire or smoke rated.
Every figure in this guide comes from the documents listed below: manufacturers' catalogs, templates and installation instructions, standards bodies' summaries, and the published code text with its official guides. We supply listed hardware and confirm in writing the part number and options you have chosen. We are not code consultants; your Authority Having Jurisdiction (AHJ) makes the final call.
Sources
The numbers and code sections on this page come from these documents, opened on the check dates shown above.
- 2010 ADA Standards for Accessible Design, sections 303 and 404.2.5 (ADA.gov)
- US Access Board, ADA Accessibility Standards
- 2010 ADA Standards for Accessible Design, section 303 changes in level, with Advisory 303.3 (ADA.gov)
- 2010 ADA Standards for Accessible Design, sections 404.2.4.4, 404.2.5 with its exception, and 404.3.3 (ADA.gov)
- 2010 ADA Standards for Accessible Design, sections 405.2 with Table 405.2, and 405.7 (ADA.gov)
- 28 CFR 36.406(a), compliance date for public accommodations, as printed with the 2010 Standards (ADA.gov)
- 28 CFR 35.151(c), compliance date for state and local government facilities, as printed with the 2010 Standards (ADA.gov)
- 1991 ADA Standards for Accessible Design, section 4.13.8, thresholds at doorways (ADA.gov)
- US Access Board, Guide to the ADA Accessibility Standards, chapter 4: entrances, doors and gates (thresholds)
- Markar and Pemko catalog, ASSA ABLOY (AADSS1015059): pages 13, 14, 16, 86 to 89, 99, 124 to 127, 131, 136 and 154 to 161
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