I have one more draft script coming – this is my fourth script for an upcoming whiteboard animation video. If you haven’t had a chance to add your input on the previously-posted scripts (panic hardware, classroom lock options, door closer arms), there’s still time! I really appreciate your comments on these drafts…I think the whiteboard animations will be really helpful for people who are new to the industry, or those who need to review the basics.
If you’re looking for today’s Wordless Wednesday post, it’s here!
Flush Bolts and Coordinators [Draft Script]
Flush bolts are used on pairs of doors to secure the inactive leaf, projecting into the frame head and into a floor strike. In this application, the active leaf would typically have a lockset which latches into a strike mounted on the edge of the inactive leaf.
Manual flush bolts and surface bolts are projected and retracted manually. Because manual bolts do not provide a positive latch and could be left in the retracted position, they are not typically allowed for use on fire doors. One exception is when the pair of fire doors leads into a room that is not normally occupied by humans, like a storage room or electrical room. If allowed by the Authority Having Jurisdiction – the AHJ, manual flush bolts can be used on these rooms.
Two types of flush bolts are available – the extension rod type, traditionally used on hollow metal doors, or the corner wrap type, designed for wood doors. Corner wrap flush bolts can sometimes weaken the top corner of a wood door because of the volume of material that is removed in preparing the door for the flush bolts, so some specifiers and suppliers use extension rod flush bolts for wood doors as well as hollow metal doors.
An automatic flush bolt is projected when the active leaf closes and depresses a trigger on the edge of the door. When the active leaf is opened, the automatic flush bolt retracts. Constant latching flush bolts are a type of automatic bolt – the bottom bolt is a regular automatic flush bolt, but the top bolt latches when the inactive leaf closes, and stays latched until it is retracted manually. Either type may be used on fire door assemblies.
Automatic and constant latching flush bolts are both available with a top bolt only, and a fire pin in place of the bottom bolt. These sets are called “LBB” or “less bottom bolt.” The top bolt functions normally – an automatic bolt is projected by the active leaf and the constant latching bolt is always latched, but the fire pin remains retracted until there is a fire. When the pin is heated to a certain temperature, it projects into a hole in the edge of the active leaf, securing the doors to compartmentalize the building. The benefit of omitting the bottom bolt is that there is no need for a strike in the floor.
In order to ensure that the inactive leaf closes first, pairs of doors with automatic flush bolts must also have a coordinator. If both leaves of a pair are opened, the coordinator will hold the active leaf open slightly during its closing cycle. This allows the inactive leaf to close fully and be in the proper position for the active leaf to then close and project the bolts. A coordinator may also be used when a door has an astragal that could inhibit a pair from closing if not sequenced properly. A carry bar may be needed if the inactive leaf can be opened before the active leaf, but carry bars are not common.
Two types of coordinators are available – the gravity type which mounts on the face of the door frame, and the bar type which mounts on the underside of the frame head. The bar type is preferred because it is less visible than the gravity type, and less prone to vandalism. When a bar type coordinator is used, a filler bar is required to extend the coordinator the full width of the door opening. Mounting brackets may also be needed if parallel arm door closers or surface-mounted vertical rod panic hardware or fire exit hardware is used. The mounting brackets are installed after the coordinator, so other hardware can be attached without damaging the coordinator.
Egress is an important consideration when using flush bolts. Manual flush bolts are allowed in limited locations in a means of egress, because the operation required to retract the flush bolts does not meet the egress requirements. When automatic flush bolts are used on a door in a means of egress, no hardware may be installed on the inactive leaf that could confuse building occupants about which door to open for egress. For example, a dummy lever or push rail cannot be installed on the egress side of the inactive leaf so it’s obvious that the active leaf is the one that can be opened.
A 2-point latch, like the Schlage LM9200, is a good solution for pairs of doors, and can be used in place of flush bolts. Lever handles retract the latches at the head and at the floor, and the doors operate independently with no need for a coordinator. This product is also available with a latch at the head only. The LM9200 meets model code requirements for egress and accessibility, and can be used on fire door assemblies. Check the listings for the fire door and the latch, to verify the maximum allowable fire rating.
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Looks good
I am thinking in the presentation there will some how be examples of all the devices.
Hi Charles –
Yes, the artist will illustrate the different products and how they work. It will be a challenge, but I’ve got my fingers crossed that we’ll finally have a good way to explain to someone how these operate.
– Lori
Forgot to add
Hope to see you one day accepting the “Doory” award at the Oscars, for your film work!!
I feel that the second to the last paragraph needs to mention the Code. And that before using bolts on doors the Code must be researched. As you point out there are limited acceptable locations. There isn’t time or space for that full discussion but a reminder that this needs to be researched for specific situations might be a good inclusion.
You should mention the maximum throw on both flush bolts.
if there will be a concealed auto door bottom does bottom flush bolt will works no matter auto or manual flush bolt.????
Hi Muhammed –
A concealed automatic door bottom will typically conflict with the bottom flush bolt. I don’t know of a good solution other than using a surface-mounted flush bolt or a surface-mounted door bottom.
– Lori
Dear Lori,
thanks for quick reply, as i was searching i found something from egger industries. in that letter it was mentioned something like this, please see below;
Conflicts with automatic door bottoms occur when other hardware is prepped in the bottom rail of the door like concealed vertical rod bottom latching, bottom flush bolts and auxiliary fire latches. When this happens we can mortise for the automatic door bottom to within ½” of the conflicting prep as long as that prep for the automatic door bottoms is not less that 18” long; automatic door bottoms are not available in sizes less that 18”.
as far as i am working in this field i tried by making hole by drilling on concealed bottom and its works but that was not the permanent solution therefore i am look for permanent solution as there are no chance to use any hardware surface mounted.
really thankful to you and please update me if you found any thing new in this regards.
I have an issues with a pair of steel doors with inactive leaf having a z-astragal installed on door. The coordinator does not hold active door open far enough for astragal on inactive leaf to clear active leaf. Is there a way to make door hold open further or is there a brand that holds door open at a wider degree?
Hi Chris –
I have not seen a coordinator that holds open at a greater angle than others, but maybe one of the iDH readers will see this and answer. Would a slightly smaller astragal work? If you could send me some photos or a video I can ask for advice from my readers, but I will not be able to post the question until July 29th.
– Lori
I have 5′-0″ double door that is an exit door from a rated stair well. 90% of the time people will pass through the 3′-0″ Active leaf. If I use an automatic flush bolt will the inactive leaf be set loose every time someone opens the active leaf.
Hi Ed –
When someone opens the active leaf, the automatic flush bolts will retract but the door closer should hold the inactive leaf in the closed position. You could also use constant-latching flush bolts if the inactive leaf is not required for egress.
– Lori
Dear Lori,
One fire rate 20min double door for main entry apartment is high rise building in Miami, has the next specification: Hollow metal frame, 2 double wood doors with astragal, 2 concealed door closer, manual flush bolts on inactive leaf, mortise lock in active leaf. Is necesary to use door coordinator?
best regards
Hi Deibis –
A coordinator wouldn’t typically be required for a door with manual flush bolts, but most fire doors are not allowed to have manual flush bolts unless the door leads to a room that is not normally occupied by people.
– Lori