What is the difference between a cylindrical lock prep and a mortise lock prep?
A cylindrical lock prep consists of a 2-1/8” cross bore through the door face and a 1” edge bore for the latch, positioned at a 2-3/4” backset. A mortise lock prep is a rectangular pocket machined into the door edge to accept the entire mortise lock body, plus a cylinder bore for the mortise cylinder. The two preps are fundamentally different and not interchangeable. The lock type specified in your hardware schedule determines which prep to order.
Can I change the door prep after the door has been manufactured?
Field modifications to change a door prep are not recommended, especially on fire-rated doors where unauthorized modifications void the fire label. On non-rated hollow metal doors, some modifications are possible as shop labor services, but the preferred approach is to order the correct prep from the factory. Contact CDF at (855) 769-9895 to discuss options if a door has been ordered with the wrong prep.
What minimum trim size is required to cover a cylindrical lock prep?
The lock rose or exit device trim plate must be at least 3-1/4” in diameter to fully cover the enhanced cylindrical lock prep with through-bolt notching. If your trim is smaller than 3-1/4”, the prep cutout will be visible around the trim edges. Verify your hardware’s trim dimensions against this requirement before ordering.
Do fire-rated doors require different preparations than non-rated doors?
Fire-rated doors (20-minute, 45-minute, 60-minute, 90-minute, and 180-minute/3-hour) use the same general prep types as non-rated doors, but all preparations must be applied at the factory in accordance with the door’s fire listing. Field modifications to fire-rated doors are prohibited. All hardware installed on fire-rated doors must be listed and labeled for the specific fire rating of the assembly.
How does door handing affect the door prep?
Door handing determines which edge of the door receives the hinge prep and which edge receives the lock prep. All preparations are machined based on the specified hand (LH, RH, LHR, or RHR). A door prepped for one hand cannot be flipped to serve as the opposite hand without the preps being on the wrong edges. Always verify handing before placing the order.
What is closer reinforcement and when is it needed?
Closer reinforcement is an internal steel plate welded inside the top rail of a hollow metal door during fabrication. It provides structural support for surface-mounted door closer mounting screws. Closer reinforcement is needed any time a surface-applied closer is specified in the hardware schedule. Without it, the closer screws may pull through the door face over time. The reinforcement location (pull side or push side) depends on the closer arm type.
Can a door be prepped for both an exit device and a deadbolt?
Yes, a door can receive multiple preparations for different hardware. For example, a door can include an exit device prep, a deadbolt prep, and closer reinforcement simultaneously. Each prep must be specified separately at the time of order. CDF’s ProBuilder allows you to add multiple hardware preparations during the door configuration process. Make sure to check required fire rating for your opening as that will limit hardware configurations available.
What happens if the exit device trim does not cover the door prep?
If the exit device trim plate or escutcheon does not fully cover the door prep cutout, the machined openings will be visible around the trim, creating an aesthetic issue and a potential security concern. In this situation, the door should be ordered with a blank face at the lock location and prepped specifically for the exit device. CDF can perform custom shop modifications to match non-standard exit device requirements.