True Stile and Rail Construction

Our Medium Density Fiberboard (MDF) doors are “made by hands” in the USA at our state-of-the-art factory in northern Colorado. Sun Mountain’s doors are true stile and rail construction (not routed or moulded), with engineered components to resist warp. Choose from a selection of contemporary designs, pre-primed in the factory, with optional finger-joint Pine jambs. We sell direct to the trade or homeowner and ship nationwide to your home or construction site.

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Our MDF doors are covered by an industry-leading Warranty.

Learn about our craftsmanship, including:

Engineered Stiles and Rails

Stiles and rails are the vertical and horizontal “frame” components, respectively, of the door. Our MDF doors are true stile and rail construction, engineered to resist bowing and warping.

We use industry-leading 1/8″ thick High Density Fiberboard (HDF) veneers, with superior quality TimberStrand® Laminated Strand Lumber (LSL) core material.

Solid MDF Panels

Panels are the large, wider boards that fill the space between the stiles and rails. Our panels are 3/4″ thick solid MDF—much higher quality than panels with thin veneers, or hollow core panels.

Cope and Stick Construction

Our doors are assembled with “cope and stick” (i.e., tongue and groove-type) construction. Stiles and rails are glued together for optimum strength and stability. Panels fit into grooves in the stile and rail components.

Flat Panel and Square Sticking Profile

Our MDF doors feature a contemporary flat panel and a square sticking profile as shown below. “Sticking” is the profile of wood on the stiles and rails, creating a “picture frame” around the panels of the door.

MDF Door Profile Illustration


We not only manufacture the highest quality door slabs, but we also offer optional pre-hanging of the doors. A pre-hung door consists of a door hung on hinges and assembled in a wood frame (the frame is also called the door “jamb”), with a door stop. We offer finger-joint Pine wood jambs. If you choose the optional pre-hanging for your door, the jambs are pre-primed in the factory (matching the primed doors). A pre-hung door is ready to install in the door opening, with no on-site assembly required. This reduces construction time (and scheduling) and lowers project cost.

Factory pre-hanging ensures that hinge pockets are mortised square and precise, and that hinges are always flush on the door and frame. Hinges are included in the price of pre-hanging, and are available in a selection of color choices. Boring and latch/dead bolt mortising are also provided at no additional cost with factory pre-hanging. This prepares the door for hardware installation. A choice of single or double bore options are available in different “backset” positions (the placement of the handle or lockset from the door edge). Factory pre-hanging also ensures that the “reveal” (the small gap between the door and the jamb when the door is closed) is always correct.

Pre-Hung Doors

MDF Door, Single Bore
Single Bore
MDF Flat Jamb
Primed Finger-joint Pine Flat Jamb with Stop
MDF Door, Flat Jamb
4″ Ball-Bearing Hinges

MDF Pre-hung Door

MDF Pre-hung Door

Pre-hung MDF Door

Solid Poplar Flat Jamb
Finger-joint Pine Flat Jamb with Stop
Solid Poplar Kerfed Flat Jamb
Finger-joint Pine Kerfed Flat Jamb with Stop
To learn more about our pre-hanging options and choices, select Pre-Hanging from the main menu.

Pre-Finishing (Prime) 

Our MDF doors are pre-primed in the factory with a white prime coating, ready for on-site painting. If the door is pre-hung (with the jamb), the finger-joint Pine jamb is also pre-primed. To learn more about our pre-priming, select Pre-Finishing from the main menu.

Crating and Shipping

All orders are shipped direct to the home or jobsite in sturdy crating. Single door units are shipped pre-hung (as applicable), ready to install. Pre-hung double doors are shipped “Knocked Down” (or KD) and must be re-assembled prior to installation. Freight and crate charges are calculated based upon volume (door count) and are assessed at the time of check out.


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