Comparing pre-assembled doors versus knockdown doors
Which is the less expensive door system? Knockdown or preassembled? Most might say the knockdown package AND the most competitive option available. However, is that right? What does each system include?
Which is the less expensive door system? Knockdown or preassembled? Most might say the knockdown package AND the most competitive option available. However, is that right?
What does each system include? Typically, for an 8-inch girt wall, the 3070 knockdown package includes a 20-gauge door, 16-gauge 8 1/4-inch frame, Grade 2 cylindrical lever lock, ball bearing hinges, threshold, sweep and weatherstripping.
The 3070 pre-assembled unit includes a 20-gauge door, 16-gauge 5 3/4-inch frame, 8-inch subframe, top and bottom jamb clips, Grade 2 cylindrical lever lock, ball bearing hinges, threshold, sweep, weatherstripping and insulation in the cavity between the frame and subframe.
Components and Labor
The components are almost the same. Both include the door, frame, lock, hinges, threshold, sweep and weatherstripping. In addition, the preassembled unit includes the subframes, subframe insulation and jamb clips. Is the knockdown package the less expensive option because it has fewer parts? Let us continue our comparison.
What about factory labor? The knockdown package takes five to seven minutes to package the frame, hinges, threshold, sweep and weatherstripping. The preassembled unit takes 35 to 45 minutes to assemble. Is the knockdown unit the less expensive option because it has fewer parts and less factory labor? Let us keep checking.
Packaging and Installation
What about shipping? The knockdown package is shipped on a wood pallet usually without a wood top or sides. The preassembled unit is shipped in a heavy-duty, wood-crated box. Is the knockdown package the less expensive option because it has fewer parts, less factory labor and less palletizing? Maybe, but we have more to compare.
What about installing the door units in the metal building wall? When comparing the knockdown and preassembled installation methods, installers have their own methods that can vary greatly. For the purpose of this article, we will try to be as generic as possible.
For the knockdown, determine the door swing. Place the frame head and jambs on a flat surface (floor) with hinges and strike sides up. Fasten the head to the jamb legs with nuts and bolts provided. Check to make sure the doorframe opening measures exactly 36 inches before tightening the nuts and bolts. Install the door into the frame with the hinges. Check for 1/8-inch clearance at head and 5/32-inch clearance at the strike jamb. Tilt the entire assembly into place. Secure hinge jamb anchor to the floor. Plumb hinge and strike jambs and level head. Anchor head and strike jamb to the building structure, the strike jamb to the floor. Install threshold and anchor into the floor. Install the lever, weatherstripping and sweep.
How much time does that take? Depending on the skill level of the installer, it can range from 30 to 60 minutes per opening. What if the lock will not latch or the door will not close? This is the responsibility of the installer. These problems often come up and can cost the contractor additional time and money.
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| Photo courtesy of Dominion Building Products |
The preassembled unit is already built so the installation takes only 20 to 30 minutes. Tilt the uncrated unit into the opening. Plumb and square the unit. Anchor the hinge side into the floor and to the overhead girt. Check for plumb and square. Anchor the strike side to the floor and the overhead girt. Attach threshold into the floor. If the door is plumb and square, the door will swing and latch properly.
Adding a closer, mortise lock or panic device on a knockdown unit adds time for installation, as much as two to three hours. There are additional problem areas for callbacks if not installed or adjusted properly.
Adding the same items to the preassembled unit does not add any more installation time. These are installed in the factory under ideal conditions and by experts. This process greatly reduces callback issues.
The knockdown unit takes longer to install and requires additional labor for every item added to the package. The preassembled unit has a fixed installation time no matter what items are added. Callbacks are common with the knockdown unit but greatly reduced with the preassembled unit. When labor and callbacks are added to the material costs, the preassembled unit seems the more cost-effective choice.
The door unit is the first impression of the quality of the building. If the owner walks through a door that does not operate smoothly the impression is the building quality is suspect and the first item on a punch list. However, if the door works smoothly no one will notice that the inspection started when they walk through the door.
The best choice is what works best for the contractor or erector. Knowing the true costs is everyone’s responsibility. Add up the cost and compare for yourself. You may be surprised at the true cost of the right choice.
Rick Kincy is director of business development and marketing at Dominion Building Products, Houston. To learn more, visit www.dominionproducts.com.
