| Rough-opening width |
Measure between the framing members at the top, middle, and bottom. Record the smallest measurement. |
The opening should be wider than the door unit to allow shimming and adjustment. Verify the manufacturer’s required clearance. |
Prevents a unit that is too large from fitting and provides space to make the frame square. |
| Rough-opening height |
Measure from the finished or intended threshold surface to the underside of the header at both sides and in the center. |
Use the smallest measurement and compare it with the complete door-unit height, including the frame and threshold. |
Helps maintain proper threshold contact, head clearance, and door operation. |
| Existing door slab width and height |
Measure the slab itself, not the frame or trim. Check width at the top, center, and bottom. |
Common residential slab widths include 30, 32, and 36 inches; common heights include 80 inches. Confirm the actual opening before ordering. |
A replacement slab may not fit an existing frame if dimensions, hinge locations, or bore locations differ. |
| Jamb depth |
Measure from the interior face of the wall to the exterior face, excluding casing and trim. |
The frame depth must suit the wall thickness or include compatible jamb extensions. |
Incorrect jamb depth can leave gaps, interfere with trim, or prevent the door from sitting flush. |
| Wall condition and plumb |
Use a level to check both jambs and the header. Inspect framing for rot, movement, cracks, or water damage. |
The opening should be structurally sound and corrected before installation. |
A weak or out-of-plumb opening can cause rubbing, uneven gaps, air leakage, and lock misalignment. |
| Door handing and swing |
Stand outside facing the door. Note which side the hinges are on and whether the door swings inward or outward. |
Specify left-hand or right-hand operation and inswing or outswing as required by the layout. |
Incorrect handing can block hallways, stairs, furniture, or required exit paths. |
| Threshold and floor height |
Check the threshold type, floor slope, finished flooring thickness, and height difference between interior and exterior surfaces. |
The threshold must sit level, drain water outward where designed, and meet local accessibility and building requirements. |
Reduces trip hazards, water intrusion, and problems with the door sweep. |
| Exterior exposure |
Identify direct sunlight, driving rain, snow, wind, coastal moisture, and the presence of an overhang. |
Choose materials, finishes, weatherstripping, and glass suited to the local climate and exposure. |
Exposure affects fading, swelling, corrosion, water penetration, and maintenance frequency. |
| Weather barrier and flashing |
Confirm that the sill pan, flashing, sealant, and water-resistive barrier can be integrated around the door opening. |
Follow the door-unit installation instructions and local building requirements for sequencing and compatible materials. |
Correct water management is essential for protecting sheathing, framing, insulation, and interior finishes. |
| Hardware preparation |
Verify hinge count and locations, lock bore diameter, backset, strike position, and deadbolt requirements. |
Common lock backsets are 2-3/8 or 2-3/4 inches, but the selected hardware must match the door preparation. |
Matching preparations avoids drilling errors and ensures the latch and strike align correctly. |
| Energy-performance requirements |
Review the product’s U-factor, solar heat gain coefficient, air leakage information, and glazing certification where applicable. |
Lower U-factor generally indicates better insulation; compare values with the climate zone and applicable code requirements. |
Improves comfort and may reduce heating and cooling loads. |
| Safety and code compliance |
Check local rules for emergency egress, safety glazing, landing dimensions, door width, sill height, and weather protection. |
Requirements vary by jurisdiction and project type; confirm them with the local building department. |
Compliance supports occupant safety and helps prevent inspection or permit problems. |
| Final pre-order verification |
Record all measurements, photos, swing direction, frame depth, threshold details, glass options, and hardware locations. |
Measure twice and order from the complete door-unit dimensions rather than the slab size alone. |
A complete specification sheet reduces ordering mistakes, installation delays, and unexpected modification costs. |
