Knock-down (KD) frames
A knock-down frame ships unassembled: the head and the two jambs arrive as separate pieces, cut and prepped but not joined. The corners are field-assembled, usually by interlocking tabs or by setting the pieces into the opening and fastening them as the wall is finished. Because the pieces lie flat, KD frames are compact to ship and easy to carry through a building.
KD frames are the common choice for drywall (gypsum board / stud) partitions, where the frame often slips over the finished wall and is fastened in place. They are typically cheaper to buy and ship, store in less space, and can have shorter lead times because they do not need a welding and finishing step at the factory.
- Ships flat in three pieces: head plus two jambs
- Assembled and set in the field
- Lower shipping cost and easier to handle on site
- Well suited to drywall / stud partition walls
- Often cheaper and faster to get
Welded frames
A welded frame is fully assembled at the factory: the corners are welded, ground and finished so the frame arrives as a single rigid unit. That makes it stronger and more dimensionally stable than a field-assembled frame, with a cleaner, seamless look at the corners once painted.
Welded frames are the usual choice for masonry or block walls, where the frame is set and the wall is built around it, and for heavier or higher-traffic openings that need the extra rigidity. The cost is that a welded frame is bulky and awkward to ship and move: it takes up full-opening space on the truck and has to be carried as one piece to its location, and it generally costs more and can take longer to produce.
- Welded, ground and finished as one unit at the factory
- More rigid and dimensionally stable
- Cleaner corner appearance
- Suited to masonry openings and heavy or high-traffic use
- Bulkier to ship and handle, usually higher cost
How to choose
Start with the wall. Drywall and stud partitions lean toward KD frames that wrap the finished wall; masonry and block walls lean toward welded frames set before the wall goes up. After the wall type, weigh the opening: a high-traffic entry, a heavy door or an opening that has to stay square under abuse is a good case for welded, while an ordinary interior office or closet opening is a natural fit for KD.
Then factor in the practical constraints. If the job is remote, the site has tight access, or lead time and freight cost are under pressure, the flat-packed KD frame has real advantages. If appearance at the corners matters or the specification calls for welded construction, that decides it. Many jobs end up with a mix, and the door schedule records which openings get which.
Install considerations
KD frames depend on being assembled square and anchored correctly in the field; because the corners are not welded, a sloppy install shows up as a frame that is out of square or a door that does not sit right. Taking care with the corner joints and the anchoring is what makes a KD opening perform like a welded one.
Welded frames remove that field variability but have to be placed with the wall construction in mind, since they are often built in rather than wrapped on. Either way, getting the frame set plumb, level and square is what determines whether the door and its hardware work smoothly for the life of the opening.
Keeping it straight on the schedule
On a job with dozens or hundreds of openings, tracking which frames are KD, which are welded, and how that interacts with wall type, lead time and freight is its own task. eMullion models openings and their frames so a distributor can keep frame type, hardware and delivery lined up per opening instead of reconciling it by hand.
