Before you approve a KONE Doubledeck elevator layout or order a pocket door for the same project, get the elevator manual and the door hardware schedule on one table. I learned that the hard way: a $3,200 order for split-jamb pocket door frames ended up unusable because I didn't check the wall depth against the frame requirement. The door vendor followed the drawings, so the fault was mine. Put the KONE CXT hoist manual, the door schedule, and the security hardware list on the same review cycle. That one habit would have caught the mistake before concrete was poured.
Short version
If you only read one section, read this. KONE Doubledeck elevators are not a trick to get two elevators for the price of one shaft. They use one hoistway, but the pit, overhead, structural supports, and door zone design are different from single-deck installations. Before you build anything, get the current KONE CXT hoist manual from the project-specific documentation set, and verify the model and revision. And if you're putting sliding patio doors in the same building, secure the lift-off problem first, then add locks and bars. Those two tasks—elevator documentation and sliding door security—feel unrelated. In a building project, they are connected by the review process. If no single person checks both, both fail.
Why I get to say this
I'm not a structural engineer. I'm a facilities coordinator who has handled elevator modernization and door hardware orders for about eleven years. I've personally made and documented maybe 27 significant mistakes, totaling roughly $50,000 in wasted budget if I include rework hours. I should add that the total is a guess—I don't keep a running total anymore because the list got too depressing.
My job is to make sure the shop drawings match the actual site. That means I read a lot of manuals, including KONE hoist manuals, and I've spent a lot of time explaining why a pocket door frame doesn't fit a wall cavity. The pattern shows up in nearly every project: the elevator drawings arrive after the door schedule is approved, and nobody checks the two against each other.
KONE Doubledeck Elevators: Not Two Elevators in a Trenchcoat
People think a KONE Doubledeck elevator saves space by stacking two cabs in a standard hoistway. Actually, it saves vertical cycles—the upper and lower cabs stop at adjacent floors at the same time, which improves handling capacity in a tall building. It doesn't save construction space. The hoistway is likely taller, the buffer requirements are more demanding, and the control layout is not the same as a single car. If you assume the shaft dimensions from a comparable single-deck layout, you will run out of clearance. I've watched a project lose two months over exactly that.
Here's an assumption failure I remember: I once assumed the shop drawing for a KONE Doubledeck would match the typical shaft section in the marketing brochure. Didn't verify. Turned out the actual layout needed a deeper pit and a stiffer rail bracket schedule. The cost of correcting the pit after excavation? I want to say $9,000, but don't quote me on that. The point is, it was a concrete problem, not an elevator problem.
- Get the project-specific layout, not a generic brochure.
- Confirm the pit depth, overhead, and buffer dimensions with the current drawings.
- Review the rail bracket spacing against the shaft wall before pouring.
Keep the KONE CXT Hoist Manual Where You Can Actually Find It
If someone on the team searches for a KONE CXT hoist manual four weeks into installation, the project is already behind. The hoist manual is not a suggestion. It includes torque values, brake inspection intervals, lockout/tagout steps, and rail bracket specs that determine whether the installation passes review. A generic PDF from a search result might be the wrong revision. In my opinion, this is where teams waste the most time: they assume manual means one document, and they do not verify the model and serial number.
I made that mistake with a modernization order. The sales rep assured me the installation crew knew the product. They knew the product, but they did not have the current manual section for rail bracket spacing. We discovered the discrepancy after we had already set the anchors. The rework took a week and cost more than printing the manual would have cost. Since then, I do not let the first site meeting happen unless the crew can show me the relevant page.
Per KONE documentation practices—and this is standard for major OEM hoist manuals—always use the current project-specific document set. If you are working from a search snippet or an old photocopy, stop until you have the verified version.
Pocket Door, Black Front Door, and Sliding Door Security: Three Places I've Wasted Money
Pocket doors: the wall depth is not optional
A pocket door is kinda like a door that hides in a cave. It only works if the wall cavity is deep enough and straight enough. I ordered twelve pocket door frames for a multifamily retrofit and approved them without checking the actual stud wall. The cavity was four and three-quarter inches; the frame needed five and a half. The order cost around $3,200, and most of it went to the scrap pile. It wasn't the door vendor's fault—they built exactly what I specified. Measure the wall cavity before you choose the frame, not after.
People think pocket door failures come from cheap rollers. Most of the installation problems I've seen are framing and clearance issues. Cheap hardware just makes a framing problem more obvious.
Black front doors: watch the heat
Black front doors look fantastic. They also absorb heat. On a south- or west-facing entry, a black door can hit surface temperatures that cause the substrate to expand. Paint cracks, the door warps, and the warranty team gets a phone call. People think the paint failed because the finish was low quality. Actually, heat drives the wood or composite to move, and the coating cannot absorb that movement. The color is not just a style choice; it is a performance spec.
If you still want a black front door, choose a fiberglass door with a factory-applied dark finish and confirm the door assembly is rated for high heat exposure. I'd rather replace a spec up front than explain to an owner why their beautiful door won't close. If you ask me, the same logic applies to elevator finishes—dark panels in a sunny lobby heat up too, but that is a complaint for another post.
How to secure sliding doors: fix the lift-off first
The question of how to secure sliding doors comes up on every security walk. The usual answer is a Charlie bar or a floor pin. Those help, but they don't address the most common exploit: lifting the door panel off the track. If the top track has no anti-lift block or screw, an intruder can lift the door upward and remove it from the frame, regardless of how strong the lock is. The lock can be the best cylinder on the market, and the door still comes off.
So my sliding-door security checklist is usually:
- Install anti-lift clips or screws in the top track, on both panels if the door is multi-panel.
- Make sure the track screws bite into solid framing, not just drywall.
- Add a bar or brace after the lift-off is fixed.
- For ground-floor units, consider a contact sensor that reports open or closed status to the building management system.
An informed customer asks better questions. When we market a unit as security-conscious, we do not use the word secure loosely. Per FTC advertising guidance (ftc.gov), claims must be truthful and not misleading, and substantiation is required. For us, that means the actual hardware list backs up any language we use in the brochure.
When to ignore my checklist
I'm not saying every KONE Doubledeck project is right for every building. If your traffic study says two separate elevators handle the flow better, a doubledeck is not a magic fix. I'm also not saying you should avoid black front doors or sliding doors. The boundary is: if a door or elevator component is load-bearing, fire-rated, or part of the building's access-control system, get a qualified engineer to review it. My checklist is for catching the gaps before you order, not for replacing professional judgment.
Also, my cost memories are probably a little off. The $3,200 and $9,000 figures are honest approximations—I might be misremembering the exact totals. What I do not misremember is the schedule delay and the phone calls with the project manager. Those numbers rhyme even when they don't match.
If you take one thing from this, make it this: the elevator manual and the door schedule are not separate kingdoms. They meet in the wall, and that's where I wasted money until I started reviewing them together. It's a boring habit. It's also the one that works.
