Lift-slide door sizes: clear opening vs frame width
Frame width is what you order; clear opening is what the wall actually gives you to walk through. On a multi-leaf lift-slide the two diverge with every added leaf — track, stiles and the fixed centre all take width — and because architectural drawings usually dimension the opening, the window schedule has to carry the conversion. Specify both numbers and the argument is over before production starts.
The two numbers
The frame width is the finished unit: outer face to outer face, including the fixed leaves and the track housings. The clear opening is the walkable width once the sliding leaves are fully opened and stacked. On the LS-60 line, a two-leaf unit opens to roughly 4.8 m clear within its frame; a three-leaf unit reaches 6 m clear; the four-leaf configuration runs to 7.2 m with a fixed centre leaf. Each added leaf adds a sliding panel to the stack and takes its share of frame.
Reading the wall opening
Three things on the drawing set decide the fit. The structural mullion spacing — if the opening is 6.1 m and the nearest mullions frame 5.8 m, the unit is 5.8 m and the architect has to move the steel, not the other way round. The head height — the lift-slide frame plus its track sits below the structural head; a 3 m opening height does not mean a 3 m glass height, because the frame and the threshold take their share. And the threshold — a flush barrier-free threshold (the DIN 18040 option) changes the door leaf height and the track depth, so it is a specification item, not a site decision.
A worked example
A terrace wants a 6 m walk-through. The schedule reads: three sliding leaves plus nothing fixed — clear opening 6,000 mm, frame width set by the stack and the track, head height 2,700 mm to the structural head, flush threshold, laminated low-E IGU at 10–16 mm per leaf. The drawing office re-issues this as a fabrication set with the stack sequence, the bearing load per leaf and the threshold detail — and the 24-hour quotation quotes those three leaves, that glass and that threshold, not a generic slider.
Where mistakes show up
- Specifying clear opening as frame width — the unit arrives 300 mm proud of the opening.
- Leaving the threshold to the site — a non-flush threshold on a barrier-free line fails the access review.
- Omitting the glass per leaf — the bearing schedule on a lift-slide changes with pane weight, and a 3 mm error is a track error.
Questions
On the LS-60 line, 3,300 × 2,700 mm per leaf — above that the mass leaves the bearing schedule impractical, so the opening splits across more leaves.