Key takeaways
- Set the sill top within ±1 mm of finished floor level, with the car-to-landing sill gap between 25 mm and the 35 mm maximum, measured with the car at the landing.
- A 3 mm stainless sill formed with a 40 mm downstand deflects 0.33 mm under 100 kg at 500 mm bracket pitch; the same strip without the downstand deflects about 98 mm.
- The tolerance stack from screed, tile, bracket and sill straightness reaches 10.5 mm worst case, so the bracket needs ±10 mm of vertical adjustment and a survey before grouting.
- Allow 0.62 mm of thermal movement on a 1,200 mm stainless sill over a 30 K swing, and never grout both ends before the sill is set and checked.
The landing sill is a 3 mm stainless pressing about 1,200 mm long, and it decides whether a passenger feels a step, a lip or nothing at all. Elevator sill level is set within a millimetre or two of the finished floor, against a building tolerance that is often five times wider. That is the whole problem: the sill is a precision part fitted to a screed and tile build-up that nobody measured.
Two numbers frame the work. The sill top should sit within ±1 mm of finished floor level (FFL), and the horizontal gap to the car sill should be 25–35 mm. Miss the first and you have a trip hazard at every landing; miss the second and you have a shoe trap or a sill that rubs as the car settles.
The sill also has to carry load without moving. A 3 mm stainless sill formed with a 40 mm downstand deflects 0.33 mm under a 100 kg person at 500 mm bracket pitch. The same 3 mm strip without the downstand deflects about 98 mm — enough to feel like a trampoline. Stiffness comes from the section, not the gauge.
Related reading: the Elevator buffer bracket: design, materials and manufacturing and the Elevator cabin panel: design, materials and manufacturing take the same problem further. See the process and inspection scope on the capability pages, or send the drawing through the RFQ route.
The sill is set from the finished floor, not the slab
A typical lobby floor is 50 mm of screed, 5 mm of adhesive and 12 mm of tile, or 67 mm above the structural slab. Each layer has its own tolerance: screed ±5 mm, adhesive ±1 mm, tile ±2 mm. Set the sill from the slab and the finished floor can end up 8 mm above or below it, which is why so many sills are 5–6 mm high on handover.
The sequence that holds ±1 mm is short. Finish the floor first, or at least set a datum that represents it. Survey FFL at the landing with a laser or a dumpy level, mark it on the wall, and set the sill top to that mark with a straight edge and a feeler gauge. The bracket has to give ±10 mm of vertical adjustment for this to be possible; a fixed bracket welded to the slab cannot absorb an 8 mm floor error.
Adjustment belongs in a slot, not in a shim stack. A pair of M10 slots 12 mm long in a 6 mm bracket gives about ±5 mm of travel before the washer loses bearing, and a serrated washer holds the setting while the grout is placed. Shims under a slotted bracket are a sign that the slot has run out of travel, and they compress after a few thousand cycles.
What the 25–35 mm gap does
The gap between the car sill and the landing sill is a running clearance, not a design feature. Below 25 mm, the car sill can touch the landing sill as the car levels and the guide shoes take up clearance, and the contact scrapes the finish and loads the door track. Above 35 mm, a heel or a walking aid can lodge in the gap; ISO 8100-1 sets 35 mm as the maximum.
Measure the gap with the car at the landing and loaded to its rated capacity, because the car floor moves down as the suspension stretches. An empty-car measurement can read 2–3 mm wider than the loaded condition on a geared machine.
The numbers to hold at the landing
| Parameter | Typical value | Ganesh limit or note |
|---|---|---|
| Sill top to FFL | ±1 mm | Surveyed off FFL, not the slab |
| Sill flatness along length | 0.5 mm/m | Checked with a straight edge and feeler |
| Car-to-landing sill gap | 25–35 mm | 35 mm is the ISO 8100-1 maximum |
| Sill thickness | 3 mm | 304 brushed, or 316 for wet lobbies |
| Sill downstand | 40 mm | Formed in one piece; a flat strip is not a sill |
| Bracket pitch | 500 mm | 400 mm where the sill carries trolley traffic |
| Bracket vertical adjustment | ±10 mm | Slotted M10, serrated washer |
| Fixing | 4 × M8 stainless | Into cast-in channel or chemical anchor |
| Grout | Non-shrink, 50 MPa, 20 mm bed | Placed after the level check |
| Door bottom clearance | 6 mm | Measured with the door closed |
| Sill surface finish | Ra 0.8 µm | Brushed along the traffic direction |
| Thermal movement, 1,200 mm sill | 0.62 mm over 30 K | 17.3 × 10⁻⁶ /K for 304 |
| Point load | 100 kg | 981 N over a 300 × 300 mm area |
| General tolerance | ISO 2768-1 class m | Sill level and gap toleranced separately |
Thermal movement is small but not zero. Stainless 304 expands at 17.3 × 10⁻⁶ per kelvin, so a 1,200 mm sill moving through a 30 K lobby swing grows by 17.3 × 10⁻⁶ × 1,200 × 30 = 0.62 mm. If both ends are grouted hard against fixed walls, that movement goes into the sill as compression and shows as a bow of a few tenths of a millimetre in the middle. Leave one end on a slotted fixing, or keep the grout back 10 mm from the end.
Sill stiffness comes from the section. With a 40 mm downstand, a 3 mm sill has a second moment of area of about 40,000 mm⁴ and deflects 0.33 mm under 981 N at 500 mm pitch. Without the downstand, the same material behaves as a flat strip with about 135 mm⁴ and deflects roughly 98 mm. The formed section is the difference between a sill and a shelf.
Elevator sill level: five ways it goes wrong
The sill is high
A 6 mm lip at the landing is above the 5 mm threshold that most accessibility guidance treats as a trip risk, and it is the most common complaint on handover. The cause is almost always sequence: the sill was fixed and grouted before the screed and tile went down, or the floor build-up was assumed rather than measured. A 50 mm screed that arrives at 56 mm lifts the FFL and leaves the sill low, not high; a screed that arrives at 44 mm leaves the sill high. Both are the same mistake.
Fix it with a survey and a slotted bracket. Set the sill after the floor datum is fixed, adjust on the slot, check with a straight edge across the landing and into the car, then grout.
The sill is low
A low sill collects water and dirt at the landing edge, and the landing door bottom rubs the tile. It also puts the sill below the car sill, so the gap becomes a step down into the car. The usual cause is a tile bed thicker than the drawing allowance, or a structural slab poured high. A low sill is harder to correct than a high one because the bracket has no downward travel left once the grout is in.
The gap is out of range
A 20 mm gap rubs; a 40 mm gap traps. Both come from measuring with the car empty and the door track unshimmed. Level the car under rated load, set the landing door track, then measure the gap at three points along the sill. If the gap is wrong, move the landing door assembly, not the sill; the sill position is fixed by the floor.
The sill bows or slopes
A flat 3 mm strip on brackets at 700 mm pitch sags in the middle and rocks at the ends. The same happens when grout does not fill the bed: the bracket bears on a high spot and the sill spans the void. Tap the sill after grouting; a hollow note is a void. Drill and inject non-shrink grout rather than leaving it.
The finish is stained or the protective film is left on
Mortar and grout stain brushed stainless if they are not washed off within the working time, and a protective film left on through a summer bakes its adhesive into the surface. Fit the sill with the film on, remove it the same day, and wipe the surface with a non-chloride cleaner. Never use hydrochloric acid-based cleaners on 304; they leave free chloride that pits the surface at the traffic line.
Sills on the Ganesh route
Elevator sills are cut on the 12 kW fibre laser with a 40 ft × 16 ft bed, which keeps the sill outline, the downstand notch and the bracket holes in one program and holds hole position to ±0.3 mm. The downstand and the end returns are formed on the 200 T 5-axis brake with a 4,450 mm bed, so a 1,200 mm sill is formed in one hit with no joint at the traffic line.
Stainless sills are brushed and protected; mild steel brackets are cut, formed, welded where needed and finished through seven-tank pretreatment and the 18 ft × 14 ft powder booth. Sills and landing door panels for lift OEMs are a regular part of the elevator work we do for customers including TKE and Eros Elevators, under ISO 9001:2015 quality control and ISO 14001:2015 environmental control.
The elevator components hub collects the landing, car and door guides. How an elevator floor sill is manufactured covers the part itself, and how an elevator landing door panel is manufactured covers the panel that sits above it and has to line up with the same door track. The elevator parts page lists sills, doors, frames and counterweight parts, and the bending capability page covers the forming side.
What to put on the drawing
- Sill length, thickness, material grade and surface finish.
- Sill section, with the downstand depth and the end returns shown.
- Sill top to FFL, with the datum defined as finished floor level.
- Flatness along the length and across the width.
- Bracket pitch, slot length and vertical adjustment range.
- Fixing size, grade and the anchor type in the slab.
- Car-to-landing gap, with the load case for the measurement.
- Grout specification, bed thickness and the check before grouting.
- Door bottom clearance and the door track that sets it.
- Protective film and the instruction to remove it on the day of fitting.
Items 3 and 5 are the two that decide whether the sill can be set on site at all. Send the sill section, the floor build-up and the door gap to request a quote; we will check the level stack and the bracket travel before the first sill is cut.
An as-built survey belongs in the drawing pack when the landing already exists. Record FFL at both ends and at the middle of the sill line, the tile and adhesive thickness at a core hole, and the slab level at each bracket position. Three readings on a 1,200 mm sill catch the fall that a single reading misses; a 4 mm fall along the length is common on a screeded landing and has to be taken out in the bracket, not in the grout.
When a formed sill is the wrong part
A sill that has to carry a heavy pallet truck or a vehicle ramp is a cast or machined section, not a 3 mm pressing. A sill in a wet or chlorinated environment may need 316 rather than 304, and a sill on a glass balustrade landing is often an aluminium extrusion. We form sheet steel and stainless, so those are different supply chains.
A site-fabricated sill cut and welded in the lobby is the most expensive option of all: it cannot be formed with a downstand, it cannot be finished to a consistent brushed grain, and it will not hold ±1 mm across its length. If the landing has already been built and the floor is finished, measure it and make the sill to that measurement rather than to the original drawing.
None of the sill work is complicated. It is a survey, a slot, a formed section and a grout check, in that order.
Frequently asked questions
What tolerance should an elevator sill level hold?
Set the sill top to finished floor level within ±1 mm and keep it flat along its length within 0.5 mm/m. The lift code allows the car to stop within ±10 mm of the landing, so a sill set to ±1 mm leaves the whole 10 mm band for levelling error rather than spending it on the sill.
What is the maximum gap between the car sill and the landing sill?
ISO 8100-1 caps the horizontal gap at 35 mm, and most specifications hold 25–35 mm. Below 25 mm the car sill can rub the landing sill as the car settles, and above 35 mm a shoe heel or a walking aid can catch in the gap.
Why is the landing sill always 5 mm high?
Because the sill was set off the structural slab instead of the finished floor. Screed at 50 mm and tile at 12 mm are added after the sill is fixed, or the bracket was not slotted. The sill must be surveyed against the finished floor level, not the concrete.
Can a sill be adjusted after grouting?
No. Once the non-shrink grout has cured under the sill, the bracket is locked and any adjustment means breaking out the grout and resetting the sill. Set and check the sill on its brackets, with the car at the landing, before grouting.
Should an elevator sill be stainless steel or galvanised?
Use 304 stainless for a brushed sill in a dry lobby, and 316 where the sill sees cleaning chemicals or a wet environment. Galvanised sills are cheaper but the zinc wears through at the traffic line and the edge rusts. A 3 mm stainless sill with a formed downstand holds level better than a 1.5 mm galvanised pressing.
Sources and further reading
- ISO 8100-1:2019 — Lifts for the transport of persons and goods, safety rules for the construction and installation of lifts · reviewed 3 Nov 2026
- ISO 2768-1:1989 — General tolerances for linear and angular dimensions without individual tolerance indications · reviewed 3 Nov 2026
- IS 14665 (Part 1) — Electric traction lifts, code of practice, Bureau of Indian Standards · reviewed 3 Nov 2026
Have a sill and landing drawing to review?
Send the sill section, finished floor build-up, bracket detail and door gap. We will check the level stack and the fixing before quoting.
Request a quote