Mast-climbing work platform safety field guide: OSHA, ties, base, and load chart

What a mast climber is, and the three things that hold it up

A mast-climbing work platform, what the trade shortens to MCWP or just a mast climber, is a powered work deck that climbs a rigid mast tower bolted to the building. A rack-and-pinion drive runs the platform up and down the mast, so the crew gets a large, solid deck that rises to the work instead of a platform hung on ropes. Masonry, restoration, cladding, EIFS, and window work on mid-rise and high-rise facades ride on one, because the deck is wide, stable, and built to carry the material a rope-hung swing stage cannot.

That stability is not free. It depends on three things being right at the same time. The mast has to be tied to the building at the engineered intervals so it cannot buckle. The base and the foundation under it have to carry the whole load that travels down the mast. And the platform has to stay within its rated capacity, loaded evenly, not piled on one end. Get any one of those wrong and the climber buckles, tips, or overstresses a component. The most dangerous moment of all is erecting and dismantling the machine, before the finished structure is fully there to hold it.

This is the mast-climbing side of facade access. The rope-hung kind, the swing stage, is its own guide, the suspended-scaffold guide, and the built-from-below kind is the supported-scaffold guide. Every number here is governed by OSHA's scaffold rules in 29 CFR 1926 Subpart L, the manufacturer's instructions for the specific machine, the engineer who designs the ties and the base loading, and the MCWP standard, ANSI/SAIA A92.9. Confirm against those, not the rule of thumb.

The framing: the ties, the base, and the load chart

Three things hold a mast climber up, and they fail in different ways. The wall ties carry the mast back to the building so a tall mast does not buckle or fold away from the wall. The base and the foundation carry the load down to the ground or the structure, because everything the machine weighs ends up bearing at the bottom. The load chart sets how much the deck can carry and how it has to be spread, because an overloaded or lopsided deck overstresses the mast and the drive, or tips the whole machine.

Treat these as the framing of the job, the parts you get right before anyone climbs. They are not independent the way a swing stage separates platform suspension from worker fall arrest. On a mast climber the deck, the mast, the ties, and the base are one structural system, and a weakness in any of them is a weakness in all of them. A mast that is under-tied buckles under a load the chart said was fine. A base that settles throws the mast out of plumb and changes how the ties are loaded.

So the framing gets hedged hard, every time, to the people who own it: the manufacturer for the machine and its limits, the engineer for the tie design and the base bearing, OSHA Subpart L for the scaffold rules, and the ANSI/SAIA A92.9 standard. The rest of this guide takes the three one at a time, then the phase where they all get built, erection and dismantling.

Mast climber vs swing stage

A mast climber and a swing stage solve the same problem, reaching a facade, in opposite ways. The mast climber climbs a rigid mast bolted to the building, so the deck is supported from a fixed structure and stands stable even when loaded heavy. The swing stage, the suspended scaffold covered in its own guide, hangs on wire ropes from rigging set on the roof, so the platform floats and sways and the crew rides separate independent lifelines for fall arrest. One is held up by a tower. The other hangs from a rope.

The difference drives the choice. Material-heavy work is where the mast climber wins. A masonry crew laying block, a restoration crew with stone and mortar, a cladding or EIFS crew with panels and pallets, all need a wide deck that holds weight and does not swing, and a mast climber gives them that. A swing stage suits lighter, faster facade work, window cleaning, caulking, coatings, where the load is a couple of workers and hand tools and the rig has to move quickly between drops.

Neither one substitutes for the other freely. The mast climber needs a base that can carry the load and a building that can take the ties. The swing stage needs roof rigging that can be counterweighted and tied back. Pick the system to the work and the building, and read the suspended-scaffold guide for the rope-hung side before you assume one rig covers every facade job.

The rack-and-pinion drive, single and twin mast

The drive on a mast climber is a rack and pinion. A toothed rack runs the length of the mast, a powered pinion gear on the platform's drive unit meshes with it, and the motor turns the pinion so the platform walks itself up and down the mast. It is the same principle as a construction hoist, geared and positive, not a rope being wound or fed. The platform climbs at a controlled, steady rate and holds position when the drive stops.

Mast climbers come as single mast or twin mast. A single mast carries the deck off one mast tower, with the platform cantilevered to one side or centered, and suits a shorter deck. A twin mast carries one continuous deck on two synchronized masts, which lets the deck run long, in some configurations past 30 m, for a full facade bay. The twin mast also spreads the load across two masts and two bases, which matters when the work is heavy.

The motor, the drive unit, and the rack and pinion are matched to the machine and rated as a system. Capacities run widely with the configuration, from around 1,000 kg on a small single mast to several thousand kilograms on a twin, so the only number that counts is the one on the load chart for the machine you are standing on. Confirm the drive, the mast configuration, and the rated capacity against the manufacturer's data for that specific climber.

The wall ties: tie the mast within its free-standing limit

The wall ties are the number one thing that holds a mast climber up, and the number one thing that gets it wrong. The mast is tied back to the building at engineered intervals, and those ties do two jobs. They keep the mast from buckling under the load running down it, and they carry the wind and the side loads back into the structure so the mast does not fold away from the wall. A mast climber is structurally supported by its anchorage system, the ties and the anchor bolts into the building, and that system is engineered, not a field guess.

Every mast has a free-standing height, the height it can stand before the first tie, and a maximum spacing between ties up the mast. As a common picture, ties land on the order of every 20 ft, and the anchor is often designed to hold something like 3,000 lb in tension and compression, but those numbers are the manufacturer's and the engineer's to set for the machine, the building, and the geometry. Never exceed the free-standing height, and never skip a tie in the schedule. A mast carried past its free-standing limit can buckle under a load the chart called safe.

This is where you hedge hardest. The tie spacing schedule, the anchor design, and the bolts that go into the building come from the manufacturer's instructions and the engineer who designed the anchorage to the structure. The building itself has to be able to take the tie loads, which is the engineer's call, not the crew's. Confirm the free-standing height, the tie spacing, and the anchor capacity against the manufacturer, the engineer, and OSHA Subpart L before the mast goes up past the first tie.

The base: the foundation has to carry the load

The base is the second thing that holds a mast climber up, and it is where the whole load ends up. Everything the platform and the mast weigh, plus the people and the material, travels down the mast and bears at the base. So the base frame and the surface under it have to carry that load without settling or moving. A level, stable surface with the load-bearing capacity the machine needs is a structural question, and the ground pressure under the base must not exceed the manufacturer's limit.

What that takes depends on the surface. On a rated slab the base can bear directly, if the slab carries the load. On soft or uneven ground the base sits on cribbing, timbers laid up in an alternating pattern to spread the load over a wider footprint and kept level. On a roof or a podium the base goes over primary structure, the beams or columns, not over insulation, a waterproofing membrane, or a span that was never sized for a point load. Outriggers extend the base where the machine needs a wider footing, deployed to the positions in the manufacturer's load diagram and jacked to bring the base level and the mast plumb.

The base is not a place to eyeball it. The bearing capacity of the slab or the ground, the cribbing layout, and whether a roof can take the load are the engineer's to confirm, and the outrigger positions and the leveling are the manufacturer's. Set the base wrong and the mast goes out of plumb, the ties load in ways they were not designed for, and the climber can settle or tip. Confirm the foundation and the base loading against the engineer, the manufacturer, and OSHA before any weight goes on the mast.

What can a mast climber carry?

A mast climber carries exactly what its load chart says, and not a pound more. The chart is the rated capacity for the machine in its configuration, and it covers everything on the deck at once, the workers, their tools, and the material. Overloading the platform is the single most common cause of a mast climber collapse, because the extra weight overstresses the mast, the drive, and the ties, or shifts the balance until the machine tips.

The chart is not just a total weight. It sets how the load has to be distributed across the deck, and it usually gives lower limits at the cantilevered ends than over the mast, because a load hung out on a cantilever puts a bigger moment on the mast than the same load carried over the support. Pile a pallet of block on one end of a deck rated for an even spread and you can overstress the machine while the total weight still looks legal. Even loading is part of the rating, not a suggestion.

This is the third thing to hedge hard. The load chart, the distribution limits, and the cantilever capacities are the manufacturer's, set for the specific machine and configuration, and they are posted on the platform for a reason. Read the chart for the climber you are on, stage material to it, and keep the deck within both the total and the distribution. Confirm the rated capacity and the loading limits against the manufacturer's load chart and the ANSI/SAIA A92.9 standard, not a number remembered from another machine.

Loading and distributing material on the deck

Loading is where the load chart meets the real deck. Masonry is heavy, and the material a facade crew stages, block, brick, mortar, stone, and cladding panels, is exactly the concentrated weight that finds the limits of the chart. The rated capacity is a budget, and it gets spent on the people, the tools, and every pallet that comes up, all at the same time.

Spread it. A load piled on one spot, or hung out on a cantilevered end, loads the mast and the drive harder than the same weight spread along the deck over the support. The cantilever ends carry less than the middle for that reason, so the heaviest material belongs over the mast, not out at the tips. Watch the deck as material lands and as the crew works it off, because the distribution changes through the shift, and a deck that was balanced at the start can end up lopsided once one end is emptied.

Staging discipline is the practical version of the load chart. Bring material up in known weights, place it to the chart, and do not let a forklift or a hoist put more on the deck than the chart allows just because there is room to set it down. The room on the deck is not the limit. The chart is the limit. Confirm the loading and the distribution against the manufacturer's load chart for the machine.

Why is erecting and dismantling a mast climber the most dangerous phase?

Erecting and dismantling a mast climber is the most dangerous phase of the work, and the record shows it. While the mast is going up or coming down, it is in partial states, sections added or removed and ties made or broken, and the structure that holds the finished machine together is not all there yet. Instability during dismantling has killed crews, and removing the mast ties out of sequence has dropped masts in collapses that were fatal. The ties are not removed on the way down unless the base and the remaining ties can still support the machine without it tipping.

This is not work for whoever is free. Erecting and dismantling a mast climber is done by a trained, manufacturer-authorized crew, working to the manufacturer's sequence under competent supervision, with fall protection in place for the people doing the build. The people who put these up carry serious requirements, manufacturer certification for erection and dismantling, scaffold safety training, and documented experience, because the judgment in the partial states is where the safety lives. A crew that has only ridden a finished deck does not have it.

Hedge this phase hardest of all. The build sequence, the tie schedule as the mast climbs, and the fall protection for the erectors come from the manufacturer's instructions and the engineer's design, and OSHA's scaffold rules require erection and dismantling under the direction of a competent person by trained workers. Confirm the crew's training, the sequence, and the fall protection against the manufacturer, the engineer, and OSHA before a single mast section goes up.

The erection sequence

The build goes from the bottom up, and the order is the safety. The base goes in first, set level on a foundation that carries the load, with the outriggers deployed and the base jacked plumb. The mast sections stack up from the base, and as the mast climbs past its free-standing height, the wall ties go in on the manufacturer's schedule, so the mast is never carried higher than its free-standing limit without a tie. The platform is rigged to the mast and tested before it carries the crew.

The rule that runs through it is simple to say and deadly to skip: never let the mast stand past its free-standing height without the next tie in place, going up or coming down. On the way up you add ties as you climb. On the way down you remove them in reverse, taking the last tie off only when the mast below it is short enough to stand free, so the mast never becomes a tall, untied pole with a deck on it.

The sequence is the engineer's and the manufacturer's, written for the specific machine, and it is not a place to improvise to save a step. Confirm the erection and dismantling sequence, and the tie schedule that goes with it, against the manufacturer's instructions and the engineer before the build starts.

The safety devices on the drive

A mast climber carries its own backup against a runaway descent. The main one is the overspeed safety device, a parachute brake or block-stop, an independent mechanical brake separate from the drive that watches the platform's descent speed. If the speed climbs past a set limit, the sign of a drive or gearbox failure, it clamps onto the mast and stops the platform. It works whether or not the drive has power, because it is mechanical and independent. That device is the difference between a drive that fails and a platform that falls.

Beyond the overspeed brake, the drive has an operating brake that holds the platform when the motor stops, and the mast carries limit switches and end stops that keep the platform from running off the top of the mast or driving into the base. The controls, the brakes, and the stops are a system, and they get tested on the manufacturer's schedule.

These devices are not a reason to run the machine carelessly, and they do not replace the ties, the base, or the load chart. They are the catch for a mechanical failure. A tripped overspeed brake or an out-of-test device takes the machine out of service until it is checked. Confirm the safety devices and their test intervals against the manufacturer's instructions.

What wind speed shuts down a mast climber?

Wind shuts a mast climber down at the limit the manufacturer sets for the machine, commonly in the range of 25 to 30 mph, about 12 m/s, but the manufacturer's figure for the specific climber and configuration governs, not a single universal number. At the limit, the platform is brought to its out-of-service position and the crew comes off. Storms, lightning, and icing are flat stops.

The platform is a large deck with a lot of area, and that area catches wind. Anything that adds to it makes it worse. Debris netting, mesh, sheeting, or signage on the guardrails turns the deck into a sail and raises the wind load on the mast and the ties, so the wind limit drops once the deck is screened. The building makes it worse again, funneling and accelerating wind around corners and through the gaps between towers, so the speed at the deck high on the facade can far exceed the forecast at the ground.

Plan the day around the wind, set the out-of-service position and the stow procedure before the crew goes up, and when the limit is reached, get the platform parked and the crew off. Confirm the wind limit, the effect of any netting or sheeting, and the out-of-service position against the manufacturer's instructions for the machine.

Fall protection on the platform

On a mast climber the primary fall protection is the deck itself: a guardrailed platform with top rails, mid rails, and toe boards around the perimeter. The crew works inside a guarded deck, which is why a mast climber used as built does not put every worker on a personal fall arrest system the way a swing stage does. The platform is a stable, enclosed work surface, not a deck hanging on ropes.

The exposure shows up when the guardrails come off. Crews drop a guardrail section to load pallets or to work tight to a feature and then do not put it back, and that open edge is where the fall happens. When any part of the guardrail system is removed, or there is a gap, the workers exposed to that gap go on personal fall arrest or restraint until the rail is back. The gap between the deck and the building face is the other one to watch, kept small enough that a worker cannot fall through it, and closed or guarded where it is not.

The harness rules ride on the guardrails. Used intact, the deck protects the crew. Opened up, the protection has to be replaced before anyone works the open edge. Confirm the guardrail configuration, the gap to the face, and when personal fall arrest is required against the manufacturer's instructions and OSHA Subpart L.

The guardrails and the gap to the building

The guardrail system runs the full perimeter of the deck, top rail, mid rail, and toe board, the same elements OSHA requires on a supported scaffold platform. The toe board does double work, keeping a worker's foot on the deck and keeping tools and material from sliding off the edge onto people below. Access gates onto the deck are part of the system, and they close and latch so an opening does not become a fall.

The gap between the deck and the building face is the one people forget. A mast climber works close to the wall, but the deck cannot touch a facade that is being built or finished, so there is a gap, and that gap is a fall and a drop hazard if it is wide. Keep it small, and where the work needs the deck held off the face, close the gap with the platform's own infill or guard it.

A guardrail you can push over is not a guardrail. The rails are part of the machine and rated with it, and a missing or makeshift rail is a removed guardrail, with the fall-protection rules that follow. Confirm the guardrail and toe board configuration and the gap to the face against the manufacturer's instructions and OSHA.

Power, the motor, and cable management

A mast climber runs on electrical power, so the supply is part of the machine's safety. The drive motor is fed from a disconnect at the base, and the cable has to climb with the platform, which is the part that gets damaged. Most machines manage the trailing cable with a festoon or a cable guide that takes up and pays out the cable as the deck moves, so it does not snag, get crushed against the mast, or get cut as the platform climbs.

Keep the supply sized and protected to the manufacturer's requirement, route the cable so it cannot be pinched or pulled, and put the disconnect where the crew can reach it to kill power. A drive that loses power mid-climb is held by its brakes, which is one more reason the brakes and the overspeed device have to work.

Overhead and facade power lines are the hazard that kills outright. The mast, the deck, and the crew are conductive, and a machine working near an energized line does not need to touch it to flash over. Identify the lines before the climber goes up, keep clear, and get them de-energized or guarded where the work brings the deck close. Confirm the power supply, the cable management, and the line clearances against the manufacturer and OSHA.

What does the inspection cover?

A competent person inspects the mast climber before it is used, and the operator runs a pre-use check at the start of each shift. The before-work inspection is the floor, not the ceiling, and the machine does not carry a crew until it passes. On top of the daily check, the machine gets thorough examinations on the manufacturer's schedule, and the erection gets inspected before the platform is handed over for use.

What gets checked runs the same spine that holds the machine up. The wall ties and their anchors into the building. The base, the foundation, the cribbing, and the outriggers, level and bearing. The mast sections and the rack. The drive, the operating brake, and the overspeed safety device. The guardrails and the deck. And the load on the platform against the chart. The erection inspection, before first use, confirms the machine was built to the design and the ties and base are right.

The way this fails is the way every scaffold inspection fails: it gets skipped on day two because the machine looked fine on day one. A tie can work loose, the base can settle after rain, a guardrail can come off and not go back. Inspect it every shift, prove it with the record, and take the machine out of service for anything that fails. Confirm the inspection scope and the examination intervals against the manufacturer, OSHA Subpart L, and the ANSI/SAIA A92.9 standard.

Training: a manufacturer-trained crew, not learn-on-the-job

A mast climber is not a learn-on-the-job machine. The operators are trained and authorized on the specific equipment, and the people who erect and dismantle it carry more, because the build is the dangerous part. Operator training, the kind that ends in an IPAF PAL card through SAIA-accredited courses, covers running the platform, the pre-use inspection, and the emergency descent. Erectors and dismantlers add manufacturer certification for that machine and documented experience on top of it.

Two roles carry weight. The competent person can spot the hazards and has the authority to take the machine out of service, and is the one who inspects it. The qualified person and the engineer design the anchorage, the tie schedule, and the base loading. The competent person runs the daily safety; the engineer decides whether the ties and the base are sound in the first place.

Putting an untrained hand on a mast climber, on the controls or on the build, is how the predictable failures happen. Train the operators, certify the erection crew on the machine, name the competent person, and put the anchorage and base design in qualified hands. Confirm the training and authorization requirements against the manufacturer, OSHA Subpart L, and ANSI/SAIA A92.9 for the specific machine.

Material handling and the masonry load

The reason a crew chooses a mast climber is usually the material, so handling it is the work. Material comes up either loaded onto the deck from the ground by forklift or hoist, or carried by a separate material hoist running alongside, and it gets staged on the deck to the load chart. Masonry is the heavy case, block and stone and mortar by the pallet, and it is exactly the load the chart is written to control.

Stage it to the chart and to the distribution. Bring material up in known weights, place the heaviest over the mast and not out on the cantilever, and keep the running total on the deck under the rated capacity as pallets land and get worked off. Loading from the ground is its own moment, because a forklift or a hoist can put more on the deck in one lift than the crew can use, and the deck has no idea what it is carrying until somebody reads the chart.

Material handling discipline is load-chart discipline with a forklift attached. Confirm the loading method, the staging, and the distribution against the manufacturer's load chart for the machine.

Protecting the people below

A mast climber puts material and tools above the sidewalk and the work below, and a dropped brick from height is lethal. The toe board on the deck is the first line, stopping tools and small material from sliding off the edge. Where material is stacked higher than the toe board, a screen or netting between the toe board and the top rail catches what the toe board cannot, with the trade-off that the netting adds wind area to the deck.

Below the machine, the ground is controlled. Barricade the drop zone so people are not walking under the deck, or build overhead protection where the path below cannot close. Hard hats are required in the area, and they are the last line, not the plan. A hard hat handles a dropped bolt. It does not handle a dropped pallet, which is what the toe boards, screens, and barricades are for.

The base and the mast also sit in the public's path at ground level, so the footprint, the outriggers, and the cabling get protected from traffic and from being bumped. Confirm the falling-object protection and the ground controls against OSHA Subpart L for the material and the site you have.

Common uses: masonry, restoration, and cladding

Mast climbers earn their place on material-heavy facade work that a swing stage cannot carry. Masonry leads the list, block and brick laid up a mid-rise or high-rise wall, where the crew needs a wide deck and a lot of material at the working height. Restoration and repointing on older facades, stone and precast cladding, EIFS and rainscreen panel installation, window and curtain-wall setting, and facade painting and coatings all run on mast climbers for the same reason: the deck is stable, it is large, and it carries weight.

The deck rising to the work is the productivity case. Instead of a crew climbing to a fixed scaffold level or riding a swaying swing stage, the platform brings the workers and the material to the exact height of the course being laid and rises with the wall. On a long facade a twin mast deck spans a full bay, and the crew works off one continuous surface.

The work it is wrong for is the light, fast, move-it-often job. For window cleaning, caulking, and coatings where the load is light and the rig has to relocate quickly, a swing stage is the better tool, covered in the suspended-scaffold guide. Match the machine to the weight of the work.

The failures that drop mast climbers

Mast climber collapses trace back to a short list, and none of it is exotic. Knowing the list is how a competent person inspects fast and catches the real problem instead of the cosmetic one.

The mast carried past its free-standing height with a missing or skipped wall tie, so it buckles or folds away from the wall. A base or a foundation that cannot carry the load, so it settles, throws the mast out of plumb, and overloads the ties. The platform overloaded past the chart, or loaded lopsided on a cantilever, so the mast and the drive overstress or the machine tips. Untrained erection and dismantling, the most dangerous phase, with ties removed out of sequence on the way down. Working through wind that should have stopped the machine. And no daily inspection, so every one of the above rides unnoticed until it fails.

What to document

After a mast climber fails, the first thing pulled is the paperwork behind the anchorage, the ties, the load chart, and the device tests, and any gap in it lands on the contractor. The records prove the anchorage was engineered and the ties were installed, the base loading was checked, the platform was loaded to the chart, the safety devices were tested, the erection was inspected, and the crew was trained. They are what an inspector, an insurer, or an investigator asks for first.

Capture the anchorage and tie design and who engineered it, the tie installation against the schedule, the base and foundation loading, the outrigger and cribbing setup, the load chart and the rated capacity, the safety-device and brake test dates, the erection and pre-use inspections with the defects found, the wind limit and the day's conditions, and the training and authorization of the operators and the erection crew. A field tool like FieldOS keeps the pre-use inspection, the photos of the ties and the base, and the sign-offs attached to the job, so the record is built as the work happens instead of reconstructed afterward.

Common mistakes

• Carrying the mast past its free-standing height, or skipping a wall tie in the schedule.
• A base or foundation that cannot carry the load, set on a membrane, insulation, or an unsized span.
• Overloading the platform past the chart, or piling material on one cantilevered end.
• Erecting or dismantling with an untrained crew, or removing ties out of sequence on the way down.
• Working through wind that the manufacturer's limit said should stop the machine.
• Skipping the daily pre-use inspection because the machine looked fine yesterday.
• Removing a guardrail section to load and not replacing it, or working an open edge without fall arrest.
• Running the machine with a tripped overspeed device or an out-of-test brake.

Field checklist

Standards and references

OSHA does not have a rule written specifically for mast climbers. They meet the definition of a scaffold in 29 CFR 1926.450(b), so they fall under OSHA's scaffold rules in 29 CFR 1926 Subpart L, including the general requirements at 1926.451 for capacity, platform construction, fall protection, falling-object protection, and inspection, and the training requirements at 1926.454. The exact paragraph letters shift between references and editions, so confirm any citation against the current standard and the jurisdiction that adopted it before you put it on a submittal.

The consensus standard for the machine is ANSI/SAIA A92.9 for mast-climbing work platforms, the 2023 edition revising the earlier 2011 version, now structured into A92.9A for design, calculation, safety requirements, and test methods, and A92.9B for safe use and training. Operator training that ends in an IPAF PAL card, delivered through SAIA-accredited courses, and the IPAF and SAIA safe-use guidelines sit alongside it. The anchorage and tie design, the base bearing, and the load path are engineering, designed by a qualified person and the project engineer to the building and the loads, and the manufacturer's instructions govern the machine, the load chart, the wind limit, the tie schedule, and the testing.

Three things carry every mast climber job: the mast is tied to the building within its free-standing limit; the base carries the load and the platform stays within its load chart; and the machine is erected and dismantled by a manufacturer-trained crew. Where the engineer or the manufacturer is stricter than the rule of thumb, they govern. Hedge the ties, the base, the loading, and the erection to OSHA Subpart L, the manufacturer, the engineer, and ANSI/SAIA A92.9, and confirm every specific against the current edition and the authority having jurisdiction.

Units and terms

Mast-climbing work carries its own vocabulary, and the same part goes by more than one name across the standard, the manufacturer's manual, and the jobsite.

A few definitions keep the rest straight. The mast, the ties, the base, and the platform are the system, and the load chart and the safety devices are how it stays inside its limits.

Mast-climbing work platform (MCWP)

A powered deck that climbs a mast bolted to the building on a rack-and-pinion drive; the whole installation, the platform, mast, ties, and base

Rack and pinion

The toothed rack on the mast and the powered pinion gear that meshes with it to drive the platform up and down

Wall tie / free-standing height

The engineered anchor tying the mast to the building, and the height the mast can stand before it needs the first tie

Base frame / foundation load

The frame and the surface that carry the whole load down to the ground or the structure without settling

Rated capacity / load chart

The weight the deck can carry and how it must be distributed, posted for the specific machine and configuration

Single vs twin mast

One mast carrying a cantilevered deck, or two synchronized masts carrying one long continuous deck

Overspeed safety device

The independent mechanical brake, a parachute or block-stop, that clamps the mast if the platform descends too fast

Erection / dismantling

Building up and taking down the machine, the most dangerous phase, done by a manufacturer-trained crew to a set sequence

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