Autolift Garage in Sioux City: Ceiling Clearance Decision Tree

A crew chief for a dirt-track team near Sioux City called us last spring with a 30×40 pole building, twelve-foot sidewalls, and a bare concrete floor — and a question we hear constantly: what fits? He wanted to strip a body shell down for metal work, store a finished car overhead, and still park the hauler pickup underneath. That is three jobs from one machine, and the answer depends almost entirely on numbers he had not measured yet. Planning an autolift garage is less about picking a favorite brand and more about walking a decision tree from budget to ceiling to door swing until only one or two configurations are left standing. Here is how we walk it.

Step one: what is the lift actually for?

Before capacity, before brand, decide what percentage of the lift’s life is storage versus work. These pull in opposite directions. Storage rewards a four-post: it rolls up, drives on, locks at height, and the vehicle sits stable on its own tires for months without loading the suspension in odd ways. Work rewards a two-post: wheels hang free, the whole underside is open, and there is nothing under the rocker panel to fight when you are cutting out rust or fitting a new floor pan.

For a restoration and metal-work project, the two-post wins on access and loses on storage. A shell sitting on a two-post for eight months ties up a machine and a footprint. What we usually recommend for a mixed-use autolift garage this size is a four-post as the primary and a mid-rise scissor as the second unit — the four-post handles storage and drive-on brake or fluid work, the scissor gets rolled under whatever is on the bench schedule that week. If the budget only supports one unit and metal work is the point, buy the two-post and accept that storage will be a compromise. Being honest about the ratio up front saves people from owning the wrong machine.

Step two: measure the ceiling, not the sidewall

Twelve-foot sidewalls sound generous, and in a pole building they usually are — but sidewall height is not clearance height. Measure to the lowest permanent obstruction in the lift footprint. In an ag-style building that is often a purlin, a truss chord, a wire run, or a hanging light. A trussed roof with a scissor web can eat eighteen inches or more over the center of the span. We have seen a customer order a lift based on a peak measurement and discover on install day that the truss bottom chord sits at ten foot two.

Do the stacking math with real numbers. A stored vehicle roof height plus the runway height plus the working clearance under the lower vehicle has to fit under that lowest obstruction. A typical sedan is about 57 inches tall; a crew-cab pickup runs 75 to 80 inches. Four-post runways add roughly 8 to 10 inches at the lowest lock. If you want a pickup underneath and a car on top, you need roughly 80 inches of under-clearance plus runway plus 60 inches of car — that is over twelve feet before you account for anything hanging down. In a twelve-foot autolift garage, the realistic answer is a car over a car, or a car over a pickup only if the roof is high in the center and you position accordingly.

Step three: door swing, door opening, and approach

Door swing is the detail that ruins otherwise good layouts. A two-post asymmetric design rotates the columns so the vehicle sits back relative to the column faces, giving you room to open a car door and get in and out. Symmetric spacing centers the vehicle and pinches the doors. For a restoration project where you are in and out of the interior twenty times a day, asymmetric is not a luxury.

Then there is the building’s own door. Measure the clear opening height and width, and measure how far into the building the overhead door track and opener assembly project. On a 30×40 shop with a fourteen-foot-wide door, the lift needs to sit far enough back that the door can travel and the opener rail is clear of the runways or overhead beam. We laid out one Sioux City shop where the lift had to move four feet deeper into the building than the owner planned, purely because of the door track — and that four feet came out of his workbench wall. Check approach angle too: a low-clearance race car or a lowered street car needs shallow approach ramps, and standard four-post ramps often will not clear a front splitter. Extended or low-profile ramps are a cheap option at order time and expensive to add later.

Step four: capacity, and why 7,000 lb is a common target

Most hobby and restoration buildings land in the 7,000 to 9,000 lb range because that covers passenger cars, most SUVs, and half-ton pickups with margin. Do not buy right at the edge. Look up curb weight for the heaviest vehicle you will realistically put up there, add fuel and cargo, and then add a comfortable buffer. A crew-cab four-wheel-drive pickup can easily hit 6,500 lb loaded, which makes a 7,000 lb unit uncomfortably tight.

The other capacity question is distribution. Four-post ratings assume the load spread across all four runway wheel contact points; a two-post rating assumes balanced arm loading. Put a stripped shell on with the drivetrain out and the balance point shifts dramatically forward or rearward — something restoration people run into constantly. That is a reason to favor a two-post with long-reach adjustable arms so you can chase the actual center of gravity rather than the factory-assumed one. For an autolift garage doing frame-off work, we generally push people up one capacity tier from what they think they need. The price difference between tiers is modest; the consequence of running a lift near its limit with an unbalanced load is not. Our overview of choosing lift capacity goes deeper on the math.

Step five: the slab, and what a pole building really has

Two-post lifts anchor into concrete and transfer serious overturning load into a handful of wedge anchors. Manufacturers typically call for a minimum thickness and strength — commonly four inches of cured 3,000 psi concrete for lighter units, more as capacity climbs — plus minimum distance from any slab edge, control joint, or saw cut. Pole building floors are frequently poured thinner than a commercial slab and often have a perimeter that is not tied to anything.

Core testing is the only way to know. We core, measure actual thickness, and check for rebar or mesh. If it comes back short, the fix is cutting out a section and pouring a proper pad with reinforcement, which takes days for cure before we can set anything. Four-post lifts are more forgiving because they are free-standing and distribute load through four base plates rather than fighting overturn — that is one legitimate reason a four-post is the better answer in a marginal-slab building even when a two-post would be the better work platform. If you are still pouring the floor, this is the moment to spend a little more: thicken the pad in the lift footprint, add rebar, and keep control joints out of the anchor zone. Our article on concrete requirements for lift installation lays out the numbers.

Step six: power, air, and the stuff people forget

Most home and shop lifts run a 220V single-phase motor on a dedicated circuit; some smaller units accept 110V with reduced cycle speed. Pull the circuit while the walls are open and put the disconnect where you can actually reach it. Air matters too — most two-post lock releases are air-actuated, so you need a line to the columns or you are pulling a release cable by hand every cycle. Neither of these is expensive during construction and both are irritating to retrofit through a finished steel wall.

Think about lighting while you are at it. Once a vehicle is at working height in a pole building, the overhead lights are above the car and everything underneath is in shadow. Ceiling fixtures positioned beside the lift footprint rather than over it, plus a couple of switched outlets at column height for drop lights, transforms how the space works. Heat is the last one. Metal work in a Sioux City winter without a heater is miserable, and a hanging unit heater is another obstruction to account for in your clearance math. We plan an autolift garage as a whole system — lift, slab, power, air, light, heat — because getting the lift right and the rest wrong still leaves you with a shop you do not enjoy using.

Where the decision tree usually ends

For that crew chief with the 30×40 and twelve-foot sidewalls, the tree ended at a 9,000 lb four-post with extended low-profile ramps and a caster kit, plus a mid-rise scissor for teardown work. The four-post handles storage and does not care about the slab thickness question. The scissor rolls where it is needed and stores flat against the wall. Two machines cost more than one, but neither one is being asked to do a job it is bad at, and the total was less than a heavy-duty two-post plus the pit-and-pour his floor would have needed.

Your answer may land somewhere else — that is the point of walking the tree instead of shopping a brochure. What we ask for is simple: ceiling height to the lowest obstruction, clear floor dimensions, door opening and track projection, heaviest vehicle you will lift, and whether the slab is poured yet. With those five numbers we can narrow an autolift garage plan to one or two real configurations and tell you what each will and will not do. We are in Ames, we cover northwest Iowa regularly, and we would rather talk you out of the wrong lift than sell it to you. Call 800-674-9302 and let us run the numbers with you.