Choosing the wrong crane size is one of the most expensive mistakes a contractor can make on lift day. Too small and the crane cannot make the lift, which means a wasted mobilization, a rescheduled crew, and a second crane call with a bigger machine. Too large and you are paying for tonnage, boom length, and mobilization costs that the job does not require.
The right crane is the one that can handle every lift on the job with a safe margin, reach every placement point from a practical setup position, and access the site without tearing up the road or collapsing a culvert. Here is how to figure out what that crane is before you pick up the phone.
The Three Numbers That Determine Crane Size
Every crane selection comes down to three variables. Get these right and the crane company can match you to the correct machine in minutes.
1. Load Weight
This is the total weight that the crane will pick up, not just the object itself. Load weight includes:
- The object being lifted (truss, beam, HVAC unit, modular section, equipment)
- Any rigging hardware attached to the load (slings, shackles, spreader bars)
- The hook block and wire rope hanging from the boom tip
The object weight should come from the manufacturer’s specifications or the supplier’s shipping documents, not from an estimate. A W12x26 steel beam weighs 26 pounds per foot. A 20-foot beam weighs 520 pounds. A 30-foot beam weighs 780 pounds. These are not numbers to guess at.
For trusses, the truss manufacturer provides the weight per truss. For HVAC units, the shipping weight is on the data plate or the spec sheet. For modular home sections, the factory provides module weights as part of the delivery documentation.
Add the rigging weight on top. A basic rigging setup (two slings, two shackles, and the hook block) might add 300 to 800 pounds depending on the crane size. A spreader bar for a modular home set can add 1,000 pounds or more.
The total loaded weight is what the crane’s load chart must support at the required radius.
2. Lift Radius
The radius is the horizontal distance from the crane’s center pin to the load’s final position. This is not the distance from the crane’s bumper or from the outriggers. It is measured from the pivot point of the crane’s upper works.
To determine the radius, you need to know two things: where the crane will set up and where the load needs to go.
On a simple job (a boom truck in the driveway setting trusses on the house next to it), the radius might be 20 to 35 feet. On a more complex job (a crane in the street placing an HVAC unit on the back of a commercial building), the radius might be 50 to 70 feet or more.
The radius at the pickup point (where the load starts) and the radius at the placement point (where the load ends) may be different. The crane’s capacity must cover both, but the critical radius is the longer one because that is where capacity is lowest.
If you are not sure of the exact radius, measure the distance from the most likely crane setup point to the farthest placement location. Add 5 to 10 feet as a buffer for the difference between the crane’s center pin and its physical position. Give that number to the crane company.
3. Lift Height
The crane’s boom needs to be long enough to reach the required height while maintaining the necessary radius. Height and radius are connected through boom angle: a longer radius at the same height requires a longer boom at a lower angle, which reduces capacity.
For residential truss sets, the lift height is typically 25 to 45 feet (roof peak height plus clearance above the structure). For commercial rooftop equipment, it might be 30 to 60 feet. For modular home setting, the height is relatively low (foundation height plus clearance), but the boom length may still be significant because of the radius.
The crane company uses all three numbers (weight, radius, height) to select a boom length and configuration that keeps the lift within the crane’s load chart.
Common Job Types and Typical Crane Sizes
These are general ranges based on typical residential and light commercial projects in Vermont. Your specific job may require more or less crane depending on the three variables above.
Residential Roof Truss Setting
Trusses for single-family homes typically weigh 150 to 600 pounds each. The crane sets up in the driveway or yard, 20 to 40 feet from the building. Lift height is 25 to 45 feet.
Typical crane: A boom truck in the 15 to 30-ton class handles most residential truss sets. This is the most common and most affordable crane option for residential work.
Residential Steel Beam Placement
Individual beams for residential openings (garage headers, basement carrying beams, ridge beams) typically weigh 300 to 1,500 pounds. Radius is usually short (15 to 30 feet) because the crane can set up close to the structure.
Typical crane: A boom truck in the 15 to 25-ton class. For single-beam placements, this is often a half-day job or less.
HVAC Rooftop Unit Placement
Residential and small commercial HVAC units range from 200 to 3,000 pounds. The crane needs to reach the rooftop from ground level, with the radius determined by where the crane can park relative to the building.
Typical crane: A boom truck for units under 2,000 pounds on single-story or two-story buildings. A mid-size hydraulic crane (30 to 50 tons) for heavier units on taller buildings or at longer radii.
Modular Home Setting
Modular sections weigh 15,000 to 40,000 pounds each. The crane needs enough capacity to handle the heaviest module at the maximum radius (the farthest point on the foundation from the crane setup position). Boom length depends on the foundation height and the distance.
Typical crane: A 50 to 100-ton hydraulic crane, depending on module weight and site geometry. This is one of the heaviest residential crane jobs and requires careful pre-planning.
Tree Removal (Crane-Assisted)
Tree sections cut during crane-assisted removal typically weigh 1,000 to 5,000 pounds per section, depending on the species, diameter, and length. The crane needs enough boom to reach above the canopy height and enough capacity at that height and radius to hold the section while the climber makes the cut.
Typical crane: A boom truck in the 20 to 35-ton class for trees up to 60 feet. A mid-size hydraulic crane for taller trees or heavier hardwood species.
Commercial Steel Erection
Structural steel for commercial buildings involves beams, columns, and connection assemblies that can weigh 2,000 to 20,000 pounds or more per piece. Radii can be 40 to 80 feet on larger buildings. Heights depend on the number of stories.
Typical crane: A 40 to 100-ton hydraulic crane for most light commercial work. Multi-story or heavy industrial steel may require larger cranes.
How to Avoid the Two Most Common Sizing Mistakes
Mistake 1: Choosing by Tonnage Alone
A crane’s tonnage rating is its maximum capacity, which occurs at the shortest radius and the shortest boom length. That number is almost never the capacity you are working with during the actual lift.
A 30-ton crane does not lift 30 tons at every radius. At a 40-foot radius, it might lift 8 tons. At a 60-foot radius, it might lift 4 tons. Choosing a crane because “it’s rated for 30 tons and my load is 5 tons” without checking the capacity at your specific radius is how undersized cranes end up on job sites.
Always provide the radius and height along with the load weight. The crane company will match the machine to the actual lift, not just the tonnage label.
Mistake 2: Ignoring Site Access
The crane has to reach the setup point before it can make any lift. If the access road, driveway, or job site cannot accommodate the crane that the load chart requires, you have a problem.
A 60-ton crane on a multi-axle carrier may be the right machine for the lift but the wrong machine for the site. If the driveway is too narrow, too steep, or too soft, the crane cannot get in. At that point, the options are either to improve the access (gravel, grading, tree trimming) or to use a different crane configuration that can reach the site.
On rural Vermont properties, site access is the constraint that overrides everything else. A crane company that knows local roads and job site conditions can recommend the right balance between crane capacity and site accessibility before you commit to a booking.
Let the Crane Company Do the Matching
You do not need to select the crane yourself. That is what the crane company does. Your job is to provide the best possible information:
- What are you lifting? (Type, dimensions, and weight from documentation)
- Where is it going? (Distance from the likely crane setup point to the placement location)
- How high? (Height of the placement point above ground level)
- What does the site look like? (Driveway width, surface type, grade, overhead lines, ground conditions)
With those four answers, an experienced crane company can match the right machine to the job, confirm the lift is within the load chart, and quote the job accurately. The better the information you provide upfront, the less likely you are to end up with the wrong crane on lift day.
See the range of equipment and project types we work with in our portfolio, or learn more about our company and our approach to lift planning.
Call Green Mountain Crane Service at (802) 370-5361 or reach out online to discuss what crane fits your next project.