- We encoded the two jobs we run most, a concrete slab and a bolted steel building on top of it, as directed graphs with 40 steps and their dependencies.
- Each step carries tools, materials, crew size, a duration distribution, and its known failure modes.
- Hands-on crew work is a small share of the timeline. From order to a scheduled install takes a median of 44 days. Raising the building itself takes about 14 crew-hours.
- The written checklists meant to verify field work are rarely completed, which is the strongest argument we have for recording the work on video.
Definition. A task graph is a directed graph where each node is a step of a job and each edge means one step must finish before the next can start.
Why do construction robots need a task graph?
Robot learning works best when the task is well defined: what counts as done, what comes before what, and what failure looks like. Most construction knowledge is not written anywhere. It lives in crews' heads, in phone calls, and in a pile of per-job paperwork.
Before collecting video of crews doing the work, we wanted a skeleton to hang that video on: a task graph that says which step a clip belongs to, what had to be true before it started, and what has to be true when it ends. This post describes that graph.
How are a slab and a steel building built?
The slab. A concrete slab is the flat foundation a building sits on. A crew grades the dirt, builds a wooden frame (forms) to the building's exact footprint, lays a plastic vapor barrier and steel reinforcement, pours concrete, smooths it, cuts control joints so cracks happen in straight lines, and lets it cure for about five days before anything heavy goes on it.
The building. Our buildings are prefabricated steel kits: garages, workshops, carports, and barndominiums (steel-frame homes). A manufacturer cuts and ships the parts. A crew lays out base rails on the slab, squares them, raises and braces the frame, anchors it to the concrete, adds horizontal members (purlins on the roof, girts on the walls), then screws on roof and wall panels, trim, doors, and windows.
What data did we use?
We built the graph from three kinds of sources. First, timestamped stage changes on 2,221 orders in our order system, 1,281 of them complete. Second, 51 internal documents: crew procedures, subcontract scopes of work, slab detail drawings, and manufacturer installation guides. Third, quality records: order holds, cancellations, and their reason codes, and an audit of concrete job paperwork. Where neither our timestamps nor our documents gave a duration, we used an industry reference value and labeled it as such.
What does the construction task graph look like?
Where does the time go on a construction job?
Raising a typical garage takes about 14 hands-on hours for a crew of two to four. The slab adds roughly two to three crew-days spread across a week, most of it waiting for concrete to cure. Yet the median time from order to a scheduled install is 44 days. The calendar goes to engineering drawings, permits, manufacturing, and scheduling, not to the physical work.
For automation this splits the problem in two. The long, expensive waits are planning and coordination problems that software can attack today. The short, physical steps are where robots eventually come in.
Which construction tasks are easiest to automate?
Base rail layout, squaring, anchoring, purlins, and sheeting are each one to four hours, done the same way on every job, with clear pass criteria: diagonals that match within a tolerance, anchors at a set edge distance, fasteners on a set pattern. These are natural first targets for camera-based verification, and later for robotic assistance.
Why are paper checklists not enough?
Each slab is supposed to have a signed checklist before work begins and another when it is complete. In an audit of 486 concrete jobs, the pre-site checklist was on file for 7% and the completion checklist for 2%. The steps happened. The records did not.
This is the central reason we are putting cameras on crews. Video records what was done whether or not anyone fills out a form, and it can be tied directly to the step in this graph and to the job's outcome.
What are the limitations?
Timestamped history in our order system starts in July 2026. Staff often advance an order through several stages at once, so measured durations are calendar waits around groups of steps, not timings of single steps. Twenty-one of the forty step durations are industry references rather than our own measurements. Crew-level timing for steel frame erection is not documented anywhere and will come from video.
What comes next?
The graph is the labeling schema for our crew footage. Each recorded clip will be segmented into these steps, timed against these distributions, and tied to the job's result. That turns hours of raw video into supervised examples of a known task with a known outcome. Research partners can request the graph in machine-readable form.
Durations are medians. Measured steps use order stage timestamps from July to October 2026. Industry references are labeled in the data file.
Frequently asked questions
What is a construction task graph?
A directed graph of every step in a job, where an edge means one step must finish before the next starts. Each step carries tools, crew size, duration, and failure modes.
How long does it take to build a steel building?
Raising a typical garage frame takes about 14 crew-hours. The median time from order to a scheduled install is 44 days, mostly permits, drawings, and manufacturing.
Which construction tasks will robots do first?
Short, repeatable steps with clear pass criteria: base rail layout, squaring, anchoring, purlins, and sheeting.
Why use video instead of checklists?
In an audit of 486 concrete jobs, the signed completion checklist was on file for only 2%. Video records the work whether or not anyone fills out a form.
Sources
Related research
- AI Data Labeling for Construction Robotics
- Physical AI: The Seven Pillars Self-Driving Proved
- Construction AI: An LLM Benchmark on 387 Questions
- Construction Progress Monitoring with VLMs
- How we capture construction data
- The Metal America Index map