2nd Day Setup: How to Re-Establish Grade on a Multi-Day Job
Quick Answer
Your laser doesn't remember yesterday. Here's the right way to pick up exactly where you left off — every time.
Your laser doesn't remember yesterday. Here's the right way to pick up exactly where you left off — every time.
The 2nd Day Problem
You spent day one establishing your laser height, grading your shot, and getting the site dialed in. Day two, you set up the laser again — but can you be sure you're at the exact same instrument height? Even a 0.05-foot error in instrument setup compounds across the site.
If you're grading to a 0.10-foot tolerance (typical for road base work), a 0.07-foot instrument height error puts you out of spec immediately — and you may not notice until the paving crew is on site.
The solution is a Temporary Benchmark (TBM): a physical point on the job site with a known elevation that you can re-shoot to re-establish instrument height with confidence, every day for the duration of the project.
What Is a TBM (Temporary Benchmark)?
A Temporary Benchmark (TBM) is any stable, durable point with a known elevation that you establish on the job site at the start of a project and protect throughout construction. It serves as your portable elevation reference — your "what everything else is measured from."
A TBM differs from a permanent benchmark (a brass disk set by a surveyor in concrete or bedrock) in that it doesn't need to last decades. It needs to last the job — which might be two days or six months. But it must be:
- Stable — won't move, settle, or get knocked over by equipment
- Accessible — you can get to it with a grade rod each morning
- Protected — marked so the crew won't disturb or drive over it
- Documented — elevation recorded in your field notes
Hub and Tack
Wooden hub driven flush to grade, brass tack at exact elevation point. Classic, cheap, effective on soil sites.
Rebar in Concrete
Bent rebar driven into a wet concrete pad or left in a structure. Excellent durability on long jobs.
Painted Curb or Structure
A paint mark on an existing curb, wall, or manhole lid. Quick to establish; fragile — needs protection.
Step-by-Step: Re-Establishing Grade with the Topcon RL-H5A
The Topcon RL-H5A is one of the most common rotary lasers on California job sites — reliable, water-resistant, and straightforward to operate. Here's the exact process for a 2nd-day setup.
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1
Set up the tripod and laser in a good working position
Place the tripod in a stable, central location that gives clear line of sight to your TBM and your working area. It doesn't need to be in the exact same position as day one — only the instrument height matters for re-establishing grade, not position.
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2
Mount and level the RL-H5A
The RL-H5A is self-leveling within ±10% grade. Place it on the tripod head, turn it on, and wait for the leveling indicator light to confirm it's leveled. This takes 5–10 seconds. Do not move the tripod after this point.
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3
Walk to your TBM with the grade rod and receiver
Place the grade rod on the exact TBM point — the hub tack, the rebar tip, or the paint mark. Make sure the rod base is sitting on the TBM itself, not on soil next to it.
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4
Read the receiver height on the rod
Hold the rod plumb and slide the receiver up and down until it locks on the beam (center signal on the receiver display). Read the height where the receiver locked — this is your rod reading at the TBM.
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5
Calculate instrument height (HI)
HI = TBM Elevation + Rod Reading at TBM
Example: TBM elevation = 104.250 ft
Rod reading at TBM = 5.47 ft
HI = 104.250 + 5.47 = 109.720 ftThis is the elevation of the laser beam plane. Write it down.
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6
Calculate rod readings for target elevations
Rod Reading = HI − Target Elevation
Example: HI = 109.720 ft
Target elevation (top of subbase) = 103.400 ft
Rod reading = 109.720 − 103.400 = 6.320 ftMark this height on the grade rod (tape or permanent marker). When the receiver locks at 6.32 on the rod, the rod base is at 103.40.
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7
Verify with a second known point
If there's a second TBM or a known elevation point on the site (curb invert, catch basin rim), take a second shot and check your HI calculation. If it matches, you're confident. If it doesn't, find the discrepancy before grading.
Common 2nd-Day Setup Mistakes
| Mistake | What Goes Wrong | Fix |
|---|---|---|
| Setting the rod on soil next to the TBM instead of on the TBM itself | Rod sinks slightly or sits at a different elevation than the benchmark point | Always put the rod on the physical TBM mark — hub tack, rebar tip, or painted mark |
| Not checking that the laser has fully leveled before taking the TBM shot | Beam is still settling → rod reading is off → all subsequent calculations are wrong | Wait for the RL-H5A leveling indicator light to confirm before shooting the TBM |
| Moving the tripod after taking the TBM shot | HI changes; TBM reading is now invalid | Never move the tripod after reading the TBM. Move it only when you need to relocate, then re-shoot the TBM |
| Not protecting the TBM over the weekend or overnight | Equipment runs over it, crew members pull it, or frost heave shifts it | Mark TBMs clearly with lath and flagging tape; tell the foreman; establish a backup TBM |
| Recording HI without noting which laser position it applies to | Confusion if the laser is moved mid-day; wrong HI used for afternoon work | Write down HI each time the laser is moved: "Laser position A, HI = 109.72" |
Keeping Grade Consistent Across Days
Working with Multiple Laser Positions
On large sites, you'll move the laser multiple times per day. Each time, re-shoot the TBM to confirm HI. It takes 5 minutes and saves hours of rework.
Grade Tolerance Reference
- Subgrade: ±0.10 ft typical tolerance
- Road base (aggregate): ±0.05 ft
- Concrete subbase: ±0.05 ft
- Finished asphalt grade: ±0.04 ft (CalTrans standard)
The tighter the tolerance, the more critical your 2nd-day TBM accuracy becomes. Subgrade at ±0.10 is forgiving; finished grade at ±0.04 is not.
Recommended Equipment
Topcon RL-H5A Self-Leveling Rotary Laser
The standard for California grading work. IP66 water resistance, ±10% self-leveling range, 800m working diameter. The most common laser on CA job sites for good reason.
Tripod + Grade Rod Package
Heavy-duty aluminum tripod and 25-foot direct reading grade rod — everything you need for TBM setup and daily grade checks.
Express Tools specializes in laser grade-control and layout equipment. For field documentation, Gradelog organizes your job logs, calibration records, and as-built reports — free to start.
Outfit Your Crew for Every Day of the Job
Express Tools carries rotary lasers, grade receivers, tripods, and accessories. We know the equipment — because we've used it.
Shop Rotary Lasers →For this application, Gradelog provides AI-assisted setup guides, calibration reminders, and job documentation. Free to start.
