Fire-Rated Shaft Enclosure Break-Even: $106K Monthly Revenue

Fixed costs $74.7K/mo Monthly base burn

Contribution margin 71.5% After variable costs

Break-even revenue $104.4K/mo Revenue needed

Break-even timing Month 8 Model break point

Break-even calculator

Use this calculator to test monthly revenue against variable expenses and fixed costs for shaft enclosure work.

Lean Base Full

Monthly revenue Revenue sets the margin pool that pays overhead. $ Slow month Busy month Variable expenses Use direct job costs that rise with each project. $ Light costs Heavy costs

Money available to cover fixed costs $275,216 $369,417 revenue - $94,201 variable expenses

Margin ratio

75%

Covers fixed costs

Yes

Fixed monthly costs Use the monthly cost base the margin must cover. $ Lean overhead Scaled overhead

Break-even chart Revenue Total costs

Which shaft enclosure contractor expenses stay fixed, and which move with sales?

Cost classification

Break-even only works if each expense follows the right behavior. Here, materials and job fees move with revenue, while rent and insurance hit cash every month whether crews are busy or idle.

Expense	Cost	Break-Even Treatment	Common Mistake
Fire-Rated Sealants and Specialized Fasteners	Variable	Model at 12.5% of first-year revenue, falling to 10.5% by the mature year.	Treating specialty materials as overhead instead of job-driven usage.
Job-Specific Safety and Testing Consumables	Variable	Model at 6.5% of first-year revenue, tied to active projects and inspections.	Leaving consumables out of gross margin and overstating contribution.
Project-Specific Travel and Logistics	Variable	Model at 5.0% of first-year revenue because travel rises with job count and site distance.	Spreading travel evenly across months with no link to backlog.
Third-Party Inspection and Certification Fees	Variable	Model at 4.5% of first-year revenue, then reduce as scale improves.	Forgetting required inspection fees until project closeout.
Warehouse and Office Rent	Fixed	Include $6,500 per month from Month 1 through Month 60.	Reducing rent during slow months even though the lease still runs.
General Liability and Workers Comp Insurance	Fixed	Include $4,200 per month as baseline overhead for operating break-even.	Moving insurance below the line and missing monthly cash burn.
Vehicle Fleet Maintenance and Fuel	Semi-variable	Keep the $2,800 monthly base, but test fuel sensitivity as job volume rises.	Modeling all vehicle spend as fixed when site activity drives fuel use.
Lead Installation Foreman and Certified Installer Payroll	Semi-fixed	Step payroll up as crews are staffed ahead of backlog; idle crew time still affects break-even.	Treating idle crew payroll as job-level labor when it still hits cash each month.

How does break-even change between lean, base, and full operating cases for fire-rated shaft enclosure work?

Scenario table

As sales grow, variable costs take a smaller share of revenue, but fixed payroll and overhead climb with more crews. That’s why lean carries launch risk, base hits Month 8 break-even, and full builds a wider cushion.

Planning assumptions only; actual results will move with project mix, labor loading, and timing.

Scenario	Monthly Revenue	Variable Costs	Fixed Costs	CM Ratio	Operating Profit	Break-Even Signal
Launch-discipline lean case	$108.2k	$30.8k	$85.0k	71.5%	-$7.7k	Still below a safe cushion; keep overhead tight.
Steady-pipeline base case	$236.8k	$63.9k	$108.1k	73.0%	$64.8k	Break-even lands in Month 8 with room to cover fixed costs.
Multi-crew full case	$753.5k	$169.5k	$238.4k	77.5%	$345.6k	Strong cushion; the backlog supports added crew costs.

What pushes break-even past Month 8?

Stress test

This plan has very little room for slippage: Year 1 revenue sits only about $20K above break-even, so underused crews, rework, or permit delays can erase the cushion fast. If overhead and margin both worsen, break-even moves past Month 8.

Stress Case	Changed Assumption	Break-Even Revenue	Revenue Gap	Risk Signal
Current plan	No change.	$1,062K	$20K cushion	Break-even is close to plan revenue.
Revenue shortfall	Year 1 revenue lands 20% below plan.	$1,062K	$196K gap	Underused crews burn through the cushion fast.
Fixed-cost pressure	Fixed overhead rises 10% to about $835K.	$1,168K	$86K gap	Higher rent, insurance, and fleet costs widen the hole.
Margin pressure	Variable expenses rise from 28.5% to 33.5%.	$1,142K	$60K gap	Waste, rework, and failed inspections cut contribution fast.
Combined pressure	Fixed overhead rises 10% and variable burden rises to 33.5%.	$1,256K	$174K gap	Combined pressure can push break-even beyond Month 8.

What should you verify before you sign the lease, buy the fleet, and hire the full crew?

Founder checklist

Yes—test the big commitments against the break-even plan first. If backlog, vendor terms, and cash do not support the Year 1 load, the Month 8 break-even target will slip fast.

1Backlog Proof$1.298M Y1

Confirm signed work can carry the Year 1 revenue plan before you lock in two foremen and four certified installers, since break-even lands in Month 8.

2Lease Load$10.7K/mo

Verify rent near $6,500 and insurance near $4,200 before signing, and check bonding early if you want to bid larger commercial jobs.

3Unit Margin71.5% CM

Hold sealants, fasteners, testing, travel, and inspection fees near the model, because those costs are what protect the margin that pays fixed overhead.

4Crew Ramp6 field FTE

Only ramp to six field FTE when backlog can keep them busy and inspectors are lined up before field mobilization.

5Cash Buffer$458K by Month 7

Keep at least $458K of working capital through Month 7, because that is where the model bottoms out and payback still runs 22 months.

6Launch Stack$271K capex

Lock supplier terms on sealants, fasteners, safety consumables, and testing supplies before you buy the $271K fleet, lift, tool, IT, and safety stack, and keep Year 1 marketing near $15K unless CAC beats $1,200.