Introduction
Hypothetical case study — illustrative example, not a real project. The scenario below is invented to demonstrate the full estimating workflow end to end: takeoff, sheet count, panel specification, budget, and the decisions in between. The numbers follow the same math as the rest of this guide series, so you can verify every step.
The OSB Sheet Calculator handles the core calculation: dimensions in, sheet count out. This walkthrough shows how that calculation fits into a realistic project — from the first tape measurement to the delivery ticket.
The Scenario
Hypothetical case study — illustrative example, not a real project. Imagine a detached 20 × 30 ft single-story workshop: slab-on-grade is already poured, walls are framed at 16-in centers, 8-ft walls, and the roof is a simple 6:12 gable with 1-ft overhangs. The builder needs a complete sheathing takeoff — subfloor (over a framed floor deck on the slab), wall sheathing, and roof decking — plus a material budget. All figures below are illustrative.
Step 1: The Takeoff
Three surfaces, measured separately per the estimating guide method:
Subfloor
Gross: 20 × 30 = 600 sq ft. Openings: none (stair opening framed but sheathed over, cut later — the safer estimating choice). Net: 600 sq ft. Sheets: 600 ÷ 32 = 18.75 → 19. Waste 10%: 19 × 1.10 = 20.9 → 21 sheets of 23/32-in T&G.
Walls
Two 30-ft walls: 2 × (30 × 8) = 480 sq ft. Two 20-ft walls: 2 × (20 × 8) = 320 sq ft. Gross: 800 sq ft. Deductions: one 3×7-ft door (21 sq ft), four 3×4-ft windows (48 sq ft), one 8×7-ft garage door (56 sq ft) = 125 sq ft. Net: 675 sq ft. Gables: two triangles, base 20 ft, height 5 ft (6:12 over a 20-ft span gives 5 ft of rise) = 2 × (20 × 5 ÷ 2) = 100 sq ft. Total net: 775 sq ft. Sheets: 775 ÷ 32 = 24.2 → 25. Waste 12%: 25 × 1.12 = 28 → 28 sheets of 7/16-in square-edge.
Roof
Each plane: horizontal run = (20 ÷ 2) + 1 ft overhang = 11 ft; slope = 11 × 1.118 (6:12 factor) = 12.30 ft; width = 30 + 2 ft overhangs = 32 ft; plane = 12.30 × 32 = 393.6 sq ft. Two planes: 787.2 sq ft. Sheets: 787.2 ÷ 32 = 24.6 → 25. Waste 12%: 25 × 1.12 = 28 → 28 sheets of 7/16-in square-edge.
Total: 21 + 28 + 28 = 77 sheets. The arithmetic for each surface follows the formula guide.
Step 2: Panel Specification
Following the material guide decision table and confirming minimums with the (hypothetical) local AHJ per the code-compliance guide:
| Surface | Panel specified | Span rating | Sheets |
|---|---|---|---|
| Subfloor | 23/32-in T&G, Exposure 1 | 32/16 | 21 |
| Walls | 7/16-in square-edge, Exposure 1 | 24/16 | 28 |
| Roof | 7/16-in square-edge, Exposure 1 | 24/16 | 28 |
Step 3: The Budget
Using typical mid-range prices from the cost guide (illustrative — actual prices vary by region and market):
| Line item | Math | Cost |
|---|---|---|
| Subfloor panels | 21 × $29.50 | $619.50 |
| Wall panels | 28 × $15.50 | $434.00 |
| Roof panels | 28 × $15.50 | $434.00 |
| Fasteners (nails, ~4 boxes) | — | $100–$140 |
| Subfloor adhesive | 6 tubes | $30–$40 |
| H-clips (roof) | 2 boxes | $30–$45 |
| Delivery (77 sheets, one trip) | — | $75–$125 |
| Estimated total | $1,723–$1,838 |
Step 4: Decisions and Lessons
- One delivery, not three. Ordering all 77 sheets at once saved two delivery fees (~$150–$250) and locked the price — panel prices can move mid-project.
- Wall waste at 12%, not 10%. The five openings destroyed nearly four sheets of coverage; 10% would have left the job one sheet short.
- The gable check. The two gable triangles added 100 sq ft — over three sheets. Skipping them (the classic mistake from the common mistakes guide) would have meant a mid-job order.
- Kept 3 spare sheets on site. The waste allowance covered the estimate; the physical spares covered a rain-damaged sheet and a miscut without a store run.
- Sheathing inspection scheduled before roofing. The (hypothetical) jurisdiction inspects nailing before cover-up — the roof deck sat one extra day, sequenced deliberately.
Related Guides
- Estimating Guide — the takeoff method this walkthrough follows.
- Cost Guide — typical prices and budget line items.
- Complete Guide — the full overview of the OSB Sheet Calculator.
- Checklist — the pre-order verification this project used.
- Formula Explained — the arithmetic behind each surface.
- Pro Tips — installation practices for the panels ordered here.
Frequently Asked Questions
Is this case study a real project?
No — it is explicitly a hypothetical, illustrative example built to demonstrate the estimating workflow. The math is real and follows the same formulas as the rest of the guide series, but the project, prices, and decisions are invented.
How many sheets did the example workshop need?
77 total: 21 for the subfloor (23/32-in T&G), 28 for walls and gables (7/16-in), and 28 for the roof deck (7/16-in) — each with its surface-appropriate waste rate.
What did the sheathing cost in the example?
Approximately $1,723–$1,838 all-in at typical mid-range prices: ~$1,488 in panels plus fasteners, adhesive, H-clips, and one delivery. Actual prices vary by region and market.
Why was wall waste 12% instead of 10%?
Five openings (door, windows, garage door) destroyed nearly four sheets of coverage while leaving only small reusable offcuts — the asymmetry that earns walls a higher waste rate than plain subfloors.
Should I order all sheathing in one delivery?
When storage allows, yes — it saves duplicate delivery fees and locks pricing. Keep panels sticker-stacked under cover until installation.
How do I adapt this to my own project?
Follow the same four steps: take off each surface separately, specify panels per the material guide, budget per the cost guide, and verify with the checklist. Run each surface through the calculator.
Get Your Number
Hypothetical case study — illustrative example, not a real project. The workflow is what transfers: separate takeoffs per surface, surface-appropriate waste rates, panel specification before ordering, one delivery, and an inspection-aware sequence. Run your own dimensions through the OSB Sheet Calculator and build your version of this walkthrough — with your measurements, your AHJ’s requirements, and your supplier’s prices.
Disclaimer: Calculator results are planning estimates based on the dimensions you enter. Actual sheet needs vary with layout, cuts, openings, and waste. Verify quantities with your supplier and consult a licensed professional or your local building authority for structural or code-related decisions.
