| Date/Time | Adj Area (m2) | Layers | Mass (t) | Dumpsters | Labor (hrs) | Total Cost | Notes |
|---|---|---|---|---|---|---|---|
| No saved runs yet. Calculate once to start a history. | |||||||
| Input | Value | Output | Result |
|---|---|---|---|
| Plan area | 240 m2 | Adjusted area | 253.0 m2 |
| Pitch multiplier | 1.054 | Total felt area | 556.6 m2 |
| Layers | 2 | Mass | 0.612 t |
| Waste allowance | 10% | Dumpsters | 1 |
| Productivity | 20 m2/hr/worker | Labor hours | 9.28 hrs |
| Disposal fee | 55 / t | Total cost | ≈ 420 |
- Plan Area = Length × Width (or input area).
- Adjusted Area = Plan Area × Pitch Multiplier.
- Total Felt Area = Adjusted Area × Layers × (1 + Waste%).
- Mass (kg) = Total Felt Area × Basis Weight (kg/m2).
- Volume (m3) = Mass (kg) ÷ Waste Density (kg/m3).
- Dumpsters = ceil(Volume ÷ Dumpster Capacity).
- Labor Hours = Total Felt Area ÷ (Productivity × Crew Size).
- Subtotal = Labor Cost + Disposal Cost + Haul Cost.
- Total Cost = Subtotal × (1 + Overhead%).
- Select a calculation mode and choose units.
- Enter roof size and select a pitch multiplier.
- Set layers, waste allowance, and material basis weight.
- Enter productivity, crew size, and labor rate.
- Provide disposal and hauling assumptions for waste removal.
- Press Calculate to view results above the form.
- Save runs to the history table, then export CSV or PDF.
Input Structure That Improves Takeoff Accuracy
Start by selecting a consistent measurement method: plan dimensions or plan area. The calculator converts imperial inputs to metric for a unified report, so crews and vendors reference the same quantities. Using one unit system per roof section prevents rounding drift when comparing history entries. Capture a short note for location, access limits, and working hours so the saved run stays meaningful.
Pitch, Layers, and Waste Allowance
Adjusted roof area equals plan area multiplied by a pitch multiplier, which approximates the true slope surface area. Total felt removal area then multiplies by the number of layers and a waste factor. Waste is commonly 5–15% for clean tear-off, but can exceed that where felts are brittle, heavily adhered, or broken into small fragments during stripping and loading.
Weight, Volume, and Container Planning
Mass is estimated from total felt area and basis weight in kilograms per square meter. Converting mass to volume requires an assumed debris density; higher compaction reduces cubic meters and lowers container demand. Dumpsters are calculated by dividing volume by container capacity and rounding up. If your hauler charges by pull, this value becomes a cost input.
Production Rates and Labor Forecasting
Labor hours are driven by total felt area and combined crew productivity. Estimate a realistic square meters per hour per worker, then multiply by crew size to obtain a crew output rate. Reduce productivity when access is limited, roof edges require hand work, staging is distant, or the roof has many penetrations. The result supports daily work plans and staffing for phased strip-off.
Cost Drivers for Bids and Control
Total cost includes labor, disposal priced per metric ton, hauling priced per dumpster pull, and an overhead percentage applied to the subtotal. For bidding, run sensitivity checks: increase layers, raise disposal fees, or lower productivity to test worst-case scenarios. For control, compare the history table across roof zones, then export CSV and PDF summaries for estimating logs, internal approvals, and client proposals.
FAQs
1) What basis weight should I use for felt?
Use product data when available. If unknown, start with 0.9–1.4 kg/m2 for many felts, then adjust after a small test strip-off and weigh a known area for calibration.
2) How do I choose the pitch multiplier?
Select the closest slope from the dropdown for a fast estimate. For mixed slopes, calculate each roof plane separately and save runs to history, or use a custom multiplier based on measured slope geometry.
3) Why are results shown in metric even with imperial inputs?
A single unit system keeps totals consistent across history entries and exports. Imperial values are converted internally so weights, volumes, and disposal rates align cleanly.
4) What if disposal is priced by volume instead of weight?
Set disposal fee per ton to zero and add the volume-based charge into the haul fee per dumpster, or treat it as overhead. Because the tool estimates volume from density, verify density with your hauler’s typical compaction.
5) How can I estimate productivity realistically?
Start with a recent job of similar access and adhesion. Reduce rates for hand removal, multiple penetrations, long carry distances, or limited staging. Increase rates when mechanized scraping, clear loading paths, and good staging are available.
6) Can I combine multiple roof sections into one report?
Yes. Keep “Add this run to the history table” checked for each section. Export CSV to combine all runs in one file, or download the PDF to capture the latest result plus the full history table.