Roof Pitch Calculator
Convert rise/run into pitch, angle, and slope factor.
Roofing
Flat Roof Membrane Calculator
Estimate membrane coverage for low-slope roofs.
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Educational US estimate only. Not engineering, structural, code, or professional construction advice. Mix designs, codes, and local conditions vary — verify with licensed professionals and your building department.
Estimator methodology
BuildToolsHub takeoffs separate net measured quantities from ordered quantities. Ordered qty = net × condition-based waste, then rounded for plant or package sizes (e.g. ready-mix to the nearest 0.5 yd³).
- Concrete bags: Quikrete / SAKRETE published yields (80 lb ≈ 0.60 ft³). Ready-mix contingencies follow ASTM C94 purchaser practice.
- Rebar: CRSI published lb/ft tables; optional lap allowance ≈ 40× bar diameter (confirm with drawings).
- Roofing: NRCA squares (100 ft²); pitch factor √(1+(rise/12)²); ~3 bundles/square for standard shingles.
- Aggregates / fill: ASTM C29-style densities; swell/compaction allowances for haul and place volumes.
- Masonry: BIA / NCMA common unit factors (e.g. ~1.125 CMU/ft² for 8×16 face).
Use the Order tab for a supplier call sheet and the Assumptions panel for the exact factors applied to this run.
Why use Flat Roof Membrane Calculator
Convert flat or low-slope roof plan area into membrane squares with waste for seams and flashings.
Attachment method, insulation, and wind uplift design require manufacturer engineering.
How to use
- Enter job dimensions. Pick a pour/layout condition to set industry waste %, or choose Custom.
- Review Net vs Order on the Summary tab — order the rounded quantity, not net alone.
- Open the Order tab for a supplier checklist, then print, export CSV, or share the link.
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About Flat Roof Membrane Calculator
Is pitch factor needed on flat roofs?
Usually near 1.0 for truly flat roofs; low slopes still use a small factor.
How much waste for membrane?
Often 5–10% plus extra for flashings and penetrations.
TPO vs EPDM?
Coverage math is similar; detailing and seams differ by system.
Is this professional engineering advice?
No. Educational estimates only. Verify with a licensed professional and local codes.