Geometry & Layout
Tip: Gothic arches often have peak height ≥ width/2
Framing
Tip: ~0.49 3/4" EMT | ~0.87 1-3/8" steel top-rail | ~0.19 3/4" PVC
Cover (Film)
Results
| Item | Value | Unit | Notes |
|---|
Semicircle assumes arc length = π × width / 2. Gothic uses two equal circular arcs meeting at the peak with continuous tangent.
Seam Layout Visual
Panel full roll width
Last partial panel
Seam lines
Panels are shown across the required film width. Seam lines run along the length. Use appropriate tapes and wiggle wire or battens.
Example Data
| Preset | Profile | Width × Length (ft) | Peak (ft) | Spacing (ft) | Purlins | Roll Width (ft) | Side Allow (ft) | End Allow (ft) | Pipe lb/ft | $/ft | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Backyard 10×20 | Semicircle | 10 × 20 | — | 4 | 1 | 20 | 1.5 | 1.5 | 0.49 | 1.25 | |
| Market 20×48 | Semicircle | 20 × 48 | — | 4 | 3 | 32 | 2 | 2 | 0.87 | 1.65 | |
| Gothic 20×48 H=12 | Gothic | 20 × 48 | 12 | 4 | 3 | 32 | 2 | 2 | 0.87 | 1.65 | |
| High Tunnel 30×96 Gothic H=16 | Gothic | 30 × 96 | 16 | 4 | 3 | 48 | 2 | 3 | 0.87 | 1.85 |
Use a waste allowance to account for offcuts, bends, fasteners, and unforeseen losses.
Formulas Used
- Hoop count = ceil( Length / Spacing ) + 1 ensures a hoop at both ends
- Semicircle hoop length = π × Width / 2
- Gothic hoop length (two equal circular arcs meeting at peak):
Given width W and peak height H, define a = H²/W + W/4 (arc radius).
Central angle per side: θ = arccos( 1 − W/(2a) ).
Hoop length = 2 × a × θ. - Total hoop pipe = Hoop count × Hoop length
- Purlin length = Purlin runs × Length
- Baseboards:
- Sides only = 2 × Length
- Perimeter = 2 × Length + 2 × Width
- Total framing pipe = (Total hoop pipe + Purlin length + Baseboards) × (1 + Waste%/100)
- Pipe weight = Total framing pipe × Pipe lb/ft
- Pipe cost = Total framing pipe × Pipe $/ft
- Required film width = Hoop length + 2 × Side allowance
- Required film length = Length + 2 × End allowance
- Film panels needed = ceil( Required film width / Roll width )
- Film area = Required film width × Required film length
- Film cost (optional) = Film area × Film $/sq ft
- Anchors = Anchors per hoop × Hoop count
How to Use
- Select a profile. For Gothic, set a peak height suitable for your climate and crop.
- Enter width, length, and hoop spacing. Choose purlin runs and baseboard option.
- Provide pipe weight and cost per foot for weight and budget estimates.
- Set film roll width and allowances to check whether a single sheet covers the structure. Review the seam layout visual.
- Click Calculate to see counts, linear footage, weights, costs, film width, and area. Export with CSV or PDF.
Always verify local code requirements, snow and wind loading, and anchoring details for your site.
Snow / Wind Load Notes
- Closer hoop spacing (e.g., 4 ft versus 6 ft) and extra purlins improve resistance to snow and wind.
- Gothic profiles shed snow better than semicircles for the same width due to steeper shoulders.
- Use diagonal bracing and strong end-wall framing; doors and vents can be weak points.
- Anchoring: Increase anchor depth and count in soft soils or high wind zones; consider helical anchors.
- Consult local codes and engineering guidance for design snow load (psf) and basic wind speed (mph) applicable to your site.
This tool provides planning estimates only and is not a substitute for engineered design.