Enter dome and snow assumptions
Use one unit system throughout. The calculator treats the dome as a spherical cap and bases vertical snow weight on plan area.
Sample planning inputs
| Input | Example | Purpose |
|---|---|---|
| Ground snow load | 30 psf | Local mapped or jurisdiction-provided starting value. |
| Exposure factor | 1.00 | Accounts for site exposure assumptions. |
| Thermal factor | 1.00 | Represents heat loss assumptions. |
| Dome diameter and rise | 20 ft and 10 ft | Defines a hemispherical example geometry. |
| Support count | 6 | Creates an average support reaction reference. |
| Planning reserve | 10% | Adds a non-code preliminary allowance. |
Calculation method
The calculator uses a screening relationship for a reference roof snow pressure. It is intentionally not a complete building-code implementation.
p_ref is reference roof snow pressure. Ce is exposure factor. Ct is thermal factor. pg is ground snow load.
Cocc is the user-selected occupancy planning multiplier. Cdome is the user-selected dome retention factor. Surcharges are added only when their local conditions apply.
For US customary inputs, psf multiplied by ft² gives pounds. For metric inputs, kPa multiplied by m² gives kilonewtons. The shell area uses a spherical-cap geometry calculation and is not used to multiply the vertical snow weight.
How to use this calculator
- Select US customary or metric units before entering values.
- Enter ground snow load from the governing local source.
- Use verified exposure and thermal coefficients where available.
- Leave the dome retention factor at 1.00 without engineering evidence.
- Add surcharge values only after identifying actual drift or rain conditions.
- Enter base diameter, rise, and the number of primary supports.
- Calculate the result, then compare options during early scope planning.
- Give the completed assumptions and result to a licensed structural engineer.
Snow planning for geodesic domes
A geodesic dome can shed snow differently than a flat roof. Its curved shape changes wind exposure, sliding patterns, and local drifting. That does not remove the need for a careful load check. Snow can remain packed on a dome after thawing and refreezing. Wet snow can also weigh much more than fresh snow. Use local ground snow information before selecting a dome location or member size.
This calculator starts with ground snow load. It applies exposure, thermal, and planning modifiers. Those inputs estimate a flat roof snow pressure. A user selected dome factor then adjusts that preliminary pressure. The factor should remain conservative unless a qualified engineer provides project data. Drift surcharge adds extra pressure where snow can collect near walls, connections, or nearby taller structures.
The dome diameter creates the horizontal projected area. Projected area matters because snow weight acts vertically. A hemisphere has more curved surface than its plan footprint. Surface area is useful for cladding estimates. However, total vertical snow weight is based here on the projected footprint. The calculator also shows an average reaction for the chosen number of supports. Actual reactions can vary greatly with geometry, bracing, foundation stiffness, and uneven accumulation.
Check the selected coefficients before trusting any output. Exposure changes with wind, terrain, and shielding. Thermal effects depend on insulation and heat loss. Importance depends on occupancy and risk category. A dome near roofs, parapets, trees, or terrain changes may need a drift study. A dome with solar panels, skylights, or attached buildings also needs special review.
Use this page during early planning, costing, and option comparison. Enter one consistent unit system. Choose pounds per square foot and feet for United States customary values. Choose kilopascals and metres for metric values. Add a reserve percentage only for preliminary budgeting. It does not replace required load combinations or structural safety factors. Verify drainage paths and maintenance access before each winter.
The result is not a permit design or a construction approval. Building codes can require balanced, unbalanced, sliding, drifting, rain-on-snow, and seismic load checks. Connection forces can be larger than the displayed average support load. Have a licensed structural engineer verify local climate data, governing code provisions, frame analysis, connectors, foundations, and construction details. Qualified engineers confirm safe dome designs for actual conditions.
Questions about dome snow load estimates
No. It is a preliminary planning estimator. Permit work needs a licensed structural professional to apply the governing code, local climate data, member analysis, connection checks, and required load combinations.
Snow weight acts vertically. The horizontal plan footprint provides a useful balanced-load estimate. Curved surface area is displayed separately because it helps with geometric and cladding review, not direct vertical snow weight.
Use the value required by your local building authority, adopted standard, or project engineer. Do not substitute a weather forecast, recent snowfall depth, or a value from another nearby town.
Not without project-specific support. Snow can bridge, freeze, drift, and remain on curved surfaces. Keep the factor at 1.00 unless a qualified engineer documents a permitted reduction.
It increases the displayed pressure for early cost comparison. It is not a replacement for load combinations, safety factors, or code-required minimum snow loads.
No. It is total balanced load divided evenly by the entered support count. Real support reactions vary with frame stiffness, geometry, opening locations, foundations, and uneven snow distribution.
No. Unbalanced loading can govern dome members and connections. It needs a code-specific load pattern and structural analysis beyond this balanced screening calculation.
Add it only when a competent review identifies a drift-prone condition. Nearby taller roofs, parapets, terrain changes, and obstructions can create localized snow accumulation.
No. Use kPa with metres for metric calculations. Use psf with feet for US customary calculations. Mixed units will produce unreliable total-load results.
Not the balanced total shown here. Frequency changes member layout and load paths. It can strongly affect individual strut and node forces, which require structural analysis.
Collect site data and consult a qualified structural engineer. Qualified engineers confirm safe dome designs for actual conditions.