Greenhouse Snow and Wind Load Calculator
Check how much the snow on your greenhouse weighs, how close it is to the roof rating, and whether your greenhouse is rated for the snow and wind where you live.
How it works
How much does snow weigh?
The weight of snow depends far more on how wet it is than on how deep it is. A foot of fresh powder can weigh less than 3 inches of ice.
Snow load (lb per sq ft) = Depth (in) ÷ 12 × Snow density (lb per cubic ft)
| Snow type | Density | Weight of 1 ft on 1 sq ft |
|---|---|---|
| Light, fluffy new snow | about 6 lb/ft³ | 6 lb |
| Average snow | about 12 lb/ft³ | 12 lb |
| Settled snow | about 18 lb/ft³ | 18 lb |
| Wet, heavy snow | about 25 lb/ft³ | 25 lb |
| Packed or drifted snow | about 30 lb/ft³ | 30 lb |
| Ice | about 57 lb/ft³ | 57 lb |
To see the design snow load where you live, look up your address on the ASCE Hazard Tool or ask your local building department, then pick a greenhouse rated for it. Our guide to the most durable greenhouses for snow and wind can help.
Certified ratings
Engineer-certified wind and snow ratings for Royal Victorian greenhouses
Structural engineers at Hollingsworth Pack analyzed the Janssens Royal Victorian greenhouses, an aluminum frame glazed with 4 mm tempered glass, against the 2015 International Building Code. Their certification letter (April 2020) rates each model for these loads:
| Model | Wind (3-second gust) | Ground snow load | Roof live load |
|---|---|---|---|
| Royal Victorian VI23, 8 x 10 ft | 130 mph | 30 lb/sq ft | 20 lb/sq ft |
| Royal Victorian VI34, 10 x 15 ft | 120 mph | 25 lb/sq ft | 20 lb/sq ft |
| Royal Victorian VI36, 10 x 20 ft | 115 mph | 25 lb/sq ft | 20 lb/sq ft |
| Royal Victorian VI46, 13 x 20 ft | 115 mph | 25 lb/sq ft | 20 lb/sq ft |
These ratings assume the greenhouse sits on a continuous concrete beam or solid-grouted masonry foundation at least 8 in wide and 16 in tall under all the walls, with a foundation anchor at every wall post (about every 30 in) and the knee brace scrolls installed: at mid bay on the VI23, VI34 and VI36, and at every bay on the VI46. Our foundation calculator works out the concrete, and our assembly crews can build it for you.
Need the letter for a permit? Ask us and we will send you a copy.
Stay safe
How to clear snow off a greenhouse
Push snow up and off from inside with a soft broom, or pull it down from outside with a roof rake that has a soft edge. Never use a metal shovel or chip at ice on glass or polycarbonate. Clear evenly from both sides so the frame is not loaded on one side only. Keeping the greenhouse heated a little above freezing helps snow slide off on its own.
Questions
Greenhouse snow FAQ
How much snow can a greenhouse hold?
It depends on its rating. A greenhouse rated for 24 lb per sq ft can hold about 2 ft of average snow or about 11 in of wet, heavy snow. Check your greenhouse spec sheet for its snow load rating.
How much does a foot of snow weigh on a roof?
About 6 lb per sq ft for light new snow, 12 lb for average snow and 25 lb or more for wet, heavy snow. Ice weighs about 57 lb per sq ft for every foot.
Should I remove snow from my greenhouse?
Yes, once it gets past about half of the rated load, or before heavy wet snow or rain is forecast. Brush it off gently and evenly, and never chip at ice.
What is the best greenhouse for heavy snow?
Look for a strong aluminum or steel frame, a steep or rounded roof that sheds snow, and a published snow load rating that matches your area. Twin-wall polycarbonate also keeps heat in, which helps snow slide off.
How much wind can a Victorian greenhouse handle?
The Royal Victorian greenhouses are certified by structural engineers for 3-second wind gusts of 130 mph (VI23), 120 mph (VI34) and 115 mph (VI36 and VI46), and for 25 to 30 lb per sq ft of ground snow, when built on the required concrete foundation.
More tools
Other greenhouse calculators
- Heater Size CalculatorHow many BTUs it takes to keep your greenhouse warm on the coldest night.
- Heating Cost CalculatorWhat a winter of heating will cost with electric, propane or natural gas.
- Fan and Ventilation CalculatorThe exhaust fan CFM and vent openings that keep summer heat down.
- Foundation CalculatorConcrete, gravel, pavers and lumber for your greenhouse base.
- Greenhouse Size CalculatorHow big a greenhouse you need for the plants you want to grow.
- Shade Cloth CalculatorThe right shade percentage and cloth size for your greenhouse.
- Grow Light CalculatorHow many grow lights it takes to give your plants enough light in winter.
- Rainwater CalculatorHow much water your greenhouse roof can collect for your plants.
Want a second opinion?
Tell us about your greenhouse and where you live, and we will help you get it right.
Call 678-408-8222Send us a message