Greenhouse Foundation Calculator
Work out how much concrete, gravel, pavers or lumber you need for your greenhouse foundation. Enter the size of your greenhouse base and pick a foundation type.
Please note: these results are estimates
This calculator gives general estimates based on typical conditions and the information you enter. Your real needs depend on your soil, frost depth, slope, drainage, the greenhouse model and your local building codes and permits. Order a little extra material to allow for waste, and check with a local contractor or your building department before you build. Your actual results may be different, so use these numbers as a starting point for planning, not a guarantee. Always follow the manufacturer's instructions, and talk to a qualified professional before making important decisions. Questions? Call us at 678-408-8222.
How it works
How much concrete or gravel does a greenhouse foundation need?
Every foundation comes down to volume: length × width × depth, converted to cubic yards. One cubic yard is 27 cubic feet.
Cubic yards = Length (ft) × Width (ft) × Depth (in) ÷ 12 ÷ 27
| Foundation | Best for | What to know |
|---|---|---|
| Concrete slab | Glass greenhouses, garden rooms, paved floors | Most stable and easiest to keep clean. An 80 lb bag of mix makes about 0.6 cubic feet. |
| Footing or stem wall | Larger greenhouses, in-ground beds, more headroom | Dig below your frost line. Many Victorian and Orangerie models are designed to sit on a low wall. |
| Gravel pad | Polycarbonate greenhouses, good drainage | Cheaper and drains well. Gravel weighs about 1.4 tons per cubic yard. |
| Pavers | A finished floor that drains | Lay on compacted gravel and sand. |
| Timber base | Small, light greenhouses | Quick to build, but it must be level, square and well anchored. |
Questions
Greenhouse foundation FAQ
What is the best foundation for a greenhouse?
For a glass greenhouse, a concrete slab or a footing with a low stem wall is best because glass needs a perfectly level, rigid base. Polycarbonate greenhouses can sit on a gravel pad or a timber base that is level and anchored.
How much concrete do I need for a 10 x 12 greenhouse slab?
A 4 in slab for a 10 x 12 ft greenhouse needs about 1.5 cubic yards, or around 74 bags of 80 lb concrete mix, including 10% extra.
How thick should a greenhouse concrete slab be?
4 inches is standard for a hobby greenhouse. Thicken the edges to 8 to 12 inches, or add a footing, for large or heavy glass greenhouses and in areas with deep frost.
Can I put a greenhouse directly on the ground?
Small polycarbonate greenhouses can sit on a base frame anchored into the ground, like the Riga foundation frame. Glass greenhouses should always go on a level, solid 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.
- Snow Load CalculatorHow much the snow on your roof weighs and when to brush it off.
- 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