There is no one ideal greenhouse size as user demands differ. For a freestanding unit though, the minimum dimensions have to be 72 square feet or 6 feet wide by 12 feet long.
Other Recommended Sizes
If you have more space, try to buy or make a unit measuring 18 feet wide and 20 feet or more long. This is equal to 360 sq ft. These dimensions will provide room for a couple of side benches, two walkways and a central bench.
There are also units measuring 4 feet by 6 feet, and others as big as 20 feet by 50 feet. A very large greenhouse size may necessitate a building permit.
Which Size is Right?
Structures that will be utilized all year for house plants will need more square feet compared to units that will be used only for cultivating budding plants. The dimensions will also be determined by the number of benches you want to make.
What Will You Plant?
This is another important factor. If you intend to grow tomatoes and heat requiring veggies in the unit, note how much space they will consume. Do not cramp the place. Keep in mind that plants growing in the soil cannot have benches over them. Plant the bench layout first before buying the unit.
The plant spacing will also have to be assessed, not just for this season, but for the next one. Dahlias for example, can take up a lot of space when it is time to put them outside.
Tools and Equipment
Don’t forget to make space for the garden tools. Containers, pots, hand tools, bags of compost etc. All of these will require their own space. The more plants you have, the more tools will be needed. A greenhouse with a workshop may be the ideal solution.
It is always better to buy a more spacious unit than buy another small one. A single large unit is more cost effective than two small ones. Aside from the cost, it is easier to put extra plants in the unit than erect another one from scratch. In other words, get the biggest unit your space and budget can allow.
When evaluating greenhouse size, keep the cost of heating in mind. Again, a larger unit is more effective heating per square meter. Compared with two small units, one large structure is more adept at keeping temperatures constant. A large unit will also make it easier to move around and manage the plants.