Greenhouse Shape?
There are three main shapes for garden greenhouses. Traditional, octagonal and the lean-to greenhouses. Other shapes are available but they are normally a combination of the above three shapes.

They offer different combinations of affordability, running costs, good light transmission and practicality. Each greenhouse shape is considered below in detail.

Lean-To Greenhouses
Click here to go to our lean-to greenhouse page.  Lots of information about the types available and their benefits.

Traditional Shaped Greenhouse
One key advantage of the traditional shaped greenhouse is that there are far more sizes available than other types, they are generally cheaper to buy and they are available from a large number of suppliers. So, if this greenhouse shape matches your needs, buy it rather than the more expensive octagonal or lean-to greenhouses.

Even with the traditional garden greenhouse shape, there are subtle variations and they generally arise in order to maximise light transmission in the winter and spring months. At these times of year, you may well be growing plants in your greenhouse, and maximum light transmission is important because the sun is so low in the sky and days are generally more cloudy. Light transmission is not so important in the summer months because there is more than enough light to go round.

When thinking about light transmission, the obvious needs to be mentioned! There is only one sun and it shines on your greenhouse from roughly the same direction each winter and spring day. The point in maximising light transmission is to provide light to all parts of the greenhouse and not just the side facing the sun. 

There are four main variations on the traditional shaped greenhouse, each is a compromise as shown below.

The positioning of a greenhouse is also a key factor for maximum light transmission. All traditional type greenhouses should be positioned such that their longest side runs east to west to allow maximum light transmission in darker months.

Octagonal Shaped Greenhouse
These do tend to be the most expensive greenhouses, but their shape makes them an attractive feature in many gardens. In addition, their shape ensures there is always part of the greenhouse at any time which is at the ideal angle of 90 degrees to the sun. 

Another advantage (although at considerable cost) is that the circular benching which can be bought for them gives a large and convenient area for potting up plants and growing them on.

One possible disadvantage of an octagonal greenhouse is that ventilation during the hot summer months is difficult. There are always pockets of heat which develop because of the round shape. Lots of opening ventilation windows are required to ensure an even temperature during the summer.