First we should define just what a lean to greenhouse is. It is a greenhouse with a single slope roof, two gable ends and a front wall. This greenhouse is typically attached to a long wall of a home. Or, it may be attached to a garage, potting shed or even a freestanding wall that was built specifically for this purpose. Another option may be a gable end attached greenhouse which would be basically a freestanding greenhouse configuration with one of the gable ends removed. This typically will mimic the wall of the structure you are attaching to. Or, it may be attached to a two-story home. With either configuration a lean to greenhouse is dependent on another structure to complete the greenhouse.
Lean to greenhouses have quite a few benefits. Just imagine being able to walk out into the greenhouse for your morning coffee. This is typically accessible without walking outside and is a great benefit if you are in an area that is extremely cold or covered with snow in the winter. You also have your utilities nearby. You will not need to dig trenches in the yard to get your water, electricity, propane or natural gas to the greenhouse. If you place your lean to on a south facing wall you may be able to harness some of the sun’s heat during the day. The back wall of your home will heat the greenhouse, but the greenhouse will not maintain any of this heat during the night unless you use solar practices.
Many people think that a lean to greenhouse will be less expensive due to the fact that it does not have one wall that a freestanding greenhouse will have. This is not true. Yes, you do have savings due to the material cost. But, you will need a different type of support for the lean to and it will typically be at a slightly higher cost.
You will need to build a better foundation for the greenhouse as it is becoming part of your structure. You will want to use the same type of foundation that is required for any other structure in your building area. This is particularly true of glass lean to greenhouses in a location where you freeze during the winter. The freeze thaw cycle will cause the ground to heave and may break some of your greenhouse glass during this cycle. It is also moving the frame as well. Depending on your area and the size of the lean to, you may need a building permit for this type of structure. Of course you may need a building permit for a freestanding greenhouse as well. This is something best determined by your local building permits department.
You are limited to the orientation of the building you are attaching to. For a lean to a Southern exposure is the best, followed by the East and West. A Northern exposure is not a desirable location, but as with any other greenhouse you can add items like supplemental lighting.
The attaching height may be an issue if you have a one story or ranch style home. The good news is that there are several ways to overcome this problem. Some manufacturers are able to reduce the roof pitch of the greenhouse so that you do not need as much attaching height. Most greenhouse kits have a roof pitch of 4 – 5 on 12. Some will have an even higher pitch. Some manufacturers will be able to reduce the pitch to as low as a 2.5 on 12. What this means is that for every foot you go out your roof will drop 2.5 inches in height.
If you are building your own greenhouse using polycarbonate sheets the minimum required pitch is a 1 on 12 or a 5 degree slope. This is to keep you from having issues with snow or rain. Another way to gain extra height is to attach to the fascia board of your home rather than to the wall. This will gain you additional height and ensure that you will have no obstacles for your roof vents to open.
Tammy has been using, selling and installing greenhouses since 1993. She is a lifelong gardener. Tammy is the owner of AdvanceGreenhouses.com. She blogs about different growing methods at Blog.AdvanceGreenhouses.com.