How a Lean To Greenhouse Works
A lean greenhouse is a half span frame fixed against a house or garden wall, with a single roof sloping down from the wall to the front. The wall does two jobs: it carries part of the structure, and it stores daytime heat that radiates back into the house after dark.
That second effect is the real advantage. A lean to greenhouse against a masonry wall holds a higher minimum temperature overnight than a freestanding frame of the same size, without any heating at all.
Choosing the Wall
A south or west facing wall gives the longest hours of direct light and the most stored heat. East facing works for propagation and shade tolerant crops. North facing will grow ferns and hostas but not fruiting plants.
The wall also has to be sound enough to fix into. Brick, block, stone and rendered masonry all take wall brackets. A lean to house greenhouse should not be fixed to a fence panel or a thin timber cladding, since the frame will pull on those in wind.
- Check the wall is load bearing rather than a screen or infill panel.
- Match plugs and fixings to the wall material rather than using what is in the box.
- Seal along the top flashing so water runs off the wall rather than behind the frame.
Installation
Installing a leaning greenhouse follows the same sequence as a freestanding one, with the wall fixings added. The base must be level and the frame square before glazing, and the wall bracket line needs to be truly horizontal or the roof slope will twist.
An anchor kit secures the front of the frame to the ground. The wall holds the back; the ground holds the front. Both are needed.
Working in Half a House
Everything is reached from one side, so depth is the constraint rather than length. Tiered staging and wall mounted shelving use height rather than floor, which is what makes the format work in a narrow space.
Tall crops go at the back against the wall, where the roof is highest and the masonry gives support for training.
Related Formats
A half greenhouse stands against a wall with its own full roof rather than leaning on it, which makes it usable against a fence. For a very narrow strip, a narrow greenhouse may suit better.
