Cultivar produce a range of three quarter lean to greenhouses that can be fitted against an existing wall. This, of course, is assuming that the wall is in good order and is plumb and true. A three-quarter lean-to greenhouse has significant advantages over that of a standard lean-to. Firstly the wall to which the greenhouse abuts need not be as high. Secondly and arguably equally important the greenhouse benefits from having a greater cubic air capacity as well as having vents on both sides of the ridge.
Of course, even our free standing greenhouses can be adapted to fit along a good wall.
In an ideal world the wall should be south facing and if this is the case you will benefit from full sun most of the day. The wall too tends to absorb the heat during the day which is useful in keeping the lean to greenhouse temperature up high into the evening and night.