ERECTING A GLASSHOUSE. 1. THE STRUCTURE by Brian Milligan
Are you thinking of building a glasshouse? Most of us who are permanently infected with the orchid bug have one or more. Whereas some orchid growers go for fancy, custom-built designs on brick bases, most settle for the DIY type with aluminium frames, which can be erected in a weekend with the assistance of a gullible friend with an adjustable spanner.
The first decision to make is where to site the glasshouse. The best spot is where the Hills Hoist is located, as it’s usually the sunniest spot in the garden. My son did exactly that – he bought his wife one of those folding clothes lines that fit on the house wall, dismantled the Hills Hoist and built the glasshouse over the concrete path that formerly led to it. There was only one problem – a few years later he and his wife decided to move house, and so I spent a couple of days helping him move his glasshouse several kilometres to the east! Fortunately the job wasn’t as involved as starting from scratch, as we used a furniture van to move each of the walls intact without dismantling them (apart from removing the glass). On the basis of experience gained during the erection of three glasshouses (one of them twice!) I offer the following advice to those planning to erect a glasshouse for the first time.
Having decided on the best spot for the glasshouse, you need to decide which way it should face. Generally, it’s best to site the glasshouse with one of its long sides facing north, so that it receives as much light as possible during the winter months. Aluminium glasshouses should be built on a base, such as a brick or concrete wall, although a heavy timber frame is much quicker and easier to construct. In the case of my son’s glasshouse, the base is made of four lengths of treated pine (cross-section, 100 x 100 mm), fastened together at each corner with metal brackets. Each corner of this base sits on a level concrete slab (450 x 450 mm). Because the site is sloping, additional smaller slabs were used at the low end to level the base. It’s important to use a good spirit level and builder’s square to ensure that the base is both horizontal and square.
My son and I then placed the four sides in position on the base and bolted them together, followed by the gable roof frame. At this stage it’s critical to use a large builder’s square to ensure that all four wall frames and both of the sloping roof frames are completely square. After adjustment they should be fixed in position with the diagonal braces that are provided as part of the kit. If you don’t get your angles right, you’re likely to insert most of the glass panes, only to find that the final ones won’t fit! Make sure that the frame is squarely situated on its base and then fasten it down with screws (because of the weight there’s no way you can move the frame after you’ve fitted the glass). Finally, fit the pre-cut glass panes.
Now comes the hard bit, digging a trench for the electrician to install his power line. It has to be 600 mm deep, which is easier to type than to dig! Fortunately your plumber can use the same trench to install the water pipe. I recommend the installation of two double waterproof power points, one at each end of the glasshouse, and at least three threaded water taps. You’ll need power outlets for one or two fans, for an evaporative cooler, for solenoid valves to operate fogging and/or misting systems and for an electric heater, unless you decide to use gas (which means digging another trench!). Taps will be needed for the fogging and/or misting systems and for the cistern that feeds water to the evaporative cooler, not to mention one for hand-watering the orchids. Make sure that your benches will fit through the doorway before fitting the glass! Part 2 deals with the various options for fitting out your glasshouse – heaters, coolers, misters, fans etc. and the various systems that enable these to function automatically. They certainly make life much easier once they’re installed.