Greenhouses are an almost essential piece of kit for any propagating gardener. They offer a warmer retreat than a garden shed and allow you to go on a grow your own frenzy. Seasons can disappear as you create your own microclimate. The most contentious question, however, is should you erect your own or get someone else to do it? This blog post favours the professionals and I'll explain why!
I’m going to be brutally honest in this blog post, in that I’ve wanted a greenhouse for so many years but never had space for one. I’ve wanted one so much that when I bought one a year ago it languished behind the garage, unpacked for over 12 months. The irony of getting what you’ve always wanted but then completely going off the idea. I’d politely refused the seemingly expensive one-day greenhouse installation offer from the company. How I would regret that choice.
The inertia of when to start erecting the greenhouse and how I would go about it completely put me off. Frozen in procrastination my greenhouse dreams were slipping away. Then my husband decided last week that today was the day. The greenhouse was going up. Armed with our slightly vague wordless instruction book and a billion small parts we began. (For some reason, I subconsciously put both a bottle of tonic water and gin in the fridge. Almost like Nostradamus, I knew what was to come.)
- Why build a greenhouse?
- Laying greenhouse foundations
- Positioning a greenhouse
- Building a greenhouse frame
- Fitting glass in a greenhouse
- Ventilation in a greenhouse
- The finished article
Why build a greenhouse?
Greenhouses are an excellent asset to any garden or gardener wanting to grow a wider variety of plants or vegetables in their garden. They serve a number of functions.
- Extending the growing season; meaning you can start earlier and finish later
- Grow tender plants and vegetables that may not survive outside otherwise ie peppers or tropical plants
- Allow you to overwinter tender specimens
- Provide optimal conditions for all sorts of plant propagation methods from seeds to cuttings.
- Somewhere to shelter in out of the rain whilst planting or to swelter in during the summer heat!
A greenhouse is not something that you can easily put together yourself on your own. I would challenge anyone to deny that it’s a two person job and requires patience, flexibility, an iron will and some psychic ability.
Laying a foundation for a Greenhouse
Fortuitously, I’d already decided that my dream greenhouse would be going on a fully flagged base. I’d toyed with the idea of a gravel base, perimeter base but thought better of getting someone in to lay some flags for me. Let’s go the whole hog, no half measures. Which turned out to be a real saving grace after reading the instructions on laying it on grass. Which seems to me to be completely pointless.
Why on earth you would want a greenhouse to sit on the grass unless you’re going to gravel over it, which then runs the risk of it all growing up and through your gravel. I still can’t find any real benefit to this other than lazy man syndrome, and believe me, I did consider it for an easy life!
So that’s my first top tip. Make sure you have a level stable surface in advance of the glasshouse arriving.
Positioning & Securing the base of a greenhouse
The positioning of the greenhouse is vital. You need to make sure you can get around all sides to clean the glass and also in case you need to replace a sheet of glass. You’ll see later on why this is more likely than you would think. You also need to consider the aspect. There are lots of online debates over the suns position and how many hours of sun it gets you in your glass house. However, most people don’t have the luxury of half an acre to play around with.
My second top tip is simple. Position your greenhouse away from buildings, football nets, croquet lawns, shadows or trees.
Then you can’t go too wrong. If you really want to go into the aspect then the RHS website has plenty of advice good for pub quiz arguments and what not.
We had a bolt down kit which you screw to the base once the glass is in. It will be fine I thought. This thing will be up in a day. There’s no way the wind will blow the frame about when the glass is in. How wrong I was.
Top tip three: mark and check the final position with a pencil, then double check when you resume greenhouse building.
Building a greenhouse frame
Now, this is where the first marriage tester begins, when clear instructions become essential. I’m not sure why but certain flat pack products seem to favour ignoring written instructions over cartoonish pictures with the odd exclamation, danger sign, brain cog impressionist logo or hammer icon. Now with a glasshouse, the hammer icon really does send shivers. I’m one of those people that see a ‘Do not push sign’ and immediately pushes it. So I moved the hammer out of arms reach and grabbed a socket set instead.
Doing our best to interpret the multiple nuts and bolts sizes, dodging the exclamation marks, I then left my husband sort out the frame. I thought it would be good comedy value given his fingers are massive and the bolts looked ridiculously small which turned out to be true. I took my smaller ‘nuts and bolt perfect hands’ to go and sort the glass out, knowing full well our roles were doomed!
Then the circus-like contortionist activity of attaching the frames together and the base begins. Any slight breeze and the frame suddenly pops off its lip or the bolt you’re about to tighten slips out. This goes on for maybe 2 hours. It’s a gloriously clumsy dance between husband and I. Me being 5ft 5 and him being significantly taller.
Top tip number four: Don’t go all strong man on tightening the bolts. They have the potential to snap, cross-thread or generally misbehave.
Installing the glass in a greenhouse
Before I come on to describe ‘shatter gate’ please make sure you’re wearing gloves. To state the obvious; the glass is heavy, dangerous and potentially sharp. I favoured my ‘spare non serious gardening’ flowery rubber tipped gloves I keep for such jobs. My spiderman fingers where ready for the glazing and the floral pattern just set off my outfit perfectly.
Greenhouse glazing choices
You have a couple of options with glazing which I’ll briefly explain here.
- Regular glass – if it breaks it turns into those serial killer shards
- Horticultural Glass – Toughened and great for exposed environments. When it breaks (see below) it kind of pops into a thousand annoying but harmless pieces. It also makes a noise a bit like you’ve been shot by a sniper when it does.
- Polycarbonate – Plastic twin walled sheets. Cheap light and totally harmless – unless it ends up in the Ocean. However, it easily discolours is a nightmare to clean and can crack under extreme heat.
The glass arrived in a number of sizes and has to be fitted onto sticky foam strips on the sills of each of the frames. This in itself is a task of endless marriage arguments. The positioning and nightmare, if you have to peel off and unstick, should be listed grounds for divorce. Whats worse is you’re holding, in your flowery gloves, big heavy sheets of glass whilst simultaneously trying to position them correctly above your head.
You also have two choices of how to then secure the glass panes into the greenhouse.
Razor sharp springy clips that will spike you at least once when you pick them up. They ping in. Look unsightly but are easy to fit.
Plastic strips designed to be more aesthetically pleasing than clips and more secure. However, getting them in involves some butt clenching force against the glass and wobbly frame (remember its still not been drilled to the floor yet).
Glass clips vs Bar Capping
I’d always favour bar capping as its more secure than clips and adds a much nicer look to the greenhouse. You’ll also have less finger pain come opening that Gin later.
My top tip five would be to use a small spanner to then squeeze it into the frame rather than your fingers. You can then run it down the edge and here it click all the way down.
Replacing Broken Greenhouse Glass Panes
Ever the optimist its now 6pm, we have about 4 panes in and I’m thinking another hour or so and this greenhouse will be complete. Then when placing a glass sheet around the back I hear the dreaded sniper pop and the explosion of shattered glass. I brush myself clear of shattered glass, check for the sniper wound and then survey the situation.
After multiple threaded screws, doing and redoing aspects of the frame, the bar capping horror and those blooming auto vent windows that snap shut on your fingers every 60 seconds. I declare defeat for today.
I grab the gin and we sit there in a kind of semi-trance state looking at a half up half down glasshouse with a layer of shattered glass in the base. Marriage bliss. Lovely.
Ventilation in a glasshouse
Ventilation is fundamental to any greenhouse, without it you’ve just created the world most efficient plant oven. I chose automatic vent and louvre openers because I’m forgetful and like an easy life. These are struts filled with wax that when they get hot expand, automatically opening your windows. Leaving you to mix Gin and tonics, and the like.
The window vents allow hot air out and the Louvre (vents on the floor) which drawn in cold air, meaning air can circulate and keep the glasshouse from overheating. You can also change the humidity by dampening down a greenhouse to increase humidity or use the vents to decrease it if it is too damp. This is a subject of a blog post all by itself.
Top tip number six would be to make sure you have both kinds of vents and use the auto vent openers. This may save your plants if you are likely to forget to open them in warm weather!
Finishing the Greenhouse
The next day I go out to find a glazier to replace the glass, we forge on in silence to get the glasshouse finished. We noticed that overnight a swift breeze has also moved the frame out of line slightly. We carefully had to move the greenhouse at one end, listening to the glass creaking and shifting. One of the prayer moments during the install wondering if we would ever finish the job with the glass intact!
Whats odd is that you only bolt down the glass house once all the glass is in. Presumably to give some play to the frame in case things are not exactly square. This has the knock-on effect of meaning its only secure at the very end meaning don’t erect one in strong winds. This is fine if an expert team are fitting it but I know of no one who has erected a greenhouse from scratch in one day. It’s definitely a lesson learnt!
We also found that the attachments required a smaller drill bit to fit through the bolt holes but the rawl plugs then wouldn’t fit. So there were a few broken drill bits trying to widen the holes.
My last top tip number seven would be to have a variety of rawl plugs and bolts sizes to hand for fastening the base without too many fall outs!
So there you have it my guide to why using a professional to fit a glasshouse may actually be a worthwhile investment. It took us two days to erect this glass house and half a day to source a broken glass pane. Whilst we do have a sense of achievement from doing it ourselves, I do wonder if my time would have been better spent on a garden design and let an expert put it together? I’m hoping this glass house will last me for a number of decades now so I guess its a question I won’t need to ask again! Also, the Gin that I refrigerated did go some way to smooth over the marital stress of the whole event.
Have you built your own greenhouse? Was it easy peasy or a nightmare? Do let me know or comment on my social media channels. You can also see my ‘How to’ garden guides on my Youtube channel or send me a message on social media Tweet, Facebook or Instagram me!