How To Build a Greenhouse

Gardening is the most popular hobby in the world. It is therapeutic, it's interesting, surprising, challenging and a source of wonder second to nothing. The earth is one big garden and its future relies upon converting sunlight, carbon and oxygen to green plants.

In climates like those of the UK and northern Europe gardening in the traditional sense is out of the question for  a large part of the year. This is why greenhouses are so popular. That glass house or plastic, polycarbonate structure we call a greenhouse has become  a passion for garden enthusiast world-wide though and not just the UK. And the desire to make a greenhouse for the gardening joy it brings continues to grow as people live longer and have the need to do constructive things in life.

So here's how to build a greenhouse ... and succeed first time round

The starting point to building a greenhouse is to understand how a greenhouse works ... and the individual components that are essential if your going to get the best out of your glasshouse for a long time to come. This latter point is an important one. A greenhouse is a structure and it's meant to withstand the test of time and the elements. As a structure in which you will be working you should make the greenhouse to be a place of relative comfort and for yourself and not just the plants. It's does not help too much for example if you have to work at the bench all bent over because the greenhouse you built was not high enough. Click here for Two Wests for when you decide to build a greenhouse

How does a greenhouse work?

Plants in general, like most life forms, grow faster when the temperature is higher. When warmer temperatures coincide with well fertilized and watered environments that suit a range of plant species then those plants grow optimally. Conversely when temperatures drop plants tend to want to stop growing in order to conserve energy just to stay alive while waiting for suitable ambient conditions to return as they always do every spring.

A greenhouse is therefore a mechanism to shelter plants from unsuitable weather and climatic environments in its simplest form. However the well designed greenhouse can be far more than a protective environment it can become an area whose climate can be controlled and here's where the well designed and constructed greenhouse comes into its own and provides such a fascinating hobby that is also a productive one.

The absolute and over-riding requirement when building any greenhouse is to design for optimum light transmission. Plants can (normally) only grow under sunlight conditions through the process of converting sugars to plant material by the process known as photosynthesis. This is why glass is the traditional material for greenhouse windows although plastic windows and polycarbonate windows in particular are chosen.

How to build a greenhouse ... a checklist to compare greenhouse information

  • Few people will choose to build a greenhouse from scratch ... most will prefer to make a good choice form the models available commercially and there are many. What's important is to consider what you really need (including a look into the crystal ball) and what you can afford. Be aware that you should ALWAYS go bigger than you think you need.
  • In reviewing this checklist and before you make any final purchase decision explore the website of the company in some detail and ring them for help and advice. Do not make guesses for the sake of a phone call. In my experience Two Wests have been around so long and have so much knowledge and experience you cannot go wrong with this UK company. They are also a complete one-stop shop for all greenhouse related products Click here for Two Wests and all your garden accessories at good prices
  • You can build a greenhouse structure or frame from a variety of materials ... wood, galvanised steel, aluminium, PVC, Polyethylene,  steel, UV stabilized resins including fibreglass. It becomes a matter of personal choice and is a cost factor. Most experts believe aluminium and especially if you paint it will last for a very long time. It will also look good. Your choice of frame will determine the height of the greenhouse. Do not build a greenhouse whose roof apex is not high enough to allow you to stand and work in comfort. The eaves of the greenhouse should also be chosen to also suit your final layout and working environment.
  • The glasshouse windows or greenhouse glazing to be used to build a greenhouse is important for the reason given above. For example if you have no intention of growing flowering plants or vegetable then you can downgrade on the light transmission aspects of your greenhouse design. Just be sure to think into the future though. Safety (breakage and fire)  and expected life are important aspects when considering the glazing of a greenhouse. Here's a brief summary of what you need to know to make a decision ...
  • Glass is great from a light transmission perspective but it can be dangerous if broken and is heavy. Glass for greenhouse glazing does not prevent much heat loss (poor insulation characteristics) and is not the ideal material to use when heating is important. It remains nevertheless an important greenhouse building material and information should be collected to make a final assessment for your greenhouse choice..
  • Polycarbonate is a polymeric glazing material having excellent light transmission properties consistent with good strength. It must be UV resistant. It can catch fire but is far safer than traditional plastic materials and fibreglass. It is available in multi walled (ie air trapped between layers) sheets to improve greenhouse insulation values. Normally available from 4mm twin-walled to 16mm triple-walled  polycarbonate sheeting. Other glazing materials that can make a greenhouse work although less effectively are PVC sheets, fibreglass sheets, and even translucent polythene sheeting and thick film as used in many commercial growing installations.
  • Do you really want a real greenhouse? Or is it a plant shelter and seed raising structure that you're really looking for. It's nice to build a large greenhouse but if you're not going to use the comforts and space then it can be a bit of a waste. There are a wide range of hobby and mini greenhouses around these days ... hobby or mini greenhouses .
  • Do you need to obtain a permit to build a greenhouse? ... don't make the mistake of erecting a greenhouse only to find that you have broken all the bye-laws in the book. Do the basic checking first.
  • The site for the greenhouse you want to build is important. Remember sunlight is vital but too much sun may require provision be made for partial shading. It will always be best to build in full sun knowing that this gives you most options because shade can be constructed ... sunlight cannot. It is generally accepted that a minimum of 6 hrs sunshine per day is ideal and that to capture heat from early morning and later afternoon sun that the axis of a greenhouse should be east to west.
  • Do you really know why you want to build a greenhouse? Sorry to harp on this but it's by far the most important decision you have to make. Will you be growing vegetables for use around the years, will you be growing orchids, will your focus be on green leaved or foliage plants only or specific fruit items? Is the space for hydroponic growing The way you answer this question will ultimately make your choice easier.
  • Sunlight considerations ... in the northern hemisphere the sun is inclined more steeply in mid summer than during winter and southern facing locations will always be warmer which means if you have a house facing south then putting the greenhouse in a small backyard will not really work because the greenhouse will be in the shade of the house for all but the longer summer months. Ideally the location should be in an arc of about 90 degrees midway between east and west on the southern side of the house (for northern hemisphere and to the north of the house for southern hemisphere). It is tempting to put a greenhouse underneath a deciduous tree but remember in high winds branches can break off trees and damage the glasshouse in particular. Create a windbreak structure close to the green-house.
  • Make it easy to get into and out of your green house. Avoid windy areas and put it as close to the house as is practical. You'll also need to move things in and out of the greenhouse so remember this when arranging your site ... and a watering point? Don't forget. And power reticulation is important too. You will pay more to make these utilities more easily accessible but you will enjoy your greenhouse far more too.
  • When you build a greenhouse make sure it is a well drained area and not to close to where the kids play cricket.

The most important accessories to consider when you build a greenhouse

All the points below are the subject of other articles being written for this site. Here we just introduce the subject so that you don't forget their importance at the planning stage.

Ventilation (the single most important requirement), heating and cooling associated with good ventilation and appropriate temperature control are vital The most basic item which no grower should ever be without is a max min thermometer (records lowest temperature recorded every day and maximum recorded during the same period).

Ventilation fans and extractor fans are very useful and when combined with evaporative cooling mechanisms make temperature control and regulation far easier. Hot and humidified and stale air is replaced using fans that suck the air out of the greenhouse.

Heating of some form will be required as winter approaches and this should normally be combined with insulation to reduce the energy bill associated with heating.

Greenhouse misting systems help to maintain a correct balance of temperature and humidity.

Watering and sprinkling and irrigation systems play a vital role in the well designed and built greenhouse.

Flooring is important to make life easier on yourself.

Benching and staging needs to be well considered before you build the greenhouse.

And plants and human beings also benefit from light in the greenhouse.

If after all this you decide you just want a cold frame, solarium, hobby or mini greenhouses then no problem ... you can always graduate to that big glass castle later. That's the beauty of dealing with Two Wests ... nothing is too small or too big. They can handle all greenhouse building projects superbly well.