Greenhouse Guide

First-time Buyer? 10 Things To Consider

In the last decade, greenhouses have become enormously popular in Ireland. Not only do they allow you to nurture shoots and seeds, cultivate exotic plants and flowers, and grow organic fruits and vegetables, but they also provide you with a tranquil space to relax in your garden. For anyone thinking of buying a greenhouse, the benefits are plain and simple. But for anyone starting out on their greenhouse journey, finding the right greenhouse is much more difficult. We have prepared a greenhouse guide to help first-time buyers to ask the right questions before they buy. 

Greenhouse sales on the up

Why you need a guide

Type “Irish greenhouses” into Google and you will find a long list of suppliers offering you hundreds of different models of varying price and quality – from the cheap and flimsy to the strong and overpriced. Not only that, but there are so many other variables to consider. Do you want a wooden or aluminium frame? Polycarbonate or toughened glass? Free-standing or lean-to?  For both novice and experienced gardeners alike, buying a greenhouse can be confusing. 

Below are ten things to think about before you buy. 

1. Site

Take your time to choose a site because it will impact on all of your subsequent decisions.  You should choose a site that is both firm and flat. Make sure you leave enough space on the sides to allow you to clean the exterior panels. Avoid positioning your greenhouse under trees or overhanging branches, and make sure you have easy access to your water and, if necessary, electricity supply.

Choose a site carefully

Above all, choose a site which receives ample sunlight. Even a state-of-the-art greenhouse won’t generate enough heat if it’s hidden in the shade. Some experts recommend facing the side of your greenhouse southwards. This is good advice if the length of your greenhouse is significantly greater than the width. But it’s not essential if you have, say, a 6 x 8 foot model. 

2. Size

The most common advice you will hear when buying a greenhouse is “buy the biggest greenhouse you can accommodate”. That this cliche probably originated with greenhouse salesmen shouldn’t put you off. Space is genuinely important – after sunlight, it’s your most important asset. Within a couple of seasons, you’ll be wishing you had some extra space to squeeze in an extra row of tomatoes.

Lastly, make sure your greenhouse has enough headroom under which you can work. Many cheaper greenhouses are built with a low eaves in order to keep costs down. If you intend to spend long periods in your greenhouse, you don’t want to end up stooping.

Small 8×8 Greenhouse

3. Style

Greenhouses come in many different shapes and sizes. Most domestic greenhouses are rectangular with a pitched roof. But you can also find hexagonal, octagonal, dome-shaped, and semi cylindrical models. You can also build customised greenhouses which are considerably more expensive than standardised models. For example, you can attach a lean-to greenhouses to the exterior wall of your house, or you can fix a greenhouse frame onto a customised dwarf-wall for aesthetic effect.   

Traditional pitched roof greenhouse

In Ireland, traditional pitched roof greenhouses are by far the most popular style. Not only do they look good but they can be positioned to maximise their exposure to to sun. In winter, their rigid structure stands firm against heavy rainfall and windstorms. 

4. Frame

The frame of a greenhouse is generally built from wood or aluminium.

Wooden frames are impressively sturdy and their soft organic features blend naturally into the greenery of any garden.  But they are expensive, require maintenance, and rot if not carefully protected. 

Aluminium greenhouse are strong, require little maintenance, and if powder-coated, they will last for up to twenty five years. They generally sell for a quarter of the price of their wooden counterparts and come in a wide range of colours that will suit almost any garden.

But be careful. Avoid aluminium framed that look flimsy or weak. A good quality aluminium frame has sufficiently thick posts and joints, as well as cantilever supports. 

Cantilever supports for roof and staging

5. Glazing

Greenhouse glazing is made from polycarbonate, horticulture glass or toughened glass. 

Horticultural glass is an old-fashioned glass which captures a wider frequency of light than polycarbonate or toughened glass.  It’s the cheapest glass you can buy, but it may cost you more in the long run because the panels often break and need to be replaced. When the glass breaks, it cracks into large jagged shards which is particularly dangerous if you have children or pets in your garden. 

Toughened glass is a modern alternative to horticultural glass. It admits almost as much light, but it’s five times as strong and significantly heavier. Unlike polycarbonate, the panels won’t blow away in heavy wind, and the extra weight helps to reinforce to the greenhouse frame. It’s much safer than horticultural glass and can withstand the full force of a leather football without breaking. In the rare event that it does break, the panels shatter instantly into thousands of tiny pieces. At worst, you will end up with a minor scratch. 

Polycarbonate glazing is a material not dissimilar to plastic. It is cheap, safe, and good for insulation.  But polycarbonate greenhouses admit less sunlight than glass and they often blow away in heavy wind. The translucent glazing is noticeably synthetic and you may  find it looks out of place in the organic surroundings of your garden. 

If you are looking for glazing that is strong, elegant, and safe, toughened glass with a bar capping system is your best option. 

6. Clips or Bar capping

Once you choose your glazing, you must decide how to secure the panels to the greenhouse frame. On cheaper greenhouses, the panels are usually held in place by metal clips.  But these clips are fragile and should be avoided if your greenhouse is on a site that is exposed to strong winds. If you are looking for a more durable option, look for a greenhouse where the glass panels are held in place by bar capping.  Not only will it firmly secure the glazing, it will also add extra insulation and reinforce the greenhouse frame. 

7. Extra Features

A greenhouse is more than a roof and four walls. You need to equip it with the tools to help you make the most of your garden.

Most suppliers offer louvre windows, roof ventilators, automatic openers, staging, gutters, downpipes, and sunshades. But be careful. These extra features are not included in the initial asking price – and like hidden airline fees, they quickly add up. 

To novice gardeners, some of these features may seem unnecessary. But anyone serious about greenhouses knows they crucial. In particular, it is essential to have enough ventilation to allow you control the temperature of your greenhouse in hot weather.

automatic roof vents

8. Foundations

Like all buildings, a greenhouse is only as strong as the foundation on which it’s built. Greenhouse foundations are usually made of bricks, flagstones or concrete into which the greenhouse is firmly bolted.  They will stop your greenhouse warping and protect it from blowing over in stormy weather. Without one, your greenhouse simply will not last. 

Before you lay the foundation, make sure the ground is firm and level. If you are laying a cement foundation leave room in the middle to grow plants and drain water.  If you are laying bricks, consider using mortar to reinforce the brickwork. 

Concrete Foundation

9. Delivery & Installation

Most greenhouses in Ireland are imported from the UK and it usually takes six weeks for delivery.

It can be complicated and time consuming to install a greenhouse by yourself.  So if you’re not handy with a set of tools consider hiring a professional. Most greenhouse companies will provide provide installation services for a fee.

10. Price & conclusion 

There’s an old joke where a man walks into a specialist wine shop and says: “Can you recommend me a cheap bottle of red?”. The owner replies: “How much do you want to spend? Cheap could mean £15 or £150 – and I don’t want to offend.” 

Like wine, how much you spend on a greenhouse depends on what you’re looking for – and, to a large extent, your budget. But there are a few things that are important to remember. 

A cheap greenhouse won’t last more than a few seasons – some may even blow down in the first windstorm. On the other hand, a well-built greenhouse will last perhaps as long as twenty five years. 

Remember that most gardeners acquire expertise over the years so the longer you have one the more you will want from it. Think of the greenhouse you will want five years from now. 

Beyond that, the hallmarks of all longstanding greenhouse are the same: broad aluminium posts, toughened glass, powder coated aluminium, cantilever supports, cement base.