A greenhouse is a major investment for your garden and one that’s not easy to move or replace once installed, so it's important to pick the right one for your needs.
Whether you want a small greenhouse to protect trays or pots of young plants or you’d prefer a larger, freestanding greenhouse that offers enough room for you to work on your fruit and veg inside, our expert guide will explain everything you need to know.
Keep reading to find out the optimal greenhouse materials and sizes to the best features, accessories and heaters, plus our top tips on how to build a greenhouse.
We run through the pros and cons of some of the most popular greenhouse types:
Most people opt for a 6 x 8ft or 8 x 10ft freestanding greenhouse. Typically square or rectangular with an apex roof, you can get them in a variety of sizes and they allow light in from all four sides.
Consider making use of a back or side wall with a lean-to greenhouse. The initial purchase costs are similar to a freestanding model, but it takes up less space and you only need access around three sides. It is also cheaper and easier to keep warm.
A mini greenhouse is like a glazed cupboard with shelves that sits on a patio or under a window, using a house wall or garage as protection – perfect if space is limited. It will protect trays or pots of young plants from late frosts in spring, and encourage borderline crops such as peppers to ripen. Ideally, a mini greenhouse should face east or west. South-facing ones overheat in spring or summer unless shaded and north-facing ones suit only shade-loving plants.
Most greenhouse frames are made of aluminium, but wooden greenhouses are also available and many gardeners find them more attractive to look at, although they need more maintenance than metal frames.
Aluminium is the most common material for greenhouses which means you’ll be spoilt for choice. Available in a variety of sizes and shapes and to suit all types of budgets, here’s some pros and cons to be aware of.
Wooden greenhouses are less common and typically cost more than their aluminium counterparts. Picking the right type of wood will help avoid a greenhouse that’s vulnerable to rot. Softwoods, such as deal (pine), are vulnerable to rot, even if the timber has been treated.
Naturally durable timber – usually western red cedar – can be left to age to a silver-brown. For looks, a western red cedar greenhouse is hard to beat. Look for manufacturers that offer a guarantee against rot. Here are some other pros and cons to be aware of.
Glass is the main glazing material used in greenhouses, hence the alternative name ‘glasshouse’. Horticultural glass is inexpensive and easily replaced, but if you are concerned about breakages or safety, you can opt for a plastic greenhouse.
Plastic greenhouses have twin-walled polycarbonate sheets. Polycarbonate greenhouses let in sufficient light for plant growth initially, but, over the years, they can become cloudy and do not age well. Toughened glass is a better option, particularly if the greenhouse is on show.
Toughened or safety glass is stronger than horticultural glass and, if it does break, the resulting pieces are not so sharp. Choosing this option adds about £200 on to the cost of a small greenhouse.
Another option is self-adhesive safety film. This is a transparent film that is applied to horticultural glass. If the glass is subsequently broken, the film holds the fragments together. However, as the film does not reduce breakages, it could prove relatively expensive over the option of choosing toughened glass from the start.
The cheapest greenhouses will almost always be smaller, aluminium models and will set you back around £200 or more.
Anything under £200 is most likely to be a mini greenhouse or a cold frame.
Larger, wooden structures and greenhouses with ready-made shelving and additional accessories can cost anywhere between £1000 and £4000.
Both generalist retailers and dedicated garden shops offer a wide range of greenhouses. To make sure you're buying a greenhouse that's well built and safe to use, only shop with trusted sellers online or in-store.
Ideally, you'd get to see the greenhouse in-store before buying, but if this isn’t possible, find out as much information about it as possible before investing.
Popular shops that sell greenhouses include:
The size of your greenhouse will be limited to what you can fit in your garden. So for most of us it will be fairly modest, especially if you live in the city. Larger structures will also typically cost more so even if size isn’t a factor, budget might be.
Your best bet is to opt for the biggest greenhouse you can. Width is an important dimension because this will determine the benches and aisles.
Common greenhouse sizes are:
Most people opt for a 6 x 8ft or 8 x 10ft freestanding greenhouse. This is wide enough for a central path, with shelving on one side to hold a propagator and potted plants, and a greenhouse border on the other side, so tall cropping plants, such as cordon tomatoes and cucumbers, can be planted direct into the soil.
12 feet wide is a semi-professional width, and anything above this is a typically for more commercial use.
One thing to remember is to make sure you can get in and out of the door easily and that you feel comfortable once inside (low greenhouses can feel claustrophobic).
If space is super-limited then you might want to opt for a mini greenhouse that will sit under a window or against the wall.
In practice, there are probably only one or two suitable places in your garden, so the size of greenhouse you opt for will be limited by that – which is why most people end up with a small one. Here some top tips to picking the perfect place for your greenhouse:
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You'll need an electric fan heater rated at least 2kW to guarantee keeping a standard 6ft x 8ft greenhouse frost free in most parts of the UK. If you opt for a gas or paraffin heater it'll need to be about 20 per cent more powerful to compensate for the heat lost via the greenhouse vents left open to allow poisonous gases and water vapour out and oxygen in.
Lining the glass with bubble insulation will also help to retain the heat and keep your greenhouse snug in the depths of winter.
Electric greenhouse heater
If you greenhouse has an outdoor socket with an RCD nearby, a thermostatically controlled fan heater is ideal. They're cheap to run and the fan not only helps distribute the heat but also encourages air movement which in turn reduces the risk of fungal diseases that favour still, damp air.
Bottle gas greenhouse heater
If you don't have an outdoor socket, a bottle gas heater with a thermostat is a good option. Bear in mind that they're heavier and bulkier than electric heaters. They're also trickier to switch on and have no fan so there may be cold spots in the greenhouse, particularly at floor level.
Gas heaters produce water vapour so you'll need to leave vents open for it to escape or you could run into problems with fungal diseases. Good ventilation also ensures that the heater doesn't run short of oxygen and start giving off toxic gases such as carbon monoxide.
Paraffin greenhouse heater
These heaters need to be filled up very frequently, and safety-wise there's not much to recommend as they tend to be easy to knock over and they're a fire risk.