Garden Greenhouse Planning Questions Checklist

Write down what the greenhouse is meant to do, whether that is raising young plants, keeping tender ones through the cold season, growing on, or somewhere to work under cover.

These purposes need different sizes, positions and fittings, and a greenhouse chosen without settling this tends to suit none of them well.

Note which parts of the year it would actually be in use, and be honest about whether anything would be happening in it outside the growing season.

A greenhouse used for only part of the year still occupies the same ground and needs the same attention when empty.

Name the person who would look after it and record roughly how often they are at home during the middle of the day in warm weather.

The attention a greenhouse needs falls at the hottest part of the day, which is precisely when many households are out.

Consider whether you would want to stand and work inside it, and note what that means for staging, a clear area and room to turn around with a tray.

A greenhouse filled to the walls has nowhere to work, which is discovered on the first day it is used.

Decide whether pots, bags of material and tools would end up stored in it, and record where those would go if the answer is that they should not.

Greenhouses become stores by default, and the alternative place for that material has to exist somewhere on the plot.

Note what else could serve the same purpose in this garden, such as a cold frame, a covered bed or a sheltered wall, and record why a greenhouse is preferred.

Writing down the comparison makes it easier to size the greenhouse sensibly rather than by ambition.

Stand in each candidate position at the start, middle and end of the day and note what is in sun and what is in shadow, writing the times down as you go.

A single visit gives a misleading picture, and several observations across a single day usually settle the choice between positions.

Note how far the shadow of the house, a hedge or a fence reaches across the plot when the sun is at its lowest, and mark that on your sketch.

Positions that are bright in the growing season can be in permanent shadow for the rest of the year, which matters if the greenhouse is used then.

Ask a qualified garden professional whether the position you prefer would need shading in strong sun, and what providing that would involve.

Shading is part of the arrangement rather than an accessory, and it is easier to allow for before a structure is chosen.

Whether and how a greenhouse needs shading in a particular position is a horticultural and product question for a qualified professional and the supplier.

Consider whether glass in that position would reflect towards your own windows or a neighbour's, and note the times of day that would happen.

Reflected light from a large glazed structure is a genuine neighbour matter and is not obvious from a plan.

Ask the supplier and a qualified garden professional which way the structure should be turned in this position, and record what each of them says.

Orientation affects light through the day and is difficult to change once a base has been laid.

Note what would land on the glass across the year at each candidate position, including leaves, needles, seed, fruit and anything sticky from a canopy above.

Debris on glass reduces the light the structure was chosen for and turns cleaning into a recurring task.

Put every question about a tree above or beside a possible position to a qualified arborist, including what hangs over it now and what might come down in a storm.

What is overhead is the single most important question at a wooded position and it is not one to answer yourself.

All questions about trees, including anything overhanging a proposed position, belong with a qualified arborist, and no tree work should be contemplated on any other basis.

Ask how much larger the surrounding trees and hedges are expected to become, and note which candidate positions would be shaded once they have grown.

A position chosen for its light can lose it within a few growing seasons, and this is straightforward to ask about now.

Ask a qualified arborist and a qualified professional what the roots near each candidate position mean for laying a base there, and record the answer.

Ground near established trees raises questions about both the tree and the base, and the two have to be considered together.

Anything involving ground near an established tree must be assessed by a qualified arborist and a qualified professional before any base is planned.

Note whether a greenhouse in that position would block access to a hedge or boundary that has to be reached for upkeep, including from the neighbour's side.

Structures placed tight to a boundary frequently make the boundary itself impossible to look after.

Note whether each candidate position is level and record roughly how much the ground falls across the footprint you have in mind.

A fall across the footprint changes what the base has to do and is the first thing a professional will want to know.

Ask the supplier what base the structure requires and a qualified professional what providing that base on this ground would involve.

These are two different questions and the answers rarely match without discussion.

What base a greenhouse requires comes from the supplier, and whether it can be provided on your ground is a matter for a qualified professional.

Ask how the structure is held down in the wind at your position, and record what that means for the base and for anything fixed into the ground.

Holding down is a base question as much as a structural one, and it is often what decides the type of base.

How any structure is anchored against wind must be established by the supplier and a qualified professional for the specific position and exposure.

Ask a qualified professional to establish what lies beneath each candidate position before any ground is opened, and record what is found.

Services and old made-up ground are common in gardens and they can rule a position out entirely.

Anything buried must be established by a qualified professional before ground is opened, however shallow the work is expected to be.

Decide what the ground inside would be, whether soil for growing directly, a hard surface, or a mixture, and record that alongside the base question.

What happens inside affects the base itself, so it has to be decided before the base is laid rather than afterwards.

Note where water would run once the footprint is covered, and ask a qualified professional what should be provided for it around the base.

A glazed roof sheds a considerable amount of water into a small area, which has to be accounted for at ground level.

Where roof water from a structure may be directed is a drainage matter for a qualified professional and should be confirmed with the local authority.

Note where wind funnels across the plot, usually between buildings or along a boundary, and record where things have blown over or been damaged before.

Past damage is the most reliable evidence available about exposure, and it is usually remembered rather than recorded.

Record what shelter each candidate position has and from which direction, distinguishing between solid shelter and something that only filters the wind.

The kind of shelter matters as much as the amount, and it is a question a designer can respond to directly.

Consider which way the door would face and what happens to it when it is open in a strong wind, and note whether it can be held back safely.

A door catching the wind is a common cause of damage and it is decided by orientation, which is settled early.

Ask the supplier and a qualified professional what glazing options exist for this exposure and what each would mean where children or animals use the garden.

Glazing choice is where exposure, breakage and household use meet, and it belongs in a conversation rather than a catalogue.

Which glazing is appropriate for a given exposure and household is a matter for the supplier and a qualified professional; nothing here can determine it.

Note how close each position is to where ball games or play happen, and record what is between them.

The relationship between a glazed structure and the part of the garden used for play is far easier to resolve before either is fixed.

Ask a qualified garden professional how often watering is likely to be needed in warm weather in this position, and record who would be doing it.

The answer decides whether the greenhouse can be at the far end of the garden or has to be near the door.

How often anything under glass needs watering depends on what is grown and on local conditions, and it is a horticultural question for a qualified professional.

Note the distance from each candidate position to the nearest outdoor water point, and whether a can could be carried that far repeatedly in hot weather.

Carrying water is the daily reality of a greenhouse, and distance is what determines whether it stays in use.

Consider whether the greenhouse roof would feed a store of its own, and note where that store would stand and where its overflow would go.

A glazed roof produces a useful amount of water, but the store and its overflow need a position like any other.

Note anything you imagine plugging in inside the structure, from an opener to a heater, and take that list to a qualified electrician before choosing where it stands.

A supply outdoors may change the position or rule it out, so it belongs in the early conversation rather than the late one.

Any electrical supply to a garden structure must be designed and carried out by a qualified electrician, who can also confirm what applies locally.

Record what the approach to the door would be underfoot, and whether it works in the wet with hands full and in the dark.

The approach is used every time and is usually the last thing considered, by which point the remaining space has been given away.

Work out who would be at home on the hottest days to open and close anything that needs opening, and write down what happens if nobody is.

This single question decides whether an automatic arrangement is needed, and it is worth answering honestly at the outset.

Ask the supplier what ventilation each option has and a qualified garden professional whether that is likely to be enough in this position.

Ventilation provision varies considerably between structures and it is not something to judge by appearance.

Whether the ventilation of a particular structure suits a particular position is a question for the supplier and a qualified garden professional.

Ask whether openers that work without anyone present are available for the structure you are considering, and what looking after them involves.

Arrangements that work unattended change what a greenhouse asks of a household that is out during the day.

Ask a qualified professional what keeping a greenhouse usable in the cold season would involve here, and record it before deciding to use it year round.

Keeping a structure above outside conditions is a different proposition from simply having one, and it should be understood in advance.

Any heating arrangement for a garden structure is a matter for qualified specialists and the supplier, and no method should be assumed from general information.

Note that condensation and damp are part of how these structures behave, and ask what that means for anything you were thinking of storing inside.

Items stored in a greenhouse are exposed to conditions quite unlike those in a dry store, which is often discovered too late.

Decide who would look after the greenhouse if the household were away in warm weather, and record what they would need to be told to do.

A greenhouse left unattended in a warm spell is where most of the disappointment happens, and cover has to be arranged rather than hoped for.

Ask what cleaning the glazing needs to keep the light coming through, and note whether the outside of every face could be reached from the position you have in mind.

A face tight against a fence or a hedge cannot be cleaned, which gradually undoes the reason for the structure.

How any glazing should be cleaned is a matter for the supplier, and any work at height belongs with a qualified professional.

Record how much clear space would remain around the whole structure, and whether a person could pass along every side with a barrow or a tray.

Clear space around the structure is needed for cleaning, upkeep and any later repair, and it is usually the first thing given away.

Note the doorway arrangement and whether the things you would be carrying, including trays, bags and containers, would go through it comfortably.

Door width and threshold detail decide how the greenhouse is used daily, and they vary between structures.

Ask the supplier what happens if a pane is broken, how a replacement is obtained and what clearing up would involve where children or animals use the garden.

Breakage is a practical certainty over the life of a glazed structure and the answer differs by glazing type.

Dealing with broken glazing, and what that means where children or animals are present, is a matter for the supplier and a qualified professional.

Consider what has to come out of the greenhouse at the end of the growing season and where it would go, including anything too large for a shelf.

The overflow at the end of the season is a storage problem elsewhere in the garden, and it needs a place before it happens.

Ask the local authority what applies where you are to a garden structure of the size and height you are considering, and record exactly what you are told.

Requirements differ from place to place and by property, so this must be established rather than assumed from anything general.

Whether any structure needs consent is determined by the local authority for your property, and no general statement about it can be relied upon.

Ask the local authority and a qualified professional what has to be considered about the distance between a structure and a boundary here, and note the answer.

Distance to a boundary affects both what is permitted and what is practical for upkeep on both sides.

Ask whether anything applies to your property or area that affects garden structures, and check any documents you hold about the property for restrictions.

Restrictions attached to a property are easy to overlook and are usually discovered by someone else at an inconvenient point.

Any restriction attached to a property is a legal question for a qualified adviser, and its effect should be confirmed with the local authority.

Ask your insurer whether a new garden structure needs to be mentioned to them, and record their answer with the rest of your notes.

This takes one conversation and is the sort of thing that is only remembered after something has happened.

Keep every answer you are given in writing with your sketch and photographs, so that a professional appointed later starts from what has already been established.

Answers held only in memory get reworked, and a written set shortens every conversation that follows.