Before you choose a greenhouse, spend a day looking at where it might go. The best spot gets enough light for what you want to grow, gives you space to work and is easy to reach with a watering can or wheelbarrow.
Watch the shadows move
Look at the site in the morning, at midday and in the afternoon. A fence that barely casts a shadow in summer can shade the same spot for much longer in spring. If you want to start seedlings early, pay particular attention to light at the beginning of the growing season.
Check the ground after rain
Look for standing water and notice where runoff from nearby roofs or paving collects. Choose a well-drained site and plan a level base that meets the requirements of your greenhouse model.
Walk the route with a wheelbarrow
Mark the footprint with stakes and string. Leave space around the greenhouse for cleaning the glazing and room at the entrance to open the door and turn a wheelbarrow. Check that a hose reaches the door without crossing a busy path. A short trial now can reveal issues that are hard to fix once the base is in place.
How much sun does a greenhouse need?
The answer depends on what you grow and when. Tomatoes and cucumbers benefit from a bright site, while some leafy crops can cope with partial shade. Look at where walls and evergreen hedges cast shadows in spring as well as summer. Mark the corners before comparing candidate locations.
Check wind, drainage and access together
Look for a location where the door is convenient to reach and where roof runoff can drain away from the base. Check whether delivery and assembly are practical along the access route. If the site is exposed, confirm the foundation and anchoring requirements for the model before preparing the base.
Compare candidate locations over a full day
Choose two possible spots and take a photo from each in the morning, around midday and in the afternoon. Use the same viewpoint so you can compare the shadows. If you plan to raise seedlings early in the year, check spring light as well as summer light. The low sun can put a location in shade even when it looks bright in June. If you want a garden room, repeat the exercise at the time you are most likely to sit inside.
Consider what creates the shade. A hedge can grow taller and change the amount of light reaching the greenhouse. A building casts a more predictable shadow. A deciduous tree can allow light through before the leaves develop and give shade during summer. Observe how much of the intended footprint is affected, since one bright corner may still suit a potting bench even if the back wall receives less light.
Check where rainwater goes
Visit the site after steady rain. Look for puddles, soft ground or a line of runoff from nearby paving. Check whether water from a shed roof or an uphill border flows across the proposed site. A photograph from a dry day can make two spots look equally suitable, while a rainy day reveals which one needs more preparation. Ask the greenhouse supplier what foundation dimensions and surface conditions the selected model requires before commissioning work.
Think about where water from the greenhouse roof will go too. If you plan to use a water butt, include it on the sketch and leave space to access the tap. Consider where the overflow can drain and how you will get to the greenhouse door without stepping through a wet patch.
Test the route for delivery and daily use
Measure the narrowest gate and note any steps, tight corners or changes in level. A clear route to the site on foot may still be awkward when carrying large components. Ask how the model is delivered and how much space the installers need around the footprint. Keep the full measurements with your photos so you can answer questions without guessing.
Then test the route you will use every week. Walk from your tap to the site, and check whether a hose can reach without crossing the most frequently used path. Carry a tray from the kitchen or shed and picture doing the same in rain. A site close to the house often makes short visits easier, while a more distant spot can suit a separate sitting area if it has a clear route.
Use the same sketch to check the door and vents
Mark the door position and the space needed to open it. Think about the direction of the prevailing wind, especially if you plan to leave the door open while working. Check whether nearby branches, a wall or an overhang could obstruct roof vents. Leave enough room beside the glazing to clean it and inspect the frame. Confirm the required access with the supplier before setting the greenhouse close to a boundary.
Choose the site that suits the main use
If two spots are similar, decide what you will do inside most often. For vegetables, compare growing light, access to water and room for beds. For dining, sit in each location and compare the view and afternoon sun. Use the greenhouse interior planning guide to check that the preferred site can fit the furniture or beds you want.