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Where should the patio face to get the most sun?

Put the patio south if you want to use it early in the year, and west if you want to use it in the evening — and keep it clear of the house's own shadow, which at midwinter is many times the height of the house.

The patio's orientation is a choice of time of day

A patio cannot be in two places, and the sun moves from east through south to west over the course of the day. So the question is not which orientation is best, but when the patio needs to be used.

• South: sun from mid-morning to late afternoon. The patio that becomes usable earliest in spring and latest into autumn, because it catches the low sun in the shoulder seasons. Can get very hot in the middle of a summer's day without shade.
• West: sun from midday until sunset. The classic choice for anyone eating outdoors in the evening. In summer, at northern latitudes, the sun sets around the north-west, so evening sun also grazes the patio's north side. No sun in the morning.
• East: morning sun until around midday, then the house's own shadow. Good for morning coffee, cool in the afternoon — and useless as an evening spot.
• North: no direct sun except quite early and quite late around the summer solstice, when the sun rises in the north-east and sets in the north-west. Suited to a shaded spot during heatwaves, not to a main patio.

Many people solve this by having two seating areas: one by the house on the west side for dinner, and a freestanding spot further out in the garden facing south for spring. It's cheaper than moving the house.

The house's own shadow is the one people forget

A patio on the north side of the house, or behind a tall house, sits in the house's own shadow for a large part of the year. The length can be calculated:

shadow length = height ÷ tan(sun angle)

The sun angle depends on how far north you live. At 56° north — southern Scandinavia and northern Germany — the sun stands around 57° above the horizon at midday at the summer solstice, 34° at the equinox and 11° at the winter solstice. Live further south and the sun stands higher, so every shadow is shorter. For a house 8 metres to the ridge, the three figures give:

• 21 June: 8 ÷ tan(57°) = 8 ÷ 1.54 = 5.2 metres of shadow to the north.
• Equinox in March and September: 8 ÷ tan(34°) = 8 ÷ 0.675 = 11.9 metres.
• 21 December: 8 ÷ tan(11°) = 8 ÷ 0.194 = 41 metres.

And that is at midday, when the shadow is shortest. Morning and evening it is longer.

The practical consequence: a patio sitting 6 metres north of the house has sun at the height of summer and shadow from late August until well into April. That is exactly the patio people build in July and regret the following May.

Design for the shoulder seasons, not for July

Every patio gets sun in July. It's March, April, September and October that decide whether a patio gets used 40 days a year or 120.

So work with the sun angle at the equinox — around 34° at 56° north, higher further south — as the measure of whether the patio works in the shoulder season. The shadow angle from whatever is in the way is found as arctan(height ÷ distance). If it's under 34°, there's sun at midday at the equinox.

Example: a 3-metre-tall carport stands 6 metres south of the patio. arctan(3 ÷ 6) = arctan(0.5) = 26.6°. Under 34, so sun at the equinox — but over 11, so shadow at midwinter. Move the patio 2 metres further away and it becomes arctan(3 ÷ 8) = 20.6°, and the spring and autumn sun reaches the paving earlier.

Five things that shift more than the orientation

• The distance from the house. Move the patio 3 metres further out from a south wall and it doesn't matter much — but move it 3 metres further out from a north wall, and it can be the difference between sun and no sun in April.
• Fences and hedges to the south and west. A 1.8-metre-tall board fence casts a 9-metre shadow at the winter solstice, 2.7 metres at the equinox and 1.2 metres at midsummer. Windbreaks cost you light — put them to the north and east, where they cost the least.
• Cover. A fixed roof takes sun all year round. A pergola with deciduous planting, or a retractable awning, gives shade in July and sun in April.
• Ground level. A patio raised half a metre above the level of the garden looks over low hedges and short shadows, and dries out and warms up faster in spring.
• Shelter matters more than degrees. A south-facing patio in a constant westerly wind gets used less than a west-facing patio that's sheltered. Screen against the direction the wind comes from — not the direction the sun comes from.

How to check a patio's placement before you build it

1. Find the house's orientation as a bearing — the north arrow on the floor plan, a map with north up, or the phone's compass held against an exterior wall.
2. Mark out the intended spot with string or spray paint.
3. Go out three times on the same day — mid-morning, midday, late afternoon — and photograph where the edge of the shadow falls.
4. Measure the height of, and distance to, anything standing south, south-east and south-west of the spot, and work out arctan(height ÷ distance).
5. Compare the figure against 34° for the shoulder season and 57° for high summer. The winter sun's 11 degrees is rarely worth optimising for — few people eat outdoors in January.

If you have the home's floor plan to scale and correctly placed on the map, the shadows can be simulated instead of guessed. In HouseSense, the home's footprint is placed on the map, so both the address's position and the house's orientation are set, and the sunlight in the 3D model is then calculated for a date and time you choose — for example 6 pm on 1 May, which shows whether the house itself stands in the way of the evening sun.