The missing question: what is above the balcony?
Compass direction describes where a balcony opens, but says little about the roof, slab or balcony above it. An overhang can intercept direct sunlight before it reaches the floor or the window behind. Side walls can block low sun arriving at an angle.
This explains why two balconies facing the same way can behave differently. One is open to the sky; the other is recessed beneath a deep slab. Even on the same balcony, the outer edge may be sunny while a chair near the wall remains shaded.
High summer sun and low winter sun take different paths
When the sun is high, an overhang can cast a deep shadow below it. At a lower angle, sunlight may pass underneath and travel further toward the wall. That does not guarantee winter sun: a building across the street can block the low-angle light first.
The US Department of Energy's passive solar home design guide illustrates how appropriately designed overhangs can limit high summer sun while admitting lower winter sun. The result depends on latitude, orientation and dimensions. A standard rule for one climate is not a design prescription for every balcony.
Four things to inspect on site
- Depth: how far does the slab or roof project beyond the window or seating area?
- Height: how much open space is there between the balcony floor and its ceiling?
- Side obstructions: do walls, screens or the building's shape block morning or afternoon directions?
- External horizon: what buildings, trees or terrain lie beyond the balcony?
Measure only where it is safe and permitted, or ask for drawings. Do not lean beyond railings to obtain dimensions. For building alterations, use a qualified designer and the applicable local requirements.
Why a street-level map cannot settle the question
Coffee in the Sun estimates shadows from mapped building outlines and heights. It does not perform a balcony-specific calculation at a chosen floor or represent every slab, railing, side screen or window. Trees, awnings and terrain are outside that model too.
A sunny patch on the map therefore does not prove that your balcony floor or indoor sofa receives direct sun. Use the map to investigate neighbouring buildings, then assess the balcony's own geometry and observations separately.
Test the usable space, not just the railing
On a clear day, photograph the floor near the outside edge, your intended chair and the window at the times you care about. Record date and local time. Repeat at another season if possible, or request dated photographs from the occupant.
If the goal is breakfast outside, ten sunlit centimetres on the railing are not the relevant result. If the goal is summer shade, a well-positioned overhang may be an advantage. Use our balcony direction guide and viewing checklist to put those observations in context.
