The vertical section is the drawing that maps how light moves. Not where light enters — that is visible in a floor plan — but how far it travels, which surfaces it illuminates in sequence, and how that sequence changes across the day and year. Light movement is a spatial event visible only in section.
Light as Geometry in Section
A ray of sunlight has a direction determined by the sun's position in the sky. That direction is measurable: for any latitude, date, and hour, the angle of the sun above the horizon and its azimuth from north are known quantities. In a vertical section drawing, we can represent that ray as a line entering through a window opening and traveling through the interior space.
Where that line strikes the floor, it marks the boundary of the sunlit zone on a given date at a given hour. Where it strikes the ceiling, it marks the illuminated upper surface. Where it is intercepted by a wall, beam, or overhang, it produces a shadow edge.
Drawing multiple ray lines — for nine in the morning, noon, and three in the afternoon at winter solstice and summer solstice — produces a map of how light moves through the space across the year. This is not a rendering; it is a geometric analysis. The section becomes a light calendar.
Ceiling Height and Light Penetration
The relationship between ceiling height and light penetration depth is one of the most useful rules in section analysis. For a standard window — head height at 2.3 meters, sill at 0.9 meters — direct light on a winter day in Mexico City enters at a steep angle and illuminates primarily the floor near the window. The back of a 5-meter-deep room receives skylight, not direct sun.
The same window in Denver, where the winter sun sits lower in the sky, sends light at a shallower angle. The ray travels deeper horizontally before reaching the floor. A 5-meter-deep room in Denver receives direct winter sun on its back wall — a different spatial experience from the Mexico City version, produced by the same window simply placed at a different latitude.
Raise the window head height to 3.0 meters — or add a clerestory above the main window — and the geometry changes again. Higher entry points allow steeper angled light to enter without being intercepted by the room's depth. They also direct more light onto the ceiling, which then becomes a secondary light source, redistributing illumination toward the parts of the room the window cannot directly reach.
This is why we develop vertical sections early. The ceiling height decision, the window head height decision, and the room depth are interdependent. Change one and the light map changes. The section makes that interdependence explicit.
Shadow as the Counterpart of Light Movement
La sombra antes que la luz. Shadow is not the absence of light — it is a designed condition that defines the quality of the light around it. In a vertical section, we design shadow as deliberately as we design light.
An overhang positioned at the correct depth casts a shadow line across the upper portion of a south-facing window during summer, when the sun is high. In winter, the lower sun angle clears the overhang and enters the room. The section shows both conditions simultaneously: the summer shadow line and the winter light cone, in the same drawing, comparing them against the window opening.
A wall return beside a window creates a shadow that frames the incoming light. A deep reveal in stone or concrete produces a gradual shadow transition from outside to inside, giving the light a quality of enclosure rather than rawness. These are section decisions — visible only when the drawing is cut vertically through the wall at the window location.
How Light Movement Changes the Experience of a Space
A room where direct sunlight moves across the floor and walls during the day is experienced differently from a room with static, diffuse illumination. The moving shadow of a structural column at midday, the slow travel of a light rectangle across a concrete floor between ten and two, the moment when afternoon light reaches the back wall of a north-facing alcove through a skylight above: these are temporal experiences of architecture that the section predicts and the design controls.
At MÉTODO, we think of light movement as a material property of a space. Just as stone has texture and weight, and timber has grain and warmth, a space has a light quality that changes with time. The section is the tool for designing that temporal quality.
Vertical Section Studies in Our Process
We typically develop three to five vertical section studies for a residence during schematic and design development phases:
- A longitudinal section through the primary axis of movement through the house
- A cross section through the main living space, showing light entry from the primary facade
- A section through any light wells, atriums, or double-height spaces
- Detail sections at key window conditions, showing reveal geometry and shadow cutoff
Each section is annotated with solar angle lines at winter solstice and summer solstice. We present these alongside the floor plans so that spatial decisions and light decisions are reviewed together, not separately.
Next Steps
If a design proposal you are reviewing does not include annotated vertical sections with solar geometry, the light quality of the spaces has not been designed — it has been assumed. In our experience, the difference between those two conditions is visible on the first clear morning after moving in.
Learn how the section-driven design method at MÉTODO produces spaces with intentional light quality from the earliest stages of the project.