What is a leaning façade (op vlucht)?
The Dutch term op vlucht means that a façade is not built plumb but deliberately leans forward, so that the top stands further out than the base. It is an intentional way of building, not a defect.
That is worth knowing when looking at old buildings: a forward-leaning façade is often mistaken for subsidence or for a hazard, when in many cases it was meant to be exactly that way. A rule of thumb for historic façades is a lean of about 25 mm per metre of height; on a ten-metre façade the top therefore stands some 250 mm forward.
Why build this way?
The main reason was water. Rain running down a vertical façade penetrates the masonry and reaches the floor joists, the timber elements of the elevation, the frames and the leaded lights. With a façade leaning forward, the water falls clear of the wall face sooner and the timber behind stays drier. The technique descends from medieval jettied timber framing, where each storey projected a little, and was used in the Netherlands mainly between about 1600 and 1750.
Later, aesthetic motives were added: a leaning façade reads better from the street and looks taller and more imposing than a strictly vertical one.
Cities did set limits on the lean, because façades overhanging too far narrowed the street and were dangerous. Amsterdam laid down a maximum of about 100 mm over 3,600 mm of height as early as 1532.
Points to note
- Tell a deliberate lean from settlement. With an intentional lean the whole face slopes evenly and the bed joints stay straight and level. With settlement you see cracks, bed joints running out of level and binding windows.
- Measure when in doubt. A plumb line or laser down the façade, and levelling along a bed joint over a few months, will show whether anything is moving.
- Keep the lean when restoring. Bringing a façade back to plumb does not suit the building and creates unresolvable junctions with the neighbouring properties.
- Allow for the lean in scaffolding, frames and roofing — every dimension at the top differs from the one at the base.
| Deliberate lean | The whole face slopes evenly and the bed joints stay straight and level |
|---|---|
| Settlement | Cracks, bed joints running out of level and binding windows |
Related terms
- Façade
- Building line
- Bricklaying
- Jetty (overhang)
- Settlement
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