In a row of arches the thrusts of neighbouring arches cancel over each intermediate pier, which may therefore be slender; at the ends of the row nothing balances them, so the outermost piers must be made wider or buttressed.
Lombard bands and pilaster strips
Articulate plain rubble walls outside with shallow vertical strips (lesenes) linked at the top by a frieze of small round arches on corbels: the Lombard band.
The motif spread with the itinerant builders of northern Italy (the magistri comacini) through Catalonia, Burgundy and the Rhine in the early eleventh century, the phase Josep Puig i Cadafalch called the First Romanesque. It costs little, needs no sculptor, and turns a blank wall into a measured one; it survives on towers, apses and eaves throughout the period.
Related rules
Over a doorway or window spanned by a lintel, turn an arch in the wall above so that the weight of the masonry is carried round the opening onto the jambs, leaving the lintel to carry only the small triangle of wall beneath the arch.
Design a rose by dividing the circle into equal sectors; fill each with the same traceried unit (a light with a cusped pointed head, an oculus above) radiating from a central hub, so that the whole is generated from one sector by rotation.
n petals · each sector 360° ⁄ n
Carry vaults on walls thick enough to absorb their thrust within their own mass; keep the windows small and set them low, below the springing of the vault, and strengthen the walls outside with shallow pilaster buttresses.
walls commonly 1½–2 m thick; buttresses shallow, window openings narrow and splayed
Run a shaft or pilaster from the floor, up the face of the pier and the wall above, to the roof or vault, so that the long nave wall is divided into a sequence of vertical bays, each containing one arch of the arcade and the windows above it.
A barrel (tunnel) vault is an arch extruded along its axis. It thrusts outward all along both sides, so it must rest on continuous thick walls, which can be pierced only sparingly, and only below its springing.
thrust per metre of wall ≈ constant along the whole length
Cite this page Chris Paton, “Lombard bands and pilaster strips”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/rom-lombard-band. Text, drawings and models licensed under CC BY-NC 4.0.