What is patina?
Patina is the layer that forms on a material surface over time through the action of air, water and light. On metals it is a corrosion product that actually protects the material beneath; on timber and stone it is a matter of discolouration, soiling and surface erosion. Patina is therefore not damage but the visible […]
What is patent glazing?
Patent glazing is a roof glazing system in which the glass is not bedded in putty but clamped between the upstands of a metal-clad bar. The bar itself — traditionally a steel inverted-T section — carries the load, while a folded zinc or lead sheath around it forms the watertight channel the panes sit in. […]
What is past performance?
Past performance is the systematic use of a contractor’s or consultant’s previously delivered performance when selecting or awarding a new contract. Instead of judging only what a tenderer promises, the client looks at what that party has actually delivered before. Performance measurement and past performance The two terms are often used interchangeably, but they differ: […]
What is passivation?
Passivation is the formation of an extremely thin, dense oxide film on a metal surface that stops the metal corroding further. In construction it almost always refers to the passivation of reinforcing steel in concrete: the strongly alkaline pore water of concrete forms an oxide skin on the steel that protects it for decades. How […]
What is header bond?
In header bond every course of the wall is a course of headers: the whole wall shows nothing but the short ends of the bricks. Each course is offset by half a header from the one below. The Dutch names are *patijtsverband* and *koppenverband*. Why headers only In a wall more than one brick thick, […]
What is a shopping arcade (passage)?
A shopping arcade — in Dutch, French and German a *passage* — is a covered route through a city block, publicly accessible at both ends, with shops or apartments on either side and usually a glazed roof above. It combines the openness of a street with the shelter of a building. Origin and make-up The […]
What is a pear-shaped bead?
A pear-shaped bead is a moulding whose cross-section has more or less the shape of a pear: a rounded, full head that narrows towards the back or the base. It is one of the characteristic Gothic profile forms and occurs in both timber and stone. The Dutch term is *peerkraal*, literally “pear bead”. Form and […]
What is a patio?
A patio is an enclosed outdoor space bounded on several sides — often all four — by building or walls, and open to the sky. The word is Spanish and refers to the courtyard of the traditional southern European and Moorish house, where the building turns inward around a cool, sheltered core. In everyday British […]
What is a paternoster lift?
A paternoster is a lift in which a series of open cars hangs from two endless chains and circulates continuously: up one shaft and down the other. It never stops; you step in and out while the car moves slowly past the floor level. The name refers to the rosary — beads on one continuous […]
What is a patera?
A patera is a disc-shaped ornament, usually made up of concentric rings or a round, leaf-like motif. The plural is *paterae*. The name comes from the Latin word for a shallow offering or drinking dish; the ornament is a stylised representation of one. Form and variants Concentric rings — the simplest form: a flat disc […]