P, Q. (PFA - quoin)
 

PFA: Pulverised Fuel Ash is a waste product from power stations burning pulverised coal. The product varies with different coals and different burning conditions, but some PFAs are pozzolanic. They are all contaminated with sulphates, some much more so than others. PFA is used in grouts with lime, and with cement where it serves two purposes: much of the material is in the form of tiny spheres of glass which help the grout to  flow readily.
Pargeting, parging, to parge: 1: rich decoration on external plasterwork by modelling the surface. 2: lining a flue or other surface with a mix of lime putty and cow dung.

Pamure: a vine ornament.

Pargetting: solid decorative plastering formed in freehand or by the use of stamp moulds.

Patera: a small circular ornament in classical architecture. The term is now often applied to any small carved ornament forming one of a series.

Pediment: a gable or triangular crowning ornament often placed on the front of a building, over doors, windows or other openings. The apex maybe open when it is then termed a ëbroken pedimentí.

Peg mould: a running mould with pegs fixed into the slipper or horse in such apposition that they will become the main bearing points.

Peristyle: a colonnade round a courtyard.

Permeability: the ease with which a liquid or vapour can pass through a solid material.

Pilaster: a flat, rectangular column against a wall.

Pitting and popping: a defect in plasterwork caused by late hydration of over-burnt quicklime when it has been incorporated into a plaster. As the quicklime hydrates it tries to expand and pressure builds up behind the surface.

Plain plastering: plastering to simple smooth surfaces without three dimensional relief or decoration.

Plain face, plaster: precast fibrous plaster to form areas of plain surfacing on either ceiling or wall.

Plain face Ordinary Portland Cement OPC/sand:  float finish cement and sand.

Planted: a term applied to mouldings and other ornamental features that are moulded or cast separately and then attached and not formed in the solid.

Planting: fixing any part of a moulding or an ornament on the main part of the work.

Plaster of Paris: calcium sulphate hemi-hydrate, CaSO₄._ H₂O derived from gypsum. Casting plaster. A very quick setting plaster which expands as it sets.

Plaster: plaster may be any material used in a plastic state to form a durable finishing coat to the surfaces of walls and ceilings and other elements of a building. Typical materials are based on lime or gypsum or cement or soil, or any combination of those.

Plaster gypsum: the basic gypsum plaster is made from mined or quarried gypsum which is washed, crushed and ground then heated till three-quarters of its water content is driven off. The product is class A gypsum plaster, which, when added to clean water, will set within a period of some fifteen to twenty minutes. Various additives and aggregates are added in bulk to produce the classification of gypsum plaster as listed in BS 1191 Parts 1 and 2.

Plaster resin-based: modern materials produced for internal and external smooth and textured finishes may be trowel or spray applied. Consist mainly of resin and aggregate and in some instances lime, usually premixed and read for use.

Plastic materials: in this context, plastic means readily moulded with very little pressure.

Plasticity: a measure of the ease with which a material may be moulded or distorted.

Plasticizer: an additive used to make a mortar or concrete more workable. Often this will be an air entraining agent to form tiny bubbles in the mix.

Plinth: the base of a wall above the ground with a projecting surface.

Pointing: the finished surface layer in the joints between masonry units.

Porosity: the extent to which a solid material has pores or voids.

Portland cement, ordinary Portland cement, O.P.C.: the common form of cement conforming to certain standards and made by grinding a clinker formed by firing a slurried mixture of clay and limestone at high temperature in a kiln. Calcium sulphate is also ground in to modify the setting rate. Originally so called because when set it was said to be as hard as Portland stone.

Pozzolan, pozzolanic material: a pozzolan is any material which contains constituents, generally alumina and reactive silica, which will combine with hydrated lime at normal temperatures in the presence of moisture to form stable insoluble compounds with binding properties. There are many naturally occurring pozzolanic materials such as certain volcanic ashes, and several artificial materials such as crushed soft bricks.

Profile: outline of a moulding or other ornament.

Quarter Round: a moulding a quarter of a circle in section.

Quatrefoil: a four-leafed flower ornamentation.

Quicklime: lime which has not been slaked. Lump lime, burnt lime, calcium oxide, CaO.

Quirk: the recessed or sunk part placed at the side of a bead or moulding, much used in Gothic architecture. In Grecian architecture ovolos and ogees are usually quirked at the top, and sometimes in Roman.  A ëdouble quirkí is when both sides of a bead or moulding are recessed.

Quoin: the external angle of a wall . The word is often used in connection with corner stones. 
 
 

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