Window

Also called: sash window, casement window, box frame window, bay window, dormer window, fanlight

A window is an opening in a wall fitted with a frame that holds one or more sashes, the openable glazed panels that let in light and air. Some early trade manuals used the word more broadly still: Audels (1923) took "window" to mean the frame, sash and blinds together, as one assembly.

The frame, sill and jambs

A window frame's width is measured as the distance between its two stiles, the frame's vertical side pieces. Its height is measured either from the point where the lower sash meets the sill, the horizontal base of the frame, or between the parting strip, the strip separating the two sashes of a sliding sash window, and the jamb, the vertical side of the opening in the wall. In masonry buildings the jambs are more often built of cut stone even within an otherwise rubble wall, though in ordinary buildings rubble alone will serve. At the sill, a window board is tongued, fitted with a projecting ridge into a matching groove, into the back of the sill; this covers the ledge left by the thickness of the wall, and the board is itself grooved to catch the edge of the plaster running up to it. Where the sill meets the frame, a groove cut along the top of the sill lines up with a matching groove in the frame's own oak sill, and a metal water bar fits into the two aligned grooves to stop rain getting in at the joint. In one seventeenth-century timber-frame practice, a timber window could be built to match the form of a brick one, projected slightly beyond the wall face with plaster set against its sides, said to protect the carcass, the building's structural frame, from the weather.

Fitting sashes, fanlights and bolts

A casement window, one whose sash is hinged at the side rather than sliding, is held shut by a cock spur, a small hooked fitting that catches the sash when it is closed; traditional casement windows were built with mortise-and-tenon joints, a tongue on one piece fitting a slot in the other, throughout. A fanlight, a window set above a door or within an arch, is often curved. Where its head is curved, the fanlight's plan curve is treated the same way as the curve of the window head above it, and it is fitted by scribing it into the rebate, the stepped recess cut to receive it, one small piece at a time; the soffit, the underside of the opening, is then lined with a wood slip cut to the width of the margin. Fanlights can also be cut to fit within knee-brace arches, where a knee brace, a diagonal timber set at a frame's corner, forms the arch in timber framing. In one style of bay window, three plain sash frames have their sills joined at the corners either by halving, notching each piece to overlap the other, and screwing, or by mitring and fastening with a handrail bolt, a bolt threaded at both ends that draws a joint tight, originally made for joining lengths of handrail. One method for fitting a window bolt marks its position with a horizontal line on the window's edge and inner face, crossed by a centreline taken from the window stop, the strip the sash or casement closes against; the bolt is then operated with the window shut, so it transfers its own mark onto the frame, and where the gap between window and frame is 3 millimetres or less, the recess for the face plate, the bolt's flat cover plate, is chiselled so it sits flush. Inside the room, exposed timber framing members can combine with built-in bookshelves and wainscoting, wood panelling lining the lower part of a wall, to frame a window opening as well.

Shutters

Wooden shutters are still occasionally fitted to close a window opening, though less common than in the past. Folding shutters, when shut, together span the full width of the opening; when open, they stack behind one another. Box shutters, folding shutters that fold back into a boxed recess beside the window, are made in different widths on each side so each folds cleanly into its box; the outermost, widest shutter also doubles as the window's lining, its inner facing. The pilaster, a shallow flat strip resembling a column, that covers the box is cut level with the window board, so it clears the shutters when they are open. Where a wall is too thin for folding shutters, sliding shutters are used instead: thin panelled frames running in guides fixed to the soffit and the window board, both made extra wide for the purpose. A related type, vertical-sliding shutters, runs up and down in metal grooves fixed at both sides of the opening, and can be mounted to work from either the room side or the exterior side of the window.