This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol2", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
(Contributed by H. Kennard)
Although there are numerous forms and varieties of windows, they may, generally speaking, all be classed under one of two heads: "Sash Windows" and "Casements," the framing to each class being known respectively as Cased and Solid.
The type of window in most general use, and one that is perhaps distinctly British, is that known as the Cased Sash Frame. This consists of a frame built hollow in order to contain the weights which counter-balance the sashes. Two sashes are fitted, and according to whether one or both are hung on pulleys with weights the window is described as "single" or "double" hung. Plate IV. shows a double-hung sash window in plan, section, and elevation; while A, Fig. 132, is an enlarged plan of one side of the cased sash frame showing the various parts. B is a section through sill showing the method of forming this, and also giving a portion of bottom sash. It will be noticed that this detail varies slightly in one or two points from windows as generally made. The guard beads are frequently planted on flush with the pulley style, and are of the same thickness as the lining. As here shown, they are slightly thicker than the lining, and so cover the joint between lining and style, and are also rebated a little way into the pulley style. They should be screwed, and never bradded on, as they can then be easily removed and replaced without damage. The screws should be fitted with cups. The piece marked V is sometimes called a "Ventilating Piece." Windows fitted with this require an extra deep rail to the bottom sash. The lower sash may then be raised, so as to secure ventilation between the meeting rails without the risk of draught at the bottom. The sills of windows should be made of some wood capable of withstanding the effects of weather; oak being most generally used, although teak is preferable. They should be shaped as shown in section to throw off all wet, the technical description of such a sill as is shown being "double-sunk, weathered, and throated, and grooved for water bar, ventilating piece, and window board." The "Water bar "or " Weather bar " is a flat bar of copper or galvanised iron running the full length of the sill and fitting between the wood and stone sills, its object being to stop wet from driving in. The "Window board " is a ledge or shelf forming a finishing to the inside of window, the width varying according to circumstances. A section through the "Head" or top of the window is shown at C.
Fig. 133. - Reversible Windows.
The following is the most approved method of building up a sash frame. After the parts have all been prepared, the pulley styles are first fitted into the sill, keyed up tight by means of a wedge, and nailed, - they must be perfectly upright and parallel, technically " Out of winding," - and the head is next nailed on. It is then laid on the bench and tested for correctness across opposite angles by means of a small rod having a wedge-shaped end to fit in the angles. The inside linings are then fixed, by means of skew brads through their edges, into the pulley style, the guard beads subsequently covering the brad heads. These beads are fitted next, being mitred in, the head and sill beads being fixed first, and the side ones sprung in afterwards. The frame is then turned over, and the parting beads are fitted in. The outside linings are next fitted and fixed, the parting slips which divide the weights inserted, the back lining nailed on, and the head glue-blocked; it is then ready for fitting in the sashes.
These windows are not without some disadvantages, an annoying one being their tendency to rattle, owing to the sashes becoming too loose through slight shrinkage. A more dangerous one, however, is the difficulty of reaching the outsides for cleaning, especially when on a first or second floor. The first of these defects may be remedied by a small fitting made for the purpose, consisting of a milled head screw with leather pad working through a bracket screwed to the guard bead. The National Accident Prevention Window Company, known as the "N.A.P.," have surmounted the second difficulty by introducing sashes with double styles, inner styles containing the glass, and the outer ones being hung in the usual way. The two styles are connected by means of thumb screws, which, upon being released, permit the sash to be revolved upon centres, thus bringing the outside of the glass within easy reach (see Fig. 133). It is advisable to have all sash frames in inaccessible places fitted with this or some similar arrangement.
In putting sashes together, the top and bottom rails are haunched and tenoned into the styles, the meeting rail of top sash being tenoned and the styles usually having the "horns" left on and moulded, these being sometimes called Brackets. The meeting rail of the bottom sash is, or should be, dovetailed, as shown at D, but they are sometimes slot tenoned and screwed in common work. The meeting rails are wider than the styles by the thickness of the parting bead, and are closed by a bevel rebated joint, as at E. Windows are usually finished inside by having an architrave fixed round them to match that round the door, and stopped on the window board.
The method of arranging sash frames in a bay window is shown in Plate IV. The angles between the frames are covered with double mouldings, and at the angles between outer frames and walls grounds are fixed, an additional lining and angle moulding forming an architrave. The section through jamb as shown differs slightly in detail from that at A in Fig. 132, and illustrates an alternative method of fixing the back lining, which would necessitate its being fixed before the outside lining, instead of as previously described. The guard bead is here shown the same thickness as lining. The section through sill shows the usual method of fixing a small guard bead when only a shallow bottom rail is used. An improvement upon this is shown in Fig. 134, which has the effect of throwing the bottom sash tight against the parting beads, and thus lessening the risk of rattling. When the window board is wide, as is the case shown in Plate IV., it is necessary to provide a supporting moulding as shown. Casement Windows are constructed of solid parts, and may be fitted with sashes either fixed or hung on butts or centres. The simplest form of solid frame consists of Side Posts, also called Jambs, Head, and Sill; but by the introduction of vertical members between the posts, called Mullions, and horizontal members between the head and sill, called Transoms, these frames may be made to any size required. There should be no planted mouldings, all the parts being moulded in the solid. Mortise and tenon joints are used, and all should be put together with white lead.