Joinery suppliers offer a range of ready-made window frames in both hardwood and softwood.
Manufactured wooden frames are treated with preserver and some are ready-primed for painting or prestained for final finishing. With the increased awareness of energy conservation, most frames are rebated to take double-glazed sealed units as well as traditional single glazing.
In addition to the stays and fasteners supplied with the frames, some windows also have the top rail of the opening sash, or the frame itself, slotted to take a ventilator kit to comply with Building Regulations for background ventilation in habitable rooms.
Self-assembly kits composed of machined framing are available to make frames of any size to fit non-standard window openings The style of the windows is important to the appearance of any house. If you are replacing windows in an older dwelling it is preferable — and not necessarily more expensive — to have new wooden frames made to measure rather than change to modern windows of aluminium or plastic.
Planning and Building Regulations Window conversions do not normally need planning permission as they come under the heading of house improvement or home maintenance, but if you plan to alter your windows significantly —for example by bricking one up or making a new window opening, or both — you should consult your local Building Control Officer.
All authorities require minimum levels of ventilation to be provided in the habitable rooms of a house, and this normally means that the openable part of windows must have an area at least one-twentieth that of the room. Also, part if not all of a top vent must be 1.75m (5ft 9in) above the floor. Trickle ventilators with a 4000mm2 (61/2 sq in) opening are also required for new installations.
If you live in a listed building or in a conservation area, you should also check with your local authority before making any changes to your windows.
Buying replacement windows
Try to maintain the character of an older house by preserving the original joinery. If you have to replace the window, copy the original style — specialist joinery
firms will make up wooden frames to fit. Specify an appropriate hardwood or, for a painted finish, softwood impregnated with a timber preserver.
Alternatively, you can approach a replacement-window company, though this is likely to limit your choice to aluminium or plastic frames. Ready- glazed units can be fitted to your old timber sub-frames or to new hardwood ones supplied by the installer. Most replacement-window companies also fit the windows they supply, and their service includes disposing of the old windows and debris.
This method saves time and effort, but you should carefully consider the compatibility of such windows with the style of your house. Choose a frame that reproduces the proportions and method of opening of the original window as closely as possible.
Measure the width and height of the window opening. If the replacement window needs a timber sub-frame (and the existing one is in good condition), take your measurements from inside the frame. Otherwise, take them from the brickwork. You may have to cut away some of the rendering or internal plaster first in order to obtain accurate measurements. Order your replacement window accordingly.
Remove the old window by first taking out the sashes and then the panes of glass in any fixed light. Unscrew exposed fixings, such as may be found in a metal frame, or chisel away the plaster or rendering and cut through the fixings with a hacksaw. It should be possible to knock the frame out in one piece, but if not, saw through it in several places and lever the pieces out with a crowbar (1). Clean up the exposed brickwork with a bolster chisel to make a neat opening.
Cut the horns off the new frame, then wedge the frame in the window opening and check it is plumb (2). Drill screw holes through the stiles into the brickwork (3), then remove the frame and plug the holes or use frame fixings. Attach a bituminous-felt damp-proof course to the jambs and sill and refit the frame, checking again that it is plumb before screwing it firmly in place.
Make good the wall with mortar and plaster. Gaps of 6mm (‘/in) or less can be filled with mastic. Glaze the new frame as required.