The sash (or double-hung) window was used a great deal on homes right into this century almost to the exclusion of any other type. It’s a period feature, often adding a touch of authentic charm. Unfortunately Sash windows can be very difficult to keep in good working order.
Sash windows actually consist of two separate windows – sashes is their proper name – each sliding vertically in its own channel. When both are closed, the sash in the outer channel is at the top, and the inner sash is at the bottom.
The channels are formed by three sets of beading, running round the inside of the frame. These are known (starting with the outermost one) as the outer, parting and staff beads. The outer and staff beads lie flat on the window frame, but the parting bead is fixed on its edge. The outer bead, in fact. may well form part of the frame itself; the other two are always separate pieces, nailed in place. For easy removal they should never be glued, or maintenance of the window becomes impossible.
How sashes work
Counterbalancing weights, each pair of which weighs the same as the sash they’re attached to, ensure that the sashes stay in whatever position you choose and don’t come crashing down – perhaps with such force that the glass is shattered. There’s a weight on each side of each sash, hidden in a compartment inside the frame. Each weight is attached to its sash by a cord that passes over a pulley at the top of the frame and is nailed to the side of the sash.
The drawback of sash windows is that it’s almost impossible to make them fully draught-proof. although some success can be achieved with brush-type draught excluders. The only sure way is to install secondary double glazing – the type that fits within the window reveal and is hinged to, or slides in. its own frame. You can’t attach fixed double glazing panels directly to each sash because they won’t slide past each other. And even if you could, the extra weight would throw the sashes out of balance. preventing the inner one from remaining in the open position and the outer one from remaining closed.
However, many lesser faults can easily be cured if you know what to do. Often you needn’t even dismantle the window.
Hacking out and replacing old. crurnblinp putty, and renewing a cracked pane of glass, for example, are two jobs where dismantling the window is unnecessary. And if a pulley squeaks – just oil it.
You can even repair a sash corner joint that has begun to open up, provided you wedge the sash firmly in place while you’re working on it. All that’s needed is a flat, L- shaped metal plate which you can easily, buy: you just screw it across the corner. It looks a hit unsightly if left exposed; but you can conceal it by first chiseling out a shallow L-shaped recess to take it, and afterwards covering it with paint (not emulsion paint), Cellulose filler and then a top coat of paint – in that order, so that the water in the filler doesn’t rust the metal and discolor the paintwork.
Filler will also take care of minor cracks, dents and other blemishes in the wood. You can do a certain amount of redecorating, too, without removing the sashes. but you’ll find it hard to get a neat edge as you approach the concealed parts.
Some jobs, however, do call for taking the window to pieces – a procedure that’s far easier than it sounds. One such task is silencing a rattle; the root of the trouble in this case is that the beads are too far apart and need repositioning.
Pries off first the staff bead and then the parting bead on each side of the frame. There’s usually no need to interfere with the sections of beading at top and bottom, but you’ll have to take out the inner sash to get at the parting bead. To remove a bead, cut down the angle with a sharp knife first to break the paint seal and avoid tearing off flakes. Then push a chisel between it and the frame, as near the nails as you can, and spring it out gradually.
The various beads may well have become damaged over the years. In that case you can simply replace them with new ones, bought from a timber merchant (ask for them by their proper names, and he’ll understand). To lessen the risk of splitting, drill pilot holes for the nails oval nails are best. When re- fixing the beads, position them close enough to each sash to cure the rattle, but not too close. or you’ll bring about the second common fault: sashes which won’t slide freely, or at all.
The other and more likely reason for that. however, is a build-up of paint in the channels? You can’t just go on putting coat upon coat of paint when you redecorate them. and the only remedy when they jam is to sand or scrape off the paint where thrashes are binding, leaving room for the primer and one or two further coats that will have to be re-applied to the bare wood.