Why Bother Saving Old Timber Windows?

Original timber windows are one of the great quiet assets of a British home. The timber is usually slow-grown, tight-grained and far denser than much of what you can buy today, which is why a hundred-year-old sash can still open sweetly when a modern unit has already been replaced twice. They also suit the proportions of older houses in a way that uPVC rarely does, and in conservation areas or listed buildings, repairing them may be the only option open to you.

The catch is that a draughty window feels like a cold window, even when the glass itself is doing a reasonable job. Cold air slipping past a loose sash or a warped casement drags the comfort out of a room and pushes your heating bill up. The good news is that most of that leakage is coming from a few predictable places, and almost all of it can be sorted without ripping out the frames.

Where the Draughts Actually Come From

Before spending anything, spend twenty minutes on a windy day working out where the air is getting in. A few reliable tricks:

• The back of the hand test. Run your hand slowly around the frame — along the meeting rails of a sash, the hinge edge and leading edge of a casement, the bottom rail, and where the frame meets the wall.
• The incense or tissue test. A lit incense stick or a strip of tissue held close to a joint will flutter and bend towards even a faint draught.
• Look for daylight. On a bright day, gaps around the closing edge often show as a thin line of light.
• Check the trickle vents. Many older windows have vents that no longer close properly and are quietly leaking air all winter.

You will usually find the culprits are the gaps between the moving parts — the meeting rails and the staff bead on a sash, or the closing stile on a casement — plus the seal between frame and masonry, which often cracks and opens up as the building moves.

Brush Seals: The Cheapest Effective Fix

For most old timber windows, brush pile seals, sometimes called draught strips, do the heavy lifting. They are a strip of fine bristles on a self-adhesive or carrier backing that compresses against the moving part to block the gap while still letting the window slide or swing.

Look for pile in the region of 4–6mm for typical gaps, and fit it into a routed groove if you can, or use a carrier strip screwed into the rebate if you would rather not cut into old timber. On sash windows, the classic approach is to seal the meeting rails and fit a brush carrier along the staff bead, which often requires a shallow rebate so the sash still runs freely. On casements, run the seal around the closing stile and the top and bottom rails, but leave the hinge edge alone — that is where the window pivots.

Two practical warnings. First, do not fit seals so thick that the window becomes stiff to open; you will end up forcing it and damaging the frame. Second, if a sash is painted shut or the cords are slack, sort that first. A seal on a window that no longer works properly just hides the problem.

Secondary Glazing: Quiet, Reversible, Surprisingly Effective

Where brush seals are not enough — a single-glazed sash on a noisy road, or a window you cannot alter — secondary glazing is the sensible middle path. It is a separate pane, usually in an aluminium or timber frame, fitted to the internal reveal on the room side, leaving the original window untouched.

It works because it traps a layer of still air between the two panes, and because it seals the room off from the outside more completely than any draught strip. Expect a noticeable improvement in both warmth and street noise. Choose a system with a sliding or lift-out panel so you can still open the original window for ventilation in summer, and consider whether you want it on the fixed pane only or across the whole window. If you are in a listed building, secondary glazing is usually the option that heritage officers are happiest to see, as it is fully reversible.

Maintenance That Keeps the Weather Out

Draughts are often a symptom of neglected timber rather than a design fault. A little routine care goes a long way:

• Repaint and repuddy. Cracked putty and flaking paint let water into the frame, which then swells, warps and opens up gaps. Rake out failed putty, refill with linseed oil putty, and repaint the frame edges and sills.
• Clear the drainage. Sills should shed water away from the frame. Check that any weep holes or drainage channels are clear of paint and debris.
• Oil the moving parts. Sash cords, pulleys and hinges benefit from occasional attention. A window that slides easily seats better when it closes.
• Adjust and ease. Hinges can be tightened or washers added to pull a casement closer to its frame; a stiff sash may just need the paint cut back along the bead line.
• Deal with the masonry joint. If the draught is between frame and wall, a neat bead of suitable external sealant, or repointing the reveal, will close it for years.

Knowing When to Bring In a Joiner

Much of this is genuinely a weekend's work with a few hand tools. But there are times when DIY draught-proofing is the wrong answer: if sashes are rotten at the bottom rails, if the frame is so out of square that no seal will sit properly, or if you suspect the window has been badly repaired in the past. A good joiner can splice in new timber, re-hang a casement or re-cord a sash, and the window will then take seals properly and last another generation.

Do the simple things first — diagnose, seal the obvious gaps, keep the timber painted — and you will be surprised how much warmer a room with original windows can feel. Old timber rewards a bit of attention, and it will repay you for decades.