Why heritage windows fail before the rest of the house
A double-hung window collects water at the sill, holds it in the glazing rebate and moves every time someone opens it. The horizontal surfaces take standing water and direct sun, the putty line shrinks and cracks, and once the coating opens up the timber underneath starts taking on moisture.
Inner-west homes add their own history: decades of overpainting that has filled the sash channels, hardware painted into place, and cords that have been cut or replaced. None of that is unusual and most of it is workable.
Assessment before any paint
- Probe the sill, bottom rail and joints for soft or decayed timber.
- Check the glazing putty for cracks, gaps and missing sections.
- Look at the sash channels for paint build-up that is jamming the movement.
- Check whether sashes currently open, and which ones have been painted shut.
- Note rusting fixings, loose beading and any water staining on interior reveals.
- Flag anything that needs carpentry rather than painting, before the job starts.
Preparation sequence
Protect
Glass, sills, floors and garden beds protected; work area controlled for dust.
Clean
Wash down to remove dirt, mould and chalking from the frame, sash and reveals.
Scrape and sand
Failed coating removed back to a sound, feathered edge using controlled, dust-reducing methods.
Make good
Cracked or missing glazing putty and minor timber defects addressed with appropriate fillers.
Prime
All bare timber primed, with end grain, sill edges and rebates sealed properly.
Undercoat and finish
Undercoat then finish coats in a compatible enamel system, kept thin on running surfaces.
Keeping the sashes moving
Stuck windows are a painting problem, not a joinery problem, more often than people expect. The fix is discipline during application: keep the coating off the mating surfaces, do not flood the channels, and move the sashes before the paint sets hard.
- Sash channels and meeting rails kept free of heavy paint build-up.
- Windows worked during and after painting rather than left closed to cure.
- Hardware removed or masked where practical instead of being painted over.
- Thin, even coats rather than one heavy coat that bridges gaps.
Primer and product choice
Heritage timber joinery usually calls for an oil-based or purpose-made timber primer where the surface is weathered, chalky or prone to tannin bleed, and a modern water-based system where flexibility, faster recoats and low odour matter — particularly on interior reveals.
Whichever way we go, primer, undercoat and finish coats stay within one compatible system. For exterior faces we use Dulux and Haymes exterior systems; interior reveals and sashes are finished in a hard-wearing enamel suited to high-touch joinery.