Sash window maintenance

This article explores the basic maintenance steps you can take to keep sash windows both functioning and looking elegant.

How do sash windows work, presumably they’re worth keeping?

A sash window has one or more opening parts (sashes) that are sliding rather than hinged. Sashes typically slide vertically, hung on cords or chains and counterbalanced by metal weights housed in a boxed frame. A ‘single-hung’ sash window has only one moving part; a ‘double-hung’ sash two. The ‘Yorkshire light’ is a notable variation, where the sash moves sideways without weights.

Popular from the late 1600s, sash windows epitomise Georgian and Victorian houses. Historic examples - including their glass – are integral to many old buildings and should almost always be retained, not replaced. This piece covers their maintenance. Other articles address the repair and upgrading of old windows, which, despite widespread misconceptions to the contrary, is usually viable.

How do I deal with a sash that doesn’t open or close easily?

Avoid forcing a sash to move because this often causes damage. Sashes sometimes stick, jam or fail to move fully for various reasons. These include broken cords, paint accumulation - requiring removal not only from running surfaces but also pulleys - or a poorly positioned or distorted bead guiding a sash, which is again easily resolved. In other cases, it is necessary to free weights that are fouled, remove debris impeding their movement in the weight pockets or trim a warped sash to allow it to slide properly.

Rubbing beeswax, candle wax or soap along sash edges makes opening and closing easier. Seasonal binding through humidity-induced swelling should be tolerated, unless it indicates redecoration is needed.

When should sash cords be replaced?

Sash cords gradually degrade and break from time to time. Assess their condition by bending them to see if they snap or are dried out and liable to fail.

If one cord breaks, it is worth replacing all those on a window. Select durable, low-stretch natural and/or synthetic yarn appropriately sized for the sash weights and pulleys. Re-cording necessitates removing the sashes to access the weight pockets. Deal with any internal projections or seized pulleys likely to fray cords. Take the opportunity, too, to remove debris from the sash pockets.

Ensure the weights are correctly sized, otherwise sashes will rise and drop by their own accord. Upper sashes should be about 0.5-0.9 kg lighter than the weights; lower sashes 0.5-0.9 kg heavier. Additional ‘make weights’ are available.

What should I do with sash windows that are draughty or rattle?

Good draughtproofing (including replacement parting and staff beads incorporating seals) will rectify draughts and rattles following general wear and tear. Alternatively, fit cam-action catches or, as a temporary solution, small timber or rubber wedges. Draughts or rattles due to poorly positioned, insufficiently thick or distorted sash beads are addressed by repositioning or replacing them.

Excessive wear of timber components causes sashes to move too freely and their overlapping horizontal or ‘meeting’ rails to settle out of level. Remove any projections responsible for the wear and fill grooves with proprietary filler. In severe cases, re-edging of sashes might be required.

A gap above a cill may indicate structural distress (wall movement or failed lintel), requiring other work.

What advice is there for painting and maintaining the appearance of sash windows?

Sash windows are predominantly of softwood so regular painting protects them against decay. The topmost layers of heavy paint build-ups are often removed effectively with chemical strippers. Where double-hung, reverse the sashes almost fully and paint exposed parts of the furthest one as required; then return them almost to their normal closing positions to complete redecoration. Avoid excessively thick coats to reduce the risk of jamming and keep sash cords paint-free to avoid causing their premature deterioration. Paint only very slightly onto the glass otherwise glazing beads will appear inappropriately wide. The use of ‘sash brushes’ with pointed ends helps achieve a neat finish.

If required, lower sashes in windows can be adapted to open inwards for easier cleaning and maintenance using bespoke ironmongery.

Further Reading: 

English Heritage (2012) Timber, Practical Building Conservation, Farnham: Ashgate Publishing Ltd

English Heritage (2011) Glass, Practical Building Conservation, Farnham: Ashgate Publishing Ltd

Townsend, A and Clarke, M (2019) Repair of Wood WindowsSPAB Technical Advice Note, London: Society for the Protection of Ancient Buildings

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