Most people who ring us about a sagging, sticking or rattling sash window have already decided it is beyond saving. Nine times out of ten it is not. Here is how to judge your own windows honestly, and how to tell the difference between a window that needs a day's work and one that is genuinely finished.
Open the window and press a bradawl, a small screwdriver or even a door key firmly into the timber at the bottom rail, the cill and the lower few inches of the frame. Sound wood resists. Soft wood takes the point in easily and comes away damp and fibrous. That simple probe tells you more than any photograph.
Then look at where the damage sits. Rot confined to the bottom rail of the opening sash, the cill nose or the outer lining is normal wear and is repairable. Rot that has travelled up the stiles, through the pulley stiles and into the box behind is a different conversation.
Splice repairs are the backbone of sash work. The decayed section is cut out back to sound timber and a new piece is scarfed in, glued and pinned, then planed flush so you cannot see the join once painted. Small areas of damage around beads and glazing rebates can be consolidated with two part epoxy repair resin, which is far more durable than filler.
Alongside that, most Jersey sashes benefit from an overhaul: new cords, balanced weights, easing the sashes so they run properly, and routing in brush and fin draught seals. That combination usually stops the rattling and cuts the draught noticeably, which is the complaint we hear most often from the older terraces around St Helier.
Replacement makes sense when the box frame itself has gone, when previous repairs have been done in filler over rot so there is nothing sound to fix to, or when so many components need renewing that you are effectively paying for a new window twice.
If you do replace, specify the timber carefully. St Helier's exposure to salt laden southwesterly weather is hard on windows, particularly on seafront and elevated properties. Accoya or a good quality slow grown redwood with properly primed end grain will outlast cheap unseasoned softwood by decades. Slim double glazed units of around 12mm to 16mm can usually be fitted into a new box sash without spoiling the sightlines, though the sash weights must be rebalanced to suit the extra glass weight.
As a rough guide, an overhaul with cord renewal and draught-proofing typically runs in the low hundreds per window. Splice repairs, reglazing and full redecoration sit higher. A bespoke replacement box sash in good timber is usually a four figure job per opening. Every figure depends on size, access, scaffolding and how much decayed material appears once the beads come off, so treat any quote given without a site visit with caution.
One Jersey specific point: if your property is on the Island's list of protected buildings, or sits within a conservation area, altering windows normally needs planning permission from the Government of Jersey, and repair is usually favoured over replacement. Check before you commit to anything. Sensitive repair is often the quicker route to approval as well as the cheaper one.
Repair is almost always cheaper in the short term, often by a factor of three or more per window. Replacement only wins on cost when the box frame is unsound and repeated patch repairs would be throwing money at a window that has already failed.
Yes. Brush and fin seals routed into the sash edges and parting beads, combined with easing and rebalancing the sashes, deal with most draughts and rattle. It is one of the most cost effective improvements you can make to a period Jersey home.
For most unlisted properties outside conservation areas, like for like replacement generally does not need permission. If the building is listed or in a conservation area you should assume permission is required and check with the Government of Jersey planning team before starting.