Fall window care: weatherstrip, balances, weep holes and sealant before winter

There is a right order for this work, and it is not the order the jobs occur to you in. Clearing the drainage path before you clean the tracks means doing the tracks once. Sealing before you lubricate keeps silicone off the substrate the sealant has to bond to. Adjusting the sash before any of it is wasted, because new weatherstrip and a cleared track both change where the sash sits. Six steps, in this order.

Step one: clear the weep path

Start here, because everything else adds debris. A window frame is not sealed against water, it is drained: the sill chamber gathers whatever gets past the sash and pushes it back outside through weep slots on the exterior face, usually behind a small hinged flap that keeps wind from driving straight back in. On some lines there is a second, interior set of weep openings that vent the chamber.

Test each one with a cup of water poured into the track; it should show at the outside face within a few seconds. If it sits, clear the slot with a nylon brush and low-pressure air, working from outside in. Do not push wire through. Deforming the baffle turns a blocked weep into a permanently open one, which is worse.

Step two: tracks, sills and screens

Vacuum before anything wet touches the frame, then wipe with mild soap and water; the aim is to lift grit out, not grind it along the track. Where the line allows the sash to be tilted or lifted out, take it out: half the debris that matters is underneath it. No pressure washer: it drives water past seals designed for wind-driven rain rather than a jet, and it will unseat a weep baffle from six feet away. Screens come out, get washed flat so the mesh is not stretched, and get labelled by opening.

Step three: read the weatherstrip by profile, not by size

Weatherstrip is where most of the winter comfort lives, and it is bought wrong more often than anything else on this list. The common families are pile (a brush strip, often with a centre fin), bulb, and leaf, and they are retained differently: pressed into a T-slot, set into a kerf, or stuck on with adhesive. Matching a replacement means matching pile height, backing width and retention method, not finding something the same colour.

To find what is worn, close the sash on a strip of paper at three points and pull. The resistance should feel similar at all three. Grip at one point and free at another means the strip has taken a compression set unevenly, and topping up the loose end with a stick-on strip is a spring repair, not a winter one.

Step four: balances, operators and what actually goes on them

Spiral balances are adjusted by unhooking, tensioning and re-hooking: quarter turns, both sides matched, testing the sash between adjustments. Block-and-tackle balances are replaced rather than rebuilt, and they are matched to sash weight, so we read what is stamped in the jamb channel before ordering. Casement operators take the grease the manufacturer specifies inside the gearbox; the hinge track gets wiped clean and left dry. Everything else takes a dry silicone or PTFE spray on a clean surface. Oil and grease hold grit in the track, and petroleum products do not belong on vinyl.

Step five: the exterior sealant joint

The perimeter joint around a window is a working joint. It has to stretch and compress as the wall and the frame move against each other at different rates, and most failed sealant we cut out failed because it was installed as a filler rather than as a joint.

• Backer rod, sized slightly larger than the gap. It sets the depth of the bead and stops the sealant bonding to the back of the joint. A bead stuck on three sides cannot stretch, so it tears at the first cold snap.
• Bead geometry. Roughly twice as wide as it is deep, tooled concave. A deep, narrow, hourglass-shaped bead is a split waiting for a night below freezing.
• The right chemistry for the substrate. Silicone moves well and does not take paint. Polyurethane takes paint and bonds to more substrates. Acrylic latex belongs on interior trim, not on a moving exterior joint.
• Application temperature. Every tube prints a range on it, and Northern Nevada mornings in October routinely sit under it. We seal in the afternoon and we do not seal a damp joint.

And the three places that stay unsealed: across the weep slots, under the head flashing lap, and any factory drip detail where the cladding meets the window head. Those are drainage paths, and a wall that cannot drain rots quietly for years.

Step six: the sash, last

Now the sash gets set. Check the reveal is even down both jambs, check the lock pulls the sashes together at the meeting rail instead of just closing over them, and check the sash is square in the opening before touching a keeper. Adjusting a keeper to chase a sagging sash buys one season and makes the real repair bigger.

What we will not do on a service visit

• Pressure wash a window, for the reasons above
• Apply aftermarket film to an insulated unit, which commonly ends the glass coverage and raises the thermal stress across the lite (the pane of glass)
• Seal a weep, add a second bead over failed sealant, or foam a shim space with the interior trim still on

The triage between service and replacement

Four findings end the service conversation and start a different one: moisture between the panes, a frame racked enough that the sash cannot be squared in it, balance or hardware parts no longer in production for that line, and rot in a wood sill that goes past the paint film into the timber. Any of those and we price the opening instead of servicing it. See replacement windows for what that involves, or the calculator for a first sense of scale.