Common Window Repairs: What Can Be Fixed, and What Means Replacement

Windows are assemblies of parts, and the parts wear at different rates. The glass and frame of a decent window can outlast its balances, rollers, and weatherstripping several times over. Replacing those parts is ordinary maintenance, and it is far cheaper than a new window.

This page goes through the common repairs one at a time: what has failed, how it is fixed, and whether it is a job for you or for a professional. It ends with how to tell when repair stops making sense. It is part of our California window guide. If the names of the parts are unfamiliar, start with parts of a window.

Repair or replace: the quick sort

Broken balances

On a single-hung or double-hung window, the sash is held up by a balance in each side jamb. Modern windows use spring balances in a few common designs: block-and-tackle (a spring and cord in a metal channel), spiral (a spring-loaded rod in a tube), and constant-force (a coiled steel ribbon). When one fails, the sash drops on that side, sits crooked, or will not stay open.

Before assuming a balance has failed, check the simple things. Milgard notes that when the top sash of a double-hung window slowly slides down, it is often because the sash was not pushed completely into place, and that raising it fully solves it. A tilt sash that has come off its pivot shoe will also behave like a broken balance.

The fix: balances are replaced, not repaired, and in pairs. The replacement has to match the old one's type, length, and weight rating, which is usually stamped on the balance itself. On a tilt-in sash, the sash comes out, the old balance unhooks from the jamb, and the new one goes in.

DIY or pro: a careful homeowner can do this on a small tilt sash. The springs are under tension, so wear eye protection and follow the manufacturer's instructions. Large sashes with heavy glass, and windows where the frame has to be partly disassembled, are for a professional.

Sash cords on older wood windows

Older wood double-hung windows use a different system: a cast-iron weight on each side, hidden in a pocket in the frame, connected to the sash by a cord running over a pulley. When the cord breaks, the weight drops into the pocket and the sash loses its counterbalance.

The fix: the interior stop is removed, the sash is taken out, the weight pocket is opened, the weight is retrieved, and new cord is run over the pulley and tied to the weight and the sash. The work is simple in principle and fiddly in practice, because old stops are brittle and layers of paint have glued everything together.

The lead issue: these windows are, almost by definition, in houses built before 1978, and their painted sashes rub against painted stops every time they move. The EPA specifically identifies surfaces subject to constant friction, like doors and window sills, as a source of lead chips and dust, and its regulatory definition of renovation includes window repair. A contractor paid to do this work in a pre-1978 home must be lead-safe certified. If you do it yourself, the rule generally does not apply, but the EPA recommends lead-safe work practices. See lead-safe work on pre-1978 homes.

Whether to restore old wood windows or replace them is its own decision, covered in historic window repair or replacement.

Cranks and operators

Casement and awning windows open with a crank handle that drives a geared operator, which pushes an arm attached to the sash.

• The handle spins without moving the window. The splines inside the handle or on the operator stud are stripped. Often it is just the handle, which is the cheap part. Pella's manual notes that the handle is held by a set screw and that running it with the screw loose wears both the crank and the operator stud. Check that screw first.
• The crank turns but is stiff or gritty. The operator and hinge tracks need cleaning and lubricating. Pella recommends cleaning the track with a dry brush and applying a dry lubricant if needed.
• The window will not pull fully closed. The operator gears are worn, the arm is bent, or the hinges have sagged.

The fix: operators are replaced as a unit. They are specific to the brand, the series, the hand (left or right), and sometimes the sash width, so identify the window before ordering.

DIY or pro: replacing a handle is a two-minute job. Replacing an operator is within reach of a handy homeowner once the right part is in hand. A sagging sash or bent hinge is better left to someone who does it regularly.

Sliding window rollers

A horizontal slider rides on small rollers or glides at the bottom of the moving sash. When it gets hard to slide, the cause is, in order of likelihood:

1. A dirty track. Grit packs into the track and around the rollers. Vacuum it, wipe it, and try again. This solves more sticking sliders than any part does.
2. Rollers out of adjustment. Many sashes have adjustable rollers. Milgard publishes a how-to guide for adjusting a window vent and a set for adjusting and replacing patio door rollers.
3. Worn or broken rollers. Flat-spotted, cracked, or seized rollers need replacing.
4. A damaged track. On old aluminum sliders the raised rail in the track can wear down or dent. Snap-on track covers exist for some profiles.

The fix: lift the sash out of the frame, swap the rollers for matching ones, and reinstall.

DIY or pro: small window sashes are manageable for one person. Large sashes and patio door panels are heavy and awkward, and dropped glass is dangerous. Get help or hire it out. Whatever you do, do not spray an oily lubricant into the track to make it slide; it collects more grit. See our window maintenance guide for what manufacturers recommend.

Latches and locks

A lock that will not engage is usually not a broken lock. It is a sash that is not sitting where it should, so the latch and its keeper no longer line up. Check for debris in the track, a sash not fully closed, or a keeper that has shifted. Many keepers are slotted for adjustment.

A lock that is physically broken, with a snapped lever or a cam that no longer turns, is replaced. Most are held by two screws. Milgard publishes a guide for replacing the lock snib on its products. Match the screw spacing and the latch style, and use the manufacturer's part where you can.

DIY or pro: DIY. Do not put it off. A window that does not lock is a security problem, and on some windows the lock is also what pulls the sash tight against the weatherstripping. For more on window security, see window security in California.

Weatherstripping

Weatherstripping flattens, tears, and shrinks with age. The signs are drafts, rattling, dust on the sill, and more outside noise than there used to be.

The fix: pull the old strip from its groove and press or slide in a new one of the same profile. The hard part is the part itself: there are many profiles (pile, bulb, fin, leaf), and the right one is specific to the window. Take a short piece of the old strip with you or send a photo to the supplier.

DIY or pro: DIY if you can get the right strip. Stick-on foam tape from a hardware store is a temporary measure, not a repair; it compresses quickly and can stop a sash from closing and locking properly.

Rotted sills and frames

Wood rots where water sits and the finish has failed, which means the sill, the bottom rail of the sash, and the lower corners of the frame.

• Small, shallow rot in an otherwise sound sill can be dug out, treated with a wood consolidant, filled with an epoxy wood filler, shaped, primed, and painted. Done well, this lasts.
• Rot through a sash rail usually means a new sash.
• Extensive sill rot means a new sill or a new window.
• Rot that extends into the wall framing below the window is no longer a window repair. It is a leak that has been running for years, and the opening has to be taken apart, the framing repaired, and the window re-flashed.

Always ask why it rotted. Peeling paint is the easy cause. Water getting in behind the trim or under the sill because of failed flashing is the other, and filling the rot without fixing that guarantees it returns. Our window flashing and waterproofing page explains what to look for.

DIY or pro: a small epoxy repair is a reasonable DIY job, with lead-safe precautions on pre-1978 homes. Anything structural, or anything where the source of the water is unclear, needs a professional.

Failed insulated glass

Fog, haze, or water droplets between the panes mean the edge seal of the insulated glass unit has failed. It cannot be cleaned and it does not get better. The unit can usually be replaced in the existing sash or frame, or the sash can be replaced.

California's Energy Code treats this as a repair, not as a window replacement: a note under Section 150.2(b)1B says glass replaced in an existing sash and frame, or sashes replaced in an existing frame, are considered repairs provided the replacement is at least equivalent to the original in performance. The full picture, including matching and when it is not worth doing, is on our page on glass-only replacement versus a new window, and the causes are covered in why windows fog between the panes.

DIY or pro: pro. Insulated units are made to order, heavy, and easy to damage, and check your warranty before paying anyone.

Cracked and broken glass

Deal with broken glass promptly. Tape a crack on both sides to hold it, keep people away from it, and board the opening if the pane is out.

The rule that matters here is about what goes back in. The 2025 California Existing Building Code, Section 402.1, states that replacement glazing in hazardous locations shall comply with the safety glazing requirements of the California Building Code or California Residential Code as applicable. In a house, those locations are defined in CRC Section R324.4 (formerly R308.4) and include:

• Glass in swinging, sliding, and bifold doors.
• Glass next to doors, where it is within 24 inches of the door and its bottom edge is less than 60 inches above the floor.
• Large panes near the floor, meeting all of the size and height conditions in R324.4.3.
• Glass around tubs, showers, hot tubs, and pools, where the bottom edge is less than 60 inches above the standing surface.
• Glass beside stairs and landings, where the bottom edge is less than 36 inches above the walking surface.

So an old patio door or bathroom window with ordinary glass does not get ordinary glass back. It gets tempered or laminated safety glass, permanently marked as R324.1 requires. Exceptions and details are on our page on California tempered glass requirements.

DIY or pro: pro. A glazier will know whether the location requires safety glazing, will order the right unit, and will handle the broken glass safely. Single panes in old wood sashes set in putty are a traditional DIY job, with lead-paint precautions and only where safety glazing is not required.

Who can do the work

• You. Cleaning, adjusting, lubricating, and replacing handles, locks, weatherstripping, screens, and small balances and rollers.
• The manufacturer or its dealer. Start here if the window is under warranty. Milgard directs owners to their local dealer for service, and says that owners without warranty coverage can contact a certified dealer for repairs.
• A glass shop. Glass units, broken panes, and often hardware.
• A window repair specialist. Balances, operators, rollers, and old-window restoration.
• A licensed contractor. Rot repair, re-flashing, and anything that opens the wall. The Contractors State License Board says a license is required for work valued at $1,000 or more in combined labor and materials. See California contractor licensing and insurance requirements.

When repair stops making sense

Stop repairing and start planning a replacement when:

• The frame is the problem. Warped vinyl, corroded aluminum, or rot beyond the sill.
• Parts are unobtainable. The manufacturer is gone or the series is long discontinued and nothing matches.
• Several things are wrong with the same window. A failed glass unit, worn rollers, and dead weatherstripping together cost a good fraction of a new window and leave you with an old frame.
• The same failure is spreading. Glass seals failing one after another across a house of same-age windows.
• The window was never good. No repair turns single-pane aluminum into a comfortable window. See upgrading from single to dual pane.
• Water is getting into the wall.

Service life by material and the signs that a set of windows is at the end are on our page on how often windows should be replaced. For budgeting, see window replacement costs in Sacramento and the Bay Area.

Sources

• 2025 California Existing Building Code, Section 402.1 (replacement glazing in hazardous locations)
• 2025 California Residential Code, Section R324 (glazing; formerly R308)
• California Energy Commission, 2025 Building Energy Efficiency Standards, Section 150.2(b)1B NOTE and Section 100.1 (fenestration repair)
• U.S. EPA, Lead Renovation, Repair and Painting Program and 40 CFR 745.83 (definitions of renovation and minor repair)
• Contractors State License Board, Hire a Licensed Contractor
• Milgard, How To Guides and Frequently Asked Questions
• Pella, Windows and Patio Doors Owner's Manual (2021), retailer-hosted copy
• Andersen, Care and Maintenance Guides

Working with Heritage Exteriors

We replace windows; we are not a parts-and-repair shop, and we will say so if a repair is what you need and point you toward the right kind of trade. When repair has run out, we will show you why on your own windows before talking about new ones. Licensed in California, CSLB #1055919. Call (916) 546-2991.