Why this skill matters

A torn screen takes 5 minutes to patch. A broken window after a storm requires knowing which temporary fix lasts and which fails overnight.

Window screens are a simple technology with a significant health function — in tick and mosquito country, a screen in good condition is part of the disease prevention system for a household. Mosquitoes carrying West Nile, dengue, and other vectors enter through a torn screen in sleeping areas. A torn screen isn't a cosmetic issue; it's a gap in the household's insect barrier. The repair is $3 and 5 minutes. The gap is left open because no one has the spline tool to re-screen properly, or doesn't know they don't need one for a patch.

Broken window glass is the acute version — most commonly from storm-related impacts. A broken window during or after a major storm means the household is immediately exposed to wind, rain, and temperature extremes. The emergency repair decision matters: duct tape and cardboard fails in rain. A properly installed polycarbonate sheet holds through the same weather that broke the window. Knowing which temporary repair to make — and having the materials to make it — converts a weather emergency into a manageable repair waiting for a contractor.

The maintenance dimension: glazing compound on old single-pane wood windows is a consumable that requires periodic replacement. Hardened, cracked, or missing glazing compound exposes the glass-to-sash joint to moisture, which works into the wood, rots the putty groove, and eventually causes the glass to shift or crack. An annual inspection and spot re-glazing keeps old wood windows functional indefinitely at minimal cost.

What you should be able to do

L1 Household Basic

Patch a screen hole under 3" with a self-adhesive repair patch

Re-screen a full window frame with a spline tool — new screen material and new spline

Apply a temporary emergency repair to broken window glass with polycarbonate sheeting

Apply an interior window film kit over a broken window for winter emergency insulation

Inspect glazing compound on single-pane wood windows — identify hardened, cracked, or missing sections

L2 Capable Homeowner

Re-glaze a single-pane wood window — remove glass, clean groove, install with new points and compound

Replace a fogged or broken insulated glass unit (IGU) in an existing sash frame

Cut a glass pane to size with a glass cutter and straightedge

Glass safety — non-negotiable: Wear leather work gloves when handling any broken glass or any glass pane being removed or installed. Glass cuts are silent — the cut happens before the sensation registers. Leather provides meaningful cut resistance; standard work gloves don't. Handle glass panes with two hands and have a clear path to set them down.

Tools and supplies

The spline roller is the tool most people don't have and need most.

Screen repair tools

Spline roller / screen installation tool ($5–$10). A handle with two wheels — a convex wheel for pressing spline into the groove, and a concave wheel for removing it. Without this tool, screen spline can't be properly seated. It's the one indispensable piece of screen repair equipment.

Screen spline ($3–$5 per roll). The vinyl or rubber cord that sits in the frame groove and holds the screen material. Comes in different diameters — bring the old spline to the hardware store to match the size.

Fiberglass screen material. Sold by the roll in various widths. More flexible and less prone to oxidation than aluminum screen. Measure the widest window and buy accordingly.

Self-adhesive screen patches. For holes under 3" — the instant repair without re-screening the whole frame. Keep a pack in the household repair kit.

Glazing tools (L2)

Glazing compound (DAP 33 or equivalent). The traditional putty that seals glass to a wood sash. Oil-based, pliable when fresh, hardens slowly over weeks. Stays flexible enough to accommodate slight movement; paintable after partial cure.

Glazier's points. Small diamond-shaped or triangular metal clips that hold the glass in the sash groove before the glazing compound is applied. Pushed in with a putty knife or push-type glazier's point setter.

Putty knife / glazing knife. A stiff-bladed knife for applying and tooling glazing compound. A 1" blade for applying; a wider blade for tooling the final bead.

Linseed oil — primes bare wood in the putty groove; prevents new compound from drying out too fast

Glass suction cups ($15–$25) — for safely handling glass panes over 24"×24"

Emergency supply to keep on hand: One sheet of ⅛" clear polycarbonate (at least 24"×36") and the appropriate fasteners. This is the material that actually works as a temporary broken window repair. Duct tape and cardboard fails in rain; polycarbonate holds through the same weather that broke the window.

Common window and screen problems

Most window problems are maintenance deferred — not structural failure.

Screen holes and tears

Most commonly from pet scratching at corners (a distinctive L-shaped tear), impact damage from tree branches or hail, or UV degradation on older fiberglass screens that makes the material brittle and prone to tearing. Under 3" anywhere in the screen: patch. Corner tears over 3": re-screen the full frame. Spline that has pulled loose from the groove (screen may be intact but sags): replace the spline, not necessarily the screen material.

Spline failure

The spline — the rubber or vinyl cord in the frame groove — shrinks and hardens over time, releasing its grip on the screen material. The screen sags inward or pulls loose at the corners. The screen material may be entirely intact; the failure is in the retention system. Remove the old spline, re-tension the existing screen material or install new screen, and seat new spline.

Broken single-pane glass

Impact damage, thermal stress (temperature cycling that causes the glass to flex beyond its tolerance), and settling of the frame that shifts the glass in its putty groove. Single-pane glass in a wood frame is the most homeowner-accessible glass repair — the glass is accessible and the materials are inexpensive and widely available.

Failed glazing compound (putty)

Old glazing compound on wood windows hardens and shrinks over decades, eventually cracking and separating from the glass or sash. Missing compound exposes the glass edge to moisture that works into the wood, rots the putty groove, and allows the glass to shift. Inspect the compound annually: press a fingernail against it — soft and flexible is fine; rock-hard and cracked means it's ready for replacement.

Fogged double-pane glass (failed IGU seal)

The white, hazy, or spotty appearance between the two panes of a double-pane window means the factory-sealed insulating gas has escaped and moisture has entered the space. This is an IGU (insulated glass unit) failure — not a structural failure. If the window frame is sound, the IGU can be replaced without replacing the whole window. Clouding between panes is irreversible without IGU replacement — no product clears the haze permanently.

Step-by-step procedures

Five procedures from screen patch to IGU replacement. The emergency glass repair comes first if that's the immediate need.

L1

Screen patch — holes under 3 inches

Five minutes, $3. The fastest resolution for a small hole that's letting insects in. Keep a pack of screen patches in the household repair kit alongside the patch supplies for the next re-screening job.

1Clean the area around the hole — remove dirt, debris, and any oxidation with a dry cloth. If the hole has bent or frayed screen wires at its edges, trim them with small scissors so the edges are clean.

2Select a patch slightly larger than the hole — at least 1" margin on all sides. Self-adhesive fiberglass patches come in pre-cut sizes; select the next size up from the hole.

3Peel the backing from the adhesive patch. Center the patch over the hole and press firmly on all edges — especially the corners, which are most likely to lift. Press with a fingernail along each edge to ensure full adhesive contact.

4For holes between 1" and 3": A cut-to-size screen material patch sewn into the existing screen provides a more durable repair. Cut a piece slightly larger than the hole. Unravel the edge wires on two sides. Weave those wires through the surrounding screen material and bend them over on the back side — the patch knits into the screen rather than adhering over the top.

L1

Re-screening a full window frame

When the screen material is extensively torn, has multiple patches, or is brittle with age. The frame stays; new screen material and spline replace the old. The spline roller is the key tool — most people don't have one.

1Remove the screen frame from the window. Lay flat on a table or workbench.

2Use the concave wheel of the spline roller (or a flat screwdriver) to pry the old spline out of the groove starting at a corner. Pull the spline out completely. Remove and discard the old screen material.

3Cut new screen material 2" larger than the frame in each direction. Lay it over the frame, centered. It should overhang all four sides.

4Start on one long side: use the convex wheel of the spline roller to press new spline into the groove over the screen material. Start at the center of the side and work toward each corner. The spline compresses the screen material into the groove, tensioning it. Don't start at a corner — corners are harder to control, and starting in the middle gives a more even tension.

5Repeat on the opposite long side: pull the screen material moderately taut before seating the spline on this side — but don't overstretch. Then do the two short sides. The screen should be taut but not bowing the frame.

6Trim the excess screen material with a utility knife run along the outer edge of the spline groove — between the spline and the frame edge. Cut away from the spline groove, not toward it, to avoid pulling the spline out. Reinstall the screen frame in the window.

L1

Emergency glass repair — polycarbonate sheeting

For broken window glass that can't be replaced immediately. Polycarbonate is impact-resistant, weather-tight when caulked, and transparent. It holds through weather. Cardboard and plastic sheeting do not.

1Immediate step — remove broken glass safely. Wearing leather gloves, remove all loose glass pieces from the frame. Work from the edges toward the center. Place glass directly in a cardboard box — never in a trash bag where it can puncture through. Seal the cardboard box before disposing.

2Measure the window opening — height and width. Add 2" to each dimension for the overlap onto the frame or surrounding siding.

3Cut polycarbonate sheet to size. Score with a utility knife and straightedge (for thin sheet) or cut with a circular saw fitted with a fine-tooth blade. Polycarbonate can also be scored and snapped like acrylic for straight cuts up to ⅛" thickness.

4Drill pilot holes at the corners and every 12" along the edges — the material will crack at un-piloted holes under screw pressure. Use a bit slightly larger than the screw shank.

5Position the sheet over the opening with the overlap on all four sides. Secure with screws and washers — the washer prevents the screw head from pulling through. Apply exterior caulk around the perimeter where the sheet meets the frame or siding.

6Winter interior alternative: For a broken window in a heated space in cold weather, an interior window film kit (3M Window Insulator or equivalent) applied from inside provides weather protection and adds a modest insulation layer. Install before the polycarbonate exterior repair if temperatures are below freezing and a storm is imminent.

L2

Re-glazing a single-pane wood window

For broken glass in an old wood sash, or for replacing failed glazing compound. Glass cut to size is available at hardware stores — bring the sash measurement minus ⅛" on each dimension for clearance. Wear leather gloves throughout.

1Remove the sash from the window frame if possible — work horizontally for easier compound application. Remove old glazing compound with a putty knife and heat gun (soften with the gun, remove while warm). Work carefully — apply the knife force outward away from the glass to avoid cracking it if the glass is intact.

2Remove glazier's points with pliers or a flat screwdriver. Remove the glass from the frame and set it flat on a padded surface — wearing leather gloves throughout. Inspect the wood groove: it should be clean and intact. Any rotted wood must be repaired or treated before re-glazing.

3Clean the wood groove completely. Brush bare wood with a thin coat of linseed oil — this prevents the new glazing compound from drying too fast (the oil in the compound migrates into dry wood, leaving the compound surface to harden before the compound has fully set). Allow the linseed oil to soak in for 30 minutes before proceeding.

4Apply a thin "setting bed" of glazing compound in the groove — a thin layer that the glass will sit on and seal against. This bed seals the back face of the glass to the sash, preventing moisture entry from behind.

5Set the glass into the setting bed. Press firmly on all four edges (not the center — this flexes the glass). Install new glazier's points every 6–8" along each side — push them in with a putty knife blade, pressing the flat of the knife against the point and sliding along the glass surface.

6Apply the exterior glazing bead: roll a rope of compound and press it into the corner between the glass and sash on all four sides. Use a putty knife held at 45° to the glass to form a triangular bead — the knife rides the glass on one side and the sash on the other. This is the visible finish bead. Allow to partially cure (5–7 days), then prime and paint over the compound before it fully hardens to seal it from the elements.

L2

Replacing a fogged insulated glass unit (IGU)

A fogged double-pane window needs the IGU replaced, not the whole window — if the frame is sound. Measure carefully, order from a glass supplier, install in the existing sash.

1Measure precisely. Height and width to the nearest 1/16". Also measure the IGU thickness — look at the edge of the existing unit between the panes; the total thickness (glass + spacer + glass) determines what you order. Most residential IGUs are either ½", 9/16", or ¾" thick. Bring these measurements to a glass supplier.

2Remove the sash from the window frame. On double-hung windows: lift the lower sash; tilt the top rail toward you; slide the sash up and out of the balance system. On casement windows: close the sash, remove the hinge pins on both hinges.

3Remove the stop molding (the narrow strip of wood or vinyl that holds the IGU in the sash frame from the interior side). Work carefully with a putty knife to pry it off without breaking it — you'll reinstall it. Remove the old IGU and all old sealant from the groove.

4Apply glazing tape or a thin bead of window glazing silicone to the clean sash groove. Position the new IGU in the sash — for any unit over 36": use two suction cups to lift and position. Set the unit on two setting blocks (small neoprene pads) placed at the quarter-points on the bottom of the sash groove to prevent the glass from sliding to one corner.

5Reinstall the stop molding, securing with finish nails or screws. Reinstall the sash. Test the window operation — it should open, close, and lock as before.

Emergency and disruption application

Three scenarios that make glazing and screen skills immediately relevant.

Storm window damage

Wind-driven debris is the most common cause of broken residential window glass during storms. Having polycarbonate sheet, screws, and caulk on hand before storm season means that a broken window can be repaired within an hour of the storm clearing — before rain re-enters the opening. A standard sheet of 4'×8' polycarbonate covers most residential window openings with material left over.

Insect protection during power outages

In mosquito season, a screen in good condition is part of the disease prevention system for sleeping areas — particularly during multi-day power outages when air conditioning isn't available and windows must be left open. An intact, well-fitted screen is the last line of defense. Inspect and patch screens before mosquito season begins, not after the first bite.

Winter heating season breaks

A broken window in a living area or bedroom during a cold weather event drops interior temperatures meaningfully. An interior window film kit (available at hardware stores) takes 20 minutes to install from inside and provides both weather protection and minimal insulation value — enough to maintain sleeping area temperatures until an exterior repair can be made. Keep one kit stored in the house through winter.

Mandatory section

When to call a glazier or window company.

Screen repair, re-glazing single-pane wood windows, and basic IGU replacement are homeowner territory. Several glass situations require professional equipment or expertise.

Large plate glass and tempered glass — requires professional cutting and handling

Glass panes over approximately 24"×36" require professional handling equipment — plate glass suction lifters, specialized cutting tables, and edge finishing tools. Tempered glass (required in most hazardous locations: shower doors, low windows, doors, sidelights) cannot be cut after tempering — it must be ordered to size from a glass supplier. Homeowners cannot cut tempered glass.

Skylight glass replacement

Skylights require working on the roof, handling large glass panels overhead, and ensuring watertight flashing integration. A glazier with skylight experience handles the glass; a roofer or skylight installer ensures the flashing and curb are watertight. The combination of height, weight, and weather-tightness requirements makes this consistently professional work.

Historic or leaded glass

Historic wood windows with divided lights (multiple small panes), original wavy or restoration glass, or leaded glass panels require a glazier specializing in historic work. Standard modern glass doesn't match the visual properties of original glass. Local preservation organizations and historic window restoration specialists source appropriate glass and apply traditional glazing techniques.

Window frame damage requiring full window replacement

If the wood sash or frame is rotted, the glazing compound groove is destroyed, or the frame is warped to the point where the window no longer seals or operates correctly, replacing the glass unit without replacing the frame produces a glass repair that won't hold. A window company assesses whether the frame can be repaired and re-glazed or whether a replacement window makes more economic sense.

Practice project

Screen inspection and re-screen — one window, this weekend.

Time: 30–45 minutes per window. Cost: $5–$15 in screen material and spline. Outcome: the full re-screening skill, a repaired screen, and the spline roller on hand for every future screen job.

1.

Inspect all window and door screens — look for holes, tears, and spline pulling loose from the groove. Identify the one most in need of attention.

2.

Buy a spline roller tool ($5), a roll of matching spline (bring the old spline to match the diameter), and screen material cut to the frame width plus 4".

3.

Remove the screen frame, remove old spline and screen, install new screen and spline using the procedure above, trim, reinstall. The first re-screen takes 30–45 minutes. By the third window it takes 15.

4.

Store the remaining spline roller, spline, and any leftover screen material — these keep indefinitely and will be needed for the next screen job.

Annual spring prep: Inspect screens before screen season (spring) and after screen season (fall). Fall: pull screens, roll and store in a cool dry location. Spring: pull them out, inspect and patch before reinstalling. Annual inspection prevents discovering a torn screen the night that mosquito season begins.

Recommended resources

Books, resources, and the credential.

Books

Windows and Doors (Fine Homebuilding / Taunton Press) — the professional trade journal's coverage of window repair, replacement, and glazing. The re-glazing and weatherstripping sections are the best available for homeowner use.

Fixing Up Old Houses (various) — older house repair manuals written when single-pane wood windows were the standard cover re-glazing clearly and in detail — often better than modern general repair guides.

Free resources

YouTube — This Old House window repair series: The re-glazing segment is thorough — the technique for tooling the glazing bead at the correct 45° angle is much clearer in video than in text. Watch before attempting the first re-glaze.

Local glass suppliers — most will cut glass to your measurements for single-pane replacement. Bring the sash opening measurements minus ⅛" on each side. They can advise on IGU sizing if you're measuring a double-pane for replacement.

Historic preservation offices — for homes in historic districts, state and local preservation offices often provide guidance on appropriate window repair approaches. Find yours through your state's Learning page.

The credential

Glazier is a skilled trade with a formal apprenticeship program through the International Brotherhood of Painters and Allied Trades. Glazier apprenticeships cover flat glass installation, specialty glass (fire-rated, acoustic, decorative), curtain wall systems, and storefronts. No credential is required for homeowner screen repair, re-glazing single-pane wood windows, or basic IGU replacement.