Will a Windshield Crack Spread? What Makes Cracks Grow

Will a windshield crack spread?

Yes, a windshield crack can keep growing after the day it appears, and no source gives a reliable timetable. Infiniti’s technical bulletin on windshield cracking states that cracks spread from the original strike point or crush mark. It names two groups of causes. The first is thermal stress from temperature fluctuation. The second is external physical stress, such as hand touch, wind force and vehicle vibration from potholes. The ROLAGS standard, the American National Standard for repairing laminated auto glass, adds the other half of the picture. It says a repair by a trained professional can stop damage from spreading by adding strength to the damaged area. A crack is a break in the outer glass layer, and every stress the car meets is concentrated at its tip. Some cracks stay the same length for months. Others run across the glass in minutes. The type of crack, its position and the conditions the car meets decide which outcome is more likely. For the full list of what starts cracks in the first place, see what causes windshield cracks.

Which cracks spread fastest: types and repair limits

Stress cracks and cracks that reach more than one edge are the hardest cases, because the repair standard rules out repairing them. ROLAGS defines a floater crack as a crack that does not reach an edge and an edge crack as one that does. A stress crack starts at an edge and has no impact point.

Safelite’s car-wash guidance calls edge cracks the most vulnerable type. Honda’s service bulletin for 2018 to 2020 Accords says the area within 30 mm (about 1.2 in) of the outer edge is susceptible to cracking. That figure applies to those cars only. The table lists the ROLAGS crack types with their repair limits.

Crack type (ROLAGS term)	What it looks like	Repair under ROLAGS
Short crack	A crack of 6 in (150 mm) or less	Yes
Long crack	A crack longer than 6 in	Yes, up to 14 in (350 mm)
Floater crack	Does not reach an edge	Yes, within the length limit
Edge crack	Reaches an edge	No, if it reaches more than one edge
Stress crack	Starts at an edge, no impact point	No, replace
Star or combination break	Short legs running out from a chip	Star up to 3 in; combination body up to 2 in

Many shops set lower limits than ROLAGS. The details are on what size windshield crack is repairable.

Will a small chip spread, and do chips need to be repaired?

A small chip can turn into a crack, which is why the repair standard and repair-kit makers stress early repair. Subaru’s service bulletin on its windshield warranty extension describes a crack type “caused by continuous stress starting from a small chip.” The bulletin says this damage comes from small external damage combined with continual stresses from body structure movements, such as twist and shock, while the car is driven. Infiniti’s bulletin adds that even small scratches in the wiper path can rupture the outer surface and later lead to a crack. Rain-X tells kit users to repair damage as soon as possible and before dirt or water contaminates the break. ROLAGS lists contamination that cannot be cleaned out as a reason not to repair. A chip left open to rain, washer fluid and road grime therefore loses repair options over time. ROLAGS allows bullseye repairs up to 1 inch across and star breaks up to 3 inches. For how the two kinds of damage differ, see the difference between a windshield crack and a chip.

What makes a windshield crack spread faster

Temperature differences across the glass and mechanical shocks to the body are the two forces that automakers and glass makers name. Pilkington, a glass maker, explains the thermal part for building glass. When the center of a pane is warmer than its edge, the edge is stretched by about 50 psi for every degree Fahrenheit of difference. Viracon, another glass maker, says damaged edges lose much of their resistance to that stress. These figures come from building glass, so they show the mechanism, not a safe number for a windshield. ROLAGS names “stress or twist” as one of the two basic causes of laminated glass damage. It means flexing within the vehicle frame or improper mounting.

Trigger	How it loads the crack	Source
Temperature swings	Uneven expansion between warm and cold areas of the glass	Infiniti ITB09-039K; Pilkington ATS-123
Potholes and road vibration	Shock and vibration passed into the glass	Infiniti ITB09-039K
Body twist and shock	Continual stress from the body moving while driving	Subaru SB 12-257-25R; ROLAGS
Wind force and hand pressure	Direct pressure on the damaged area	Infiniti ITB09-039K
Slamming doors in the cold	A vibration through cold glass	Safelite (cold-weather page)
Hot or cold water on the glass	Thermal shock	AAA; Mazda owner’s manual; Safelite

Safelite’s heat page says the most common heat case is a car parked in the sun for hours and then hit by cold rain.

Do windshield cracks get bigger in cold weather?

Cold weather can make an existing crack grow, mostly through fast temperature changes rather than the cold itself. Safelite explains that in winter the outer surface cools and contracts while the heater keeps the inner surface warm, and existing damage is where that tension releases. Safelite also warns that water inside a chip can freeze and force the glass apart. It lists three habits that make cracks worse: high defroster heat pointed at a cold windshield, wipers run over ice, and slammed doors. AAA’s deicing advice starts the defroster at full heat but forbids hot water, which it says can crack glass by thermal shock. Mazda’s owner’s manual also says never to use warm or hot water on ice. The two pieces of advice fit together: AAA writes for intact glass, while Safelite’s warning is about damaged glass. A cracked windshield is unlikely to shatter in the cold. Safelite says laminated windshields are designed to stay in one piece. Side and rear windows are usually tempered and behave differently, as explained in laminated glass vs tempered glass. More on temperature and intact glass is on can cold weather cause a windshield to crack.

Can you go through a car wash with a cracked windshield?

Safelite does not recommend an automated car wash with a cracked windshield, in a guide dated July 23, 2026. It names four risks. High-pressure jets can push water into the crack and widen it. Many washes use hot water or steam followed by a cold rinse, which puts thermal stress on the glass. Brushes in soft-touch washes press and flex the windshield. Water that reaches the plastic interlayer can speed up delamination. Safelite ranks touchless washes as the lowest-risk automated option, but not risk free. It rates brush washes higher risk, especially for edge cracks and cracks longer than a few inches. A home pressure washer carries similar risks. The safest option is a hand wash with a gentle hose and water at outdoor temperature, without aiming the stream at the crack. After a resin repair, Safelite says most technicians recommend waiting at least an hour before the repair gets wet, and longer before an automated wash.

How fast cracks spread, and what to do next

Spread speed varies from minutes to months, and no standard or automaker publishes a rate. CarGlassFix counted NHTSA owner complaints about windshield cracks with incident dates from 2010 to 2025. Out of 5,974 complaints, nearly 200 describe a crack that spread quickly, immediately, or within minutes or hours. One owner describes a gravel chip that grew past 18 inches within 20 minutes. These are unverified owner reports found by keyword search. Unusual events are more likely to be reported, so they do not show how often fast growth happens. Most of them involve Subaru models, which also lead the overall windshield-crack complaints. The practical point is that a crack can outrun a repair appointment. Temporary measures and repair options are covered in how to stop a windshield crack from spreading. Whether it is safe to keep driving is covered in how long you can drive with a cracked windshield.

Frequently asked questions

How quickly will a windshield crack spread?

No standard or automaker gives a rate. NHTSA owner complaints include cracks that grew across the glass within minutes, while others stayed the same length for months. Temperature swings, vibration and body twist decide the pace.

Can a windshield crack stop spreading on its own?

A crack can stay stable for a long time, but the forces that move it, such as temperature changes and road shocks, return every day. ROLAGS says a professional repair stops spreading by adding strength to the damaged area. See how to stop a windshield crack from spreading.

Do edge cracks spread faster than cracks in the middle?

Safelite calls edge cracks the most vulnerable type in a car wash. Under ROLAGS, stress cracks that start at the edge and edge cracks that reach more than one edge cannot be repaired. No source measures relative spread speed.

Can a cracked windshield shatter in the cold?

It is unlikely. A windshield is laminated glass, two glass layers bonded to a plastic interlayer, and Safelite says it is designed to stay in one piece. The crack can still grow and block the driver’s view.

Can I use the defroster with a cracked windshield?

Safelite warns that high defroster heat aimed at a cold, damaged windshield can make a crack spread. Keep high heat off the damaged area and never pour hot water on the glass, which AAA and Mazda both warn against.

Sources

• ANSI/AGSC/NWRD ROLAGS 002-2022, Repair of Laminated Automotive Glass Standard (approved Dec 8, 2022; checked Oct 28, 2026)
• ROLAGS definitions (checked Oct 28, 2026)
• Infiniti Technical Bulletin ITB09-039K, Windshield Cracking (Apr 29, 2024)
• Subaru Service Bulletin 12-257-25R, windshield warranty extension (revised Feb 13, 2025)
• American Honda Service Bulletin 20-118, windshield stress crack (Dec 18, 2020)
• Pilkington North America, ATS-123 Thermal Stress (Jan 14, 2013)
• Viracon, VTT-011 Thermal Stress Breakage
• Mazda 2025 CX-5 owner’s manual, Winter Driving
• AAA, How to Deice Your Car’s Windshield
• Safelite, Does Cold Weather Make Windshield Cracks Worse? (Apr 2, 2026)
• Safelite, Why Do Windshields Crack in the Heat? (Jun 23, 2026)
• Safelite, Can You Go Through a Car Wash with a Cracked Windshield? (Jul 23, 2026)
• Rain-X Windshield Repair Kit product page
• NHTSA complaint data files (complaints received to Oct 22, 2026; CarGlassFix keyword count)