Windows leaking water most commonly traces back to failed exterior caulk, improper flashing, a cracked insulated glass seal, or worn weatherstripping. Serving 730+ towns across Massachusetts, New Hampshire and Maine, Coastal Windows & Exteriors is a woman-owned, InstallationMasters-certified window contractor with 7,000+ installations completed since 2011, and our inspections trace a leak to its true failure point so you only pay for the repair your window actually needs.
Each cause of windows leaking water points to a different fix. Maintenance requirements matter to 78% of windows and doors industry professionals surveyed. Coastal Windows & Exteriors can help you determine why is my water leaking water inside. Many times, weatherstripping and caulk are the culprits.
The Most Common Reasons Windows Leak in Cold-Climate Homes
- Caulk Failure: Cracked or pulled-away exterior caulk lets wind-driven rain inside. The freeze-thaw cycle ages exterior caulk fast, making it one of the most common causes of windows leaking water inside.
- Flashing Problems: Improper or missing head flashing above the window is one of the most serious causes of water entry.
- Failed Glass Seals: Insulated glass units lose their seal integrity over time. This allows condensation to form between panes and water to enter at the perimeter.
- Weatherstripping Wear: Worn compression weatherstripping along the sash allows wind-driven rain to push past the frame during storms. Casement windows, the second most requested window type, are especially prone to hinge-related leaks at the top corner of the sash.
- Hardware Misalignment: Damaged or worn latches allow the sash to sit unevenly against the frame, creating a gap where wind and water enter. Impact resistance and extreme weather protection is a priority for 61% of windows and doors professionals, and proper hardware function is a key part of that protection.
- Repair vs. Replace: Window replacement averages $21,922 nationally with a 76% return on investment at resale. When the same window has leaked repeatedly after caulk or weatherstrip repairs, the insulated glass unit or the full window has likely reached end of useful life.
Fixing Window Water Leaks the Right Way
Top Recommendation: A free in-home inspection that pinpoints the actual failure point for a window leaking water inside. Schedule your free estimate today.
Best for Caulk and Weatherstrip Issues: A DIY re-caulk with silicone-rated exterior sealant and fresh compression weatherstripping. This is best for windows under 15 years old with no signs of flashing or seal failure.
Ideal for Persistent or Recurring Leaks: A full window replacement evaluation for any home. Call us if the same window has leaked more than once after surface-level repairs.
Tired of patching the same leak every season? Let a specialist find the real source and give you a straight answer. Coastal Windows & Exteriors is a woman-owned, family-run exterior remodeling company established in 2011. We hold a 4.8-star Google rating with 1,000+ verified reviews and rank as the #1 Woman-Owned Replacement Company in New England (Qualified Remodeler Top 500). We’ve completed 7,000+ installations across MA, NH, and ME.
Request a free window estimate from Coastal Windows & Exteriors.
Browse our complete window FAQ guide from Coastal Windows & Exteriors.
Explore the Coastal Windows & Exteriors Windows Exterior Remodeling Home Improvement Help Center.
Still have questions about Why Are My Windows Leaking Water? See the areas we serve and talk to your local window contractor.
Last Updated: September 2026
Sources:
- The average cost of window replacement in the US is $21,922, with a 76% return on investment at resale. Remodeling Magazine (JLC Online) New England Cost vs. Value Report Regional cost and ROI data for window replacement in New England. (2026)
- Maintenance requirements matter to 78% of windows and doors industry specialists surveyed. Fixr Windows and Doors Report Fixr survey of windows and doors contractors and industry specialists on homeowner priorities and industry trends. (2026)
- Thermal performance including U-factor and R-value is a priority for 87% of windows and doors professionals. Fixr Windows and Doors Report Fixr survey of windows and doors contractors and industry specialists on homeowner priorities and industry trends. (2026)
- Impact resistance and extreme weather protection is a priority for 61% of windows and doors professionals surveyed. Fixr Windows and Doors Report Fixr survey of windows and doors contractors and industry specialists on homeowner priorities and industry trends. (2026)
- Casement windows are the second most requested window type, favored by 30% of industry specialists for their airtight seals and unobstructed views. Fixr Windows and Doors Report Fixr survey of windows and doors contractors and industry specialists on homeowner priorities and industry trends. (2026)
