Certified Building Contractor CBC1265305 · Certified Roofing Contractor CCC1334811
Why is water leaking under my window frame after heavy rain?
A straight answer from a Florida state-certified contractor — then what you can check yourself and when to call. Free estimate: (954) 620-7812.
Water showing up under a window frame after heavy rain almost always means water is getting behind or around the frame rather than through the glass. The usual culprits are failed perimeter sealant, cracked stucco or a bad joint at the opening, blocked weep holes that stop the window from draining itself, or flashing that was never installed correctly at the sill.
The nuance is wind. Florida storms drive rain sideways, so a window that stays dry in a calm shower can leak hard in a squall — which points to a pressure-driven path through the frame joints or the surrounding wall, not a simple drip.
Why it happens
Windows are not watertight boxes. They are designed to let a small amount of water in and drain it back out through weep holes at the bottom of the frame. When those weeps fill with dirt, paint, caulk or salt crust, the sill track turns into a bathtub and overflows at the interior — which looks exactly like a leak.
The second path is the perimeter. Sealant at the frame-to-stucco joint hardens and cracks under constant UV and heat, and hairline cracks in stucco above a window can carry water down inside the wall to the sill. On concrete block homes that water can track sideways; on wood frame, it can wet the buck and framing and cause rot that is invisible until the trim is opened up.
Older aluminum units add a third path. Corner joints loosen, gaskets shrink, and near the coast salt air corrodes frames and fasteners, so the frame itself leaks at its seams. When that is happening, resealing the outside does little — the water is already inside the assembly.
What you can check yourself
Find the weep holes
Look for small slots or flap-covered openings along the bottom outside edge of the frame. Gently clear debris with a soft brush or a stream of water and see whether the sill drains.
Trace where the water starts
After rain, note whether the wet line begins at the sill corners, the center of the sill, or runs down the wall from above. Water from above usually means the wall or a joint higher up, not the window.
Inspect the outside joint
From the ground, look at the sealant bead around the frame for gaps, chalking or separation, and at the stucco for hairline cracks above the opening.
Try a controlled hose test
Wet the sill and lower frame first with a garden hose, then work upward in stages while someone watches inside. Keep both feet on the ground and skip this on upper floors.
Check the interior finishes
Soft drywall, bubbling paint, stained casing or a musty smell suggests water has been getting in for a while and the wall behind should be opened and checked.
When to call a pro
Call when clearing the weeps and resealing does not stop it, when the frame itself leaks at its corners, or when the drywall, buck or trim below the window is soft. Those point to flashing or framing issues behind the finish, and repeated caulking just hides them.
If the fix turns into replacing the unit, that is permitted work. A permit is normally required for window and exterior door replacement — including like-for-like impact units — because of structural attachment and egress, and anchoring and installation inspections are common. Units generally need Florida Product Approval, and in Miami-Dade and Broward, which make up the High-Velocity Hurricane Zone, a Miami-Dade NOA and HVHZ installation details apply. Confirm the specifics with your local building department. We are Final Touch Builders, Florida Certified Building Contractor CBC1265305, working statewide — call (954) 620-7812 for a free estimate and a written scope.
What a pro will do
- Diagnose the actual pathWe test the window and the surrounding wall in stages to separate a drainage problem from a flashing or stucco problem before anything is removed.
- Repair the buck and waterproofingWhere the opening is wet or rotted, the buck is repaired and the opening waterproofed so the new or reset frame drains outward.
- Install to the product approvalImpact windows and entry or French doors are anchored to the approved details for the host substrate, block or frame, using the fasteners and spacing the approval calls for.
- Patch stucco and trimStucco, sill and interior trim are patched back so the perimeter sheds water instead of holding it.
- Handle permits and close-outWe pull the permit under our own certification where one is needed, schedule the inspections, and close the permit out at the end.
Related questions
- Can I just caulk around the window to stop the leak?
- Sometimes, if the only failure is the exterior perimeter bead. But never caulk over the weep holes — sealing them traps water in the sill and usually makes the leak worse.
- Will new impact windows stop water intrusion?
- They can, when the leak is coming from a tired frame and the new unit is installed to its approved details with proper flashing and waterproofing at the opening. If the water is actually coming from cracked stucco or a problem above the window, that has to be corrected too.
- Does an open or unpermitted window job cause problems later?
- It can. Unpermitted or open permits often surface at sale, refinance or insurance renewal and may be cited by code enforcement, which is why we close permits out after the final inspection.
- Do impact windows affect my insurance?
- Impact-rated openings are one of the items wind-mitigation inspections look at, and documented, permitted installation is what supports that. Your insurer or inspector can tell you what credits may apply to your policy.
- Do I need HOA approval before replacing windows?
- Often yes. Condominium, townhome and HOA communities are very common in Florida and frequently have their own architectural approval requirements for exterior changes, separate from the building permit.
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