Perimeter Joint Failure
Cracked, missing or poorly bonded sealant between the window frame and surrounding wall can provide a direct rain path.
Brick Walls & Window Leaks
Why Does My Brick Wall Leak Around a Window?
Water appearing beside or below a window does not necessarily mean the brick itself is “leaking.” The entry point may be a failed perimeter joint, flashing, a blocked drainage path, cracked masonry, the window assembly, or a location higher in the wall.
The key is to understand how the wall is supposed to manage rain, then trace where that system has stopped working.
Openings are vulnerable transitions. Brick, mortar, flashing, steel, sealant, window frames and drainage details all meet within a relatively small area.
The interior stain may be where the water stopped, not where it entered.
Follow the Water Path
First Question: What Kind of Wall?
Brick veneer and solid masonry handle rain differently.
In a modern drainage-type brick veneer wall, the outer brick is not intended to be perfectly waterproof. Some rain can pass through the masonry. The cavity, water-resistive barrier, flashing and weeps are intended to collect that water and return it to the exterior.
Older solid masonry walls manage water differently. Their thickness and material mass can absorb and release moisture, and many do not contain a modern drainage cavity or concealed flashing system.
That distinction matters because a repair that makes sense on modern veneer may not apply to an older multi-wythe brick wall.
Before diagnosing the leak, identify:
1Brick veneer or solid masonry
2Approximate age of the wall and window
3Whether the window was replaced after the brickwork was built
4Whether visible weeps or flashing are present
5When the leak occurs: wind-driven rain, steady rain or snowmelt
Six Common Leak Paths
The same interior symptom can come from several different exterior defects.
More than one path can be active at the same opening.
Head Flashing Failure
Water collected above the opening may not be directed safely outward if flashing is absent, damaged, short, poorly terminated or buried incorrectly.
Blocked Weeps or Cavity
Water can collect when weeps are blocked or mortar droppings bridge the drainage space and prevent moisture from reaching the flashing.
Sill or Sub-Sill Leakage
Water can enter at the sill, end joints, window corners or concealed sill-pan details and then appear below the opening.
Cracked Masonry
Open mortar joints, cracked brick or movement around the lintel can provide additional rain paths near the window.
The Window Itself
Glazing seals, frame joints, window weeps and installation details can leak independently of the masonry.
Brick veneer is a drainage wall. The goal is not to pretend that no rain ever crosses the brick face. The hidden drainage system has to manage the water that does.
Why Brick Veneer Can Get Wet Without “Failing”
The outer brick is the first line of defence, not the entire water-control system.
NRC Canada research on rain penetration and masonry walls emphasizes that good construction details are necessary to control rain, including flashing, weep holes and details that direct water away from vulnerable areas.
Brick Industry Association guidance likewise treats drainage walls as systems: brick, an air space or cavity, a water-resistive barrier, flashing and weeps work together.
If one component is missing or interrupted, water that would normally drain harmlessly can find a path into the window opening or interior wall.
Follow the Water Path
Where water appears inside can be surprisingly far from where rain entered.
Water Above the Window
Investigate masonry, flashing, roof or wall details higher up. Water can descend inside a cavity before reaching the top of the opening.
Water at an Upper Corner
Perimeter joints, head flashing, lintel-area cracking and water travelling from above are all possibilities.
Water Below the Sill
Check sill joints, concealed pan flashing, window-frame drainage and whether water is entering the wall at the jambs and collecting below.
Only During Wind-Driven Rain
Wind pressure can drive water through joints and defects that remain dry in ordinary vertical rainfall, making exposure direction an important clue.
Head Flashing & Weeps
Water collected above the opening needs a continuous route back outside.
BIA guidance recommends flashing where the drainage cavity is interrupted, including at lintels over openings. Weeps should be installed immediately above the flashing so collected water can drain.
Flashing also has to terminate properly at its ends. End dams or turned-up ends help prevent water from simply running off the flashing into the adjacent wall.
A leak can therefore occur even when flashing technically exists if it is discontinuous, punctured, poorly lapped, terminated incorrectly or unable to drain because the cavity is blocked.
Look above the frame. The masonry directly over a window is where lintel support, flashing, weeps and movement all meet.
Window Perimeter Sealant
Caulking can be part of the repair, but it should not become the entire drainage strategy.
The joint between a window frame and adjacent construction has to manage movement while limiting direct rain entry. Failed sealant can absolutely leak.
But NRC work focused on Atlantic Canada specifically cautions against relying on external caulking or face-sealing as both the rain deflector and air barrier. That approach can compound leakage when the wall and joint behind it are not properly detailed.
Good perimeter-joint repair means removing failed material where appropriate, preparing clean bonding surfaces, using compatible backer and sealant details, and preserving the wall's intended drainage paths rather than indiscriminately smearing sealant over masonry joints and weeps.
Caulking is more likely to help when:
✓The failed perimeter joint is a confirmed rain path
✓The flashing and drainage system remain functional
✓The joint can be cleaned and detailed properly
✓Weeps and drainage openings are not being sealed shut
Movement changes the water path. A crack at a window corner can open a new route through otherwise sound brick and mortar.
Cracks, Lintels & Movement
A water leak may be secondary to a masonry movement problem.
Cracking around an opening can come from settlement, thermal movement, corroding steel, lintel deflection or other support conditions.
Once joints or brick units open, wind-driven rain has a more direct route into the wall. Recaulking the window perimeter may not affect that path at all.
If the masonry is lifted, sagging, displaced or repeatedly cracking around the lintel, diagnose the movement before treating the opening as a simple sealant leak.
Read the lintel and opening cracks guide →Sills & the Bottom of the Opening
The sill has to shed exterior water while the concealed assembly manages anything that gets behind it.
Window sills should direct water away from the wall. End joints, cracks, insufficient slope or poor drip details can allow water to remain against the opening.
In modern assemblies, concealed sill-pan or sub-sill flashing may provide a second line of defence beneath the window. If that system is absent, damaged or poorly connected to the wall's water-resistive layer, leakage may appear directly below the window.
BIA guidance also emphasizes flashing and end conditions at masonry sills so collected moisture drains outward rather than running into adjacent wall areas.
Horizontal surfaces deserve attention. Sills, ledges and projections collect more water than a vertical wall and need reliable slope and drainage.
The Window Can Leak Too
Do not assume every wet stain beside brick is a masonry defect.
Window frames contain their own joints, gaskets, glazing seals and drainage paths. Some window systems intentionally collect small amounts of water and discharge it through frame weeps.
If those pathways are blocked or frame joints fail, water may enter the interior even when the surrounding masonry is functioning correctly.
Replacement windows can add another complication. A newer window may be installed into an older masonry opening with altered perimeter details, incomplete sill flashing or sealant bridging that does not recreate the original drainage strategy.
Clues the window system itself deserves attention
•Water appears within the frame or sash
•Frame weeps are blocked
•Glazing seals or frame joints are visibly failed
•The leak began after window replacement
•Exterior masonry remains dry while the frame leaks during testing
Look higher and wider than the window. Concentrated runoff can enter the wall above the opening and travel before it becomes visible inside.
Water From Somewhere Else
The window may simply be where water finds an easy exit.
Roof intersections, overflowing gutters, parapets, upper windows, cracked masonry and other penetrations can introduce water above the affected opening.
Gravity then carries it down through a cavity, along framing or across flashing until the window interrupts the path.
This is why repeatedly recaulking the same window can fail when the actual entry point is a metre or more above it.
A Better Diagnostic Sequence
Start broad, then narrow the leak path.
Avoid changing several details at once before you understand which one failed.
1. Record the Weather
Note wind direction, rain intensity, duration and whether the leak follows snowmelt or only certain storms.
2. Inspect the Whole Elevation
Look above and beside the opening for cracks, roof runoff, upper openings and transitions.
3. Inspect the Opening
Check perimeter joints, sill, lintel, weeps, flashing clues and masonry movement.
4. Compare Interior & Exterior
Map the interior stain to the wall assembly rather than assuming the entry point is directly opposite it.
5. Test Systematically
Where controlled water testing is needed, isolate small areas in a planned sequence rather than saturating the entire wall at once.
6. Repair the Confirmed Path
Restore flashing, drainage, joints, masonry or window details according to the actual failure found.
About Hose Testing
More water does not automatically produce a better diagnosis.
Spraying an entire wall or directing a pressure washer at masonry joints can force water into places ordinary rain would not reach and create misleading results.
Controlled diagnostic testing works best when individual zones are wetted in a deliberate sequence, starting low and progressing upward while enough time is allowed to observe the interior.
Complex or persistent leaks may justify professional water testing because window, masonry and concealed wall components can all be involved.
Avoid during informal testing
×Pressure washing joints or window seals
×Soaking the entire elevation at once
×Changing several sealants before locating the path
×Blocking weeps to “stop” water
Possible Repair Scopes
The correct repair depends on which part of the water-management system has failed.
Perimeter Joint Repair
Remove failed sealant where necessary, prepare the joint and install a compatible, properly detailed replacement.
Masonry Repair
Repoint open joints, replace damaged units and address movement around the lintel before expecting the opening to remain dry.
Flashing & Drainage Repair
Selective brick removal may be required to access concealed flashing, end dams, weeps or cavity obstructions.
Sill Repair
Correct damaged joints, slope, drip details or concealed sill flashing where those are confirmed leak paths.
Window-System Repair
Frame, glazing, drainage or installation defects may require a window contractor rather than masonry work.
Combined Repair
Some openings require both masonry and window work so flashing, sealant, framing and drainage connect as one system.
Atlantic Canada Context
Wind-driven rain makes window-wall transitions especially important in this region.
NRC Canada research prepared through the Nova Scotia construction research community specifically identified rain penetration at window-wall joints as a major concern in Atlantic Canada.
Prince Edward Island, Nova Scotia and New Brunswick regularly combine coastal winds with prolonged rain, wet snow and freeze-thaw conditions. A joint that performs adequately in gentle rainfall may leak when wind creates pressure across the wall.
That makes good drainage, flashing and connected air/water-control layers more important than simply applying more caulk to the exterior face.
Wind changes rain behaviour. Water does not always travel straight down the face of a wall. Pressure can drive it through small defects around openings and transitions.
What to Photograph
Show the window, the wall above it and the interior stain.
Whole Exterior Opening
Include several feet of brick above, below and beside the window.
Head & Lintel
Show cracks, rust staining, weeps, visible flashing and the courses directly above the window.
Both Jambs
Photograph perimeter sealant, gaps and where the frame meets brick or other trim.
Sill
Show slope, joints, end conditions, cracks and the bottom corners of the frame.
Wall Above
Include rooflines, upper windows, downspouts and other possible water sources.
Interior Moisture
Show where staining starts and ends, including trim, ceiling, jambs and the wall below the sill.
Technical References
Why this guide treats a window leak as a wall-system problem rather than a caulking problem.
NRC Canada's Rain Penetration of the Window-Wall Joint, prepared in connection with the Nova Scotia construction research community, explains that controlling the forces that drive water through joints is central to preventing leakage and cautions against depending on exterior face-sealing as the entire rain and air-control strategy.
NRC guidance on masonry walls also emphasizes flashing, weep holes, cracking and architectural details that direct rain away from vulnerable locations.
Brick Industry Association Technical Notes 7 and 7B describe drainage-wall design, flashing and weep practices. BIA Technical Note 36 further discusses flashing at sills and openings and the importance of end conditions and drainage.
NRC Canada: Rain Penetration of the Window-Wall Joint →
NRC Canada: Rain Penetration and Masonry Wall Systems →
Brick Industry Association Technical Note 7: Water Penetration Resistance - Design →
Brick Industry Association Technical Note 7B: Construction & Workmanship →
Brick Industry Association Technical Note 36: Sills & Soffits →
About the Author
Prepared by Dean MacArthur, DinoMac Masonry Ltd.
Dean is a third-generation mason with more than 20 years of hands-on experience working with brick, natural stone, chimneys, foundations, repointing and masonry restoration in Prince Edward Island.
The DinoMac Masonry Knowledge Centre uses PEI field experience to explain masonry conditions that are also common across Atlantic Canada and other cold, wet climates.
Last reviewed: August 26, 2026
Brick Window Leak FAQ
Common homeowner questions.
Why does water leak around a window in brick?
Possible causes include perimeter joints, flashing, blocked drainage, cracked masonry, the window assembly or water entering higher in the wall.
Is brick veneer supposed to be waterproof?
No. It normally relies on a drainage cavity, water-resistive layer, flashing and weeps to manage rain that passes through the outer masonry.
Will caulking around the window stop it?
Only if the failed perimeter joint is the actual leak path. Caulk will not repair missing flashing, blocked drainage or cracks elsewhere.
What are weeps above a window for?
They allow water collected on flashing inside drainage-type brick veneer to drain back to the exterior.
Can the window itself be leaking?
Yes. Frames, glazing, internal drainage and installation details can leak independently of the surrounding brick.
Why is the interior stain not opposite the entry point?
Water can travel along cavities, flashing, framing and finishes before it becomes visible inside.
Related Knowledge Centre Guides
Use the leak location to investigate the wall system, opening support and water-management details around it.
Brick Window Leak in PEI?
Send the whole opening and the wall above it.
Include exterior photos of the head, jambs and sill, several feet of brick above the window, nearby cracks or weeps, any visible flashing, and matching interior photos showing where the water appears. DinoMac can help determine whether the visible problem appears masonry-related, drainage-related or more likely part of the window system.