Wet glazing vs. dry glazing: why older Vancouver towers leak at the windows
Wet glazing seals the glass to the frame with a continuous bead of gunned silicone that cures in place. Dry glazing holds and seals the glass with pre-formed rubber gaskets, usually EPDM, compressed against the frame. Both keep water out when new. But on aging Metro Vancouver towers the gaskets dry out, shrink, and harden under years of UV, the compression seal is lost, and the windows leak. When the original gasket profile is discontinued, which is normal on a 30- to 40-year-old system, cutting in a UV-stable neutral-cure silicone weather seal is usually the durable fix, because a high-movement silicone is rated to plus or minus 50 percent movement and does not shrink out of a channel the way an old gasket does.
Dry glazing is right when the gaskets are still fresh, resilient, seated, and the profile is still made: leave a working seal alone. Wet glazing is right for structural glazing curtain walls, for curtain wall weather seals in general, and for resealing older dry-glazed towers where the gaskets have aged out and the parts are gone. Structural glazing is its own case, an engineered silicone specification set by the building envelope engineer and not a field pick at all. This page shows how to tell which situation you are in, how to trace the leak before touching a joint, and how to read a reseal proposal so you fix the joint that is actually leaking.
Two ways to seal a piece of glass to a frame
Every window and curtain wall panel has the same basic problem: hold the glass in place and keep water from getting past the edge of it. There are two ways to solve that. Wet glazing runs a continuous bead of silicone between the glass and the frame, gunned in place and cured, so a bonded sealant does the sealing. In structural glazing, that same silicone bond also holds the glass structurally. Dry glazing uses pre-formed rubber gaskets, almost always EPDM, that are compressed between the glass and the frame, so the squeeze of the rubber does the sealing and there is no wet sealant at the glass line.
The mechanical difference is simple but it decides everything that follows. A wet seal is a material bonded to two faces, the glass and the frame, and it stretches and compresses as those faces move. A dry seal is a solid rubber shape held under compression, and it works only while it stays springy and stays the right size in its channel. When a wet seal reaches end of life it lets go at the bond line. When a dry seal reaches end of life the rubber itself changes, hardening and shrinking until the compression is gone. Both fail; they just fail differently, and they get repaired differently.
Both work when they are new and installed correctly. The reason they matter to a strata is what happens after 20 or 30 years on an exposed Metro Vancouver facade, because that is where the two systems part ways. A wet silicone seal that was bonded to a clean, primed frame is still doing its job at that age. A dry gasket in the same exposure is often at the end of its life, and the part to replace it may no longer exist.
How a wet silicone seal actually works
A wet seal is not caulk squeezed into a gap. It is a bead of silicone bonded to the glass on one face and to the frame on the other, sized and shaped so it can flex as the glass and metal move with temperature and wind. That two-sided bond is the whole point. Behind the bead sits a backer rod or a bond breaker so the silicone bonds only to the two faces you want and not to the back of the joint, which lets the bead stretch and compress instead of tearing. The geometry, how deep and how wide the bead is against the joint width, follows the joint design guidance in ASTM C1193. Get the shape wrong and even a good product fails early.
The chemistry matters as much as the shape. On a curtain wall the sealant is almost always neutral-cure silicone. Silicone is inherently UV-stable, so it holds up on a sun-exposed face for many years where other chemistries chalk and crack. Neutral-cure is chosen over acetoxy, or acid-cure, silicone because the acid-cure type releases acidic byproducts as it cures, and those can attack some metals and stone. Against an aluminum frame or a stone spandrel, that is exactly what you do not want, so neutral-cure is the correct chemistry for a frame reseal. High-movement weatherseal grades are rated to ASTM C920 Class 50, meaning the bead can take plus or minus 50 percent of the joint width in movement without failing, which is what a glazing joint needs as the building expands and contracts through the seasons.
Because the seal is a bond and not a squeeze, its life comes down to how well it was bonded on day one. A bead tooled onto a clean, primed frame lasts. A bead put over a dirty, wet, dusty, or unprimed surface lets go at that surface within a few years, and when it lets go it peels away cleanly, which is the tell that the failure was adhesion, not the product. That is why the field work on a reseal is skilled work and why the prep is not a step you can shortcut.
How a dry gasket seal works and why EPDM eventually fails
A dry-glazed opening seals by compression. A pre-formed EPDM gasket is fitted into a channel in the frame and squeezed against the glass, and that squeeze closes the path water would take. There is nothing wet in the joint. When the system is new, this is a clean and reliable way to glaze a window, and it is fast to install because the gasket is a made part that just fits into place. EPDM is used because it resists weather and holds its memory, meaning it springs back rather than staying flattened.
The problem is that EPDM is still rubber sitting in the sun. Over decades of UV exposure the rubber dries out, hardens, and shrinks. As it hardens it loses the springiness that kept it pressed against the glass and frame, so the compression eases off. As it shrinks it pulls back, often first at the corners of the glass, and it can work its way partly or fully out of its channel. Any of those three, hardening, shrinking, or slipping, breaks the compression seal, and because there is nothing wet in the joint to take over, water gets straight through. On an exposed Vancouver face this can begin within 20 to 30 years, sooner on a south or west elevation taking the most sun.
There is a second trap that has nothing to do with the rubber. The exact gasket profile for a 30- to 40-year-old aluminum system is very often discontinued. The frame needs a specific cross-section to seal, and if the maker no longer produces it, the correct part simply does not exist. So even a strata that wants to keep the dry-glazing approach and just swap the gaskets can be stuck. That combination, a gasket at end of life and no replacement part, is the moment most aging Vancouver towers move to a wet reseal.
Why Metro Vancouver changes the answer
The coast is hard on seals in a specific way. On south and west faces the buildings take strong sun, which is what drives the UV aging of EPDM gaskets, and they take wind-driven rain off the water, which is what finds any weakness in a seal and pushes water through it. The two work together: the sun ages the gasket until the compression eases, and the wind-driven rain then drives water through the gap. That is the common pattern behind leaking windows on older downtown, West End, and North Shore towers.
Salt adds another factor on the oceanfront. West Vancouver waterfront and other exposed oceanfront faces carry salt air, which is corrosive and leaves a film on surfaces. For a reseal, salt matters twice: it is one more reason to use neutral-cure silicone rather than an acid-cure product that could attack metal, and it is a contamination risk on the surface that makes thorough cleaning before the bead goes in even more important. A bead bonded over salt film is a bead that will peel.
There is also the age of the stock. A large share of the aluminum-and-glass towers built downtown, in the West End, and on the North Shore date from the 1970s through the 1990s, and many of those were dry-glazed. Those are exactly the buildings now reaching the end of their gasket life. The leaky-condo era taught the region a hard lesson about water getting into wall assemblies and travelling before it shows, and that lesson applies directly here: a leak at a glazing seal rarely shows up at the glass. Water travels laterally inside a frame and a wall before it appears on a suite ceiling metres away, which is why finding the real entry point is the first job, not the reseal.
The failure modes owners never budget for
The first is the discontinued gasket profile. A strata gets a leak report, learns the windows are dry-glazed, and reasonably assumes the fix is new gaskets. Then the profile turns out to be unavailable, and the plan has to change to a wet reseal, which is a different scope and a different budget than the one the council was expecting. Knowing early, from a proper survey or a depreciation report, that the parts are gone lets you plan the wet reseal instead of being surprised by it.
The second is resealing the wrong joint. Because water travels inside the assembly, the stain on a ceiling is not a map to the leak. If a crew reseals the opening under the stain without tracing the water path, they can seal a sound joint and leave the real entry point open, and the leak comes back at the next storm. Worse, the fresh silicone can hide the symptom for a while, so the strata pays for a repair that did nothing and does not find out until the ceiling stains again. Tracing first is not an extra; it is what makes the reseal worth paying for.
The third is lateral water travel showing up as a whole-building question when it is really a few failed seals. One leak on the tenth floor and another on the fourth can look like a facade-wide failure and trigger talk of a full recaulk, when a targeted survey might show two failed openings on the same wind-exposed corner. The opposite is also true: a single visible leak can be the tip of a face that is aging out all at once. Only the investigation tells you which, and that is why the survey drives the scope rather than the other way round. Where the seals are genuinely near end of life across a face, our page on full recaulk versus spot repair walks through how to decide between fixing individual joints and resealing the whole elevation.
Trace the leak before you reseal anything
The most expensive mistake on a leaking glazed tower is resealing the wrong joint. Water that shows up on a suite ceiling may have entered several metres away and travelled through the frame and the wall before appearing inside. So the work starts with tracing the real water path, looking at the glazing seals, the gaskets, the frame joints, and the transitions around the opening. On a high-rise, that survey is done by rope access so every seal can be reached and checked up close rather than guessed at from the ground. Up close you can see whether a gasket has hardened and pulled back, whether a bead has peeled at the bond line, or whether the water is coming from a transition rather than the glass at all.
Where the source is not obvious, controlled water testing reproduces the leak. Water is applied in a controlled way to a suspected area while someone watches inside for entry, working methodically from low to high so you know which element is letting water through. This is the same field water-test approach used across the industry to confirm a leak path before committing to a repair. Only once the actual entry point is confirmed does resealing make sense. The point of the test is to stop guessing, so the money goes into the joint that is actually leaking. When the leak involves several trades or spans a wall transition rather than just the glass, it becomes a broader water ingress problem, which is the work covered on our leak and water ingress service.
Surface prep and correct wet-reseal specification
When the investigation points to failed gaskets and the reseal is the fix, the silicone work has to be done to a proper standard, and the standard is not complicated but it is unforgiving. Cut out the failed gasket or old sealant so the joint is clean and open. Clean both the frame and the glass edge so the surfaces are free of dust, salt film, and old residue. Apply the primer the sealant manufacturer specifies for aluminum and for glass, because the primer is often what makes the bond hold on those surfaces. Set backer rod or a bond breaker so the bead bonds to the two faces and not to the back of the joint, following the joint geometry in ASTM C1193. Then gun and tool the neutral-cure high-movement silicone to a clean, two-sided bonded profile.
After the bead has cured, verify it. A field hand-pull adhesion test per ASTM C1521 checks that the installed bead is actually bonded to the frame on this building, on a set number of openings. That is different from ASTM C794, which is a lab peel test on prepared samples used before the job to confirm the sealant and primer combination will bond to the intended surfaces. Both have a place, but the one that proves the reseal worked on the tower is the field test. A bead smeared over a dirty or wet frame fails at the adhesion line within a couple of years no matter how good the product is, so the prep and the field check are the difference between a reseal that lasts 15 to 20 years and one that fails in two. For how we survey, water-test, and reseal glazed facades, see our sealant and caulking service page.
Standards and what to verify on the proposal
A few standards tell you whether a reseal proposal is serious. ASTM C920 is the specification for elastomeric joint sealants, and its movement classes, 12.5, 25, 35, 50, and 100, are given as a percentage of the joint width; a high-movement weatherseal silicone reaches Class 50, plus or minus 50 percent. On a glazing joint you want that high-movement rating, sized to the joint, because an undersized product tears loose the first time the building moves hard in a heat wave or a cold snap. ASTM C1193 is the joint design guide covering geometry, backer rod, and the two-sided bond, and it is the reference for a correct wet-reseal bead shape.
For adhesion, ASTM C1521 is the field hand-pull test on installed joints and ASTM C1401 is the guide for structural sealant glazing. A proposal that names the movement class, describes the prep and the primer, and commits to a field adhesion check and water testing is a proposal from someone who knows the work. A proposal that skips all of that and just offers to caulk the windows is not. You do not have to be a building scientist to ask which movement class the silicone is, whether it is neutral-cure, how the frame will be prepared, and how the bond will be verified. The answers tell you a lot.
Where structural glazing is different
One case is not a field decision at all. On a true structural glazing curtain wall, the silicone holds the glass in position as well as sealing it against water, so the joint is an engineered element with a defined hardness, adhesion, and movement rating. ASTM C1401 is the guide for structural sealant glazing, and it is clear that only silicone sealants specifically formulated, tested, and marketed for structural glazing are acceptable, that the sealant provides both the structural attachment and the water and air barrier, and that the guidance applies to walls not more than 15 degrees from vertical. This is not a spec you set in the field.
That specification comes from the building envelope engineer, and the contractor follows it. Resealing or altering a structural glazing joint without engineering direction is not appropriate, because the seal is also carrying load. On those buildings the reseal decision, the product, and the method all flow from the engineer specification, and we coordinate the field work to it as part of our building envelope repair service. If you are not sure whether a given curtain wall is structural glazing or a weather-sealed system with separate glazing support, that is one of the first things a survey establishes, because it changes who makes the decision.
Cost drivers, without a made-up price
There is no honest per-window price for a glazing reseal, because the drivers change with the building. Access is usually the biggest: on a high-rise the crews reach the openings by rope access under a WorkSafeBC Part 11 rope access plan, which is efficient for a seal-by-seal survey and reseal but is a real line item. Then comes the number of openings in scope, the amount of frame preparation and priming each joint needs, whether the glass has to be reset or only the perimeter resealed, and the water testing to confirm the repair held. Structural glazing adds engineering involvement, since the product and method come from the envelope engineer rather than the contractor.
The way to control the cost is to scope it from the survey, not from a guess, and to phase it. A reseal planned by elevation, starting with the wind-exposed faces that are failing first, spreads the cost across budget years and usually beats waiting for leaks to force emergency work at a worse price on the worst face. A Strata Property Act depreciation report that flags the glazing seals aging out is the tool that lets a council plan this rather than react to it.
Lifecycle reasoning and warranty reality
Think in service lives, not single repairs. A dry-glazed system has a gasket service life that the coastal sun shortens, and once a face reaches the end of that life, spot-fixing one leak at a time on that face is usually chasing the problem, because the neighbouring gaskets are the same age and the same exposure. A wet reseal of that face resets the clock with a UV-stable material that typically performs 15 to 20 years or more when bonded correctly. That is the trade: a larger scope now for a long, predictable life, versus repeated small repairs on a system that keeps failing next to wherever you just worked.
On warranty, be clear-eyed. A sealant manufacturer warranty covers the product, and an installer warranty covers the workmanship, but neither is worth much if the bond was never verified. The warranty that matters is the one backed by proper prep and a field adhesion check, because an adhesion failure from poor prep is a workmanship issue, and it shows up years after the crew has left. Ask what the workmanship warranty covers, whether it includes an adhesion failure, and whether the field adhesion test results are recorded. A reseal done to standard and documented is one you can stand behind; a smear over a dirty frame with a paper warranty is not.
How to read a glazing-reseal proposal
Read a proposal for four things. First, does it start with an investigation, a rope access survey and water testing to find the real leak, or does it jump straight to resealing a face? Second, does it name the product chemistry and movement class, neutral-cure silicone rated to ASTM C920 Class 50, and does it describe the prep and the primer? Third, does it commit to verifying the work, a field adhesion pull per ASTM C1521 and a confirming water test, rather than declaring victory when the last bead is tooled? Fourth, if any glazing is structural, does it put the engineer in charge of that portion per ASTM C1401 rather than treating it as ordinary caulking?
A proposal that does those four things is telling you it understands the failure and the fix. One that offers to caulk the windows for a flat price, with no survey, no chemistry named, and no verification, is telling you the opposite. The material choices here connect to the wider sealant picture, so if you want the background on why silicone is the weatherproofing default over polyurethane and where each belongs, our comparison of polyurethane versus silicone covers it, and the full sealant and caulking resource hub links the related guides.
Four Metro Vancouver scenarios
1980s dry-glazed aluminum window tower, West End, multiple suite leaks
A 1980s residential tower in the West End reports water at several suite windows on the south and west faces after wind-driven rain. The windows are dry-glazed with EPDM gaskets. Up close by rope access, the gaskets are hard, shrunken, and pulling back from the glass corners, and the original profile is long discontinued. This is the textbook aging-tower case. There is no exact gasket to buy, and the compression seal is gone. The durable fix is a wet reseal: cut out the failed material, clean and prime the aluminum and glass, and tool a neutral-cure high-movement silicone weather seal, then water-test a sample of the resealed openings. Phase it by elevation so the strata can budget it against the depreciation report rather than treat every storm as an emergency.
Call: Wet reseal with neutral-cure silicone, phased by elevation.
Newer curtain wall, resilient gaskets, no leaks
A tower built in the last 10 to 15 years has a curtain wall with fresh, resilient EPDM gaskets. There are no leaks, and an inspection shows the gaskets are still soft, seated, and the right size. The honest call here is to leave the dry glazing alone. Nothing is failing, the parts are still made if a spot repair is ever needed, and cutting wet silicone over a healthy gasket system introduces a bond you now have to maintain, plus the risk of trapping water behind a bead that was never needed. Not every glazed facade needs a reseal, and a contractor who proposes one on a sound system is selling work, not solving a problem. Keep it under normal inspection and revisit when the depreciation report flags the seals aging out.
Call: Leave the dry glazing in place. Inspect, do not reseal.
Structural glazing curtain wall, downtown Vancouver
A downtown Vancouver office tower has a true structural glazing curtain wall, where the silicone holds the glass in position as well as sealing it against water. A suite reports a leak. This is not a field decision. The joint is an engineered element governed by ASTM C1401, with a defined hardness, adhesion, and movement rating set by the building envelope engineer. Any reseal or repair to a structural glazing joint has to follow the engineer specification, because the same silicone is carrying load, and the guide applies to walls not more than 15 degrees from vertical. The correct path is to bring in the envelope engineer, confirm whether the failure is at the structural silicone or at a separate weather seal or transition, and then execute the engineer-directed repair with the specified structural silicone. The contractor coordinates the field work to that spec, and does not substitute a product or a method.
Call: Engineer-directed, engineered structural silicone per ASTM C1401.
Oceanfront West Vancouver face, salt air and strong sun
A low-rise on the West Vancouver waterfront has aluminum glazing on the ocean side. This face takes strong sun, salt air, and driving rain off the water, and the seals age faster here than on a sheltered elevation. When the seals reach end of life, the reseal product has to match that exposure. A UV-stable neutral-cure silicone in a high-movement grade holds up to the sun and salt far better than an aging gasket that keeps drying and shrinking in the same conditions, and neutral-cure avoids the acidic cure byproducts that would be the wrong thing to introduce against the metal in a salt environment. Prep matters even more here: a bead has to be bonded to a genuinely clean, primed frame, because salt film left on the surface is exactly the kind of contamination that causes an early adhesion failure.
Call: UV-stable neutral-cure high-movement silicone, extra care on surface prep.
Decision framework: nine questions for an aging glazed facade
| Question | Recommendation | Reason |
|---|---|---|
| Older tower with dried, shrunken, hardened gaskets? | Wet reseal | Hardened gaskets have lost their compression seal and the exact replacement profile is often no longer made. Cutting in a UV-stable silicone weather seal restores the seal without hunting for discontinued parts. |
| Curtain wall or structural glazing? | Wet (structural silicone) | Structural glazing carries load and seals water at the same time. It is an engineered wet-silicone specification set by the envelope engineer per ASTM C1401, not a gasket choice and not a field call. |
| Newer system, gaskets still resilient and seated? | Keep dry glazing | If the gaskets are fresh, correctly sized, and seated, the dry seal is doing its job. Do not cut wet sealant over a gasket system that is still performing. Disturbing a good seal creates the leak you were trying to avoid. |
| Active leak at the glass line? | Investigate, then wet seal | Trace the actual water path first with a rope access survey and controlled water testing. If the leak is at a failed gasket, a wet silicone reseal over a properly prepared frame is the durable fix on an aging tower. |
| Original gasket profile still made? | Gasket replacement possible | If the original gasket can still be sourced in the exact profile, replacing it keeps the system as designed. When it is discontinued, a wet reseal is the practical route. |
| Facade exposed to strong sun and salt air? | Wet silicone for the reseal | On an exposed West Vancouver or oceanfront face, UV-stable neutral-cure silicone outlasts an aging gasket that keeps drying and shrinking in the same exposure. Match the product to the surfaces, not to habit. |
| Aluminum frame with acid-cure silicone proposed? | Reject, use neutral-cure | Acetoxy (acid-cure) silicone releases acidic byproducts during cure that can attack some metals. Neutral-cure is the correct chemistry against aluminum and glass on a curtain wall reseal. |
| Leak shows on a suite ceiling well inside the building? | Trace before you seal | Water travels laterally inside a frame and wall before it appears on a ceiling metres from where it entered. Sealing where the stain shows, without tracing, leaves the real entry point open. |
| Depreciation report flags glazing seals near end of life? | Plan a phased reseal | A Strata Property Act depreciation report that shows glazing seals aging out lets you budget and phase a wet reseal by elevation before the leaks force an emergency scope at a worse price. |
The two systems compared
Wet glazing (silicone seal)
The glass or panel is sealed to the frame with a continuous bead of gunned-in-place silicone. The weather seal, and in structural glazing the structural bond, is a wet-applied sealant that cures in place. A face-sealed approach.
Dry glazing (EPDM gaskets)
The glass is held and sealed by pre-formed rubber gaskets, typically EPDM, compressed between the glass and the frame. There is no wet sealant at the glass line. Common in older aluminum window and curtain wall systems built from the 1970s to the 1990s.
Questions to ask before you approve the scope
A strata manager does not need to be a sealant specialist to keep a reseal honest. You need the right questions and you need to know the answer that should worry you. Here are the ones that matter, each with the answer to look for and the red-flag answer that should make you slow down.
- Did you trace the actual water path before proposing a reseal? Good answer: Yes. We ran a rope access survey and controlled water testing to confirm where water enters before scoping any seal. Red flag: A proposal to reseal a face, or a whole elevation, with no leak tracing. Resealing the wrong joint leaves the real leak open and hides it under fresh silicone.
- What silicone chemistry are you using against the aluminum frame? Good answer: Neutral-cure silicone, matched to the glass and aluminum, with the primer the manufacturer calls for on those surfaces. Red flag: Acetoxy or acid-cure silicone on aluminum. The acidic cure byproducts can attack the metal, and this is the wrong product for a frame reseal.
- How will you prepare the frame and glass edge before the bead goes in? Good answer: Cut out the old seal, clean both surfaces, prime per the manufacturer data, set backer rod or a bond breaker, then tool a two-sided bonded bead. Red flag: Smearing new silicone over the existing gasket or over a dirty, wet frame. A bead with no prep fails at the adhesion line within a couple of years.
- Will you water-test the reseal before you call it done? Good answer: Yes. We confirm the repair holds with a controlled water test in the same way we found the leak, on a sample of the resealed openings. Red flag: No verification of any kind. Without a water test you do not know if the reseal actually stopped the leak until the next storm proves it did not.
- How do you check the bead is actually bonded to the frame? Good answer: A field hand-pull adhesion test per ASTM C1521 on installed joints, after cure, on a set number of openings. Red flag: No adhesion check at all, or confusing the lab peel test (ASTM C794) with the field test. The field pull is what tells you the bond holds on this building.
- Is any of this glazing structural, and if so is an engineer directing it? Good answer: We identified the structural glazing, and the product, joint, and method follow the envelope engineer specification per ASTM C1401. Red flag: A plan to reseal or cut into a structural glazing joint with no engineer involved. That joint carries load, and altering it without engineering is not appropriate.
- What movement class is the weatherseal silicone rated for? Good answer: A high-movement weatherseal grade, ASTM C920 Class 50 (plus or minus 50 percent), sized to the joint width for the movement it will see. Red flag: No movement rating given, or a low-movement product on a wide glazing joint. Undersized movement capacity tears the bead loose the first hot summer or cold snap.
- How will crews reach the openings, and under what safety plan? Good answer: Rope access under a WorkSafeBC Part 11 rope access plan, which reaches every seal on the face for both the survey and the reseal. Red flag: Vague access, or a swing stage priced for a job that rope access does more cheaply and more thoroughly on a seal-by-seal survey.
If the material chemistry side of this raises more questions, our guides on polyurethane versus hybrid MS sealant and one-part versus two-part polyurethane explain where those other chemistries belong and why silicone remains the default on an exposed glazed facade.
Quick answers
What is the difference between wet glazing and dry glazing?
Wet glazing seals the glass to the frame with a continuous bead of gunned-in-place sealant, almost always silicone, that cures in place. In structural glazing, that silicone also bonds the glass structurally, not just against water. Dry glazing seals the glass with pre-formed rubber gaskets, usually EPDM, that are compressed between the glass and the frame with no wet sealant at the glass line. In simple terms, wet glazing relies on a bonded sealant bead, and dry glazing relies on a compressed rubber gasket. Both can keep water out when they are new and correctly installed. The difference shows up over time in how they fail and how they are repaired.
Why do older Vancouver towers leak at the windows?
On many older Metro Vancouver towers the glazing was dry-glazed with EPDM gaskets, and the common failure is the gasket itself. EPDM is a good material, but decades of exposure to UV light dry it out, shrink it, and harden it. Once the gasket loses its resilience or slips out of its channel, the compression that kept water out is gone, and the joint leaks at the glass line even though nothing looks obviously broken from a distance. Wind-driven rain against a south or west face then drives water through the weakened seal and into the wall. This is one of the most common water-entry patterns on aging Vancouver curtain wall and aluminum window towers.
Can you reseal an old dry-glazed window with silicone?
Yes, and it is a normal repair on aging towers. When the original gaskets have hardened and the exact replacement profile is no longer available, which is common on a 30- to 40-year-old system, cutting in a wet silicone weather seal restores the seal without hunting for discontinued parts. The work has to be done properly: the frame and glass edge must be cleaned, the right neutral-cure silicone and primer selected for the aluminum and glass surfaces, and the bead tooled to a clean, two-sided bonded profile. A silicone bead smeared over a dirty or wet frame fails at the adhesion line quickly, so this is skilled work, not a quick smear of caulk. Done right, a wet reseal gives an old dry-glazed tower a durable, UV-stable seal.
Glazing seal questions
What is the difference between wet glazing and dry glazing?
Wet glazing seals the glass to the frame with a continuous bead of gunned-in-place sealant, almost always silicone, that cures in place. In structural glazing, that silicone also bonds the glass structurally, not just against water. Dry glazing seals the glass with pre-formed rubber gaskets, usually EPDM, that are compressed between the glass and the frame with no wet sealant at the glass line. In simple terms, wet glazing relies on a bonded sealant bead, and dry glazing relies on a compressed rubber gasket. Both can keep water out when they are new and correctly installed. The difference shows up over time in how they fail and how they are repaired.
Why do older Vancouver towers leak at the windows?
On many older Metro Vancouver towers the glazing was dry-glazed with EPDM gaskets, and the common failure is the gasket itself. EPDM is a good material, but decades of exposure to UV light dry it out, shrink it, and harden it. Once the gasket loses its resilience or slips out of its channel, the compression that kept water out is gone, and the joint leaks at the glass line even though nothing looks obviously broken from a distance. Wind-driven rain against a south or west face then drives water through the weakened seal and into the wall. This is one of the most common water-entry patterns on aging Vancouver curtain wall and aluminum window towers.
Can you reseal an old dry-glazed window with silicone?
Yes, and it is a normal repair on aging towers. When the original gaskets have hardened and the exact replacement profile is no longer available, which is common on a 30- to 40-year-old system, cutting in a wet silicone weather seal restores the seal without hunting for discontinued parts. The work has to be done properly: the frame and glass edge must be cleaned, the right neutral-cure silicone and primer selected for the aluminum and glass surfaces, and the bead tooled to a clean, two-sided bonded profile. A silicone bead smeared over a dirty or wet frame fails at the adhesion line quickly, so this is skilled work, not a quick smear of caulk. Done right, a wet reseal gives an old dry-glazed tower a durable, UV-stable seal.
Is wet glazing better than dry glazing?
Neither is simply better; they suit different situations. On a newer system with fresh, correctly sized, well-seated gaskets, dry glazing is doing its job and there is no reason to disturb it. On an older tower where the gaskets have dried and shrunk and the replacement profile is discontinued, a wet silicone reseal is usually the more durable and practical fix, because neutral-cure silicone is UV-stable and does not shrink out of a channel the way an aging gasket does. For curtain wall and structural glazing, the wet structural silicone is an engineered specification set by the envelope engineer and is not a field choice at all. The right answer depends on the age, condition, and whether parts are still available.
What silicone is used to reseal a curtain wall?
Curtain wall weatherproofing is dominated by high-quality neutral-cure silicone, chosen for its combination of high movement capability, UV resistance, and long service life on an exposed facade. High-movement weatherseal grades are rated to ASTM C920 Class 50, which means the bead handles plus or minus 50 percent of the joint width. Neutral-cure is the safe default because it does not release acidic byproducts that can attack some metals and stone during cure, the way an acetoxy or acid-cure silicone can. On any curtain wall reseal, the specific product and any required primer come from the sealant manufacturer data matched to the actual glass and metal surfaces on the building, and for structural glazing from the engineer specification, not chosen at the tube.
How do you find where a curtain wall is leaking before resealing?
By tracing the water path, not by guessing from where the stain appears inside. Water that shows up on a suite ceiling or wall may have entered several metres away and travelled through the frame and the wall assembly before appearing. A proper investigation looks at the glazing seals, the gaskets, the frame joints, and the transitions around the opening, often using controlled water testing to reproduce the leak. Only once the real entry point is confirmed does resealing make sense, because resealing the wrong joint leaves the actual leak open. On a high-rise this survey work is done by rope access so every seal can be reached and inspected up close.
How long does a silicone weather seal last on a Vancouver high-rise?
A correctly specified and installed neutral-cure silicone weather seal on a Metro Vancouver curtain wall typically performs for many years, often 15 to 20 or more, because silicone is inherently UV-stable and holds up to the coastal climate far better than most other sealant chemistries on an exposed joint. The service life depends on the joint movement, the exposure, and above all the quality of the installation: a bead bonded to a clean, primed, properly prepared frame lasts, while a bead applied over a dirty or wet surface fails at the adhesion line in a few years regardless of the product. On an aging tower being resealed from dry to wet glazing, the reseal effectively resets that service life.
Why does EPDM gasket fail if it is a premium material?
EPDM is chosen because it resists weather and holds its shape well, but it is still a rubber compressed under load and exposed to sun. Over decades of UV, the rubber slowly dries, hardens, and shrinks. As it hardens it loses the springiness that kept it pressed against the glass and frame, and as it shrinks it can pull back from the glass corners or work its way out of its channel. When either of those happens, the compression that formed the seal is gone, and there is nothing wet in the joint to take over. So the failure is not a defect in the material, it is the end of a service life that the sun and the coastal exposure shortened.
What is structural glazing and can we reseal it ourselves?
Structural glazing is a curtain wall where the silicone bonds the glass to the frame so that it holds the glass in position, not only sealing it against water. It is governed by ASTM C1401, the guide for structural sealant glazing, which applies to walls not more than 15 degrees from vertical and requires a silicone specifically formulated, tested, and marketed for that use. Because the same joint carries load, you cannot treat it as a normal caulking repair. Any reseal or alteration has to follow the building envelope engineer specification, using the engineered structural silicone the engineer calls for. A contractor coordinates the field work to that spec but does not substitute a product or a method.
What is the difference between ASTM C1521 and ASTM C794 for adhesion?
They both test whether the sealant is bonded, but in different places. ASTM C794 is a lab peel adhesion test done on prepared samples, used before the job to confirm the sealant and primer will bond to the intended surfaces. ASTM C1521 is a field hand-pull adhesion test done on the installed joints after cure, used on the actual building to verify the bond held under real conditions. For a glazing reseal, the field test is what tells you the bead is bonded to this frame, on this tower, so a proposal that promises adhesion verification should be referring to the field test on installed openings, not only a lab number.
Should we replace the gaskets or switch to a wet silicone seal?
It depends entirely on whether the exact gasket profile is still made. If the original profile is available and the glass can be reset, replacing the gaskets keeps the system as it was designed and is the clean option. On a 30- to 40-year-old aluminum system the profile is very often discontinued, and at that point chasing a custom die is slow and costly, so a wet reseal with neutral-cure high-movement silicone becomes the practical and durable route. The wet seal does not dry and shrink out of a channel the way the old gasket did, and the material is a current, off-the-shelf product, so the building is not dependent on a part that no longer exists.
How is a glazing reseal priced, and what drives the cost?
We do not price glazing reseals from a fixed per-window rate, because the drivers vary by building. The main ones are access, which on a high-rise means rope access rigging under a WorkSafeBC Part 11 plan, the number of openings to be resealed, the amount of frame preparation and priming each joint needs, and the water testing to confirm the repair. Structural glazing adds engineering involvement, since the specification comes from the envelope engineer. A phased approach by elevation, planned against the depreciation report, usually costs less over time than waiting for leaks to force emergency work on the worst face first. We scope it after the survey, once we know the real condition of the seals.
Windows leaking on an older glazed tower?
We trace the real water path and reseal glazed facades across Vancouver, North Vancouver, West Vancouver, and Burnaby, all by rope access, so you fix the joint that is actually leaking rather than the one that shows the stain.