DOWSIL
Professional silicone, ~99% of our work
What we seal with
The Royal Seal.
The same silicone specified on commercial buildings.
Around 99% of our work is done with DOWSIL Contractors Weatherproofing Sealant — a 100% silicone from Dow's professional weatherproofing line, the family architects specify for curtain wall and high-rise weatherseals. It costs us several times what the acrylic tube at the big-box store costs. This page is why we pay it.
10 yr
Written workmanship warranty
300+
Properties sealed & under warranty
A+
BBB Accredited business
Why the product decides the job
A reseal is only as good as what goes into the joint.
Sealant is the cheapest material on a caulking job and the only one that matters. Labour, access, removal and prep are most of what a reseal costs — which means the difference between a bargain tube and a professional one is a small fraction of the price, and the entire difference in how long the work lasts.
That maths is why cutting the product is such a tempting shortcut for a contractor, and such a bad deal for the homeowner. You pay nearly the same money for the same day of work, and get a bead that starts failing in a handful of seasons instead of holding for decades.
| Behaviour | Builder-grade acrylic latex | DOWSIL CWS (100% silicone) |
|---|---|---|
| Movement | Cures rigid and keeps hardening. A joint that moves works it until it splits — usually down the middle or clean off one face. | Cures to a rubber and stays there. Stretches and recovers with the joint through every freeze-thaw cycle. |
| UV & weather | Chalks, crazes and yellows under sun and ozone. The south and west elevations go first. | Silicone's backbone is inherently UV-stable — the reason it is trusted on the sun-facing face of a high-rise. |
| Adhesion | Adequate on painted wood; poor and short-lived on glass, aluminum and masonry — exactly where a window joint lives. | Bonds properly to glass, aluminum, brick, stone and concrete, which is what a window perimeter is actually made of. |
| Shrinkage | Water-based, so it loses volume as it dries. The bead you approved is not the bead you keep. | Cures by reacting with moisture in the air rather than drying out — negligible shrinkage. |
| Service life | Commonly replaced on a five-to-ten-year cycle, and often looking rough well before that. | Built for the service life of a commercial envelope — the same family of sealant specified on curtain wall and high-rise weatherseals. |
| Paintable | Yes — which is the one job it is genuinely good at. | No. Paint will not bond to silicone and will peel. Joints that get painted need a paintable sealant instead. |
Note the last row: neither product wins every category. That is the point — the right sealant depends on the joint, and using one tube for the whole house is how a caulking job comes back early.
What you are paying for
Four properties that decide whether a bead survives.
It moves with the house
A window joint is not a static crack — it is a designed movement gap, opening and closing as the frame and the wall expand at different rates. A professional silicone is formulated to stretch and recover through that cycle for decades. A rigid filler simply loses.
It survives the sun
UV and ozone are what age a bead on the south and west faces of a house. Silicone's chemistry is inherently stable under both — it does not chalk, craze or go yellow the way an acrylic latex does after a few summers of direct sun.
It bonds to the real materials
Glass, aluminum, brick, stone, concrete. These are difficult surfaces for a water-based caulk and routine ones for a professional silicone — which matters, because they are exactly what a window perimeter is made of.
It doesn't shrink away
Silicone cures by reacting with moisture in the air rather than by drying out, so the bead keeps the shape and volume it was tooled to. An acrylic loses volume as its water leaves, pulling thin at the very edges it needs to hold.
The honest caveat
Silicone is not paintable. We'd rather say so.
Our company name has "& Paint" in it, so this is the awkward part to put on a website — and it is the part that decides whether a caulk-and-paint job holds.
Paint does not bond to cured silicone. It beads, it fails to wet the surface, and within a season it peels off the joint in strips while the rest of the elevation still looks fine. No primer reliably fixes this. It is a property of the material, not a technique problem.
So we plan for it at quoting, not at painting. Any joint that is going to be painted gets DOWSIL Contractors Paintable Sealant instead — a silane-modified hybrid from the same family, made to be coated. Joints that stay unpainted get the silicone. Most houses need both, in different places.
Our sequence on a caulk-and-paint job is paint first, seal second. Trim, frames, fascia and lintels are prepped and painted with Benjamin Moore Command, the coating is left to cure, and only then is the joint sealed with colour-matched DOWSIL CWS over backer rod — so nothing ever has to be painted over the bead. Steel lintels are stripped back to sound metal and rust-primed before paint; rot-prone door-frame bottoms are cut back, filled and shaped before they are primed. How a caulk-and-paint job is sequenced →
If a contractor tells you otherwise
"We'll silicone it and paint right over" is a job that will fail.
It is a common enough promise that it is worth knowing the tell. If someone quotes a single silicone product for an exterior that is being repainted, either they intend to paint over silicone — which peels — or they have not thought about the sequence at all.
Ask which joints get which product and why. Any sealing contractor who takes the work seriously will have an answer ready.
The two products, named
What actually goes on your house.
Two sealants cover almost everything we do, and which one a joint gets is decided at quoting — not improvised on the day. Every figure below is from the manufacturer's published data sheet.
~99% of our work
DOWSIL™ Contractors Weatherproofing Sealant
One-part, neutral-cure, medium-modulus 100% silicone
- Standard
- ASTM C920 Class 35
- Joint movement
- ±40%
- Service range
- −40°F to 250°F
- Adhesion
- Primerless, most non-porous
- Paintable
- No
Window and door perimeters, masonry joints, transitions, penetrations — every joint that stays exposed rather than getting painted.
Joints that get painted
DOWSIL™ Contractors Paintable Sealant
One-part, neutral-cure silane-modified hybrid
- Standard
- ASTM C920 Class 50
- Joint movement
- ±50%
- Skin / full cure
- 30–60 min / 7–14 days
- Adhesion
- Primerless, porous & non-porous
- Paintable
- Yes, once tack-free
- Colour
- Six factory colours
Trim, frames and any joint going under a coat of paint. It actually carries more movement than the silicone — it gives up UV life, not flexibility.
The concrete finish
Silica sand, blasted into the bead while it is still tacky.
On stone, stucco, block and concrete a smooth bead reads as a line of caulk. So on those surfaces the fresh silicone is sandblasted with B&M silica sand before it skins over: the grains bed into the surface of the bead and it takes on the grain of the masonry around it. Same DOWSIL silicone underneath, same joint — it just disappears. The sanded-versus-smooth comparison is on the process page.
Where the shortcuts are
What we won't put on your house.
These are the three things that make a caulking job cheap, and the three reasons it comes back. None of them are exotic — they are the standard practice at the bottom of this trade.
- Bargain acrylic latex by the caseUnder $5 a tube, easy to gun, easy to tool, and hard and cracking within a few Ontario winters. It has a place — interior trim, and joints that will be painted and repainted — but it does not belong on an exposed exterior window perimeter.
- A new bead over the old oneThe single most common shortcut there is. It looks finished on the day and it is bonded to a failing surface, so it lifts with that surface. If the old material is not removed, nothing about the joint has actually been repaired.
- Skipping the backer rodRod costs pennies and takes time, so it is the first thing dropped. Without it the sealant runs deep into the cavity, bonds on three faces, and tears the first time the joint moves — with a perfectly good product in it.
Backed in writing
10 years on our work. In writing.
10
Year workmanship warranty
In writing. If our bead fails, cracks, pulls away or leaks because of how we applied it, we come back and fix it — free.
Our warranty covers application. Written exclusions apply for structural or foundation movement, substrate failure, damage caused by other trades, and any bead later painted or altered. Non-transferable at resale.
Put it to work
Where these products go.
Same materials, same standard, applied across the whole envelope — starting at the windows, which is where most of the joint and most of the failure is.
Exterior window resealing
Our hero service — priced per opening with volume pricing, and the page where the numbers live.
Everything else on the envelope
Exterior caulking, flashing and roof penetrations, leak detection, and caulk-and-paint bundles.