Three chemistries cover almost every sealing job on a jobsite, and picking the wrong one is the most common reason a bead fails within a year. Silicone, acrylic latex and polyurethane each solve a different problem. Here is how to match the tube to the joint.
Start with two questions: does it move, and does it get painted?
Those two answers narrow the choice immediately. If the joint moves a lot and will never be painted — a tub surround, a shower pan, glass to tile — use silicone. If the joint barely moves and must be painted — interior trim, crown moulding, a gap between baseboard and drywall — use acrylic latex. If the joint moves and lives outdoors under UV and thermal load — concrete slabs, roof flashing, siding laps — use polyurethane.
Everything else is refinement. Get those two questions right and you have eliminated most sealant failures before you open the tube.
| Chemistry |
Paintable |
Best For |
Movement |
| Silicone |
No |
Tub, tile, glass |
High |
| Acrylic latex |
Yes |
Trim and drywall |
Low |
| Polyurethane |
Yes |
Concrete and roofing |
High |
Silicone: the wet-area and glass answer
Silicone stays flexible essentially forever, does not shrink as it cures, and shrugs off standing water. That combination is why it owns kitchens, baths and glazing. It is also why it cannot be painted — paint will not bond to a cured silicone surface, and trying it produces a peeling mess.
For a tub or shower, a mildew-resistant formula matters more than anything else, since the failure mode in a Los Angeles bathroom is rarely a split bead and almost always black staining at the grout line. Our tub and tile silicone sealant in clear and the mold-free kitchen and bath silicone in white are the two we sell most for that work.
For exterior glazing and door perimeters where nothing gets painted, use an all-purpose window and door silicone. Clear disappears against most frames; white matches painted trim closely enough for a caulk line, though if that trim will be repainted later you want acrylic instead.
One practical note for SoCal: silicone tolerates the wide day-night temperature swing in the high desert and valley communities better than acrylic does, which is worth remembering on Antelope Valley and Santa Clarita work.
The middle ground: siliconized acrylic
Siliconized acrylic latex splits the difference — more flexibility than straight latex, still paintable. It is a genuinely useful category, not a marketing hybrid. Our acrylic latex plus silicone caulk handles the kitchen and bath trim work that has to take some movement and then take paint, and the fast-dry version lets you paint the same day on a tight punch list.
Acrylic latex: paintable, forgiving, interior-first
Acrylic latex tools with a wet finger, cleans up with water, and takes paint beautifully. On interior finish carpentry nothing else comes close for speed. The limitation is movement capability — a latex bead in a joint that cycles significantly will eventually split.
For baseboard, casing and crown, our moulding and trim acrylic caulk is formulated for exactly that joint. For general interior gaps, the all-purpose paintable acrylic latex is the workhorse tube.
Modern premium acrylics stretch the category outdoors. Our Dynaflex 230 premium interior/exterior sealant is rated for exterior use with far more joint movement than standard latex, and comes in crystal clear and almond alongside white. For a siding or window perimeter that has to be painted, that is usually the right specification.
Polyurethane: the exterior and structural answer
Polyurethane bonds aggressively to concrete, masonry, metal and wood, handles heavy joint movement, and holds up under sun and traffic. It is the sealant for the parts of a building that are working hardest.
On horizontal concrete — driveway control joints, patio slabs, garage floors — you want a self-leveling formula that flows into the joint and finishes flat on its own. Our self-leveling concrete polyurethane in limestone and the Sika self-leveling flex in textured grey are both built for that. For vertical cracks that would sag, use a non-sag grade like the textured mortar repair polyurethane instead.
Roof penetrations and flashing are a polyurethane job — our S30 roof and flashing sealant in black is formulated for that exposure. For siding, door and window perimeters on the exterior, the door, window and siding polyurethane and the Vulkem 116 exterior sealant in grey are the standard specifications.
Sealants and Los Angeles fire exposure
If you are working in a Very High Fire Hazard Severity Zone, the joints matter as much as the cladding. Chapter 7A assemblies depend on eliminating the gaps where embers can enter — around eave vents, at siding terminations, and at roof-to-wall transitions. A durable exterior sealant is part of that assembly, and specifying a fire-appropriate product for those joints is worth confirming with the manufacturer's listing rather than assuming. Our guide to WUI and Chapter 7A compliant materials covers the surrounding assembly in detail.
Sealant, caulk or adhesive?
The words get used interchangeably on jobsites, but the distinction is real. Caulk fills a gap and is expected to be cosmetic and low-movement. Sealant is engineered for a defined amount of joint movement and weather exposure. Construction adhesive is designed to bond two substrates structurally and is not a weather seal at all.
Some products genuinely do both — a hybrid like the marine fast-cure polyether adhesive sealant bonds and seals in one pass, which is useful on exterior trim and panel work. If your job is primarily bonding rather than sealing, start in the adhesives and glue collection instead.
Getting the bead to last
Surface prep beats product selection more often than anyone admits. Remove the old sealant completely — new material will not bond through a failed bead. Clean and dry the substrate. On joints deeper than about half an inch, use backer rod so the sealant bonds to two sides and can stretch, rather than filling the cavity and tearing itself apart.
Watch the weather. Acrylic latex needs to cure above freezing and out of rain, which is rarely a constraint here but does matter on a coastal morning with heavy marine layer. Polyurethane skins over faster in direct summer sun on a west-facing wall, so tool it promptly. Silicone cures with ambient humidity, which in a dry inland August can take longer than the label suggests.
Browse the full caulk and sealant collection to compare tubes side by side. If you are deciding whether to run the bead yourself or bring in a pro, our article on when to caulk yourself and when to call a pro in LA covers that judgment call, and for weather-barrier detailing behind the sealant, see the housewrap guide.
Frequently asked questions
Can I paint over silicone?
No. Paint will not bond to cured silicone. If the joint must be painted, use acrylic latex, siliconized acrylic, or polyurethane instead.
Can I apply new silicone over old silicone?
Not reliably. Cut and scrape the old bead out completely, then clean the substrate before applying new sealant.
What is the difference between self-leveling and non-sag polyurethane?
Self-leveling flows to a flat finish and is for horizontal joints only. Non-sag holds its shape on vertical surfaces and overhead.
Which sealant for a shower or tub?
A mildew-resistant silicone. It stays flexible, resists standing water, and will not shrink away from the tub edge as it cures.
Do I need backer rod?
For joints deeper than roughly half an inch, yes. It controls bead depth and prevents three-sided adhesion, which is what causes sealant to tear rather than stretch.
