Caulk and sealants for gaps, joints and cracks before you paint, plus the foam, backer rod and concrete sealants that go with them. This collection covers DAP Alex Plus, Alex Fast Dry, Alex Flex, Dynaflex 230 and 800, AMP, Extreme Stretch, Kwik Seal Plus, Touch 'N Foam HomeSeal and MaxFill; Sashco Lexel, Big Stretch, Mor-Flexx and closed-cell backer rod; Sikaflex Construction and Self-Leveling sealants and Sika AnchorFix-1; and Loctite PL S10 and PL S20 concrete sealants.
Pick by where the joint is and how much it moves. Indoors on trim and baseboards, DAP Alex Plus and Alex Fast Dry are paintable acrylic latex caulk plus silicone, and Alex Flex is made for molding and trim joints. Outside on windows, doors and siding, DAP says Dynaflex 230 is a paintable, waterproof latex sealant with silicone-like toughness, and Sashco rates Big Stretch, a 100% acrylic, at 500% maximum stretch. For joints that move a lot or stay wet, Sashco Lexel is a synthetic rubber sealant (no silicone) rated for up to 747% joint movement on wet or dry surfaces, and Sikaflex Construction Sealant is a non-sag polyurethane rated for plus or minus 35% movement.
| Job |
Products for it |
Notes (maker) |
| Interior trim, baseboards, molding gaps |
DAP Alex Plus, Alex Fast Dry, Alex Flex |
Acrylic latex caulk plus silicone; paintable; Alex Flex is made for molding and trim joints |
| Windows, doors, siding, exterior trim |
DAP Dynaflex 230 and 800, DAP AMP All Weather, Sashco Big Stretch |
Dynaflex 230 is paintable and waterproof with soap and water cleanup; Big Stretch is water-based 100% acrylic, 500% stretch, not for roofs |
| High-movement and crack-prone joints |
DAP Extreme Stretch, Sashco Lexel, Sikaflex Construction Sealant |
Lexel handles up to 747% joint movement and stays flexible to minus 30°F; Sikaflex Construction is plus or minus 35%, ASTM C 920 Class 35 |
| Tubs, sinks, kitchen and bath |
DAP Kwik Seal Plus, DAP AMP Waterproof Kitchen and Bath, Sashco Lexel |
Sashco lists Lexel for tubs, showers, sinks and countertops; it is paintable and scrubbable |
| Concrete cracks and slab joints |
Loctite PL S20 and PL S10, Sikaflex Self-Leveling, DAP AMP Self-Leveling Concrete |
Self-leveling grades are for flat joints in driveways, sidewalks and garage floors; non-sag PL S10 is for vertical masonry; full cure about 7 days for Loctite |
| Mortar, stucco and stone joints |
Sashco Mor-Flexx (Gray, Beige, White, Ironstone, Charcoal) |
Textured like mortar, stretches like rubber, water cleanup; not for concrete under 6 months old or high traffic |
| Large gaps around windows and doors |
DAP Touch 'N Foam HomeSeal, DAP MaxFill |
HomeSeal is minimum expanding foam; MaxFill is maximum expanding for larger voids |
| Deep joints |
Sashco closed-cell backer rod, 3/8 in, 5/8 in and 3/4 in |
Bond breaker for two-point adhesion; uses less sealant; joints under 1/4 in are too small for rod |
| Setting rods and bolts in concrete |
Sika AnchorFix-1 |
Two-part styrene-free polyester anchoring adhesive from a standard caulk gun; short-term loads only per Sika |
Shop related: DAP, Sashco, Sika, Loctite, concrete and masonry sealers, primers and sealers, and the prep and patch cart.
FAQ
Which caulk should I use on interior trim?
DAP Alex Plus and Alex Fast Dry, both acrylic latex caulk plus silicone, are the common interior trim and gap-filling choices, and both are paintable. Alex Flex is made for molding and trim joints.
Caulk or wood filler?
DAP says wood filler cures hard like wood and is for holes, cracks, gouges and scratches. Joints between boards that move need a flexible caulk or sealant instead.
Lexel or Big Stretch?
Big Stretch is a water-based 100% acrylic with 500% maximum stretch and soap and water cleanup for windows, doors, siding and trim. Lexel is a synthetic rubber sealant rated for up to 747% joint movement that sticks to more surfaces, including PVC, metal, glass and wet areas like tubs and showers.
What do I use for driveway or garage floor cracks?
Use a self-leveling sealant on flat cracks and joints. Henkel lists Loctite PL S20 for concrete floors, driveways, sidewalks and garage floors, and Sika lists Sikaflex Self-Leveling Sealant for horizontal expansion joints in driveways, garages and sidewalks. On walls and foundations use the non-sag Loctite PL S10.
Do I need backer rod?
In deep joints, yes. Henkel calls for backer rod in PL S10 joints deeper than 1/2 in and PL S20 joints deeper than 3/8 in, and Sika specifies closed-cell backer rod for Sikaflex Construction. Sashco's rule is rod one size smaller than the joint width, so 3/8 in rod for a 1/2 in joint.
Can I paint over these sealants?
The makers list Alex Plus, Dynaflex 230, Big Stretch, Lexel, Mor-Flexx, both Sikaflex sealants and both Loctite PL concrete sealants as paintable. Loctite says to wait for full cure, about 7 days; check each label for dry time before painting.
