Let new concrete cure first, and the wait depends on the product: 7 days for Sherwin-Williams’ Loxon primer, 28 days for Rust-Oleum’s Concrete & Garage Floor Paint and Porch & Floor and Sherwin-Williams Porch & Floor, 28 to 30 for DRYLOK Original and Extreme, and 30 for Benjamin Moore Ultra Spec Masonry and Aura Exterior. Then test for moisture and remove efflorescence, the white powder, before you paint.
How long new concrete must cure
| Product | Wait | Moisture or pH | Not for |
|---|---|---|---|
| Sherwin-Williams Loxon Concrete & Masonry Primer | “at least 7 days old”; cured “at least 7 days at 75°F” | pH 6 to 13; damp but not wet surfaces | Must be topcoated within 14 days (a limit, not a surface) |
| Sherwin-Williams Porch & Floor Enamel | “at least 28 days @ 75°F” | Plastic-sheet test: 2 ft by 2 ft, 48 hours | “not suitable for use on garage floors” |
| Sherwin-Williams Emerald Urethane (on masonry) | “usually about 30 days”, or 7 days then prime with Loxon | Not stated | Not stated |
| Benjamin Moore Ultra Spec Masonry; Aura Exterior | 30 days before priming or painting | Aura: pH 10 or more, prime first (608 or N609) | Aura: walking surfaces |
| Rust-Oleum Concrete & Garage Floor Paint | “minimum of 28 days” | Not stated | Asphalt |
| Rust-Oleum Porch & Floor | “minimum of 28 days” | Not stated | Not stated |
| DRYLOK Original; DRYLOK Extreme | “28 to 30 days or reach a pH of below 10” | Remove efflorescence | Over old coatings: warranty void |
| DRYLOK Concrete Floor Paint | “must cure 30 days” | 1 ft plastic test, 24 hours; water-drop porosity test | Bare masonry only, unless previously coated with DRYLOK Concrete Floor Paint or treated with DRYLOK Wet Wall Bonding Primer (or another DRYLOK product its sheet names) |
| DRYLOK Wet Wall Bonding Primer | Green concrete “safe up to alkalinity of a pH of 13.0” | A wet wall that is not actively leaking | “Does NOT resist hydrostatic pressure” |
From each product’s data sheet. Benjamin Moore’s Fresh Start 094 and 032 primer sheets also say 30. Sherwin-Williams’ concrete how-to says its Loxon XP Masonry Coating suits new concrete at least seven days old.
Test for moisture
Sherwin-Williams’ Porch & Floor data sheet gives a plastic-sheet moisture test, a 2 ft by 2 ft sheet left for 48 hours, and says moisture “seldom drops below 15% in concrete.” Its interior concrete how-to says moisture should be no higher than 5%. We’d use the data sheet’s plastic-sheet test rather than a percentage. DRYLOK’s floor paint sheet gives a 1 ft plastic test for 24 hours, and says that if sprinkled water beads stay on the surface, etching is required.
Efflorescence
- Sherwin-Williams (maintenance FAQ): “Salts should be removed by mechanical brushing,” and high-pressure water “may exacerbate the problem.” It says to delay painting if efflorescence continues.
- DRYLOK Original: efflorescence “must be removed,” with an etching solution or muriatic acid, “used according to manufacturer’s directions”.
- Rust-Oleum Masonry 3000: remove mildew or efflorescence; if pressure washed, let it dry three days. Not for glazed or non-porous surfaces, and it says it won’t stop moisture coming through cracks in mortar.
Brick
Sherwin-Williams’ exterior and interior brick how-tos prime with Loxon, and the interior one says to “Allow 24-48 hours for the brick to dry completely.” It also says paint “won’t allow the brick to breathe.” Zinsser’s 2017 chart rates Bulls Eye 1-2-3 “E” (excellent) on brick and concrete (its footnote on that row says to let new cement and stucco cure 60 to 90 days, longer than Zinsser’s newer data sheets); Benjamin Moore Fresh Start 046 lists concrete, masonry and brick. Benjamin Moore’s Aura Exterior sheet says very smooth poured or pre-cast concrete should be etched or abraded.
Floors and old coatings
- Rust-Oleum Concrete & Garage Floor Paint: 5 days before vehicles.
- Sherwin-Williams Porch & Floor: 7 days before heavy traffic. Sherwin-Williams’ concrete how-to says you can skip priming on a concrete floor.
- Rust-Oleum Concrete & Garage Recoat Primer: goes over a previously coated or sealed floor “without having to scuff, sand, or grind,” but its data sheet also says to sand (60 to 80 grit) or spot etch any exposed bare concrete, and that it is not a replacement for etching.
- DRYLOK Original can go over coatings in sound condition, but the warranty is void; it can be topcoated with latex paint after 24 hours. DRYLOK Extreme over existing coatings also voids the warranty.
EPA says that if your home was built before 1978, it is more likely to have lead-based paint. If you sand or scrape old paint yourself, EPA says to use its lead-safe work practices, and not to attempt to remove lead-based paint yourself. See epa.gov/lead.
Hanging something on brick instead? See hanging on brick without drilling. For anything heavy, we’d use a fastener: see choosing a masonry anchor on our drill bit site.