# How to paint brick, block and concrete walls

Canonical: https://colorswatchlab.com/guides/how-to-paint-brick-and-concrete/
Author: Color Swatch Lab Editorial Team
Published: 2026-11-02
Updated: 2026-11-02
This markdown file is a text alternate. The HTML page is the canonical version.

> Masonry can be painted, but it has to be cured, dry and clean first. Fresh mortar, concrete and stucco are strongly alkaline, and that alkali can destroy paint. Sherwin-Williams says fresh materials read pH 13 to 14 and take about 30 days to drop to about pH 9, and Benjamin Moore’s exterior data sheet asks for 30 days before priming or painting new masonry. If the wall has white, powdery salt deposits (efflorescence), water is moving through it. Fix the water, brush off the salts, and do not paint until the deposits stop coming back. Then clean off dirt, chalk and loose material, prime with an alkali-resistant masonry primer, and finish with two coats of acrylic paint. Before you start, decide whether to paint at all: paint is very hard to remove from porous brick, and unpainted historic masonry is usually best left unpainted.

## Decide first: should this brick be painted?

Paint changes masonry for good. Benjamin Moore’s guide to painting interior brick warns that removing paint from brick is very difficult because brick is porous, so be sure of the color before you start. On older buildings there is a second question. The National Park Service’s brief on cleaning and water-repellent treatments for historic masonry notes that many buildings were painted when they were built or soon after, and in that case keeping them painted may be the historically appropriate choice. The same brief shows why coatings on masonry matter. It separates water-repellent coatings, which keep out liquid water but let water vapor through, from waterproof coatings, which seal against both, including some elastomeric paints. It warns that salts trapped inside a wall can crystallize under the surface and make it spall, especially when a coating slows the moisture leaving the wall. If your building is historic, or the brick is soft and old, get advice before you seal it in.

## New masonry: wait for the alkali to drop

Fresh mortar, concrete, block fill and stucco are highly alkaline. Sherwin-Williams’ problem solver for alkali burning gives the numbers: the pH of fresh materials is 13 to 14, and it takes about 30 days for them to drop to about pH 9. A coating has a better chance on the less alkaline surface. It also says the alkali in “hot” surfaces will destroy an alkyd or oil product within 6 months, that a vinyl acrylic will do slightly better but still fail, and that an acrylic coating gives the best service. That is why oil paint is the wrong choice on fresh masonry.

| Source | Cure time before painting new masonry | Alkalinity limit |
| --- | --- | --- |
| Sherwin-Williams, alkali burning problem solver | Usually about 30 days. If you cannot wait, at least 7 days with an alkali-resistant masonry primer | pH below 13 for the 7-day route |
| Sherwin-Williams Loxon Concrete & Masonry Primer/Sealer data sheet | New surfaces must cure at least 7 days | Can be applied at pH 6 to 13 |
| Benjamin Moore Ultra Spec Masonry sealer (608) data sheet | At least 7 days under normal drying conditions | pH 13 or less |
| Benjamin Moore Ultra Spec EXT (W448) data sheet | 30 days before priming or painting | pH 10 or more: prime with a masonry sealer first |
| Benjamin Moore, how to paint brick walls | Let new mortar cure at least one month | Not stated |

The 7-day figures apply only to the specific alkali-resistant masonry primers named on those sheets. Your primer’s label decides.

A protective coatings guide from AMPP, the coatings industry association, also says coating manufacturers usually recommend at least 28 days of curing for concrete before coatings go on. If you are not sure of the pH, pH test strips or a pH pen pressed against a wetted spot give a rough reading. When in doubt, wait the full month.

## Efflorescence: the white powder is a water problem

Efflorescence is the white, fluffy or crusty salt deposit that appears on brick, block and concrete. Sherwin-Williams explains it simply. The salts are already in the mortar, block or concrete, and water carries them to the surface. Crystals keep growing as long as both salt and moisture are present. On brick and block walls it often shows up as narrow white bands along the mortar joints. The causes it lists are moisture escaping from inside the building through the wall, rain driven in from outside, basement walls not sealed against ground moisture, new cement or mortar that was not cured long enough, and old efflorescence that was never removed before the last coat of paint.

Paint does not stop efflorescence. The salts push the paint off from behind. Sherwin-Williams’ order of work is to fix the water first, then remove the deposits, then paint. That means repairing the roof, clearing gutters and downspouts, sealing cracks, and adding vents or exhaust fans if the moisture comes from inside. Then remove the efflorescence and anything loose with a wire brush, power brush or low-pressure washing, and rinse thoroughly. Its last line is the one that matters most: painting should be delayed if efflorescence continues. The National Park Service brief makes a related point: cleaning masonry with water can draw salts to the surface as efflorescence, and a wall can take more than a week to dry after it has been washed.

## Is the wall dry enough? The plastic sheet check

A simple way to see whether moisture is coming through concrete or block is the plastic sheet method, ASTM D4263. AMPP describes it: tape an 18 by 18 inch polyethylene sheet tightly to the surface, sealing all the edges, and leave it for at least 16 hours. If condensation forms under the sheet or the concrete darkens, there is enough moisture to put a coating at risk. AMPP also notes the test’s limit: it shows moisture at the surface but says little about how severe the problem is deeper in the concrete. On a basement wall that reads wet, solve the water problem before you think about paint. A basement may need a waterproofing product rather than ordinary paint.

## Step by step

- **Check the age and the lead risk.** If the masonry is new, wait out the cure time above. If it was painted before 1978, the old paint may contain lead. Test before scraping or wire-brushing, and follow [lead-safe painting](https://colorswatchlab.com/guides/lead-safe-painting/) practices.

- **Fix water problems.** Gutters, downspouts, leaks, cracks and missing caulk come first. A wall with active efflorescence is not ready.

- **Clean.** Benjamin Moore’s brick guide starts with a wire brush and vacuum, then a cleaner and scrub brush for dirt. Its masonry sealer sheet asks for a surface that is dry, clean and sound, free of chalk, peeling paint, form oils, efflorescence and mildew, and says power washing is the most practical way to remove chalk outdoors. Sherwin-Williams’ Loxon sheet says to remove form-release and curing agents from new concrete. Benjamin Moore’s W448 sheet says to etch or abrade very smooth poured concrete. Let everything dry before priming.

- **Repair.** Fill cracks and holes with a suitable patching compound or sealant. Benjamin Moore suggests filling small cracks in interior brick with acrylic caulk after priming, because flaws show more once the wall is painted. Sherwin-Williams’ Loxon sheet also says to caulk gaps around windows and doors after priming.

- **Prime the whole surface.** Use an alkali-resistant masonry primer or sealer on new or high-pH masonry, or a high-adhesion, stain-blocking primer on cured interior brick, as Benjamin Moore suggests. The Loxon sheet warns that spot priming can leave a patchy final coat, so prime the whole wall. It also says that, outdoors, the primer must be topcoated within 14 days.

- **Paint two coats of acrylic.** Brush the mortar joints and cut in first, then roll. Rough brick and block take a thick nap: Benjamin Moore’s brick guide uses a 1/2 inch or thicker roller cover, and the Loxon sheet lists 1/2 to 1-1/2 inch. Both masonry primer sheets we read list a 50°F minimum application temperature. For outdoor timing, see [exterior painting weather](https://colorswatchlab.com/guides/exterior-painting-weather/).

## How much primer and paint

Masonry drinks paint. The Loxon primer sheet lists 200 to 300 square feet per gallon on ordinary masonry but only about 80 square feet per gallon on porous, rough stucco. The Benjamin Moore masonry sealer sheet lists 200 to 400 square feet per gallon. Rough block and split-face surfaces sit at the low end. Plan quantities with the low number and the method in [how much paint you need](https://colorswatchlab.com/guides/how-much-paint-do-i-need/), and pick a sheen with [the paint sheen guide](https://colorswatchlab.com/guides/paint-sheen-guide/). Benjamin Moore notes that many people choose flat for brick, while semi-gloss and high-gloss finishes are easier to clean.


## FAQ

### How long should new concrete or mortar cure before painting?

Usually about 30 days. Sherwin-Williams says fresh masonry is pH 13 to 14 and takes about 30 days to fall to about pH 9, and Benjamin Moore’s exterior data sheet asks for 30 days. Some alkali-resistant masonry primers allow 7 days if the pH is 13 or less.

### Can I paint over efflorescence?

No. The white deposits are salts carried out by water, and they will push paint off. Fix the moisture source, brush or wash off the deposits, rinse, and wait. Sherwin-Williams says to delay painting if efflorescence keeps coming back.

### Do I need a primer to paint brick?

Yes. Prime the whole surface with a masonry primer or sealer on new or alkaline masonry, or a high-adhesion primer on cured interior brick. Spot priming can leave the final coat looking patchy.

### What kind of paint should I use on brick or concrete?

An acrylic (100% acrylic latex) masonry or exterior paint. Sherwin-Williams says the alkalinity of fresh masonry will destroy an alkyd or oil product within 6 months and that acrylic coatings give the best service.

### How do I know if a concrete wall is too wet to paint?

Tape an 18 by 18 inch plastic sheet tightly to the wall and leave it at least 16 hours (the ASTM D4263 method). Condensation under the plastic or darkened concrete means there is too much moisture to coat it safely.

## Sources

- [Alkali Burning / Discoloration, problem solver (Sherwin-Williams)](https://www.sherwin-williams.com/painting-contractors/problem-solver/resources/SW-ARTICLE-PRO-ALKALIBURN)
- [Efflorescence (White Crystal Deposits), problem solver (Sherwin-Williams)](https://www.sherwin-williams.com/homeowners/how-to/problem-solver/dirt-stain-discoloration/efflorescence-white-crystal-deposits)
- [Loxon Concrete & Masonry Primer/Sealer A24W8300 data sheet (Sherwin-Williams, PDF)](https://sherlink2.sherwin.com/sher-link/ViewHearsCountryCodeDoc?language=E&sku=650178775&type=DP)
- [Ultra Spec Masonry Interior/Exterior 100% Acrylic Sealer 608 technical data sheet (Benjamin Moore, PDF)](https://media.benjaminmoore.com/WebServices/prod/assets/production/datasheets/TDS_0608/608_TDS_US.pdf)
- [Ultra Spec EXT Exterior Acrylic Satin W448 technical data sheet (Benjamin Moore, PDF)](https://media.benjaminmoore.com/WebServices/prod/assets/production/datasheets/TDS_0448/W448_TDS_US.pdf)
- [How to Paint Brick Walls (Benjamin Moore)](https://www.benjaminmoore.com/en-us/interior-exterior-paints-stains/how-to-advice/interiors/paint-brick-walls)
- [Preservation Brief 1: Assessing Cleaning and Water-Repellent Treatments for Historic Masonry Buildings (National Park Service, PDF)](https://www.nps.gov/orgs/1739/upload/preservation-brief-01-cleaning-masonry.pdf)
- [Concrete moisture testing and mitigation (AMPP)](https://www.ampp.org/technical-research/what-is-corrosion/protective-coatings-learning-center/concrete-moisture-testing-and-mitigation)
- [Reduce the Risk of Lead Exposure at Home (US EPA)](https://www.epa.gov/lead/protect-your-family-exposures-lead)