How to Paint Cement to Look Like Flagstone

Paint plain cement to look like a flagstone mosaic.

Although this would be too large of a driveway project, the random shapes and subtle colors of flagstones are forgiving for a novice decorator first attempting to paint cement. Faux-painted cement is an inexpensive and low-labor alternative to laying flagstones on a walkway, patio or deck. It also provides a radical upgrade to outdoor areas and is done by using sponges, paint, and flagstone stencils.

Things You'll Need

• Metal scraper
• Broom
• Garden hose
• Cold power washer
• Trisodium phosphate powder
• Bucket
• Hard-bristled scrub brush
• Plastic wrap
• Tape
• Concrete sealant
• 5 paint pans
• 1 paint roller
• Cement primer, tinted the color of flagstone
• 5 stencils, cut in different flagstones shapes
• White chalk
• Painters and masking tape
• 5 different colors of brown and gray cement paint
• 5 faux finishing sponge
• Thin trim paintbrush
• Long handle for paint roller
• Urethane paint sealer
• Polyethylene sheeting

Instructions

1. Scrape the cement free of old paint with the metal tool, then sweep away dirt and other debris.Wash with a garden hose on the highest pressure setting. For very greasy cement, clean with the cold power washer. In a bucket, blend water with powdered trisodium phosphate, an alkaline cleaning agent and degreaser -- following package directions. Clean the cement with the solution and scrub brush, rinsing thoroughly with the hose. Allow to dry for a minimum of three days.

2. Tape a square of plastic wrap to the cement, sealing on all four sides, and allow to sit overnight. If there is no condensation under the plastic after 24 hours, the concrete is already sealed. If there is condensation under the wrap, it needs sealing. Pour concrete sealant into a paint pan and use a clean paint roller to apply a thin layer to the concrete. Allow to dry for 24 to 48 hours, based on the sealant directions and the humidity of the location. Wash the roller and pan.

3. Pour the tinted primer into a paint pan and saturate a clean paint roller. Roll primer over the entire surface of the concrete. Allow to dry for one hour, then apply a second layer. Allow the second layer to dry for three hours. Wash the roller and pan.

4. Place a flagstone stencil at one corner of the cement. Trace around the borders with chalk. Select a different stencil, placing it on the cement next to the first traced flagstone, outlining that with chalk. Continue to trace the shapes, moving from one corner out to the opposite to avoid smudging the lines.

5. Apply painter's tape to the spaces in between all outlined flagstones to simulate grout areas. Pour the five paint colors into five separate paint pans. Dip a sponge into the first color and pat the paint on the cement, following suit with clean sponges in the next four paint colors to create the flagstone finish. Allow to dry for 48 to 72 hours.

6. Peel off the painter's masking tape, once the flagstone finish is dry. With the lightest gray paint, create faux flagstone grout. Fill in the formerly masked areas between the painted flagstones using the thin trim brush. Begin at one corner and move diagonally to the opposite corner to avoid smudging the paint. Allow to dry for 48 to 72 hours.

7. Screw a paint roller onto the long handle and pour urethane sealer into a clean paint pan. Saturate the roller, then apply the sealer over the entire painted concrete area. Allow to dry for 24 to 48 hours. Apply a second coat, allow it to dry for 24 to 48 hours, then apply a final coat. Allow to dry for another 48 hours.

Tips & Warnings

• Newly poured concrete must cure for 30 days before painting.

• Do not begin this process on outdoor cement if it threatens to rain within the next week.

• If it rains before the paint or sealant on the concrete is dry, cover the entire area with polyethylene sheeting held down with stones. Remove once the rain stops and allow area to dry for 24 hours.

• It may be necessary to apply the paint or sealant again.

References

• "50 Ways to Paint Ceilings and Floors: The Easy Step-by-Step Way to Decorator Looks"; Elise Kinkead; 2008
• "The Complete Book of Decorative Paint Techniques"; Annie Sloan, Kate Gwynn; 1989
• North Dakota State University: House Fax Series; "Painted Finished for Special Effects"; Annette L. Bach, April 1993
• Concrete Network: Stamped Concrete