Stamped project handbook

Stamped concrete is a pour that reads as flagstone, slate, brick, wood plank, cobble or ashlar — a decorative surface pressed into fresh concrete against a colored base, using rubber or polyurethane stamps. It is the closest concrete comes to hardscape masonry, at a price closer to a poured slab than to laid stone.

A stamped project has more design in it than any other service Local Concrete Charlotte pours. The conversation about pattern and color has to happen before the mix is ordered. The stamp window on the day is short. The sealer regime that follows is the difference between a stamped surface that reads true for years and one that goes gray in a season.

The design conversation is the first work on a stamped project. It happens at the site visit and it drives every later choice.

• What the surface is — patio, walkway, pool deck, driveway, entryway.
• What it abuts — the house, an existing patio, a pool coping, a landscape bed.
• The pattern — flagstone, slate, brick, wood plank, cobble, ashlar. The stamps are physical tools; the pattern is chosen from the stamp set Local Concrete Charlotte carries or from a rented set at project cost.
• The layout — is the pattern running with the house, at an angle, herringbone, running-bond, offset. Layout is set on the job sheet before pour.
• The base color and one or two accent colors — see §03 below.
• Any borders, feature bands or medallions.
• The scoring plan — saw-cut lines that follow the pattern grout lines rather than cross-cut through the middle of a flag.

The conversation ends when the client has signed off on a sample or a photograph of a previous pour, and the pattern, color and layout are written on the job sheet.

Stamped concrete color comes from three sources — integral color in the mix, color hardener broadcast on the fresh slab, and release agent that contrasts the base to give the pattern depth.

Two working rules on color. First, base colors that read light on a sample chip read one to two shades darker in a full pour under sun. Second, release agent color drives the pattern depth — a contrasting release makes the pattern read strongly; a close-toned release makes it read subtly. The choice on the sample chip is not the choice under the sun.

Pattern is chosen from the stamp set at project cost. The commonest patterns and their working notes:

• Flagstone (Ashlar Slate, Random Stone) — the routine choice for patios. Reads well at any scale.
• Roman slate — smaller repeat than flagstone; reads formal.
• Wood plank — long thin stamps that read as decking or barn wood. Directional; layout runs along the length of the plank.
• Brick (running bond, herringbone, basket weave) — reads formal; good for entryways and borders.
• Cobblestone — small round stamps; reads Old-World. Longer stamp time per square foot than flagstone.
• Ashlar / cut stone — regular rectangular pattern; reads dressed stone.

Layout is drawn on the job sheet. Every stamped project has a starting corner, a stamp direction, and a saw-cut plan that follows the pattern grout lines rather than cutting through a flag.

The mix is 4000 psi, 3/8-inch aggregate, 4–5 inch slump with mid-range plasticizer, integral color per selection, no air entrainment. The reinforcement is a mesh mat on chairs plus polypropylene micro-fiber in the mix.

Once the slab is placed, screeded and bull-floated:

1. Color hardener is broadcast on the fresh surface — two passes for even coverage — and floated in.
2. Release agent is applied before stamping.
3. The stamp window opens once the slab is firm enough to hold a stamp cleanly and closes once the slab is too stiff to take a full impression. Typically 30 to 90 minutes.
4. Stamps are laid in the pattern selected, tamped to a full impression, lifted cleanly, and re-laid to keep the pattern registered.
5. Edges are hand-stamped or worked with a texture skin.
6. Cure kick-off — the stamped slab is covered against wind and cured under a curing compound compatible with the sealer that will follow.

The next morning the release residue is pressure-washed off. Saw-cutting follows the pattern grout lines in the 24–48 hour window. Cure runs seven days.

Sealer is the difference between a stamped surface that reads true for years and one that goes gray in a season. It carries the color hardener and release into the pattern and it holds them there against sun, water and traffic.

• First sealer application 7 to 14 days after pour, per the sealer product spec. Two thin coats, out of direct sun, on a dry slab at 50–90 °F.
• Re-seal every 2 to 3 years. A stamped surface that has faded to a chalky matte is a slab overdue for re-seal, not a slab whose color has failed.
• Cleaning — soft brush and mild detergent; no pressure-washer above 1500 psi on a stamped surface; no de-icing salt in the first winter.
• Joint filler — control joints in a stamped patio can be filled with a self-leveling polyurethane sealant color-matched to the release. Filled joints keep debris out and prevent water freezing in the joint.

The maintenance sheet the client leaves the walk-through with sets out the re-seal interval, the cleaning notes, and a contact for a re-seal at project rates.