How to stamp concrete

Any concrete pour, decorative or not, begins with proper preparation of the sub-grade and forms to give the slab shape.

If you know how to stamp concrete, you can deliver the an attractive driveway, patio, walk or interior floor, at a fraction of the cost of stone or pavers.

Decorative concrete, which is concrete that has been stamped with a pattern to mimic stone or pavers, is an increasingly popular option that is economical, durable and very attractive when done correctly. And unlike pavers and stones, which can shift with the seasons and allow weeds to grow through the joints, the only maintenance needed for stamped concrete is a sealer applied every four years.

Distribute the concrete around the formed area, getting it reasonably close to the desired level. Try to avoid low spots or deposits of too much concrete, which will make screeding more difficult and time-consuming.

Here’s how to stamp concrete

Step 1

Prepare the sub-grade by excavating, if necessary, and leveling the area. Make sure the area is properly compacted before pouring the concrete.

Perform initial tooling around the perimeter or where the new slab will meet an existing one.

Step 2

Set up forms to give your pour whatever shape is desired. Ensure the forms are level or sloped as necessary and provide required slab depth. Coat the inside of the forms with low-grade oil or form release agent so they separate easily from the cured slab. Place any required reinforcement (rebar, wire mesh, etc.).

Step 3

Pour the concrete. Move the mixture around with spreaders or a garden rake to fill the forms. Screed to the desired height. Go around the perimeter with an edger and perform the initial floating with a darby or bull float. Don’t overwork the concrete, which can result in water pooling on the slab surface.

Run a bull float to smooth the surface and use hand floats to touch up small rough spots. Take care not to allow too much bleed water to accumulate on the surface.

Step 4

Unless you’re using a mixture with integral color (where liquid color is added during mixing), now is the time to apply the broadcast color. Most broadcast colors are powders, which are applied by throwing it in a wide, sweeping arm motion to cover as much concrete as possible with each throw.

Allow it to soak in for several minutes until it can be worked into the concrete with one or two passes of the bull float or by working gently with a hand float. Again, avoid excess tooling.

Some contraction or control joints can be installed after stamping, but deeper ones in a larger slab may be best installed with a groover before stamping.

Step 5

Apply release agents to the texture mats. Slabs with broadcast color applied to them require powdered release agents on the mats. For integral color slabs spray a liquid release agent on the mats. This will allow for a clean release and crisp patterns on the slab surface.

Stamps should be coated with a release agent. Integral-color color concrete requires a liquid spray, while concrete colored with broadcast powders requires a powdered release agent.

Step 6

Set the first row of stamps, which typically “lock” together with notches and tabs, in a straight line as a reference for subsequent rows. Simply standing on the stamps or a light tamping usually sets the stamp deep enough into the surface of the concrete.

Apply the mats when the surface is ready. Too soon and the concrete won’t hold the weight of the workers or hold a well-defined pattern. Too late and you’ll have to expend more effort for less texture. First, test a small area by pushing your fingers into the surface at several points on the slab. When you leave a clean imprint about ¼-inch deep, you can start stamping.

Lay the mats. Start at one corner or perimeter edge (typically where you first started pouring the concrete) and place the first mat. You may need to use a hand mat to reach into odd-shaped corners or at the end of a row do you don’t overhang the mat on any of the other forms, which will prevent that edge from sinking into the surface properly. Lay the first row in a straight line, as that will be the benchmark for future rows.

Many stamp sets are labeled to indicate placement and sequence. You should be able to press the stamps by simply walking on them or with a light tamping. After one row is completed, begin the next row by removing the first stamp and “leapfrogging” it to the next row.

Check the alignment of the stamps every couple of rows with a string line. Stamps will often shift as much ¼ inch per row.

Step 7

Hand tool as necessary. Perform any detailing in the pattern with rollers, chisels or texture skins as you remove the mats. Once the entire slab has been stamped, install any needed contraction or control joints at the proper depth and spacing. Be cautious with control joints as they can disrupt the visual pattern of the stamping, especially with repetitive designs such as running bond or herringbone. Remove the forms.

After the slab has properly cured, all that is required is application of a suitable sealer.

Step 8

Seal the concrete. Once the slab has cured, apply a finish coat of sealer. Many manufacturers recommend applying sealer several weeks later after a light cleaning. Do not apply the sealer too heavily or it could trap moisture in the slab.

—By Rob Fanjoy