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TECHNICAL BULETIN FOR CRACK REPAIR FOR SYNTHETIC AND CEMENT STUCCO

Crack repair for either synthetic or cement stucco products should be addressed if the crack exceeds 1/8” wide (the width of a nickel) or greater on vertical walls and extends into the base coat, and for any size crack on parapet caps, flat wall surfaces. If the crack is less that 1/8” wide on a vertical wall, the repair is optional and would be mostly for aesthetic consideration.

Materials and tools needed:

            Sponge
            Duct tape or masking tape that will adhere to the wall surface
            Small pail or container with water
            Butter knife or optionally a tool called a caulking spatula.
            Flat head screw driver
            Rags
            Colored caulking
            Caulking Gun
            Painters mineral spirits (Only necessary for urethane caulk for tooling).
            Lacquer Thinner or Toluene (Only for clean up of urethane caulk)
            Stucco Fog Coat – (Only for stucco crack repair, not synthetic)
            Backer Rod (foam rope on a roll) - For cracks exceeding ¼” wide.
            1” to 2” Paint brush.

Caulking Choices:

There are several choices for the type of caulking you may use for crack repair. Pure silicone is not recommended. Exterior grade acrylic / silicone blend, often referred to as paintable caulk, is a water base product and is the easiest to work with, and cleans up easily with water. For homeowner application, acrylic / silicone is mostly recommended for its ease of use while being able to achieve a good result. Urethane is more difficult to work with, but offers superior performance than acrylic / silicone blends. Whatever your choice, purchase the highest quality (the longest year indicated on the label) available. You will need to ask for a “Non Sag” caulk that is stiffer and will stay in the crack as opposed to a self leveling caulking that is more viscous and will run down a vertical surface. Most caulking offered at Home Depo or Lowes is non sag.

It is important to purchase a caulking that blends as close as possible to your wall color. With small cracks, the color is less important than with larger cracks. If it is important to achieve very close blend to the wall color, a blended exterior paint or a synthetic finish compatible with the caulking can be applied over the caulking, once it dries.

Caulking can be purchased at Home Depo or Lowes for standard colors and for a larger selection of colors at, Pro Build located at 4200 2nd St NE, Albq., Ph: 345-1755, or in Santa Fe at 1137 Siler Rd., Ph: 471-7474; Chaparral Materials Inc. located in Albq., at 912 1st St. NW or in Santa Fe at 5946 Agua Fria, Ph: 471-3491 and Smalley & Company located at 8920 Adams NE, Albq., Ph: 797-7222.

Fog Coat can be purchased at Hope Lumber, Home Depo, New Mexico Plaster Supply located at 4100 4th St. NW, Albq., Ph: 345-6881, or Chaparral Materials Inc. located at 912 1st St. NW, Albq., Ph 217-1051, or in Santa Fe at 5946 Agua Fria, Ph: 471-3491. For our market, El Rey Stucco and Western Blended Products are the two major brands of stucco and the associated fog coat colors that are available. If you know either the brand and or color of stucco that is on the wall, it is best to first attempt to procure that brand of Fog Coat, so as to achieve a closer color blend. Fog Coat comes in a plastic pail and is the raw pigment of the bagged stucco, and looks like a colored powder.

Repair Procedure:

With a screwdriver, lightly remove loose material at the margins (edges )of the crack. Do not rout, gouge or enlarge the crack.
With tape, mask off on either side of the crack as close as practical, to protect the surrounding wall area from the caulking product.
Cut off the tip of the caulking tube to reveal a small hole at first, or a hole size that will allow the injection of the caulk into the crack with one pass.
With the colored caulking in the caulking gun, inject the caulking into the crack by pulling the caulking along the crack line. Do not build up the caulking too much past the plane of the wall.
The caulking now needs to be tooled down. For acrylic caulking this is best done with a wet finger. For urethane caulking, dip the butter knife or spatula into mineral spirits and draw the knife tip or tool over the caulk, knocking the caulking bead down flat and even with the wall surface.
The caulking is most effective, when it is adhered to just the sides of the crack. Leaving excess caulking on the surface or beyond the edges of the crack, makes the repair less effective and re-cracking of the caulking is more probable. With acrylic / silicone caulk, use a damp sponge to wipe off the excess caulking from the wall surface by wiping across (perpendicular) to the crack to remove excess caulk from the surface, leaving only the caulk in the crack. With urethane caulk do not wipe with a sponge, use only the butter knife or spatula to tool.
For stucco walls, “Fog Coat” can be broadcast by hand or dabbed into the wet caulking with a paint brush that has been loaded up with fog coat, to blend the color and to create a more realistic stucco appearance.
Clean up for acrylic / silicone caulk is done with water. For urethane caulk clean up is best achieved with lacquer thinner or toluene. Exercise caution with these products.
Remove tape and you are done.
With any of the products mentioned above, be sure to follow the recommended procedures on the packaging.

Crack repair that exceeds ¼” should utilize urethane caulking. It will be necessary to use a backer rod to create a backing for the caulking for the caulking to obtain an optimum depth. Backer rod comes on a roll and comes in varying diameters, depending on the size of the crack or gap being sealed. It is best to check with Smalley and Company for the recommended size of backer rod, based on your requirements.