Q-The stucco on my house has been painted many times and now large areas are peeling. Concrete, which is virtually maintenance-free, seems very similar to stucco. If this is so, does stucco require painting? Are there alternatives to using paint?
A-Your observation concerning the similarities between stucco and concrete is right on target. The two materials have very much in common. Concrete usually consists of cement, sand, and varying sizes of aggregate (gravel). Stucco, on the other hand, usually consists of cement, lime and sand. When concrete is finished, its surface is virtually identical to stucco’s.
However, there is a big difference. In a majority of residential applications, concrete is applied in direct contact with the ground. Stucco, on the other hand, is applied to the sides of houses in lieu of brick, stone, siding or similar weather-shielding material. Untreated concrete and stucco will readily absorb water. Both will allow water vapor to freely pass through them. Do you see where I am headed with this one?
If a concrete sidewalk or driveway gets wet, it’s no big deal. However, if stucco gets wet for extended periods, the moisture can cause problems. The water may eventually wick through the stucco and begin to rot the wood sheathing or wood framing members. Water vapor may be pulled into the house. This may cause insulation to absorb moisture, drywall or plaster to crumble, and interior paint to peel.
Thus, stucco needs a protective coating of some type to prevent interior or structural damage to your home. Fifty years ago, paint was the only material available to readily protect the stucco. Paint is a coating. Because of its viscosity, paint does not readily penetrate things that it covers. That is why you are experiencing the peeling problems. Water vapor from the inside of your house may be pushing the paint off the stucco. This is a very common problem on thousands of houses.
Fortunately, advancements in coatings technology have produced products that will enable you to avoid peeling in the future. If you are able to completely remove the paint from your stucco, or if it had never been painted before, you would have two alternatives: penetrating masonry stains or clear penetrating finishes.
These products are extremely effective because they take advantage of the microscopic makeup of concrete and stucco. Stucco and concrete look very much alike under a microscope. The space between the aggregate (sand and gravel) is composed of interlocking crystals.
There are empty spaces between the interlocking needles of each crystal.
The penetrating finishes take advantage of these voids. The products’ initial liquid consistency allows it to penetrate into the crystalline matrix. After the liquid portion of the product evaporates, solids are left behind to partially plug the empty spaces. Some of the products are designed so that liquid water molecules cannot pass by, but water vapor can readily pass through. This feature enables water vapor inside your house to escape to the outside air.
I recommend that you give serious consideration to these products as you prepare to recoat your peeling stucco.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For a list of manufacturers of penetrating concrete stains and clear sealers and for other tips on stucco maintenance, send $1.50 and a business-size, stamped, self-addressed envelope to Carter at the above address. Ask for Builder Bulletin Number 37.
You can obtain a free order form for a wide variety of individual job bid sheets by sending a business-size SASE to the same address.
