Stuck on Stucco

Exterior stucco. When I think of it, I  think first of Tudor Revival or maybe Spanish Colonial (Cincinnati could be considered something of a “Tudor Town” but we have some Spanish Colonial homes too!). Stucco is more widespread here and elsewhere though.

Early stucco examples are the Federal, Greek, and Gothic Revival homes of the 18th and 19th centuries. By the turn of the 20th century, advances in the production and availability of Portland cement–used to make stucco and still the most commonly used cement used around the world–triggered a stucco frenzy.  From 1900 through the 1940s, stucco used with many architectural styles: Prairie; Art Deco; Art Moderne; Spanish Colonial; Mission; Pueblo; Mediterranean; English Cotswold Cottage;  and Tudor Revival. It can frequently been seen on bungalow and “four-square” homes too.

You ever wonder how that historic stucco meets the test of time?

Unfortunately, there’s no exact answer to this question. Stucco durability relies heavily on environmental conditions. Things like rainfall, humidity and temperature all dictate how long a stucco exterior will last.

Some experts claim even in the worst-case scenario, a stucco finish will last at least 50 years. On the other hand, under the right conditions, stucco can last more than a HUNDRED years!

Stucco is a hardy material–if you treat it right. Like just about everything with a historic home, neglect is the most common reason for the stucco failure. It needs regular maintenance to prevent excessive water penetration and surface breakdown. Historically, homeowners typically whitewashed their stucco, often annually. The lime in the whitewash offers protection and helps to harden the stucco. It also fills hairline cracks before they became even larger cracks and let in moisture. To improve water repellency, stucco could also be coated with paraffin or another type of wax, or even an oil.

Stucco deterioration also results from poorly done repairs. Historic stucco can be tricky–repair is more like that of mortar or plaster. The use of the wrong materials speeds up the rate of decay rather than slowing or preventing it. Moisture creeps up and under poorly repaired sections, and the stucco can start peeling off. There are also areas on a house where a bad repair job leads to a bad seal, such as where the stucco meets windows, flashing, and other joints.  Damage often appears in the form of drip-like staining or discoloration, commonly referred to as “stucco tears.” Don’t make your house cry!

Based on the National Park Service’s Preservation Brief #22, here are some general tips for historic stucco repair:

  1. Mix only as much stucco that can be used in 1-2 hours. If you try to go longer than that, it will not bode well (again, no crying houses). And do not try to skimp things–discard any extra stucco that you do not use.
  2. Do not over mix stucco. Too much mixing can cause crazing and discoloration and it will set too fast–you will end up with cracking and poor bonding.
  3. If you are putting stucco over wood lath or masonry, it must be thoroughly wetted before application or it will draw moisture out of the stucco too rapidly (result: not pretty).
  4. To prevent cracking, do not let the stucco dry too quickly. You can shade the area, or cover it, if the weather is hot. Likewise, trying to do stucco repair in cold weather (below 40 degrees Fahrenheit) is definitely not a good idea.

And finally,

5. How about just use a skilled professional plaster? He/she will help you avoid the headaches you might end up with if you go with someone less experienced or even try to go “Do-It-Yourself”!