Wednesday, August 10, 2016

Stucco is Stucco, Right? Not Exactly.


If you love traditional Old English homes, there can be no doubt you will run into some type of stucco or exterior plaster at one time or another. It may be on the exterior of an ancient cob house, the roughcast finish on a Voysey house, the fancy plaster pargetting of an Elizabethan townhouse or even some exterior panels on a “stockbroker Tudor”.

Built in 1914, the traditional-styled English Cottage I lived in for 8 years in Akron’s Goodyear Heights had asbestos stucco covering its first (ground) floor and foundation, with cedar shingles on the upper floor. (I’ve always thought wall shingles were a poor-man’s substitute for the clay tiling used on many English vernacular houses.) The stucco on that house had been painted over, and due to some neglected maintenance, had begun to crack in several places.

On the driveway side of the house, the stucco and its expanded wire lath were both coming loose from the exterior sheathing, to the extent that I could easily insert my hand fully into the gap for almost a foot, which was right next to our dining room window. This could have been the result of some foundation settling and some moisture penetration, but it eventually resulted in the decision to remove a 6’ x 4’ section of the stucco and make a major repair.

Of course, I did not know this was asbestos stucco at the time—but it came off in large pieces, and not being too concerned with short term exposure outdoors—I have no regrets or adverse effects some 25 years later. There was horse-hair in that stucco, too!

What I did know is that I could not just go out and buy modern stucco mix and plop it onto the wall. I first reattached the wire lath, which was actually still in pretty decent shape, and added some securely stapled chicken wire here and there, just for good measure. I then referenced an old-fashioned stucco recipe which I probably sourced from The Old House Journal—remember, this was pre-Internet. That meant plenty of lime and not just Portland cement.

Having a substantial section of the house exposed while repairs are being made can be discomforting, but thankfully I was blessed for an extended dry period. A thick base coat, covered with a second, thinner brown coat, brought the surface to the proper level. This was followed by a finish coat—with some small pebbles added—to try and match the rest of the exterior wall surface as best as I could. I wasn’t too happy with the match until I got the hose and sprayed the surface ever-so-lightly with some water from our hose, which smoothed it to the extent that it finally matched the old stucco perfectly. Once this section of the house was coated with paint to match the rest, you could not tell the repair from the original work.

The house needed more repairs higher up on the facade, which had more cracks but was not failing to the extent that it was on the one side, probably due to the fact that it was sheltered from the prevailing winds, rain and direct sunlight. Sadly, I never got around to doing more repairs before we began the process of designing and building our new house in 1992. Nevertheless, I was proud to note during a recent neighborhood visit that the house still retains its original exterior materials and my repair looks just as solid as it did 25 years ago. Even the front of the house has held up to some extent, though it does look worse for the wear.

When we built our new(er) house, I considered using some synthetic stucco for the exterior, but decided against it for cost reasons. Over the years, some of these newer, lighter synthetic blends, installed over various types of insulating foam, have come under fire, having failed due to poor installation techniques or unsuitability for a particular climate. If I was to utilize stucco today, I would probably go with a more traditional type.

Which brings me to the discovery of a third type of stucco, with which I was totally unfamiliar—and that is magnesite stucco.

Some of the more popular brands were Kragstone,  Kellastone and Rocbond, proprietary blends of magnesium carbonate powder, asbestos and sand, which was mixed with an oily, magnesium chloride solution. It was not a cement-like product at all, and contained no lime, gypsum, or water. The result was a more plastic-like, all-mineral stucco product that was highly resistant to cracking and dried rock-hard when applied at least a half-inch thick.

Magnesite stucco was applied in two coats, and its unique properties allowed it to be applied even during freezing weather. Apparently it was introduced some time before WWI, and became quite popular before fading into obscurity a few decades later. In a few places, like California, there are some stucco specialists who can still repair and apply it, as it was often used for flooring surfaces, interior and exterior steps, and even countertops, sinks and bathtubs!

Here in Ohio, I know magnesite stucco was used in a number of locations many years ago, though I have not personally come across it myself. It seems obvious that repairs would represent quite a challenge, and I can’t see the use of more traditional types of stucco for repair being compatible. If you have any experience with this unique type of stucco, I’d like to hear about it.
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