When I lived in DC I went to Baltimore from time to time, to visit friends, go to the aquarium, buy Johns Hopkins stuff... I always noticed the townhouses and how many of them seemed to have a uniform, multi-toned grey covering. It didn't quite look like bricks, or cement, and in a way it looked kind of fake. So when I moved to Baltimore three months ago, I was curious to investigate this interesting phenomenon.
A quick search for "Baltimore rowhouses" led me to a Wikipedia entry on The Culture of Baltimore. And right there, all the info I needed. The covering is called Formstone and must have made the inventor very rich, since so many houses in Baltimore are covered with it!
Allow me to quote from Wikipedia:
"A tour through many of Baltimore's rowhouse neighborhoods will reveal a façade style not found in many other cities, Formstone. Introduced in the 1950s, Formstone was a modern day solution to early Baltimore brick that was so poor it needed frequent painting to keep it from deteriorating. But soon Formstone became an icon of status for many homeowners.
The appeal of Formstone was that, once installed, it virtually required no maintenance. Salesmen boasted that the insulation lasted forever and that the first cost was also the last as no upkeep or repair was required. Salesmen also pointed out that Formstone was also about one-third the cost of other façade improvement solutions. Its colorful stucco-veneer gave a stone-like appearance that could be shaped into different textures."
Today, many homeowners try to remove the Formstone to show the original brick walls of the house. It is a time consuming process but once completed, gives the house its original look which is usually a lot prettier than the Formstone!
The picture below gives a good view of what a Formstone house looks like. As you can see the side wall is left with the original brick.