Changing Skyline: Mercer Museum adds space with a well-crafted concrete addition

Nothing separates architects from the rest of humanity like concrete. Architects will go into raptures over its tough, tactile quality. But among the general public, who tend to associate the material with no-frills highways and bad public housing, concrete buildings evoke a visceral dislike. Maybe attitudes would be different if more people encountered Doylestown's Mercer Museum, a quirky French chateau formed entirely of concrete, window frames and roof included.

Henry Mercer, the anthropologist, tile maker, and amateur architect who designed the improbable Bucks County castle in 1916, chose concrete for the most practical of reasons: He needed a fireproof building to house his astounding collection of wooden tools. But he also was drawn to the material because he loved things that reveal the hand of their maker. Concrete is something you have to mix, pour, and shape, and its nubby surface holds the memories of those labors.

Unfortunately, not many architects dare to build in concrete nowadays. It's difficult to get concrete done right, especially in Pennsylvania, a diehard steel state where metal frames remain the preferred means of construction. Louis Kahn, Philadelphia's concrete mixmaster, had to travel to California to do his greatest work. Those who use concrete today, like Tod Williams and Billie Tsien, designers of Penn's Skirkanich Hall, must endure having their buildings compared to parking garages.

I admit to having a weak spot for concrete - its color, its naturalness, its revealing texture - so it was a pleasant surprise to see Philadelphia's Voith & Mactavish take on concrete in their new entrance to the Mercer. Suppressing their usual neo-traditional impulses (another nice surprise), they have produced a sophisticated, modern addition that nods affectionately to Mercer's building, while standing smartly on its own as architecture.

The one-story addition, which opened last week, was commissioned to give the Mercer the space it lacked for basic museum amenities, including a special exhibition gallery, classroom, and coat check. Despite the castle's seven rambling stories of turrets, dormers, and niches, it always has been incredibly cramped because Mercer filled the place literally to the rafters.