Textured Concrete at the Clyfford Still Museum

Although there are numerous historic masonry buildings in Denver, the city also has a good amount of unique, contemporary masonry structures.  One such building is the Clyfford Still Museum with its textured concrete façades.  The Still Museum was designed by Allied Works Architecture and built between 2009 and 2011.  One of the many cultural sites in the Golden Triangle Museum District, the Still Museum houses the collection of artist Clyfford Still.


The contemporary design of the Still Museum is elegant and stately, but I am most fascinated by the textured concrete of the exterior façades.  According to several news reports about the opening of the museum, the textured-concrete skin was designed by architect Brad Cloepfil with numerous installation mockups by contractor Saunders Construction, Inc. and a custom concrete formulation developed by the Martin Marietta Corp.


The north, west and south façades are clad with this textured concrete, which was cast in place using wooden formwork.  In the photo below, you can see the wood grain of the formwork on the soffit of the overhang, which imparts a nice organic texture.  The formwork at the soffit was also installed at a diagonal to offset the vertical stripes of the façades.


To create the vertical texture on the façades, the contractor constructed wood formwork fins.  According to the Architectural Record: “The contractor created the fins by beveling the sides of some of the formwork boards to leave gaps; when the boards were pulled off, parts of the fins’ outside edges broke off to produce a jagged surface. The fins’ irregularity is an essential part of their character.”  You can see the irregular corduroy pattern of the textured concrete in the photo below.  It almost looks like a cascade of water running down the side of the building.


As to the composition of the concrete, a case-study [PDF] from the Sika Corporation indicates that the concrete was custom blended from sources in Wyoming and Texas mixed with coarse and fine aggregate.  There is a prevalence of pink aggregate in the Denver area due to our proximity to the pink and gray granite of the Rocky Mountains, but the design team wanted the concrete skin to be a more neutral yellowish gray color.  Therefore, they selected aggregate that contained no pink granite.

The concrete was poured over the course of several months in varying temperatures and humidity levels, so the contractor had to pay close attention to the consistency of the concrete, its color (which can change as more or less water is added to the mix), and how fast the concrete set up.  As a result, several admixtures were included in the concrete mix to account for temperature, humidity, and varying set times of the concrete. [Update: I was asked about admixtures. Admixtures are chemicals or additives mixed into concrete that are used to improve the concrete’s strength or hardness, the speed at which it hardens, or the temperature at which it hardens, amongst other things.]

Although I have not yet been inside the Still Museum, I hear that that the architects made extensive use of textured concrete throughout the building.  The Still Museum website has some excellent photographs of the interior galleries and ceilings, which look amazing.