There are materials that have a natural richness and warmth. When they are truly natural materials, they are even more amazing. This is the case with the flooring in the Gallery space. The Gallery is the most richly appointed space in the Visitor Center with wood ceilings, natural stone walls, metal wall panels, broad expanses of glass and the natural slate flooring.
There is a lot of effort that is not recognized in making sure that materials installed in a building will last. The design for the Visitor Center is one that we want to last for a long time and FSB paid extra attention to the design of each assembly of materials to assure that the finish product would endure time. The floor assembly in the Gallery is one that received special attention.
An assembly in the design/construction world is used to describe a group of materials that are brought together to work as a unit. The floor assembly for the Gallery is made up of several components; steel beams, metal decking, headed studs, reinforcing bars and concrete on top of which is laid the flooring material.
The flooring material for the Gallery is a natural slate and the color is referred to as “Earth.” It is a large format tile meaning that the individual pieces are quite large; in our case 24” by 24”. The flooring varies in thickness from 3/8 inch to 5/8 inch. The installation of the flooring is a built up process beginning with an uncoupling membrane, thin set mortar, slate tiles, the grouting of 3/8 inch joints and finally a floor sealer.
While there is great care taken in setting the stone, a lot of care went into the design of the elevated floor slab to ensure a level concrete surface. The stone is stiff and brittle and cannot take bending or deflection without cracking. The normal deflection design for tile floors is L (span) / 360. Manufacturer’s recommendations for larger, more brittle tile is L/720. Our structural engineers went with the more conservative and restrictive deflection limit of L/720.
Concrete slabs want to crack as they shrink and cure; it’s natural. Cracks in concrete slabs will telegraph through into the surface material which will crack along the same line (also known as reflective cracking). To minimize this effect, the concrete slabs were designed with additional reinforcing steel. The steel and concrete assembly was also approached as a composite design through the use of welded headed studs which lock the steel and concrete together so they act in unison which further stiffens the assembly.
Attention was given to the steel beam spans which more directly and effectively addresses deflection. Columns were introduced to limit those spans. The stone flooring specification also called for an uncoupling membrane which decouples the tile from the floor slab. It is a waterproof, vapor-proof membrane with a sacrificial layer of fabric that shears away when exposed to excessive substrate movement. All this technical attention to the design of the floor assembly to ensure the beauty and longevity of the slate flooring is addressed in greater detail by Tom Bush/FSB Senior Structural Engineer in his review of the design of the Gallery space structural floor system.
The end product is one that the FSB Team is proud of and one that the Chickasaw Nation and visitors will enjoy for years to come.
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Design Matters 