QUESTION

I am an architectural designer in NYC. I'm working on a project where I want to use cement terrazzo floor on the first floor. I understand that monolithic cement terrazzo application would not be possible, because of structural deflection and potential cracking. I am assuming that the ideal installation would be sand cushion cement terrazzo. But what would be the ideal structural system to receive the sand cushion terrazzo assembly? We are considering either TJI engineered lumber with plywood sheathing, or metal deck with 2" concrete. Can the sand cushion terrazzo bond to both types? And if we manage to design both systems for minimal deflection, which system is better for the terrazzo?

ANSWER

ANSWER - First of all, a monolithic cement terrazzo application when a better is only 1/2" thick, where a sand cushion terrazzo assembly is about 3.5 inches thick.

Regardless of which installation method you use, the deflection of the sub-floor should not exceed L/360. The sub-floor can be strengthened by providing added blocking and bracing if needed.

I know they say that the sand layer in the sand cushion terrazzo assembly will absorb minor substrate defects and prevent mirroring to the surface, but considering the thickness and what is required to install it, it doesn't seem practical to me.  The monolithic cement terrazzo system or the epoxy terrazzo system should before well and will be more practical; particularly since you are installing a structural system as well.

The metal deck with concrete would likely be better than the wood sub-floor application.  I would recommend a cleavage membrane or crack isolation system.  You might consider a sound control system depending on your needs.

CTaSC does write architectural specifications for new projects or renovations.  We can specify the products and methods, perform quality assurance testing, and perform quality control services during the installation to make sure it is done correctly.