Terrazzo in Elevator Cabs
I’m commonly asked about the use of terrazzo in elevators. Is it acceptable? Will it hold up? Will it crack? We’ll discuss this in today's post about terrazzo in elevators.
Is it acceptable to use terrazzo flooring in an elevator cab? Yes but it depends on the terrazzo system binder. Epoxy terrazzo is the acceptable system to use for this application. Cement terrazzo systems should not be used for the application because it can not accommodate the stresses of the cab movement. Epoxy terrazzo is the correct system because the epoxy binder provides excellent physical properties, particularly a very high flexural strength which allows the terrazzo system to flex and accommodate the loading of the elevator cab. The graph below shows the differences in strengths between epoxy and cement binders.
Now that we know we can use epoxy terrazzo in an elevator cab installation let's look at the different options and installation specifics. There are 3 main options when considering epoxy terrazzo for your elevator application:
Poured in Place Terrazzo
Precast Terrazzo Panels
So what’s best for your project? Any of the three options can be used but one may be better suited than the others based on project specifics.
Poured in place terrazzo is always a great option because it offers more design flexibility than the other options. Poured in place terrazzo will offer the lowest weight per square foot of any of the options as its the thinnest at just ⅜”. Further, it allows a designer to accommodate larger elevator cab sizes as well as easily integrate designs. Poured in place epoxy terrazzo is readily with a short lead time, the only downside is that it takes longer to install. A prefabricated option will offer a faster installation but longer lead times.
Precast Terrazzo Panels can be a good option for smaller elevator cabs with no designs or where a quicker installation is needed. These panels will weigh slightly more as they are typically precast to a ½” thickness and will require ⅛” of setting material.
Precast epoxy terrazzo tiles are typically the least expensive option but aesthetically introduce grout joints which just do not look or perform as well as the seamless options.
Exterior grade plywood 1-¼” thick with tongue and groove offers the best substrate. Minimum thickness is at least ¾” thick. The plywood should be firmly attached to the steel deck of the elevator cab. This requires not only a screw attachment, but also and adhesive between the metal and the plywood.
The longer joints of the 8ft sides that butt adjacent sheets should be spaced ⅛”-¼” apart. One the 4ft side the space should be 1/16” to ⅛”. Once the plywood is anchored, the surface must be sanded to remove any foregin matter from the boards and also to open up the pores of the wood.
The joints must be filled with epoxy and then a 4” wide pand of Terroxy Iso-Crack Membrane and fiberglass scrim should be placed over each joint. Depending on the size of the cab, divider strips may be positioned and anchored to the plywood with epoxy. The use of these divider strips are optional, as these strips are not necessary in the system.
Once the preparation work has been completed, the terrazzo contractor can install the poured in place, precast panels or tiles.
We hope this has been helpful and we are happy to answer any questions you may have. Thanks!