Precast vs Poured in Place Terrazzo
Updated: Jul 8, 2022
What's right for my application? Well it depends...
We really need to evaluate each application individually and understand your vision to make the best recommendation. In this post, we’ll look at a variety of applications and explore the difference between precast and poured in place terrazzo.
Traditional terrazzo is a poured in place terrazzo application. Raw materials such as resin or cement along with aggregates are then mixed on site. Once mixed the terrazzo is hand troweled to the substrate and allowed to cure. After the terrazzo has cured, the installer will grind and polish to a seamless finish. Historically Poured in place terrazzo has had short lead times (Approx 1-2 weeks) as the majority of raw materials are readily available but with the labor that is performed on site the installation has a longer duration. However, in the COVID world material lead times have pushed out to 4-8 weeks.
Precast terrazzo as the name implies is prefabricated and finished in a factory, then shipped to the project site for installation. As a poured material, terrazzo has virtually unlimited design potential. Precast manufacturing companies build custom millwork forms then fill with the terrazzo mix to create different shapes and designs. Precast will have a longer lead time because all the fabrication takes place at the factory, however, once complete and shipped to the site the installation will go quickly.
Now that we’ve explored the difference between the precast and poured in place terrazzo, let's look at some individual applications.
Typically terrazzo stairs are fabricated with precast terrazzo. Most stairs have repeating treads that are more efficiently produced in a factory. Precast terrazzo stairs will also have a better finish and tolerances than what can be accomplished in the field with poured in place terrazzo. Now there are some exceptions to the rule.
For example, if the project you’re designing also has terrazzo flooring and there long runs of stairs or complex curves, a poured in place terrazzo stair could be a great option.
It's also common to have projects with a stand alone terrazzo stair and in these applications it's best to use precast terrazzo as it is costly to have a terrazzo contractor mobilize for a smaller application.
Some projects could have a combination of poured in place and precast terrazzo like the Duke Ellington School of the Arts. One thing to note is the precast terrazzo has varying tread thickness depending on the length of the tread being produced. Be sure to consult with your precast manufacturer to ensure the proper thickness is being specified or you may get a seam when it could have been eliminated.
Typically a precast terrazzo stair treads are produced up to a maximum length of 8-9 ft. before a seam is required. Generally precast terrazzo stair lead times are 8-10 weeks depending on manufacturer workload. Please contact us for our cad and revit terrazzo stair details.
Terrazzo Stair Landings
Now, let's discuss the stair landings. We see more variety in this application. The primary variables we consider are the size of the landing and if there is other poured in place terrazzo on the project. If you have a stand alone stair you’ll want to use precast terrazzo panels for the landing. However, if you have poured in place terrazzo in other areas of your project you can consider using poured terrazzo for the landing, particularly if you have a large landing area. Keep in mind that it's difficult to get the installation equipment up the stairs so contractors typically prefer precast.
Typical landings match the width of the stair and usually extend for a similar depth. If the stair makes a 180 turn, the landing is typically a larger rectangle but can still be fabricated from precast terrazzo panels.
We are happy to consult and assist in figuring out the optimal panel layout for the best looking landing. Lastly, check with your precast manufacturer to verify the panel thickness as it could be different than the adjacent tread thickness and you need to make adjustments in your elevations.
There are two types of terrazzo base. The first is called flat base (aka straight base) which is always precast and then set after the floor has been installed.
The second type is called cove base can be poured in place or precast. Typically terrazzo cove base is precast. To install it correctly the precast cove base should be installed prior to the floor. Designers and General Contractor should be aware of this and schedule accordingly as precast cove base has longer lead times. Regardless if the terrazzo base is flat or cove epoxy terrazzo base is commonly produced at ⅜” thickness in 4’ lengths.
We can also produce precast radius or column wrap terrazzo cove base.
Occasionally projects will specify poured in place cove base. The advantage is no seams and short lead time, however, it's a slower and you should expect more variation in the finished material due to the hand finishing. Please contact us for our base details.
Terrazzo Plinth / Seating
It's also common to have a terrazzo plinth or seating around the bottom of the stair. These can be either precast or poured in place terrazzo. Again, it depends if you have other terrazzo in the project. If you don’t, then precast is the way to go. If you do, this area can be poured in place. You’ve got to watch as you get close to the rear of the stair and the angle get tight as it approaches the plinth. Sometimes it may not permit for grinding equipment to properly finish and could require a precast panel. Again, please contact us and we’ll help figure out what is the best for your specific application.
Multipurpose terrazzo seating areas such as the one see here at Goucher College can be poured in place or precast. The Goucher College is a great example of a poured in place application as there was additional terrazzo flooring and the designer preferred a seamless look. This area could have been fabricated using precast terrazzo but would have had more frequent seams.
Terrazzo Walls or Vertical Applications
Occasionally, we are asked to clad walls with terrazzo. This can be done with either precast panels or a poured in place system.
Precast is certainly easier and more cost effective but poured in place terrazzo walls can certainly be achieved as seen here at the Fairlane Hotel and LAX Bradley Concourse. Poured in place wall applications require a skilled installer that has experience with vertical applications. Again feel free to consult with us to help you find a quality terrazzo contractor for your area.
Precast terrazzo is most commonly used for countertop applications. Be sure to check with your precast supplier regarding the maximum panel sizes.
Other vertical surfaces such as wainscoting or planters can also be clad with precast terrazzo. Typically these are precast at a ½” thickness.
A thin set epoxy terrazzo system is the way to go. Hands down outperforms a precast terrazzo tile option. For more on this please check our post on poured in place terrazzo vs terrazzo tile.
Epoxy terrazzo works well in an elevator cab. We see both precast panels and poured in place used in this application. Generally the larger cabs are poured in place. Smaller elevator cabs are commonly precast. More on this in our post about terrazzo in elevators.
We hope this has been an informative post and are here to help with the details of your project. We look forward to serving you.