Terrazzo Design Consideration
Information about terrazzo installation and its sustainability as a durable flooring solution
Definition of Terrazzo
“Terrazzo consists of marble, granite, onyx, or glass chips in Portland Cement, polyacrylate modified Portland Cement, or resinous matrix binder. The Terrazzo is poured, cured, ground, and polished. Terrazzo is typically used as a finish for floors, stairs or walls.” – The National Terrazzo & Mosaic Association
- Sand Cushion Portland Cement Terrazzo
- Bonded Portland Cement Terrazzo
- Venetian/Pallidiana Portland Cement Terrazzo
- Rustic/Washed Portland Cement Terrazzo
- Polyacrylate Modified Cement Terrazzo
- Resin Matrix Terrazzo
Considerations for System Selection
- Is proposed terrazzo system for interior, exterior, or both?
- Will the terrazzo system be placed over a concrete or wood sub-floor?
- Does the terrazzo system need to be breathable if being installed slab on grade over an existing concrete slab which may not have an effective moisture vapor barrier.
- Is there a terrazzo system thickness constraint, as systems range from 3/8” to 2-1/2” and typically require a depressed sub-floor for systems greater than ½”
- If terrazzo is being proposed for an upper level of a structure, is there a weight restriction
- The proposed matrix colors may be a factor in selecting a terrazzo system
- Use of glass, plastic, or metal aggregate will be a factor in selecting a terrazzo system
- Metal divider strip design and terrazzo panel sizes may determine which terrazzo system to use.
- Time constraints for installation of terrazzo system may be a factor in system selection
- Washing terrazzo for non-slip finish is a factor in terrazzo system selection
The Terrazzo matrix binder in Terrazzo allows virtually any color of Terrazzo to be produced. While there is a wide but limited range of marble and glass colors, virtually any color can be produced with Epoxy Resin Matrix Terrazzo. And a wide range of colors can be produced with Portland Cement and Polyacrylate Matrixes.
Excellent quality domestic and imported marble chips are available for use in Terrazzo in a wide range of colors, which can be combined to create an infinite variety of color harmonies.
To compliment the marble chip colors, and also to create colors in which marble is not available, there are a wide variety of color ed glass chips available. Glass chips can be used in Epoxy Resin, Polyacrylate Matrix es, however is not recommended in cement matrix terrazzo. Metal chips and shell are also commonly used in Thin-set Epoxy Matrix Terrazzo.
Marble Chip Size
Terrazzo marble/glass chips vary in size for approximately 1/16” in diameter to 1” in diameter. There is a number designation used with #00 being the smallest chips up to #7 being the largest chips. Use of the largest chip sizes is commonly referred to as Venetian Terrazzo.
As with colors, marble chip sizes can be co mbined to create variations in the appearance of the Terrazzo. Terrazzo chip sizes have limitations based on the type of Terrazzo systems being used. (See Allowances For Terrazzo Finish below).
Divider Strip Layout & Patterns
White alloy zinc and brass divider strips are used in Terrazzo for function and Aesthetics. The dividers strips is some systems act as control joints, transitions between Terrazzo colors, transitions from vertical to horizontal installations, and for termination to adjacent flooring finishes.
Divider strips are commonly use aesthetically to create custom designs and patterns in the Terrazzo. Intricate logo artwork and lettering can be created with Terrazzo divider strips.
Interior & Exterior Terrazzo
Terrazzo is used in both interior and exterior applications. Portland Cement and Polyacrylate Matrix Terrazzo can be used for both interior and exterior applications, however. Epoxy Resin Matrix Terrazzo is not recommended for exterior use.
When optimum slip-resistance is desired for an exterior Terrazzo surface, Rustic or Acid Washed Portland Cement Terrazzo can be used. After grinding and before final polishing and sealing, a mild acid solution is applied t hat will dissolve the Portland Cement matrix until neutralized. This process leaves a slight depression in the matrix causing the marble chip surface to protrude slightly and provide the added slip-resistance. Upon final sealing, the Terrazzo appearance is similar to polished Terrazzo without high gloss.
Allowance for Terrazzo Finish
When considering which Terrazzo system is best suited for the pro posed application, the required minimum thickness for each type of Terrazzo system may become the deciding factor. The following minimum varying thickness and weight apply for each respective Terrazzo system:
- Exterior Sand Cushion/Venetian Terrazzo 2-½” (30 lbs./sq.ft.)
- Exterior Bonded Acid Washed Terrazzo 2” ( 20 lbs./sq.ft.)
- Interior/Exterior Polyacrylate Terrazzo ½” (3 lbs./sq.ft.)
- Interior Epoxy Resin Terrazzo 3/8” (3 lbs./sq.ft.)
Terrazzo Type Advantages & Limitations
Portland Cement Sand Cushion & Bonded Acid Washed Terrazzo
- Can be used for interior or exterior use
- Can be acid washed for added slip resistance in exterior use
- Topping thickness will accommodate the largest (#7) chip size
- Is breathable and not affected by moisture vapor transmission
- Sand Cushion system can accommodate substrate defects
- Requires minimum 2” depression for system installation
- Vibrant colors are very limited with Portland Cement
- Glass chips have limited use in Portland Cement
- Design flexibility due to size of panel limitations
- Lengthy cure time to achieve final appearance
Epoxy Resin Matrix Terrazzo
- System thickness of 3/8” total, can be used over concrete or wood substrate
- Virtually unlimited range of vibrant colors available
- Glass chips can be used in epoxy resin Terrazzo
- Design flexibility due to minimal divider strip requirements Accelerated chemical cure allows for faster installation due to significantly decreased cure time prior to grinding
- Color uniformity on large installations due to sophisticated manufacturing process for resin
- Most cost effective system for interior use
- 3/8” total thickness requires high flatness tolerance of ¼” per 10 sq.ft. in the substrate.
- Not recommended for exterior use.
- System not breathable, moisture vapor transmission barrier may be required for slab on grade applications.
- Maximum chip size that can be used is #2.
Polyacrylate Modified Cement Terrazzo
- System thickness of ½” total, can be used over wood substrate.
- Glass chips can be used in polyacrylate matrix Terrazzo.
- Can be used for exterior applications.
- System is breathable and not affect ed by moisture vapor transmission.
- Can be acid-washed for added slip resistance in exterior applications
- ½” total thickness requires hi gh flatness tolerance of ¼” per 10 sq.ft. in the substrate.
- The most vibrant colors cannot be achieved with polyacrylate matrix.
- Maximum chip size that can be used is #2.