Design Tools
Design Considerations

Terrazzo Systems

  • Sand Cushion Portland Cement Terrazzo
  • Bonded Portland Cement Terrazzo
  • Venetian / Palladiana Portland Cement Terrazzo
  • Rustic / Washed Portland Cement Terrazzo
  • Polyacrylate Modified Cement Terrazzo
  • Resin Matrix Terrazzo

Considerations for System Selection

  • Does the terrazzo system need to be breathable if installation is 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 subfloor for systems greater than 1/2"?
  • 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.

Matrix Colors

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.

Terrazzo Aggregates

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 to compliment the marble chip colors, and also to create colors in which marble is not available, there are a wide variety of colored glass chips available.

Glass chips can be used in Epoxy Resin, Polyacrylate Matrixes, 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 combined 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 used 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 that 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 proposed 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 1/2" (30 lbs./sq.ft.)
  • Exterior Bonded Acid Washed Terrazzo 2" (20 lbs./sq.ft.)
  • Interior/Exterior Polyacrylate Terrazzo 1/2" (3 lbs./sq.ft.)
  • Interior Epoxy Resin Terrazzo 3/8" (3 lbs./sq.ft.)

Terrazzo Type Advantages and Disadvantages

Portland Cement Sand Cushion / Bonded Acid Washed Terrazzo:

Advantages:
  • 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
Limitations:
  • 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:

Advantages:
  • 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
Limitations:
  • 3/8" total thickness requires high flatness tolerance of 1/4" 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:

Advantages:
  • System thickness of 1/2" 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 affected by moisture vapor transmission.
  • Can be acid-washed for added slip resistance in exterior applications
Limitations:
  • 1/2" total thickness requires high flatness tolerance of 1/4" 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
Specifications

Epoxy / Resin Matrix

Description:

A nominal 1/4" or 3/8" thick resin matrix veneer placed upon a level concrete slab; Also can be specified with glass, synthetic, or granite aggregates in lieu of marble to provide brilliant colors or chemical resistance; The best "thin-set" system.

NEW!
AVAILABLE DOWNLOADS:

Word Doc with LEED

Word Doc without LEED

PDF with LEED

PDF without LEED

DWG - CAD ready


Advantages:

Unlimited matrix colors, color control, resiliency, chemical resistance and tensile- compressive strengths not found in cement based systems. Excellent for multi-colored patterns and designs. Light weight and flexibility make it ideal for multi-story use. It has the lowest maintenance cost due to non-absorbancy. In sanitary areas can be installed with minimal dividers providing seamless characteristics. When used in conjunction with a flexible membrane as a specified extra, it can absorb some horizontal concrete crack or control joint movement. It also has the quickest pour to grind installation time. Can also be used over properly installed and prepared plywood. Glass and other decorative aggregates increased costs.

Thickness: Nominal 1/4" or 3/8" Epoxy Terrazzo topping. 0-1 chip sizes opt.#2 chip for 3/8".
Weight: 3-4 lbs. PSF.

Dividers:

Most systems adhere to the concrete and require dividers to be placed precisely above any concrete joints. To prevent the concrete from cracking and therefore the terrazzo, "ACI 302.1 R.89 Concrete Joint Placement" must be followed. Some of these requirements include: Concrete joints should occur a maximum of three times in feet the depth of the concrete in inches. (Example: A 4 inch slab should have concrete joints at a maximum spacing of 12 feet). Concrete joints should run off all corridor intersections and corners. They should not be spaced more than 1.5 times the width of the concrete pour. (Example: A 6 foot wide corridor should have concrete joints at a maximum of 9 feet.)

In addition other dividers can be set to separate colors or as an accent themselves. In these systems the dividers not located over concrete joints are strictly decorative. They do not function as leveling devices or crack preventers.

Dividers vary in width from 18 gauge to 1/2 inch. 16 gauge or 1.8 inch are standards. Zinc is standard but brass and colored plastic are readily available.

Architects should design structural inset expansion plates between areas where major movement is anticipated.

End

Sand Cushion

Description:

A cement matrix topping underbed with wire reinforcing, isolation sheet, and sand layer system for interior floor use. This is the best cement system.

NEW!
AVAILABLE DOWNLOADS:

Word Doc with LEED

Word Doc without LEED

PDF with LEED

PDF without LEED

DWG - CAD ready


Advantages:

Due to the underbed's depth, wire mesh reinforcing, isolation sheeting and sand layer it will absorb minor substrate defects and prevent mirroring to the surface.

Thickness: 2.5" to 3" including a .5" terrazzo topping.

Weight: 25-30 lbs. PSF.

Dividers:

The position of divider strips is essential to performance, serving a dual function: a control for anticipated contraction and an aesthetic enhancement in separating colors. 5 feet or less on centers.

Architects should design structural inset expansion plates between areas where major movement is anticipated.

End

Bonded

Description:

A cement matrix and underbed system for interior and exterior areas where conditions require 1.25" to 1.75" of recessed depth to be filled in addition to the .5" terrazzo topping.

NEW!
AVAILABLE DOWNLOADS:

Word Doc with LEED

Word Doc without LEED

PDF with LEED

PDF without LEED

DWG - CAD ready


Advantages:

With sand-cement underbed it has less dependence on the concrete slab for flatness when compared to monolithic.

Thickness: 1.75" to 2.25" including .5" terrazzo topping.

Weight: 18-22 lbs. PSF.

Dividers:

Most systems adhere to the concrete and require dividers to be placed precisey above any concrete joints. To prevent the concrete from cracking and therefore the terrazzo, "ACI 302.1 R.89 Concrete Joint Placement" must be followed. Some of these requirements include: Concrete joints should occur a maximum of three times in feet the depth of the concrete in inches. (Example: A 4 inch slab should have concrete joints at a maximum spacing of 12 feet). Concrete joints should run off all corridor intersections and corners. They should not be spaced more than 1.5 times the width of the concrete pour. (Example: A 6 foot wide corridor should have concrete joints at a maximum of 9 feet.)

In addition other dividers can be set to separate colors or as an accent themselves. In these systems the dividers not located over concrete joints are strictly decorative. They do not function as leveling devices or crack preventers.

Dividers vary in width from 18 gauge to 1/2 inch. 16 gauge or 1.8 inch are standards. Zinc is standard but brass and colored plastic are readily available.

Architects should design structural inset expansion plates between areas where major movement is anticipated.

End

Monolithic

Description:

This 1/2" thick cement matrix veneer placed upon a provided concrete slab is dependent on the concrete quality for flatness and crack prevention. On grade or below grade only.

NEW!
AVAILABLE DOWNLOADS:

Word Doc with LEED

Word Doc without LEED

PDF with LEED

PDF without LEED

DWG - CAD ready

(coming soon)


Advantages:

Fast installation and the most economical price make it ideal where time and budget are critical but where the beauty, low maintenance and the performance of terrazzo is desired.

Thickness: 1/2" Terrazzo topping

Weight: 5-7 lbs. PSF.

Dividers:

Most systems adhere to the concrete and require dividers to be placed precisey above any concrete joints. To prevent the concrete from cracking and therefore the terrazzo, "ACI 302.1 R.89 Concrete Joint Placement" must be followed. Some of these requirements include: Concrete joints should occur a maximum of three times in feet the depth of the concrete in inches. (Example: A 4 inch slab should have concrete joints at a maximum spacing of 12 feet). Concrete joints should run off all corridor intersections and corners. They should not be spaced more than 1.5 times the width of the concrete pour. (Example: A 6 foot wide corridor should have concrete joints at a maximum of 9 feet.)

In addition other dividers can be set to separate colors or as an accent themselves. In these systems the dividers not located over concrete joints are strictly decorative. They do not function as leveling devices or crack preventers.

Dividers vary in width from 18 gauge to 1/2 inch. 16 gauge or 1.8 inch are standards. Zinc is standard but brass and colored plastic are readily available.

Architects should design structural inset expansion plates between areas where major movement is anticipated.

End

Polyacrylate

Description:

A nominal 3/8" thick polymer modified cement matrix veneer placed upon a provided level concrete slab. Polymer provides strength to allow for thinner applications of cementitious systems.

NEW!
AVAILABLE DOWNLOADS:

Word Doc with LEED

Word Doc without LEED

PDF with LEED

PDF without LEED

DWG - CAD ready


Advantages:

Fast installation and moderate price range make it ideal to replace vinyl or carpet without depth transition difficulties; also good to use in areas subject to moisture vapor transmission where Epoxy terrazzo or other non-breathing floors will not adhere.

Thickness: Nominal 3/8" polyacrylate with terrazzo topping. Chip sizes 0,1 and 2.

Weight: 4.5 lbs. PSF.

Dividers:

Most systems adhere to the concrete and require dividers to be placed precisey above any concrete joints. To prevent the concrete from cracking and therefore the terrazzo, "ACI 302.1 R.89 Concrete Joint Placement" must be followed. Some of these requirements include: Concrete joints should occur a maximum of three times in feet the depth of the concrete in inches. (Example: A 4 inch slab should have concrete joints at a maximum spacing of 12 feet). Concrete joints should run off all corridor intersections and corners. They should not be spaced more than 1.5 times the width of the concrete pour. (Example: A 6 foot wide corridor should have concrete joints at a maximum of 9 feet.)

Architects should design structural inset expansion plates between areas where major movement is anticipated.

End

Rustic / Exterior

Description:

Terrazzo with a non-ground, textured surface, for exterior use. This system is available with Bonded and Monolithic Terrazzo.

NEW!
AVAILABLE DOWNLOADS:

Word Doc with LEED

Word Doc without LEED

PDF with LEED

PDF without LEED

DWG - CAD ready


Advantages:

Inifinitely variable textures, colors and patterns may be created in a weather-resistant, skid-resistant deck surface.

Thickness: Bonded 1.75" to 2" including a .5" terrazzo topping. Monolithic .5" terrazzo topping.

Weight: Dependent on system selected.

Dividers:

Temporary wood strips are used, then replaced by a pourable sealant inserted into the joint.

Rustic Monolithic Terrazzo



End

System Details

Crack Detailing & Joint Treatments for Epoxy Terrazzo

THIN-SET EPOXY TERRAZZO

Thin-set epoxy terrazzo has many years of successful history dating back to the introduction of epoxies over 40 years ago. Thin-set epoxy was traditionally placed directly onto a prepared structural concrete slab. The crack resistance of the terrazzo was based primarily on two functions. First, the epoxy terrazzo formulations were extremely high in tensile strength and second, they did not contain excess water that leads to shrinkage cracks or volume change during the curing process.

In the 1990s, the major epoxy formulators introduced flexible epoxy membranes that are installed at a nominal 40 mils. Thickness and engineered for high tensile strength and high elongation, relative to the epoxy binder matrix. These membranes have become industry standard for crack detailing and, in some cases, full slab coverage prior to the installation of the thin-set epoxy terrazzo. The combinations of high tensile low shrinkage binder resins with the high performance flexible epoxy membranes allow architects to specify and detail thin-set terrazzo with confidence.

CONCRETE JOINTING: SETTLEMENT & CRACK CONTROL

Concrete has been the standard flooring substrate in the commercial construction industry for many years. The concrete industry has developed many industry guidelines and recommendations to minimize cracking. While there have been many improvements in mix designs, placement techniques and industry standards, the concrete industry has not perfected the placement of slabs without cracks. Cracks in concrete are a result of any number of issues, including volume change during the curing process, load deflection, settlement cracks and cracks induced from thermal stresses, which are typically due to non-climate controlled environments during the construction process. While shrinkage cracks, which account for most concrete cracking, become static once the volume change from curing is complete, any crack has the potential to become a dynamic, moving crack under thermal and load movement stresses. To accommodate dynamic loading, slabs should be designed for maximum deflection of L/360.

Disclaimer

The details contained herein provide general information to use as a starting point for detailing site conditions that frequently occur on epoxy terrazzo projects. They represent generally accepted practices of terrazzo contractors and suppliers across the United States under typical circumstances. These details do not replace the direction or advice of an architect or engineer regarding a specific project or for specific project conditions. Architect or engineer must specify movement joints and show location and details on drawings.It is not the intent of this guide to make movement joint recommendations for a specific project. For your particular project(s), you should consider contacting an NTMA Member Contractor/ Associate in your area to discuss details that may be most applicable for a given circumstance/ location.

Available Downloads:


End

Crack Detailing & Joint Treatments for Monolithic Terrazzo Systems

MONOLITHIC TERRAZZO

Monolithic terrazzo has many years of successful history as cement terrazzo system. These systems are traditionally placed directly onto a prepared structural concrete slab.

CONCRETE JOINTING: SETTLEMENT & CRACK CONTROL

Concrete has been the standard flooring substrate in the commercial construction industry for many years. The concrete industry has developed many industry guidelines and recommendations to minimize cracking. Cracks in concrete are a result of any number of issues, including volume change during the curing process, load deflection, settlement cracks and cracks induced from thermal stresses, which are typically due to non-climate controlled environments during the construction process. While shrinkage cracks, which account for most concrete cracking, become static once the volume change from curing is complete, any crack has the potential to become a dynamic, moving crack under thermal and load movement stresses. To accommodate dynamic loading, slabs should be designed for maximum deflection of L/360.

Disclaimer

The details contained herein provide general information to use as a starting point for detailing site conditions that frequently occur on monolithic terrazzo projects. They represent generally accepted practices of terrazzo contractors and suppliers across the United States under typical circumstances. These details do not replace the direction or advice of an architect or engineer regarding a specific project or for specific project conditions. The architect or engineer must specify movement joints and show location and details on drawings. It is not the intent of this guide to make movement joint recommendations for a specific project. For your particular project(s), you should consider contacting an NTMA Contractor Member in your area to discuss details that many be most applicable for a given circumstance/location.
To mitigate cracking and curling in concrete at thin set cement terrazzo areas follow recommendations in ACI 360R-10.
Terrazzo divider strips must precisely follow the concrete joint - even if crooked.
Terrazzo divider strips are not flattening or leveling devices. They must adhere tightly to the concrete.
Tooled edges on concrete joints are not to be used at areas to receive thin set cement terrazzo systems.

Available Downloads:


End

Poured in Place Base

Poured in Place Stairs