+---
+title: Terrazzo
+category: Architectural / Finishes
+toc_depth: 3
+description: >
+ When to use: Poured-in-place terrazzo floor and base finishes for commercial, institutional, civic, educational, healthcare, and transportation interiors — epoxy (resinous) thin-set terrazzo and the cementitious systems (polyacrylate, monolithic, bonded, and sand-cushion). Covers matrix system selection, marble/granite/glass/recycled aggregate, divider and control strips, substrate flatness and moisture testing, physical-property requirements for the resin matrix, crack-isolation and joint detailing, grinding/grouting/polishing/sealing, integral cove and topset base, and precast terrazzo bases and stair treads. Suitable for new construction and for terrazzo restoration where the existing system is sound.
+ Not intended for: Resilient floor coverings such as vinyl, rubber, and linoleum (see [[sync/resilient-flooring]]); fluid-applied epoxy, urethane, and other resinous coatings and broadcast floors that contain no ground aggregate matrix (see [[sync/resinous-flooring]]); ceramic, porcelain, and natural stone tile (see [[sync/ceramic-tile]]); carpet (see [[sync/carpet]]); exterior rustic (non-ground) terrazzo on paving and plazas; the design and placement of the structural concrete slab and its under-slab vapor retarder (see [[sync/cast-in-place-concrete]]).
+---
+
+# Scope
+
+This standard governs the materials and installation of poured-in-place terrazzo flooring and base — the epoxy (resin matrix) thin-set system and the cementitious systems — over concrete substrates in commercial and institutional construction. Terrazzo is a composite finish: a matrix of resin or cement is placed, seeded with decorative aggregate, cured, and then ground and polished to expose the aggregate and produce a dense, monolithic, jointless wearing surface. It is specified where the owner wants a finish that lasts the life of the building, carries heavy foot traffic and rolling loads without wearing through, and can be cleaned and maintained indefinitely without recoating or replacement — lobbies, concourses, corridors, atria, museums, and transportation terminals are its natural home. The defining characteristic of terrazzo is that its service life is measured in decades rather than years, which is why the quality of the substrate preparation and the crack-isolation detailing matters far more than for any replaceable floor covering: a crack telegraphed up from the slab into a terrazzo floor is permanent and cannot be patched invisibly.
+
+A terrazzo floor is a system consisting of the structural slab, any crack-isolation or moisture-mitigation membrane, the matrix and its aggregate, the divider and control strips that define the field and accommodate movement, the integral or applied base, and the sealer. The single most important decision is the matrix system, because it determines the system thickness, the substrate it can be placed over, the moisture tolerance, the crack behavior, and the cost. Epoxy thin-set terrazzo, placed at a nominal 3/8 inch directly on a level interior slab, is the dominant modern system and is the default of this standard; the cementitious systems remain the correct choice for exterior work, for wet areas, for very large monolithic fields, and where structural movement demands a sand-cushion isolation layer. The Contractor shall treat the floor as a system, shall confirm that the matrix, aggregate, strips, membrane, and base selected are mutually compatible and approved by the matrix manufacturer for the measured substrate condition, and shall not begin placement until the substrate has passed the flatness and moisture acceptance criteria of this standard.
+
+Terrazzo crack control is governed by what is underneath, not by the terrazzo itself. Epoxy terrazzo is a thin rigid veneer fused to the slab; any crack that opens in the slab will reflect through the terrazzo unless it is isolated. Coordinate the structural slab, its control-joint layout, its surface finish, and its under-slab vapor retarder with [[sync/cast-in-place-concrete]] — the slab control joints and construction joints must be located and detailed before terrazzo work begins so that crack-isolation membrane or divider strips can be placed directly over them. Coordinate transitions to adjacent finishes with [[sync/resilient-flooring]] and [[sync/ceramic-tile]] so that thresholds and finish-floor elevations reconcile.
+
+# Referenced Standards
+
+All materials, testing, and installation shall comply with the latest edition adopted by the Authority Having Jurisdiction for each of the following standards. Where the contract documents, a referenced standard, or the matrix manufacturer's written instructions impose a more stringent requirement than the minimum of any other standard, the more stringent requirement governs unless the Architect of Record directs otherwise in writing. For terrazzo, the National Terrazzo and Mosaic Association (NTMA) technical data, system definitions, and details are the recognized industry reference, and the matrix manufacturer's written instructions define the conditions under which the matrix warranty is valid; the Contractor shall follow both in addition to this standard.
+
+| Standard | Title |
+|----------|-------|
+| ASTM C307 | Standard Test Method for Tensile Strength of Chemical-Resistant Mortar, Grouts, and Monolithic Surfacings |
+| ASTM C579 | Standard Test Methods for Compressive Strength of Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes |
+| ASTM C580 | Standard Test Method for Flexural Strength and Modulus of Elasticity of Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes |
+| ASTM C413 | Standard Test Method for Absorption of Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes |
+| ASTM C1353 | Standard Test Method for Abrasion Resistance of Dimension Stone Subjected to Foot Traffic Using a Rotary Platform, Double-Head Abraser |
+| ASTM D4541 | Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers |
+| ASTM E84 | Standard Test Method for Surface Burning Characteristics of Building Materials |
+| ASTM C97 | Standard Test Methods for Absorption and Bulk Specific Gravity of Dimension Stone (marble aggregate) |
+| ASTM C503 | Standard Specification for Marble Dimension Stone |
+| ANSI A326.3 | Test Method for Measuring Dynamic Coefficient of Friction of Hard Surface Flooring Materials |
+| ASTM F1869 | Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride |
+| ASTM F2170 | Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes |
+| ASTM E1745 | Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill under Concrete Slabs |
+| ASTM C150 | Standard Specification for Portland Cement (cementitious matrix systems) |
+| NTMA | National Terrazzo and Mosaic Association technical data, system definitions, and details |
+| IBC | International Building Code (current edition adopted by jurisdiction) |
+
+ASTM C1028, formerly cited for terrazzo slip resistance, has been withdrawn and shall not be specified for acceptance; dynamic coefficient of friction is now measured per ANSI A326.3. The chemical-resistant mortar test methods (ASTM C307, C579, C580, C413) are the methods by which epoxy terrazzo matrix physical properties are reported, because a cured epoxy terrazzo matrix is a polymer concrete in the meaning of those standards.
+
+# Submittals
+
+## Action Submittals
+
+The Contractor shall submit the following for the Architect's review prior to procurement and installation. Installation shall not begin until the moisture-test reports have been submitted and reviewed, because the moisture condition of the slab determines both the matrix compatibility and the mitigation requirement, and a moisture-related epoxy terrazzo failure is a full-depth replacement, not a repair.
+
+- Product data for the matrix system, identifying the system type, nominal thickness, mix design, and the matrix manufacturer's written installation instructions and physical-property data
+- Product data for the aggregate, identifying type (marble, granite, glass, recycled, or mother-of-pearl), source, and gradation by NTMA size number
+- Product data for divider strips, control-joint strips, and base strips, identifying material, gauge, profile (L-type or T-type), and depth
+- Product data for the crack-isolation / membrane system, primer, grout, and sealer
+- Samples of the cured terrazzo, not less than 6 by 6 inches, ground and polished and sealed, for each color and aggregate blend, showing the actual aggregate, matrix color, and finish
+- Samples of each divider, control, and base strip in the specified material and finish
+- Moisture and relative-humidity test reports for the actual slab, conducted in accordance with ASTM F2170 (relative humidity) and, where used, ASTM F1869 (moisture vapor emission rate), identifying test locations and ambient conditions
+- Shop drawings showing the divider-strip and control-joint layout, the location of all slab control and construction joints to be isolated, aggregate-blend zones, patterns, logos, and base details, coordinated with the [[drawing: finish plan and architectural details]]
+- Maintenance instructions describing initial cleaning, sealing, and the recommended periodic maintenance program
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Matrix system product data and physical-property data"
+ - "Aggregate product data (type, source, gradation)"
+ - "Divider, control, and base strip product data"
+ - "Membrane, primer, grout, and sealer product data"
+ - "Cured terrazzo samples (each color/blend, ground and sealed)"
+ - "Strip samples (each material and finish)"
+ - "Slab moisture and RH test reports (F2170 / F1869)"
+ - "Strip-layout and pattern shop drawings"
+ - "Maintenance instructions"
+default: "Slab moisture and RH test reports (F2170 / F1869)"
+```
+
+## Closeout Submittals
+
+- Matrix manufacturer and installer warranty documentation, executed in the Owner's name
+- Record of the final slab moisture and RH test results, the crack-isolation method installed, and the matrix and sealer used, retained for warranty purposes
+- Attic-stock transmittal documenting the quantity, matrix color, and aggregate blend of spare material delivered to the Owner
+
+# Quality Assurance
+
+## Installer Qualifications
+
+Terrazzo shall be installed by a contractor in good standing with the National Terrazzo and Mosaic Association, or by an installer with documented experience completing not fewer than five commercial terrazzo installations of the system type and scale required within the preceding five years, employing mechanics experienced in the placement, grinding, and finishing of the specified matrix system. Terrazzo is a craft trade in which the visible result depends almost entirely on workmanship — aggregate seeding density, grinding depth, grout filling of pinholes, and polishing all determine the appearance of a finish that the owner will live with for decades. The Contractor shall not assign terrazzo placement or finishing to labor inexperienced in the specified system.
+
+```datasheet
+label: Installer Qualification
+type: radio
+options:
+ - "NTMA member contractor"
+ - "Five years documented commercial terrazzo experience in the specified system"
+ - "Either NTMA member or five years documented experience"
+default: "Either NTMA member or five years documented experience"
+```
+
+## Mock-Up
+
+```datasheet
+label: Mock-Up Required
+type: radio
+options:
+ - "Yes — install a representative field area including a divider strip, a control-joint detail, and base"
+ - "No"
+default: "Yes — install a representative field area including a divider strip, a control-joint detail, and base"
+```
+
+Where a mock-up is required, the Contractor shall install a representative field area of each terrazzo type at a location and size directed by the Architect, fully ground, grouted, polished, and sealed, and including at least one divider strip, one control-joint detail, one aggregate-blend transition where blends change, and the integral or applied base. The mock-up establishes the acceptable standard for aggregate distribution and density, matrix color, grinding and polishing quality, strip alignment, and base detailing, and shall remain available for comparison throughout the work. Because aggregate seeding density and grinding depth are judgment calls that vary between crews, the mock-up is the only reliable way to fix the acceptable appearance before the full floor is committed.
+
+## Pre-Installation Conference
+
+Before installation begins, the Contractor shall hold a pre-installation conference with the Architect, the terrazzo installer, and the concrete contractor to review the slab moisture-test results, the slab flatness and control-joint locations, the crack-isolation requirement, the divider-strip and pattern layout, the aggregate blends, the matrix and sealer selection, and the environmental conditions. The most common cause of an epoxy terrazzo crack is a slab control or construction joint that was not honored with a divider strip or membrane directly above it; the conference exists to reconcile the slab joint layout with the terrazzo layout before any matrix is placed.
+
+# Environmental and Service Conditions
+
+## Temperature During Installation
+
+The installation area shall be enclosed and maintained at a minimum of 60 °F (16 °C) and a maximum of 90 °F (32 °C) for 48 hours before, during, and for not less than 72 hours after placement of an epoxy matrix, and within the range the matrix manufacturer specifies. Epoxy matrix cure is temperature-dependent: below the minimum, the resin will not cure to its specified physical properties and will remain soft and grindable only with difficulty; above the maximum, pot life shortens and the placed matrix can flash-cure before it is properly leveled and seeded. The permanent HVAC system or equivalent temporary conditioning shall maintain the space; the slab surface temperature, not only the air temperature, shall be within the manufacturer's range, because a cold slab cools the matrix at the bond line regardless of air temperature.
+
+```datasheet
+label: Minimum Ambient and Slab Temperature During Placement
+type: range
+unit: °F
+options:
+ min: 50
+ max: 65
+ step: 5
+default: 60
+```
+
+## Slab Moisture and Relative Humidity Limits
+
+The acceptable slab moisture condition is a governing service condition for epoxy terrazzo, and it shall be established by test before placement and confirmed against both the matrix manufacturer's limit and the limit of this standard. Internal relative humidity measured by in-situ probe per ASTM F2170 shall not exceed the limit stated below. Epoxy terrazzo is more moisture-tolerant than most resilient flooring, and many epoxy terrazzo matrix systems are warranted to a maximum internal relative humidity of 85 to 90 percent, but the lower of the manufacturer's limit and the project limit governs, and an epoxy primer or vapor-mitigation coating rated for the measured relative humidity shall be installed where the slab exceeds the matrix limit. Internal relative humidity per F2170 is a more reliable predictor of long-term moisture behavior than a surface emission measurement because it reflects the moisture distributed through the slab thickness.
+
+```datasheet
+label: Maximum Slab Internal Relative Humidity (ASTM F2170)
+type: range
+unit: % RH
+options:
+ min: 80
+ max: 90
+ step: 5
+default: 85
+```
+
+## Slab Moisture Vapor Emission Limit
+
+Where moisture vapor emission rate is used as a screening or supplementary measure per ASTM F1869, the rate shall not exceed the matrix manufacturer's limit, commonly 3 to 5 pounds per 1,000 square feet per 24 hours for epoxy terrazzo. The calcium chloride method measures only the surface condition and shall not be used as the sole acceptance criterion for slabs on grade or below grade — F2170 internal relative humidity is required for those conditions because surface emission can read deceptively low while the slab interior remains wet, and moisture trapped beneath a cured epoxy veneer drives osmotic blistering and bond loss.
+
+```datasheet
+label: Maximum Moisture Vapor Emission Rate (ASTM F1869)
+type: range
+unit: lb/1000 sq ft/24 hr
+options:
+ min: 3
+ max: 5
+ step: 1
+default: 5
+```
+
+## Under-Slab Vapor Retarder
+
+For slabs on grade, a vapor retarder conforming to ASTM E1745 Class A shall be installed directly beneath and in contact with the slab, coordinated with [[sync/cast-in-place-concrete]]. The under-slab vapor retarder is the single most effective moisture-control measure for slab-on-grade terrazzo and is placed long before terrazzo work begins; its presence or absence is verified during slab review, not at the time of terrazzo placement, but it governs whether a vapor-mitigation coating will later be required.
+
+```datasheet
+label: Under-Slab Vapor Retarder (slab on grade)
+type: radio
+drawing_ref: true
+options:
+ - "ASTM E1745 Class A vapor retarder beneath slab (required for slab on grade)"
+ - "Not applicable — slab above grade / suspended"
+default: "ASTM E1745 Class A vapor retarder beneath slab (required for slab on grade)"
+```
+
+## Lighting for Inspection
+
+Permanent or equivalent temporary lighting shall be operating during finishing and inspection so that aggregate distribution, grinding uniformity, residual pinholes, scratch patterns, and strip alignment can be evaluated under realistic conditions. Terrazzo is frequently accepted under raking construction lighting that either conceals or exaggerates surface defects; the floor shall be inspected under the lighting in which it will be viewed in service.
+
+# Terrazzo System
+
+## Matrix System
+
+The matrix system is the primary selection and determines the system thickness, the substrate it may be placed over, the moisture and crack behavior, the interior-versus-exterior suitability, and the cost. It shall be selected for the substrate condition, the field size, the exposure, and the design intent, and shall be indicated on the [[drawing: finish schedule]].
+
+```datasheet
+label: Terrazzo Matrix System
+type: select
+drawing_ref: true
+options:
+ - "Epoxy (resin matrix) thin-set — nominal 3/8 in over level interior slab"
+ - "Polyacrylate (polymer-modified cement) — nominal 3/8 in over level interior slab"
+ - "Monolithic cement — 1/2 in cement matrix bonded to interior slab"
+ - "Bonded cement — 1/2 in topping over a bonded underbed (1-3/4 to 2-1/4 in total)"
+ - "Sand-cushion cement — 1/2 in topping over reinforced underbed, isolation membrane, and sand layer (2-1/2 to 3 in total)"
+default: "Epoxy (resin matrix) thin-set — nominal 3/8 in over level interior slab"
+```
+
+Epoxy thin-set terrazzo, a nominal 3/8-inch resin matrix veneer placed directly on a level interior concrete slab, is the dominant modern system and the default of this standard because it is the thinnest, lightest, and most chemically resistant system, offers the widest color range, cures quickly, and accepts dense aggregate seeding. It is an interior, above-grade-or-on-grade system only and is not used for exterior or continuously wet areas. Polyacrylate terrazzo is a polymer-modified cementitious veneer of similar nominal thickness used where a cement matrix is preferred but slab depth is limited; the polymer permits the thin section and improves moisture-vapor tolerance over a plain cement topping. Monolithic terrazzo is a 1/2-inch cement matrix bonded directly to the slab and depends entirely on the quality and crack-control of that slab for its own crack behavior. Bonded terrazzo adds a bonded sand-cement underbed to build up a recessed slab and to provide a controlled bonding bed, and is suited to interior and protected exterior work. Sand-cushion terrazzo — a 1/2-inch topping over a wire-reinforced underbed placed on an isolation membrane over a sand dusting layer — is the most movement-tolerant system: the sand-and-membrane layer mechanically isolates the terrazzo from the structure so that slab movement and minor cracking do not reflect into the finish, which makes it the choice for buildings with anticipated structural movement and for the largest jointless fields, at the cost of the greatest thickness and dead load.
+
+## System Thickness
+
+```datasheet
+label: Nominal System Thickness
+type: select
+unit: in
+drawing_ref: true
+options:
+ - "1/4 in — epoxy thin-set, fine aggregate only"
+ - "3/8 in — epoxy thin-set, standard"
+ - "1/2 in — monolithic / polyacrylate topping"
+ - "1-3/4 to 2-1/4 in — bonded system total"
+ - "2-1/2 to 3 in — sand-cushion system total"
+default: "3/8 in — epoxy thin-set, standard"
+```
+
+Epoxy terrazzo is placed at a nominal 3/8 inch, which accommodates aggregate up to NTMA size No. 2; a 1/4-inch placement is used only where the recess depth is limited and the aggregate is restricted to the finer sizes, because there must be sufficient matrix depth above the slab to embed and lock the largest aggregate. The matrix manufacturer's minimum thickness for the selected aggregate gradation governs; placing too thin for the aggregate size leaves chips that loosen and pop out during grinding and service. Cementitious system thicknesses are dictated by the system definition and the available slab recess.
+
+## Aggregate Type
+
+```datasheet
+label: Aggregate Type
+type: select
+drawing_ref: true
+options:
+ - "Marble chips"
+ - "Granite chips"
+ - "Recycled glass"
+ - "Marble and recycled-glass blend"
+ - "Mother-of-pearl / specialty (accent only)"
+default: "Marble chips"
+```
+
+Marble chip is the traditional and most common terrazzo aggregate; it grinds and polishes readily to a high luster and is the basis of the widest range of standard colors, which makes it the default. Granite and other hard silica aggregates are harder to grind but are specified for added abrasion resistance and a distinct appearance, and are common in epoxy systems where the resin matrix tolerates the harder grind. Recycled glass — including post-consumer and post-industrial glass — is widely used both for appearance and for recycled-content credit in green-building programs, and is fully compatible with the epoxy matrix; certain glass colors are sensitive to the high alkalinity of cement matrices and shall be confirmed compatible with a cementitious matrix before use. Mother-of-pearl and other specialty aggregates are typically used as accents within a field of marble or glass rather than as the full blend. All aggregate shall be the calcareous or siliceous stone or glass capable of being ground and taking a polish appropriate to the matrix.
+
+## Aggregate Gradation
+
+```datasheet
+label: Aggregate Size (NTMA gradation number)
+type: select
+drawing_ref: true
+options:
+ - "No. 0 (1/8 in and finer)"
+ - "No. 1 (1/8 to 1/4 in)"
+ - "No. 2 (1/4 to 3/8 in)"
+ - "Blend of No. 1 and No. 2 (standard)"
+ - "Blend of No. 0 through No. 2"
+default: "Blend of No. 1 and No. 2 (standard)"
+```
+
+Terrazzo aggregate is graded by NTMA size number from No. 0 (the finest, 1/8 inch and smaller) through No. 2 (3/8 inch); the conventional standard terrazzo appearance uses a blend of No. 1 and No. 2 chips. Epoxy terrazzo commonly uses blends spanning No. 0 through No. 2 to achieve a dense, fully-seeded surface with minimal visible matrix between chips. The maximum aggregate size shall not exceed the limit the matrix thickness can embed — a No. 2 chip requires the full 3/8-inch epoxy section. Larger decorative aggregate, where used in palladiana or feature work, is set and detailed individually and is outside the standard gradation.
+
+## Matrix Color
+
+The matrix color shall be as selected by the Architect from the manufacturer's full color range and indicated on the [[drawing: finish schedule and color schedule]]. Epoxy matrices accept a far wider and more saturated color range than cement matrices, including deep and bright colors that cement cannot achieve; this color flexibility is one of the principal reasons epoxy terrazzo dominates contemporary design work.
+
+# Resin Matrix Physical Properties (Epoxy System)
+
+## Compressive Strength
+
+```datasheet
+label: Minimum Matrix Compressive Strength (ASTM C579)
+type: range
+unit: psi
+options:
+ min: 8000
+ max: 12000
+ step: 500
+setpoints: [10000]
+default: 10000
+```
+
+The cured epoxy terrazzo matrix shall develop a compressive strength of not less than the value stated when tested per ASTM C579. A compressive strength on the order of 10,000 psi is characteristic of a properly formulated epoxy terrazzo matrix and is what allows a 3/8-inch veneer to carry the rolling loads and point loads of a high-traffic public floor without crushing or indenting; this property, combined with the bond to the slab, is why epoxy terrazzo outperforms thicker but weaker toppings.
+
+## Tensile Strength
+
+```datasheet
+label: Minimum Matrix Tensile Strength (ASTM C307)
+type: range
+unit: psi
+options:
+ min: 1500
+ max: 3000
+ step: 250
+setpoints: [2500]
+default: 2500
+```
+
+The cured matrix shall develop a tensile strength of not less than the value stated when tested per ASTM C307. Tensile strength governs the matrix's resistance to cracking when the slab beneath it moves or shrinks; a higher tensile strength lets the thin veneer bridge minor substrate movement that would crack a brittle cement topping, but it does not substitute for crack isolation over an active slab joint.
+
+## Flexural Strength
+
+```datasheet
+label: Minimum Matrix Flexural Strength (ASTM C580)
+type: range
+unit: psi
+options:
+ min: 2500
+ max: 4000
+ step: 250
+setpoints: [3500]
+default: 3500
+```
+
+The cured matrix shall develop a flexural strength of not less than the value stated when tested per ASTM C580. Flexural strength reflects the matrix's ability to span and resist bending stresses, which matters where the floor bridges minor substrate irregularities and at the edges of divider strips.
+
+## Water Absorption
+
+```datasheet
+label: Maximum Matrix Water Absorption (ASTM C413)
+type: range
+unit: %
+options:
+ min: 0.1
+ max: 0.5
+ step: 0.05
+setpoints: [0.25, 0.5]
+default: 0.5
+```
+
+The cured matrix shall exhibit water absorption not greater than the value stated when tested per ASTM C413. Low absorption — typically below 0.5 percent for epoxy terrazzo — is what makes the floor effectively non-porous, stain-resistant, and cleanable, and is a principal advantage of the resin matrix over a cementitious matrix, which is comparatively porous and requires more diligent sealing.
+
+## Bond Strength
+
+```datasheet
+label: Minimum Bond to Substrate (ASTM D4541, pull-off)
+type: range
+unit: psi
+options:
+ min: 200
+ max: 400
+ step: 50
+setpoints: [200, 300]
+default: 200
+```
+
+The cured matrix system, including its primer, shall develop a pull-off bond strength to the prepared slab of not less than the value stated when tested per ASTM D4541, or shall fail in the concrete substrate rather than at the bond line. Bond is the foundation of a thin-set system: an epoxy terrazzo veneer that debonds becomes a drum-hollow, cracking shell. Adequate bond depends on correct surface preparation, a clean dry slab, and the manufacturer's primer applied at the specified rate.
+
+## Abrasion Resistance
+
+```datasheet
+label: Abrasion Resistance Reporting (ASTM C1353)
+type: radio
+options:
+ - "Required — report Taber abrasion resistance for the matrix and aggregate blend"
+ - "Not separately required"
+default: "Not separately required"
+```
+
+Where abrasion resistance is a governing requirement — in transportation, retail, and other very-high-traffic floors — the terrazzo abrasion resistance shall be reported per ASTM C1353. Terrazzo is among the most abrasion-resistant of all floor finishes, and for most projects the system selection alone assures adequate wear life; explicit abrasion testing is reserved for the highest-traffic applications or where a hard aggregate such as granite is being substituted for marble.
+
+## Surface Burning Characteristics
+
+```datasheet
+label: Surface Burning Characteristics (ASTM E84)
+type: radio
+options:
+ - "Class A — flame spread index 0-25, smoke developed index 0-450"
+ - "Not separately regulated at this location"
+default: "Class A — flame spread index 0-25, smoke developed index 0-450"
+```
+
+Where the building code regulates the surface burning characteristics of the finish, the terrazzo system shall be tested per ASTM E84 and shall achieve a Class A rating (flame spread index not greater than 25 and smoke developed index not greater than 450). Properly formulated epoxy terrazzo is inherently Class A because the cured matrix is highly filled with mineral aggregate and contributes little fuel; the product data shall document the tested indices.
+
+## Slip Resistance
+
+```datasheet
+label: Dynamic Coefficient of Friction (ANSI A326.3)
+type: range
+unit: DCOF
+options:
+ min: 0.42
+ max: 0.55
+ step: 0.01
+setpoints: [0.42, 0.55]
+default: 0.42
+```
+
+The dynamic coefficient of friction shall be measured per ANSI A326.3 and shall meet the minimum for the applicable use classification — not less than 0.42 for level interior spaces expected to be walked on when wet. A polished terrazzo surface can be slick when wet, so where slip resistance is a concern the finish may be honed rather than polished to a high gloss, or an abrasive aggregate or anti-slip additive may be incorporated at entries, ramps, and wet areas. Slip resistance is a function of both the finish and its maintained sealer; the specified value applies to the floor as installed and as maintained per the manufacturer's program.
+
+# Strips and Joints
+
+## Divider Strips
+
+```datasheet
+label: Divider Strip Material
+type: select
+drawing_ref: true
+options:
+ - "White zinc alloy"
+ - "Brass"
+ - "Aluminum"
+ - "Plastic"
+default: "White zinc alloy"
+```
+
+Divider strips define the field of the terrazzo, separate aggregate blends and colors, form patterns and logos, and provide a screed line that controls matrix thickness and flatness during placement. For epoxy thin-set terrazzo the most common divider strip is an L-type strip in white zinc alloy, which is corrosion-resistant, takes the grind cleanly, and leaves a neutral line; brass is specified where a warmer metallic line is desired, aluminum where a bright line and lower cost are acceptable, and plastic where a colored line matched to the matrix is desired or where dissimilar-metal corrosion must be avoided. Zinc and aluminum strips shall not be placed in continuous wet exposure where they would corrode. The strip layout, including patterns and aggregate-blend boundaries, shall be as shown on the [[drawing: terrazzo layout plan]]. Epoxy terrazzo may also be poured as a seamless free-form field with no divider strips where the design and the slab crack-control permit.
+
+```datasheet
+label: Divider Strip Profile
+type: radio
+options:
+ - "L-type (single angle, standard for thin-set epoxy)"
+ - "T-type (for thicker sections and double-pour cement systems)"
+default: "L-type (single angle, standard for thin-set epoxy)"
+```
+
+```datasheet
+label: Divider Strip Gauge
+type: select
+unit: B&S gauge
+options:
+ - "14 gauge"
+ - "16 gauge"
+ - "18 gauge"
+default: "16 gauge"
+```
+
+Divider strip gauge is specified in Brown & Sharpe (B&S) gauge; 16 gauge is the standard for thin-set epoxy terrazzo, with 14 gauge used for heavier or wider strips and 18 gauge for the finest lines. The strip depth shall match the nominal system thickness so that the top of the strip finishes flush with the ground terrazzo surface.
+
+## Control-Joint Strips
+
+```datasheet
+label: Control-Joint Treatment Over Slab Joints
+type: radio
+drawing_ref: true
+options:
+ - "Divider strip directly over every slab control and construction joint"
+ - "Flexible epoxy crack-isolation membrane over slab joints in lieu of strips"
+ - "Both — membrane plus aligned divider strip"
+default: "Divider strip directly over every slab control and construction joint"
+```
+
+Every slab control joint and construction joint shall be honored in the terrazzo above it, because the joint will move and any movement that is not relieved at the surface will crack the terrazzo. The standard treatment is a divider strip placed directly over and aligned with each slab joint, so that the joint in the finish coincides with the joint in the slab. As an alternative or supplement, a flexible epoxy crack-isolation membrane may be applied over the slab joints and known cracks beneath the terrazzo to absorb movement; this is required where the design calls for a jointless field across a slab that is jointed. The Contractor shall not place terrazzo across a slab control joint without either an aligned divider strip or a crack-isolation membrane — doing so guarantees a reflective crack. Joint and crack-isolation locations shall follow the [[drawing: slab joint plan and terrazzo layout plan]].
+
+## Expansion Joints
+
+```datasheet
+label: Expansion Joint Treatment
+type: radio
+drawing_ref: true
+options:
+ - "Carry building expansion joints full-depth through the terrazzo with a compressible joint and cover"
+ - "No building expansion joints within the terrazzo area"
+default: "No building expansion joints within the terrazzo area"
+```
+
+Building expansion joints shall be carried full-depth through the terrazzo system and finished with a compressible joint filler and an appropriate joint cover; terrazzo, divider strips, and matrix shall never bridge a building expansion joint, because the differential movement at an expansion joint is far greater than any surface strip or membrane can absorb. Expansion-joint locations are determined by the [[drawing: structural and architectural drawings]].
+
+# Crack Isolation and Substrate Preparation
+
+## Slab Preparation
+
+The slab shall be prepared in accordance with the matrix manufacturer's instructions and NTMA recommendations: structurally sound, fully cured, clean, and free of dust, paint, oil, grease, curing and sealing compounds, laitance, and any other bond-inhibiting substance. The standard preparation for epoxy terrazzo is mechanical abrasion — shot-blasting or diamond grinding — to remove surface contaminants and laitance and to open the surface to a profile that the primer can key into. Acid etching shall not be substituted for mechanical preparation for epoxy terrazzo, because etching leaves residue and does not reliably remove curing compounds. The condition of the slab is the Contractor's responsibility to verify before placement; placing terrazzo over a noncompliant slab transfers a known defect into a finish that cannot later be lifted and corrected without full removal.
+
+## Flatness
+
+```datasheet
+label: Slab Flatness Tolerance Before Terrazzo
+type: radio
+unit: in / 10 ft
+options:
+ - "1/4 in in 10 ft (standard for thin-set epoxy)"
+ - "1/8 in in 10 ft (where a tighter finish is required)"
+default: "1/4 in in 10 ft (standard for thin-set epoxy)"
+```
+
+The slab to receive epoxy or other thin-set terrazzo shall be flat within a maximum variation of 1/4 inch in 10 feet and finished with a steel trowel, because a thin-set system follows the slab and cannot correct slab unflatness — the terrazzo thickness is nearly constant, so a wavy slab produces a wavy floor. High spots shall be ground down and low spots filled with a patching compound compatible with the matrix and primer. Where the slab cannot be brought into tolerance, a cementitious self-leveling underlayment approved by the matrix manufacturer shall be installed to establish the required plane before priming.
+
+## Crack-Isolation Membrane
+
+```datasheet
+label: Crack-Isolation Membrane Extent
+type: radio
+drawing_ref: true
+options:
+ - "Over slab joints and observed cracks only"
+ - "Full-coverage crack-isolation / anti-fracture membrane over entire field"
+ - "None — divider strips aligned to all slab joints"
+default: "Over slab joints and observed cracks only"
+```
+
+A flexible epoxy crack-isolation (anti-fracture) membrane shall be applied over slab control joints, construction joints, and observed cracks before the terrazzo is placed, to absorb the small in-plane movement at those locations and prevent it from reflecting into the rigid terrazzo veneer. Full-coverage membrane over the entire field is specified where the slab is of uncertain crack history, where a continuous jointless appearance is required across a jointed slab, or where the matrix manufacturer requires it for the measured slab condition; full coverage adds cost but is the most reliable defense against reflective cracking. Membrane shall be rated and installed per its manufacturer's instructions and shall be compatible with the matrix primer.
+
+## Moisture-Vapor Mitigation
+
+```datasheet
+label: Moisture-Vapor Mitigation
+type: radio
+drawing_ref: true
+options:
+ - "None required — slab passes F2170/F1869 within matrix limits"
+ - "Epoxy vapor-mitigation coating rated for measured slab RH"
+default: "None required — slab passes F2170/F1869 within matrix limits"
+```
+
+Where the measured slab relative humidity or moisture vapor emission rate exceeds the matrix system's limit, an epoxy vapor-mitigation coating shall be applied to the prepared slab before priming and placement, rated by its manufacturer for the relative humidity actually measured at the slab. A coating rated to a lower relative humidity than the slab exhibits will blister and debond, taking the terrazzo with it; the mitigation coating is selected to the measured condition, not a generic value, and is part of the bonded system below the primer.
+
+# Installation
+
+## Layout
+
+The Contractor shall establish the divider-strip layout, pattern, logo, and aggregate-blend boundaries from the control lines and details shown on the [[drawing: terrazzo layout plan]], coordinated with the slab joint locations so that control-joint strips align with slab joints and field strips produce a balanced pattern. Strips shall be set and secured before matrix placement and shall be dry-fit and approved where the pattern is intricate. A terrazzo floor laid without a coordinated layout produces strips that miss the slab joints, unbalanced borders, and patterns that fail to align through openings.
+
+## Matrix Placement and Seeding
+
+The matrix shall be mixed in the proportions and with the aggregate loading the manufacturer specifies, placed between the set strips, screeded to the top of the strips, and seeded with additional broadcast aggregate as required to achieve the specified aggregate density and distribution before the matrix gels. Epoxy matrix has a limited pot life and working time that shorten as temperature rises; the Contractor shall mix only the quantity that can be placed, seeded, and rolled within the working time, and shall not retemper gelled material. Aggregate density at the surface is what gives terrazzo its characteristic appearance — under-seeding leaves excessive visible matrix between chips, and the seeding rate shall match the approved sample and mock-up.
+
+## Curing
+
+The placed matrix shall cure undisturbed for the period and at the conditions the manufacturer specifies before grinding begins. Grinding into an under-cured epoxy matrix tears and smears rather than cutting, dislodges aggregate, and produces a defective surface; the Contractor shall confirm full cure by the manufacturer's method before the first grind.
+
+## Grinding
+
+```datasheet
+label: Grinding Method
+type: radio
+options:
+ - "Wet grinding"
+ - "Dry grinding with dust collection"
+default: "Wet grinding"
+```
+
+After cure, the terrazzo shall be ground to expose the aggregate and produce a flat, uniform surface, beginning with a coarse abrasive to cut down to the aggregate and progressing through successively finer abrasives. Wet grinding is the traditional method and controls dust and heat; dry grinding with continuous high-efficiency dust collection is used where water cannot be introduced into the space. The first grind shall remove enough matrix to expose the aggregate uniformly across the full field, including tight to strips and into corners, where a hand or edge grinder shall be used so that the edges match the field.
+
+## Grouting
+
+After the initial grind, the surface shall be grouted with a matrix-compatible grout worked into the pinholes and voids opened by grinding, then cured, to produce a void-free surface. Grinding inevitably opens small voids and pinholes at the aggregate-matrix interface; grouting fills them so that the polished surface is dense and continuous rather than pitted. Cement-matrix systems are grouted with a cementitious grout; epoxy systems are grouted with a compatible epoxy grout.
+
+## Polishing
+
+```datasheet
+label: Surface Finish
+type: radio
+drawing_ref: true
+options:
+ - "Polished (high gloss)"
+ - "Honed (satin, lower gloss for slip resistance)"
+default: "Polished (high gloss)"
+```
+
+After grouting and cure, the floor shall be polished through progressively finer grits to the specified finish. A high-gloss polished finish is the conventional terrazzo appearance and is the default; a honed satin finish is specified where a lower-gloss appearance or improved wet slip resistance is required, and at ramps, entries, and wet areas the finish should be honed or treated for slip resistance even where the field is polished. The final finish shall match the approved mock-up.
+
+## Sealing
+
+The finished terrazzo shall be cleaned and sealed with a sealer recommended by the matrix manufacturer for the system and finish, applied after the floor is fully cured and clean. The sealer is what resists staining and eases maintenance; cementitious terrazzo, being more porous, depends more heavily on sealing than epoxy terrazzo, but both shall be sealed. The sealer shall be compatible with the matrix and shall not reduce the dynamic coefficient of friction below the specified slip-resistance value.
+
+# Base and Stair Treads
+
+## Integral and Topset Base
+
+```datasheet
+label: Base Type
+type: select
+drawing_ref: true
+options:
+ - "Integral cove base (terrazzo coved up from floor)"
+ - "Topset terrazzo base (precast or cast against wall)"
+ - "Precast terrazzo base units"
+ - "No terrazzo base"
+default: "Integral cove base (terrazzo coved up from floor)"
+```
+
+Where a terrazzo base is specified, an integral cove base — the floor terrazzo coved up the wall over a cove former and ground continuous with the floor — provides the most durable and cleanable wall-to-floor junction with no joint for dirt to collect, and is the default where the wall construction permits. A topset base is a separate terrazzo base set against the finished wall where an integral cove is not practical. Precast terrazzo base units are shop-cast, ground, and polished and set in place, and are used where field placement is impractical or where a crisp factory edge is required. Base height, profile, and cove radius shall be as shown on the [[drawing: base details]].
+
+## Precast Terrazzo Treads and Risers
+
+```datasheet
+label: Precast Terrazzo Stair Components
+type: checkbox
+drawing_ref: true
+options:
+ - "Treads"
+ - "Risers"
+ - "Stringers / skirts"
+ - "Landings"
+ - "Abrasive nosing strips at treads"
+default: "Abrasive nosing strips at treads"
+```
+
+Where terrazzo stairs are specified, treads, risers, stringers, and landings shall be precast, ground, and polished in the shop using the specified matrix and aggregate to match the field, and set in place. Treads shall incorporate an abrasive nosing strip or an abrasive aggregate band at the leading edge for slip resistance and code-compliant visual contrast, because a polished terrazzo stair nosing is otherwise slick and hazardous. Precast component dimensions, profiles, and the nosing detail shall follow the [[drawing: stair details]] and comply with the applicable accessibility and stair-geometry requirements of the building code.
+
+# Field Testing
+
+## Moisture Test Verification
+
+The Contractor shall not place terrazzo until the documented ASTM F2170 relative-humidity results, and ASTM F1869 emission results where used, confirm the slab is within the matrix manufacturer's governing limit, or until the specified vapor-mitigation coating has been installed and confirmed for the measured relative humidity. The moisture-test record is the documentary basis for the matrix warranty and shall be retained in the closeout submittals.
+
+## Bond and Surface Inspection
+
+```datasheet
+label: Post-Installation Inspection Required
+type: radio
+options:
+ - "Yes — full-floor inspection under permanent lighting for bond, cracks, and finish"
+ - "No"
+default: "Yes — full-floor inspection under permanent lighting for bond, cracks, and finish"
+```
+
+After finishing and sealing, the floor shall be inspected under permanent or equivalent lighting for full bond (no drummy or hollow areas, verified by sounding), uniform aggregate exposure and density, absence of cracks and pinholes, flush and aligned strips, uniform color and finish, and a continuous base and tread detail. Drummy areas indicate a bond failure and shall be removed and replaced; pinholes indicate incomplete grouting and shall be re-grouted and re-polished. Where bond strength is in question, a pull-off test per ASTM D4541 may be performed.
+
+# Cleaning and Protection
+
+After sealing, the floor shall be cleaned of all construction residue by the method the matrix manufacturer specifies and protected from traffic and other trades until the project is turned over, using a breathable protective covering that does not trap moisture against the floor or transfer color. Terrazzo is durable but is finished early enough in many projects that it is exposed to heavy trade traffic; staining from spilled construction materials and scratching from dragged equipment are the common construction-phase damages and shall be prevented by protection rather than corrected by re-grinding. Non-breathable sheeting taped directly to a freshly sealed floor shall not be used, because it can trap moisture and discolor the sealer.
+
+# Delivery, Storage, and Handling
+
+Matrix components, aggregate, strips, membrane, and sealer shall be delivered in the manufacturer's original unopened packaging with labels intact, identifying product, color, and batch. Epoxy matrix components have a limited shelf life and a storage temperature range below and above which they are damaged; material that has frozen, exceeded its shelf life, or been stored outside its temperature range shall be discarded. Aggregate shall be kept dry and clean, because moisture and contamination on the aggregate interfere with matrix wetting and bond. All aggregate for a continuous area shall be from the same source and batch wherever possible, because natural aggregate color and pattern vary between batches and a batch change within a single visual field will be apparent.
+
+# Warranty
+
+```datasheet
+label: Installer Workmanship Warranty Period
+type: select
+options:
+ - "1 year from substantial completion"
+ - "2 years from substantial completion"
+default: "2 years from substantial completion"
+```
+
+The Contractor shall warrant the terrazzo installation — including substrate preparation, crack isolation, bond, matrix placement and finishing, strips, base, and sealing — against defective workmanship for the period stated. The matrix manufacturer shall warrant the matrix system materials against defects. The Contractor shall be aware that most matrix warranties are void unless the slab moisture and relative-humidity conditions were within the system's stated limits and documented at the time of placement; the moisture-test record is therefore part of the warranty basis and shall be retained and delivered. Reflective cracks arising from slab control or construction joints that were not isolated, and failures arising from subsequent structural movement, water intrusion, or maintenance contrary to the manufacturer's instructions, are evaluated against the as-built crack-isolation detailing.
+
+```datasheet
+label: Matrix Manufacturer Material Warranty Period
+type: select
+unit: years
+options:
+ - "1 year"
+ - "5 years"
+ - "10 years"
+default: "1 year"
+```
+
+# Spare and Extra Materials
+
+```datasheet
+label: Attic Stock Quantity
+type: range
+unit: % of installed area
+options:
+ min: 1
+ max: 3
+ step: 1
+default: 2
+```
+
+The Contractor shall deliver to the Owner spare matrix and aggregate of each color and blend installed, in the percentage of installed area stated, in unopened original packaging labeled with the matrix color and aggregate blend and batch. Because terrazzo is repaired by grinding out and re-pouring a patch with matching matrix and aggregate, attic stock of the original materials allows a future repair to be blended into the floor; a later-purchased replacement aggregate from a different batch will not match the surrounding field. Spare material shall be stored by the Owner in the conditioned environment the manufacturer recommends.