092400_PORTLAND_CEMENT_PLASTER_Addendum_4_06.03.25.pdf

Pinellas County Schools 09 24 00 Portland Cement Plaster

Facility Name: Northeast HS Roof Replacement - Buildings 3, 6, 19, & 28

PCS Project No.: 9505 / WDA 2412-02

Issued by WDA: 6/3/25

PART 1 - GENERAL

1.1 RELATED DOCUMENTS

A. Drawings and general provisions of Contract, including General and Supplementary Conditions and Division 01 Specification Sections, apply to this Section.

1.2 SUMMARY

A. This Sections includes the following:

1. Exterior Portland cement plasterwork (stucco) on metal lath and CMU.

2. Water resistive barrier

3. Metal furring and lathing.

4. Gypsum sheathing.

B. Related Sections include the following:

1. Division 05 Section “Cold-Formed Metal Framing” for structural, load-bearing

(transverse and axial) steel studs and joists that support lath and Portland cement plaster.

2. Division 06 Section “Rough Carpentry” for wood framing and furring, sheathing, and water- resistant barriers included in Portland cement plaster assemblies.

3. Division 07 Section “Joint Sealants” for sealants installed with exterior Portland cement plaster (stucco).

1.3 SUBMITTALS

A. Product Data: For each type of product indicated.

B. Samples for verification in units at least 12 inches square of each type of finish indicated, in sets for each color, texture, and pattern specified, showing the full range of variations expected in these characteristics.

1.4 QUALITY ASSURANCE

A. Mockups: Before plastering, install mockups of at least 100 sq. ft. (9 sq. m) in surface area to demonstrate aesthetic effects and set quality standards for materials and execution.

1. Install mockups for each type of finish indicated.

2. Approved mockups may become part of the completed Work if undistributed at time of Substantial Completion.

1.5 DELIVERY, STORAGE AND HANDLING

A. Deliver materials in original packages, containers or bundles bearing brand name and identification of manufacturer.

Facility Name: Northeast HS Roof Replacement - Buildings 3, 6, 19, & 28

B. Store materials inside, under cover and in manner to keep them dry, protected from weather, direct sunlight, surface contamination, aging, corrosion, and damage from construction traffic and other causes. Neatly stack gypsum lath flat to prevent deformation.

C. Handle gypsum lath to prevent damage to edges, ends or surfaces. Protect metal corner beads and trim from being bent or damaged.

1.6 PROJECT CONDITIONS

A. Comply with ASTM C 926 requirements.

B. Exterior Plasterwork:

1. Apply and cure plaster to prevent plaster drying out during curing period. Use procedures required by climatic conditions, including moist curing, providing coverings and providing barriers to deflect sunlight and wind.

2. Apply plaster when ambient temperature is greater than 40 deg F (4.4 deg C).

C. Environmental Requirements, General: Comply with requirements of referenced plaster application standards and recommendations of plaster manufacturer for environmental conditions before, during, and after plaster application.

D. Protect contiguous work from soiling and moisture deterioration caused by plastering.

Provide temporary covering and other provisions necessary to minimize harmful spattering of plaster on other work.

PART 2 - PRODUCTS

2.1 ACCEPTABLE MANUFACTURERS

A. Manufacturer: Subject to compliance with requirements, provide products of one of the following:

1. Manufacturers of Expanded Metal Lath:

a. Bostwick Steel Framing Company.

b. Chapman Industries.

c. Gold Bond Building Products Div., National Gypsum Company.

d. Milcor Division; Inryco, Inc.

e. United States Gypsum Company.

f. Western Metal Lath Company.

2. Manufacturers of Accessories:

a. Fry Reglet Corporation.

b. Gold Bond Building Products Div., National Gypsum Company.

c. Keene Corporation.

d. Vinyl Corp.

e. United States Gypsum Company.

3. Manufacturers of Gypsum Sheathing:

a. Gold Bond Building Products Div., National Gypsum Company.

b. United States Gypsum Company.

c. G-P Gypsum, Georgia-Pacific

4. Manufacturers of Metal Support:

a. Allied Structural Industries, Inc.

b. Bostwick Steel Framing Company.

c. Chicago Metallic Corporation.

d. Dale Industries, Inc.

e. Gold Bond Building Products Div., National Gypsum Company.

f. Milcor Division; Inryco, Inc.

g. Marino Industries.

h. United States Gypsum Company.

2.2 METAL SUPPORT FOR EXTERIOR SUSPENDED AND FURRED CEILINGS

(by delegated Engineer)

A. General: Size metal ceiling supports to comply with the following, unless otherwise indicated.

1. Portland Cement Plaster Installation: ANSI A42.3.

B. Wire for Hangers and Ties: ASTM A 641, Class 1 zinc coating, soft temper.

C. Rod Hangers: Mild steel, zinc or cadmium coating.

D. Flat Hangers: Mild steel, zinc or cadmium coated or protected with rust inhibitive paint.

E. Channels: Cold-rolled steel, 0.0598" min. thickness of base metal (uncoated), allowable bending stress of 18,000 psi, protected with rust inhibitive paint or galvanizing complying with ASTM A 525 for G 60 coating designation, and as follows:

1. Carrying Channels: 1-1/2-inch-deep x 7/16-inch-wide flanges, 475 lbs. per 1000 feet painted, 508 lbs. per 1000 feet galvanized.

2. Furring Channels: 3/4-inch-deep x 7/16-inch-wide flanges, 300 lbs. per 1000 feet painted, 316 lbs. per 1000 feet galvanized.

3. Provide hot dipped galvanized channels for exterior installations.

F. Hanger Anchorage Devices: Screws cast-in-place concrete inserts or other devices appropriate for anchorage for ceiling hangers and whose suitability for use intended has been proven through standard construction practices or by certified test data.

1. Size devices for 3 x calculated hanger loading except size direct pull-out concrete inserts for 5 x calculated hanger loading.

2.3 WATER-RESISTIVE BARRIER

A. Exterior Frame

1. Layer 1 - STO Guard VaporSeal 80263, spray applied, ready mixed air and vapor barrier membrane over sheathing board.

2. Layer 2 - 15# felts complying with ASTM D 226, Type 1. Over layer 1 under metal lath.

B. Exterior CMU

1. STO Extra Seal 80739, trowel applied water resistive barrier scratch coat over CMU.

2.4 LATH

A. Diamond Mesh Lath: Comply with the following requirements:

1. Configuration: Self-furring.

a. Weight: 3.4 lbs. per sq.yd.

b. Galvanized

B. Lath Attachment Devices: Devices of material and type required by referenced standards and recommended by lath manufacturer for secure attachment of lath to framing members and of lath to lath.

2.5 ACCESSORIES FOR PORTLAND CEMENT PLASTER (DESIGN BASIS)

A. General: Comply with ASTM C 1063 and coordinate depth of trim and accessories with thicknesses and number of plaster coats required.

1. CONTROL JOINTS/REVEALS ON CMU , VERTICAL AND HORIZONTAL

VINYL CORP ITEM 1558 (5/8” GROUND) CONTROL JOINT ACCESSORY.

2. EXPANSION JOINTS (AT ALL VERTICAL CMU CONTROL

JOINTS) VINYL CORP 5058-50 (5/8” GROUND) SLIP JOINT

ACCESSORY.

3. CASING BEADS @ CMU - VINYL CORP 6658W (5/8” GROUND) CASING

BEAD W/ WEEP HOLES SHOULD BE USED ALONG THE BOTTOM EDGE

OF ALL STUCCO – BOTTOM OF BEAD SHOULD BE FLUSH TO FINISH

FLOOR.

VINYL CORP 6658 (5/8” GROUND) CASING BEAD SHOULD BE AT ALL SIDES

AND TOP RUNS OF STUCCO. STUCCO CASING BEADS SHOULD BE HELD ¼”

AWAY FROM ALL STOREFRONT.

4. CONTROL JOINTS/REVEALS ON FRAME, VERTICAL AND

HORIZONTAL VINYL CORP ITEM 1578 (7/8” GROUND) CONTROL

JOINT ACCESSORY.

5. CASING BEADS @ FRAME- VINYL CORP 6678 (7/8” GROUND) CASING

BEAD SHOULD BE AT ALL SIDES AND TOP RUNS OF STUCCO. STUCCO

CASING BEADS SHOULD BE HELD ¼” AWAY FROM ALL STOREFRONT.

6. F CHANNEL REVEAL @ SOFFIT TO WALL – VINYL CORP FC578

(7/8” GROUND)

7. SOFFIT VENT – VINYL CORP CS78-200V.

2.6 PORTLAND CEMENT PLASTER MATERIALS

A. Base-Coat Cement: Type as indicated below:

1. Portland cement, ASTM C 150, Type I or III.

B. Finish Coat Cement: Type as indicated below:

1. Portland cement, ASTM C 150, Type I, white.

C. Factory-Prepared Finish Coat: Manufacturer’s standard product requiring addition of water only; white in color unless otherwise indicated.

1. Product: Subject to compliance with requirements, provide Oriental Exterior Finish

Stucco as manufactured by United States Gypsum Company.

D. Lime: Special hydrated lime for finishing purposes, ASTM C 206, Type S.

E. Sand Aggregate for Base Coats: ASTM C 897.

F. Aggregate for Finish coats: ASTM C 897.

2.7 GYPSUM SHEATHING: ASTM C 1177, with glass mats both sides and long edges and water-resistant core.

1. Type: Plain, square edged.

2. Thickness: 5/8”

2.8 PORTLAND CEMENT PLASTER MIXES AND COMPOSITIONS

A. General: Comply with ASTM C 926 for Portland cement plaster base and finish coat mixes as applicable to plaster bases, materials and other requirements indicated.

1. Fiber Content: Add fiber to base-coat mixes after ingredients have mixed at least two minutes.

Comply with fiber manufacturer’s written instructions for fiber quantities in mixes, but do not exceed 1 lb of fiber/cu. Ft. of cementitious materials. Reduce aggregate quantities accordingly to maintain workability.

B. Portland Cement Plaster Base Coat Mixes and Compositions: Proportion materials for respective base coats in parts by volume for cementitious materials and in parts by volume per sum of cementitious materials for aggregate to comply with the following requirements for each method of application and plaster base indicated. Adjust mix proportions below within limits specified to attain workability.

1. Three-Coat Work Over Metal Lath: Base coats as indicated below:

a. Scratch Coat: 1 part Portland cement, 0 to 3/4 parts lime, 2-1/2 to 4 parts sand.

(1) lb. chopped polypropylene fibers per bag of Portland cement.

b. Brown Coat: 1 part Portland cement, 0 to 3/4 parts lime, 3 to 5 parts sand.

2. Two Coat Work Cover Concrete Unit Masonry: Base coat as indicated below:

a. Scratch Coat: 1 part Portland cement, 3/4 to 1-1/2 parts lime, 1-1/2 to 4 parts sand.

(1) lb. chopped polypropylene fibers per bag of Portland cement

b. Brown Coat: 1 part Portland cement, 3/4 to 1-1/2 parts lime, 3 to 5 parts sand.

C. Factory-Prepared Portland Cement Finish Coats: Add water only; comply with finish coat manufacturer’s directions.

2.9 MISCELLANEOUS MATERIALS

A. Water for Mixing and Finishing Plaster: Potable, free of substances capable of affecting plaster set or of damaging plaster, lath or accessories.

B. Bonding Agent for Portland Cement Plaster: ASTM C 932.

C. Fiber for Scratch and Brown Coat: Polypropylene fibers, ½ inch (13 mm) long, free of contaminants, manufactured for use in Portland cement plaster.

D. Bonding Compound: ASTM C 932, when required.

E. Steel Drill Screws: For metal-to-metal fastening, ASTM C 1002 or ASTM C 954, as required by thickness of metal being fastened; with pan head that is suitable for application; in lengths required to achieve penetration through joined materials of not fewer than three exposed threads.

F. Fasteners for Attaching Metal Lath to Substrate: Complying with ASTM C 1063.

PART 3 - EXECUTION

3.1 EXAMINATION

A. Examine areas and substrates, with Installer present, and including welded hollow-metal frames, cast-in anchors, and structural framing, for compliance with requirements and other conditions affecting performance.

1. Proceed with installation only after unsatisfactory conditions have been corrected.

3.2 PREPARATION

A. Protect adjacent work from soiling, spattering, moisture deterioration, and other harmful effects caused by plastering.

B. Prepare solid-plaster bases that are smooth or that do not have the suction capability required to bond with plaster according to ASTM C 926.

3.3 INSTALLATION OF LATHING AND FURRING, GENERAL:

A. Portland Cement Plaster Lathing and Furring Installation Standard: Install lathing and furring materials indicated for Portland cement plaster to comply with ASTM 1063.

B. Isolation: Where lathing and metal support system abuts building structure horizontally, and where partition/wall work abuts overhead structure, isolate the work from structural movement sufficiently to prevent transfer of loading into the work from the building structure. Install slip or cushion type joints to absorb deflections but maintain lateral support.

1. Frame both sides of control and expansion joints independently, and do not bridge joints with furring and lathing or accessories.

C. Install supplementary framing, blocking, and bracing at terminations in the work and for support of fixtures, equipment services, heavy trim, grab bars, toilet accessories, furnishings, and similar work to comply with details indicated or if not otherwise indicated, to comply with applicable published recommendations of gypsum plaster manufacturer, or if not available, of “Gypsum Construction Handbook” published by United States Gypsum Company.

3.4 INSTALLING EXTERIOR NONSTRUCTURAL STEEL FRAMING (By Delegated

Engineer)

A. General: Comply with ASTM C 754 for installation of items not addressed in ASTM C 1063.

1. Comply with ASTM C 754 for installation of items not addressed in ASTM C 1063.

B. Install supplementary framing, blocking, and bracing at terminations in plaster assemblies to support fixtures, equipment services, heavy trim, grab bars, toilet accessories, furnishings, or similar construction.

3.5 INSTALLATION OF EXTERIOR CEILING SUSPENSION SYSTEMS (by Delegated Engineer)

A. Preparation and Coordination: Coordinate installation of ceiling suspension system with installation of overhead structural systems to ensure that inserts and other structural anchorage provisions have been installed to receive ceiling hangers in a manner that will develop their full strength and at spacings required to support ceiling.

B. Hanger Installation: Attach hangers to structure above ceiling to comply with

ML/SFA “Specifications for Metal Lathing and furring” and with referenced standards.

1. Do not attach hangers to metal deck tabs.

C. Install ceiling suspension system components of sizes and spacings indicated but not in smaller sizes or greater spacings than that required by referenced lathing and furring installation standards.

1. Wire Hangers: Space 8-gauge (0.16" diameter) wire hangers not over 4'-0" o.c.

parallel with, and not over 2'-0" perpendicular to, direction of carrying channels, unless otherwise indicated, and within 6" of carrying channel ends.

2. Carrying Channels: Space carrying channels not over 2'-0" o.c. with 4'-0" o.c. hanger spacing.

3. Furring Channels to Receive Metal Lath: Space furring channels not other 16" o.c.

for 3.4 lb. diamond mesh lath or 24" o.c. for 3.4 flat rib lath.

4. Furring Channels to Receive Gypsum Lath: Space furring channels not over 16" o.c.

for 3/8" thick, clip-attached gypsum lath, unless closer spacing indicated or required for fire-resistance rated assembly.

3.6 METAL LATHING

A. Install expanded metal lath for the following applications where plaster base coats are required. Provide appropriate type, configuration and weight of metal lath selected from materials indicated which comply with referenced lathing installation standards.

1. Suspended and Furred Ceilings: Minimum weight of diamond mesh lath, 3.4 lbs. per sq.yd.

3.7 GYPSUM LATHING

A. Install gypsum lath for the following applications using attachment method indicated where plaster base coats are required.

1. Suspended and Furred Ceilings: Attach lath to furring members with clips.

3.8 INSTALLATION OF PLASTERING ACCESSORIES

A. General: Comply with referenced lathing and furring installation standards for provisions and location of plaster accessories of type indicated. Miter or cope accessories at corners; install with tight joints and in alignment. Attach accessories securely to plaster bases to hold accessories in place and alignment during plastering.

B. Accessories for Portland Cement Plaster:

1. Corner Bead: Install at external corners.

2. Casing Beads: Install at terminations of plaster work unless otherwise indicated.

3. Control Joints: Install control joints at locations indicated on drawings.

a. As required to delineate plasterwork into areas (panels) of the following maximum sizes:

1) Vertical Surfaces: 144 sq. ft.

2) Horizontal and other Nonvertical Surfaces: 100 sq. ft.

b. At distances between control joints of not greater than 18 feet o.c.

c. As required to delineate plasterwork into areas (panels) with length-to-width ratios of not greater than 2-1/2:1.

d. Where control joints occur in surface of construction directly behind plaster.

e. Where plasterwork areas change dimensions, to delineate rectangular-shaped areas (panels) and to relieve the stress that occurs at the corner formed by the dimension change.

3.9 PLASTER APPLICATION, GENERAL

A. Prepare monolithic surfaces for bonded base coats and use bonding compound or agent to comply with requirements of referenced application standards for conditioning of monolithic surfaces.

B. Tolerances: Do not deviate more than 1/8" in 10'-0" from a true plane in finished plaster surfaces, as measured by a 10'-0" straightedge placed at any location on surface.

C. Sequence plaster application with the installation and protection of other work, so that neither will be damaged by the installation of the other work.

D. Bonding Compound: Apply on unit masonry and concrete plaster bases.

E. Plaster flush with metal frames and other built-in metal items or accessories which act as a plaster ground, unless otherwise indicated. Where plaster is not terminated at metal by casing beads, cut base coat free from metal before plaster sets and groove finish coat at the junctures with metal.

F. Number of Coats: Apply plaster of composition indicated, to comply with the following requirements and referenced standards.

1. Three Coats: Over metal lath – 7/8” overall thickness.

2. Three Coats: Over concrete unit masonry – 5/8” overall thickness

G. Concealed Plaster: Where plaster application will be concealed above suspended ceilings and similar locations, finish-coat may be omitted; where concealed behind cabinets and similar furnishings and equipment, apply finish-coat; where used as a base for adhesive application of tile and similar finishes, omit finish-coat and coordinate thickness with overall dimension shown, and comply with tolerances specified.

H. Relief from Stress

1. Provide incised control joints 1/4” depth in brown coat immediately after the initial set, in location indicated on drawings.

2. Where dissimilar materials abut and surfaces are to receive a continuous application of plaster, provide a continuous 8” wide strip of fiberglass mesh set in scratch coat, lapping 4” to either side of joint. EXCEPTION: Where cast in place concrete has been poured on or against masonry, the joints do not require reinforcing.

I. Curing

1. ASTM C 926 – 17 Section 8, Curing and time between coats – Section 8.1, 8.2 Appendix X 1.4.2.

2. Scratch coat: Moist cure a minimum of 48 hours unless next coat is applied between 4 and 12 hours of installing scratch coat. Maintain finished work in a continuously moist condition indicated by surface having uniform A “dark gray” color.

a. Moist curing shall be executed using a nursery fogging nozzle, applying a light mist to the stucco. Do not saturate the stucco. Surface shall be free of visible water prior to application of the next coat of stucco.

3. Brown coat: Moist cure a minimum of 48 hours. Maintain finished work in a continuously moist condition indicated by surface having uniform dark gray color.

4. Finish coat: Moist cure a minimum of 72 hours after applying finish coat. Maintain finished work in a continuously moist condition indicated by surface having a uniform dark gray color.

5. Final cure: Allow a minimum of 21 days before the application of sealer paint.

3.10 PORTLAND CEMENT PLASTER APPLICATION

A. Portland Cement Plaster Application Standard: Apply Portland cement plaster materials, compositions, and mixes to comply with ASTM C 926.

B. Number of Coats: Apply Portland cement plaster, of composition indicated, to comply with the following requirements:

1. Use three-coat work over the following plaster bases:

a. Metal lath.

b. Concrete unit masonry.

2. Finish Coat: Floated sand finish / Heavy textured finish per exterior elevations and Architect’s approved sample for texture.

C. Curing: Moist cure Portland cement plaster base and finish coats to comply with

ASTM C 926, including recommendations for time between coats and curing in “Annex A2 Design Considerations.”

3.11 CUTTING AND PATCHING

A. Cut, patch, point-up and repair plaster as necessary to accommodate other work and to restore cracks, dents and imperfections. Repair or replace work to eliminate blisters, buckles, excessive crazing and check cracking, dry-outs, efflorescence, sweat-outs and similar defects, and where bond to the substrate has failed.

3.12 CLEANING AND PROTECTION

A. Remove temporary protection and enclosure of other work. Promptly remove cement plaster from door frames, windows, and other surfaces. Repair floors, walls and other surfaces which have been stained, marred or otherwise damaged during the plastering work. When plastering work is completed, remove unused materials, containers and equipment and clean floors of plaster debris.

END OF SECTION