Specification:Cast stone properties and repair

__NUMBEREDHEADINGS__

=GENERAL=

DESCRIPTION
 This specification provides guidance for repairing and replacing cast stone. This specification has been developed for use on historic properties (defined as any district, site, building, structure, or object that is listed in or eligible for listing in the National Register of Historic Places) and provides an overview of accepted practices. The Architect will provide site-specific specifications, when appropriate. All work described herein and related work must conform to the Secretary of the Interior’s Standards for the Treatment of Historic Properties. The Contractor shall provide all labor, material, equipment, and operations required to complete the rehabilitation work indicated herein. All work described herein and related work must have the approval of a Cultural Resources Manager, Conservator, Historic Architect, or other professional who meets the standards outlined in the Secretary of the Interior’s Standards – Professional Qualifications Standards pursuant to 36 CFR 61. Such person is referred to in this document as the Architect. 

SECTION INCLUDES
 Cast Stone Properties Criteria for Replacement</li> Procedure for In-Kind Replacement</li> Substitute Materials</li> </ol>

RELATED SECTIONS
<ol type="A"> 03710.01 – Cleaning and Testing of Atmospheric Soiling, Graffiti, Stains and Biogrowth on Historic Concrete</li> 03732.01 – Mechanical and Composite Historic Concrete Repair</li> 04100.01 – Removal of Mortar Joints and Repointing</li> 04100.02 – Preparation of Lime and Cement Amended Mortars</li> 04500 – Masonry Restoration</li> 04510 – Masonry Cleaning</li> </ol>

DEFINITIONS
<ol type="A"> Cast Stone: A manufactured concrete building unit made to simulate stone.</li> Dry Tamp: A process in which stiff, low slump concrete mix is pressed and compacted into molds. Generally, decorative aggregate is distributed at the exterior around a core of concrete.</li> Wet Cast: A plastic mix of concrete is poured and vibrated in molds. Decorative aggregate is dispersed throughout the unit.</li> </ol>

SUBMITTALS
<ol type="A"> Submit a detailed schedule to the Architect for approval of the work to be conducted, including an assessment of the problem areas, historic cast stone analysis, detailed procedure for cast stone replacement and repair.</li> Product Literature  Submit manufacturer’s product literature to the Architect for new cast stone or cast stone replacement material. Provide test data as described in Paragraph 1.07B below and technical data as required to demonstrate conformance with the referenced standards. Product literature shall also include Material Safety Data Sheets and instructions for storage, handling and use.</li> Submit manufacturer’s product data for all cast stone restoration materials including, but not limited to, patching materials, adhesives, anchoring devices and grouts.</li> </ol> </li> <li>Shop Drawings <ol> <li>Submit manufacturer’s shop drawings for review and approval by the Architect. Show dimensions, profiles and cross-sections of the cast stone replacement units. Show details of exposed faces and relationship to adjacent material in sufficient detail to address manufacture, handling and erection. Field verification of required dimensions is the responsibility of the Contractor and the cast stone manufacturer. Show arrangement of the joints and connections for fastening the block units. Identify anchorage, flashing, counter-flashing and accessory items. Details shall be at least half size. </li> <li>Assign each replacement unit a separate identification mark. Label units with this identification mark on the shop drawings to show the location of the replacement units for installation. Permanently mark each replacement unit with year of manufacture and identification.</li> </ol> </li> <li>Material Samples <ol> <li>Cast Stone Unit: Provide samples of new cast stone material. Submit at least three samples of each color and surface texture as required to match original material. Samples shall show the expected range of color and texture of surface finish. Samples selected and approved by Architect shall be standard for reproduction units.</li> <li>Anchors: Submit two of each of the dowels, anchors, bolts and fasteners to be used in the work under this section. Samples will be approved by the Architect</li> </ol> </li> <li>Test Reports <ol> <li>Arrange for sampling and testing of new cast stone prior to shipment in accordance with Paragraph 1.07B. Allow at least 30 days from time of sampling for completion of tests. Expense of sampling and testing shall be borne by the Contractor.</li> <li>All testing shall be performed by an independent testing facility meeting “Recommended Requirements for Independent Laboratory Qualifications” published by the American Council of Independent Laboratories and ASTM E 699.</li> </ol> </li> <li>Statement of Application. Submit letter from Manufacturer verifying that new cast stone units are suitable for intended use.</li> </ol>

QUALITY ASSURANCE
<ol type="A"> <li>Work Experience. The Contractor performing the work in this section shall have a minimum of seven years of recent experience in cast stone restoration and installation. Such experience must include projects of comparable scope to this project. The contractor shall demonstrate a working knowledge of The Secretary of the Interior's Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring and Reconstructing Historic Buildings.</li> <li>Testing. Where new cast stone is required, a minimum of six representative samples of existing cast stone material will be submitted for testing. The following tests will be undertaken by a laboratory that meets the conditions specified in 1.06 E above to correctly identify the characteristics of the original material: <ol> <li>Absorption</li> <li>Compressive Strength</li> <li>Petrographic Examination</li> <li>Coefficient of Thermal Expansion</li> </ol> </li> <li>Manufacturers <ol> <li>Obtain materials from manufacturers who will send a qualified technical representative to the project site for the purpose of advising the installer of the procedures and precautions for the use of their materials.</li> <li>Obtain cast stone units from an established specialty plant having the capacity and facilities for producing material of specified quality and finish, and in sufficient quantity so as to not delay progress of the work. Plant shall be that of a producer recognized by the industry as a manufacturer of this type of material and that can show successful completion of work of comparable quality and scope.</li> </ol> </li> <li>Fabrication. Do not proceed with fabrication of products prior to completed review and approval of shop drawings, and approval of material samples and mockup.</li> <li>Warranty. Installer shall provide a warranty, in writing, against defects in material and installation for a period of five years.</li> </ol>

MOCK-UPS
<ol type="A"> <li>Prior to the start of demolition and installation, install a single cast stone replacement unit at a location selected by the Architect. Demonstrate all methods, materials, and workmanship required for the project. <ol> <li>Do not proceed with further removals and replacements until mock-up is approved by the Architect.</li> <li>Retain mockups during construction as standard for judging complete work.</li> <li>Incorporate approved mock-up into the finished work as directed by the Architect.</li> </ol> </li> <li>The Contractor shall prepare up to three additional mock-ups at no additional cost to the Owner if required to achieve approval.</li> </ol>

DELIVERY, STORAGE AND HANDLING
<ol type="A"> <li>Materials shall be delivered to the site in original packaging, unopened, with manufacturer name and product identification thereon. Protect cementitious materials from contamination by foreign matter and deterioration by moisture or temperature. Store cementitious materials off the ground in a clean, dry location. Do not use contaminated or deteriorated material or products stored longer than six months.</li> <li>Inspect cast stone immediately upon delivery to site. Reject cast stone units damaged in transit or failing to meet specifications and samples. Rejected units should be stored off-site or returned to manufacturer. Notify manufacturer in writing of any materials that have been rejected.</li> <li>Store cast stone units on pallets or dunnage in an area away from general construction operations to avoid damage by other trades. Store units according to sequence of installation to avoid unnecessary handling of cast stone. Maintain units in their original packing material until ready for use. Crates shall not be stacked and shall remain in an upright position. Store units on a firm, level, smooth surface. Protect the units from weather before setting to prevent staining.</li> <li>Store materials so as not to interfere with the operation and daily maintenance of the facility. Proposed storage locations shall be approved by the Owner prior to the delivery of materials.</li> </ol>

SEQUENCING AND SCHEDULING
<ol type="A"> <li>Furnish the cast stone manufacturer with schedule of pieces to be manufactured and an installation sequence so that cast stone may be produced in the variety and quantity needed to match the installation sequence. <ol> <li>Provide for the manufacturer a photograph or isometric sketch showing the dimensions of each type of unit to be produced. Field verification of required dimensions is the responsibility of the Contractor and the cast stone manufacturer.</li> <li>Elevations and a site plan showing the location of units to be replaced.</li> <li>A performance specification based on original material and location conditions.</li> <li>An installation schedule showing piece counts and time frames for installation.</li> <li>At least three samples of the original material to be used for color matching and compatibility of the body and finish.</li> </ol> </li> <li>Schedule should reflect other considerations such as costs, weather, structural repairs, building use requirements.</li> </ol>

PROJECT/SITE CONDITIONS
<ol type="A"> <li>The normal temperature range for the work of this Section shall be when the air and surface temperatures are 40 degrees F and rising or less than 90 degrees F and falling. When temperatures are expected to fall outside this range, the Contractor shall employ hot and cold weather procedures as published by the Cast Stone Institute, Masonry Institute of America.</li> <li>The Contractor is responsible for protecting existing adjacent materials and surfaces during the execution of the work. Provide all necessary protection and work procedures to prevent damage to existing material assemblies not a part of the work in this Section. <ol> <li>Prevent masonry patching and setting materials from staining the face of masonry or other surfaces to be left exposed. Immediately remove all patching materials that come in contact with such surfaces. Protect sills, ledges and projections from mortar droppings.</li> <li>Minimize levels of dust during mortar removal and masonry demolition operations.</li> <li>Protect open copings, reglets and other vulnerable areas from water penetration to prevent leakage during the course of the work. Open areas shall not be left exposed overnight or when inclement weather is predicted.</li> <li>During cast stone work, temporarily remove and store metal downspouts and downspout boot covers. Install temporary drainage leaders if required. Reinstall immediately upon completion of work in the immediate area.</li> <li>Protect existing scuppers and downspout outlets from damage and accumulation of mortar debris during restoration of cast stone parapets.</li> <li>Where existing masonry components are to be removed, protect adjacent masonry units and surfaces from chipping and cracking during the removal process. Where components are to be reinstalled, the Contractor shall store salvaged components in a safe location. Protect from theft and damage until reassembly.</li> </ol> </li> <li>Provide visible barriers and/or warning tape around the perimeter of the work area for visitor protection. Protect nearby vehicles and adjacent structures from damage during the course of the work.</li> <li>Cover partially completed work when work is not in progress.</li> <li>The Contractor shall coordinate masonry repointing with the other trades involved in exterior and interior restoration work including—but not limited to—masonry cleaning, sealants, and painting.</li> </ol> =PRODUCTS=

CAST STONE DESIGN
<ol type="A"> <li>Cast stone units shall be outlined on Architectural Drawings with respect to exterior appearance and profile <ol> <li>Manufacture all pieces for particular installation conditions to minimize any cutting in the field. The Contractor shall adjust individual pieces to accommodate setting sequence. In concrete or steel frame building, the veneer or facing material should be fully and continuously supported at each floor level on shelf supports, of adequate strength and stiffness and rigidly connected to the structural frame. In all cases, steel shelf angles or supports should be located in mortar joints. The strength of the cast stone should not be unnecessarily reduced by cutting the webs that receive the steel.</li> <li>Adjust cast stone to accommodate relieving angles, vents, weeps, expansion joints, etc.           <li>Proper provision should be made for expansion joints, at shelf supports, over column cases, etc., to prevent the development of disruptive stresses caused by deflection, wind pressure, temperature changes, settlement and like forces.</li> <li>Properly constructed flashing should be provided.</li> <li>Reglets shall be provided to receive gutter linings and flashing when the joints cannot be used for the purpose. Reglets shall be not less than 3/4-inch deep, unless otherwise specified.</li> <li>The volume changes incident to the setting and hardening of concrete, and the variations in volume of concrete due to humidity and temperature conditions, require provisions that allow free movement of the supporting frame and make it undesirable to completely fill a facing applied to a concrete structure.</li> </ol> </li> </ol> </li> </ol>

CAST STONE PROPERTIES
<ol type="A"> <li>Cast stone to match existing units shall be fabricated using Portland cement, aggregates and pigments as required. Replacement cast stone shall meet the following requirements: <ol> <li>Compressive strength: 6500 psi minimum at 28 days in accordance with ASTM C 1194.</li> <li>Absorption: 6 percent maximum at 28 days in accordance with ASTM C 1195.</li> </ol> </li> <li>Cast stone materials <ol> <li>Portland Cement: ASTM C 150, Type I, gray or white, as required to match existing.</li> <li>Aggregate: Well-graded and washed sands and gravel meeting ASTM C 33.</li> <li>Pigments: Inorganic, lime-proof and non-fading mineral pigments.</li> <li>Reinforcing Steel (where required): New billet steel bars ASTM A 615, Grade 40 or 60, epoxy coated in accordance with ASTM D 3963.</li> </ol> </li> <li>Fabrication <ol> <li>Fabricate new cast stone units with a minimum wall thickness of one inch and partitions of such thickness and spacing as to provide maximum strength and reinforcement. Each piece shall be provided with the necessary anchor holes or slots and hand holes, formed so as to properly engage the anchor system with the substrate below.</li> <li>Fabricate new cast stone units to exactly match the dimensions, profiles and surface texture of the existing units. Exterior faces shall be plumb, straight and level. Molded edges shall be straight and crisp.</li> </ol> </li> </ol>

ACCESSORIES
<ol type="A"> <li>Anchors: Stainless steel, ANSI A167, type 316, 1/2-inch diameter round stock or square bars of equal cross section.</li> <li>Dowels: Threaded stainless steel, ANSI A167, type 316, 1/4-inch minimum diameter, by length required.</li> <li>Manufacturer ties and anchors, where required, shall be stainless steel or hot dipped galvanized steel.</li> </ol> =EXECUTION=

GENERAL
<ol type="A"> <li>Project-specific specifications are required for all cast stone work contained herein. As material and methods of construction vary greatly, each building must be evaluated and work scheduled accordingly. The Contractor shall submit schedules, including methods and materials to be used.</li> <li>Cast stone repair and replacement shall use techniques, methods and materials as similar as possible to those of the original. Work shall be sequenced not only to assure the stability of the structure and protection of personnel during the work, but also to address a sensible order of construction to integrate new work with existing work.</li> <li>The Contractor shall complete a survey to determine the extent and severity of the deterioration and whether the deterioration involves visual aspects of the surface of the cast stone, or (as appropriate) the failure of joints between units, the structural failure of the units themselves, the failure of support systems or the overall structural stability of the building façade. <ol> <li>Existing general failures that contribute to cast stone deterioration shall be noted and should be scheduled for repair prior to completion of the work scheduled or in conjunction with cast stone repair and replacement.</li> <li>The extent and type of material and structural analysis shall be determined by the Architect.</li> </ol> </li> <li>The Contractor shall protect adjacent materials, installed non-masonry materials and openings.</li> <li>Follow manufacturer instructions for mixing and installation of materials and equipment use.</li> <li>Façade cleaning shall be completed prior to beginning replacement work.</li> <li>Deteriorated and loose units that are not scheduled to be removed or that can not be easily removed shall be stabilized. Areas where units are missing or have been removed should be protected against moisture penetration until replacement units can be installed.</li> </ol>

REPAIR OR REPLACEMENT OF HISTORIC CAST STONE
<ol type="A"> <li>Assessing Need For Cast Stone Repairs: Often historic cast stone can be repaired in place or left untreated. As the cast stone weathers, it develops a patina of age that is lost when units are replaced. The following are common situations that require repair, but not necessarily replacement: <ol> <li>Separated Surface Facing: Utilize injection grouts to re-secure decorative facing that has detached from the core layers of dry tamped cast stone. Reattach with cementitious grouts or other compatible material.</li> <li>Reinforcement Spalls and Mechanical Damage: Repair damaged corners, drilled holes and spalls from rusting reinforcement bars and anchorage through composite repairs using compatible mortars formulated to match the color, texture and finish of the cast stone. Many of the methods are similar to those for stone masonry repairs. <li>Small Composite Repairs. Methods for composite repair of cast stone closely follow repairs used for stone masonry. Repairs to cast stone require that the cement matrix color and the aggregate size and coloration match the historic unit.</li> <li>Spalls Caused by Deteriorated Reinforcement or Anchors: Remove the cracked concrete in the area of the spall, remove rust and scale from the reinforcement, apply rust inhibiting primer, and apply cementitious composite patching material.</li> <li>Install new anchorage as required and/or install pins to support repairs. Follow procedures for repair of stone.</li> </ol> </li> <li>Surface Refinishing: It is extremely difficult to successfully match or restore the original patterned pigmentation once it has weathered away or otherwise been lost. Applied cementitious surface coatings are not recommended as they are visually incompatible, can trap moisture in the units, and cause surface spalling.</li> </ol> </li> <li>Accessing Replacement of Cast Stone <ol> <li>Individual Cast Stone Units: Deteriorated copings, balusters and railings which are exposed to weather and are located where disassembly will not damage adjacent surfaces, may require replacement. This should be determined in consultation with the Architect.</li> <li>Deterioration or Erosion of Cement Matrix: Deficiencies of the cementing mix and methods of manufacture in historic (pre-twentieth century) cast stone can cause flaking of exterior surfaces and porous concrete that is susceptible to frost damage and scaling.</li> <li>Rusting Reinforcement (Severe): Units exposed to heavy wetting and with reinforcement that is close (less than two inches) to the surface can lose alkalinity in the concrete, promoting rust. Severe splitting of the concrete and exposure of rusted reinforcement generally requires replacement.</li> </ol> </li> <li>Both structural and visual compatibility are major considerations when choosing replacement materials.</li> </ol>

IN KIND REPLACEMENT OF HISTORIC CAST STONE
<ol type="A"> <li>When replacing cast stone, all of the original deteriorated material should be completely removed. Half bricks or similar cosmetic replacement techniques are not recommended. <ol> <li>Remove the deteriorated units and anchoring. Anchoring must be replaced with new anchors when installing replacement units.</li> <li>Remove scaling and rust from any reinforcement. Prime with a rust inhibitor primer. Severely rusted units should be replaced.</li> <li>Retain the original backfill.</li> </ol> </li> <li>Prepare the area to accept new mortar. Area should be free from dust, dirt, mortar and other debris. Brush free of debris and dirt with a natural or nylon bristle brush. Do not use metal bristle brushes.</li> <li>Where applicable, replacement units should be anchored to the existing back-up masonry. Type and placement of anchors will be determined by the type and condition of the back-up masonry.</li> <li>The procedure for pointing cast stone is similar to pointing masonry joints. Surfaces should be well-sealed to prevent moisture penetration. Mortar should be compatible with current building conditions as well as the existing cast stone units. See Section 04100 Historic Mortar.</li> <li>Protect cast stone from splatter when using sealants and caulking. The units must be cleaned immediately.</li> </ol>

SUBSTITUTE MATERIALS
It is generally preferred to retain as much of the original fabric as possible and to replicate replacement units as closely as possible to match the original. For extensive projects, since most cast stone requires custom replication and expense, and the length of time to manufacture and install new units may hinder repairs, compatible substitute materials such as glass fiber reinforced concrete (GFRC) may be used. Its use and type requires evaluation; sampling to find the most desirable substitute that is compatible in material properties, weight, and finish; and approval by the Architect. GFRC is NOT appropriate for load bearing applications.

FINAL REPORT
<ol type="A"> <li>Document the work and the finished product with photographs taken before, during and after completion of the work.</li> <li>Provide a written summary of the project and results upon final inspection and approval. Outline steps taken or new findings not specified in the initial documentation.</li> </ol>