Specification:Adobe properties and in-kind replacement

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=GENERAL=

DESCRIPTION
 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. Site-specific specifications, when appropriate, will be provided by the Architect. 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, materials, 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
 Historic adobe properties Criteria for replacement Procedure for in-kind replacement</li> </ol>

RELATED SECTIONS
<ol type="A"> Section 04290.02 – Repair Through Patching, Surface Coatings, and Structural Supports</li> Section 04100.01 – Removal of Mortar Joints and Repointing</li> Section 04400.01 – Identifying Masonry Types and Failures</li> </ol>

DEFINITIONS
<ol type="A"> Raw Adobe or Natural Adobe. Adobe, or sun-dried bricks are never kiln fired. Unbaked adobe bricks consist of sand, silt, clay, and water mixed together by hand, formed in wooden molds, and dried by the sun.</li> Stabilized Adobe. Stabilized adobe is common today, consisting of the same elements of raw adobe, but with the addition of stabilizers, i.e., cement, asphalt, and/or bituminous materials. Stabilized adobe differs from traditional raw adobes in appearance, permeability, and strength.</li> Adobe Mortar. Walls composed of raw adobe bricks are laid with mud mortar. The adobe mortar shall have the same components and characteristics as the material used as raw adobe bricks. Such mortar exhibits the same properties as the bricks: relatively weak and susceptible to the same rate of hygroscopic (moisture absorptive) swelling and shrinking, thermal expansion and contraction, and deterioration. Cement and lime mortars are incompatible with raw adobes.</li> </ol>

SUBMITTALS
<ol type="A"> The Contractor shall submit a detailed schedule of the work to be conducted, including an assessment of the problem areas, adobe analysis, and detailed procedures for adobe repairs, to the Architect for approval Analysis shall include both microscopical examination and sieve analysis of the historic material.</li> Product Literature: The Contractor shall submit manufacturer’s product literature to the Architect for all proprietary products proposed for adobe repairs and replacement. Product literature shall include specification data, Material Safety Data Sheets, and instructions for storage, handling, and use.</li> Samples:  The Contractor shall submit three (3) samples of proposed bricks for analysis by testing laboratory at the Owner’s expense, to determine that the compressive strength, soil components and sieve analysis are compatible with existing adobe. Multiple trial batches and tests of submitted samples may be necessary before a product is found to be compatible with the existing adobe bricks.</li> After approval of analysis, submit three (s) samples of finished bricks to the Architect to determine that the visual characteristics, texture and dimensions are compatible with existing adobe.</li> </ol> </li> </ol>

QUALITY ASSURANCE
<ol type="A"> Work Experience: The Contractor to perform the work in this section shall have a minimum of ten (10) years experience with historic adobe construction. He/she shall demonstrate a working knowledge of the Secretary of the Interior’s Standards for Guidelines for Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring, and Reconstructing Historic Buildings.</li> Contractor shall work in conjunction with the Architect and/or other preservation professional proficient in adobe preservation and stabilization.</li> Warranty: The Contractor shall provide a warranty in writing against defects in material and installation for a period of five (5) years.</li> </ol>

MOCK-UPS
<ol type="A"> The Contractor shall construct a sample adobe wall on-site, in a location as directed by the Architect, 4 feet high and 4 feet long, for approval by Architect. The sample shall serve as a guide for workmanship and a quality standard for all adobe work for the project.</li> <li>The Contractor shall provide an adobe plaster sample, 24 inches long and 24 inches high, applied to the building as directed by the Architect. If other adobe repairs are to be conducted, the plaster sample shall be applied to a portion of the masonry repair sample. See Section 04290.02, Repair Through Patching, Surface Coatings, and Structural Supports.</li> <li>The Contractor shall prepare up to three additional test panels at no additional cost without further compensation. Approved test area(s) shall become part of the work and shall serve as the quality standard for all subsequent work.</li> </ol>

DELIVERY, STORAGE AND HANDLING
<ol type="A"> <li>The Contractor shall store products in a dry location and protected from dampness and freezing.</li> <li>The Contractor shall stockpile and handle aggregates to prevent contamination from foreign materials. Store materials in separate piles to avoid intermingling.</li> </ol>

PROJECT / SITE CONDITIONS
<ol type="A"> <li>Adobe work shall be executed only when the air and surface temperatures are 40 degrees F and rising. Minimum temperature for adobe work shall be 40 degrees F and above for at least 2 hours after completion and above freezing for at least 24 hours after completion. Work shall not commence when rain, snow, or below-freezing temperatures are expected within the next 24 hours. All surfaces shall be free of standing water, frost, and ice.</li> <li>The Contractor is responsible for protecting existing adjacent materials and surfaces and substrate during the execution of the work, and shall provide all necessary protection and follow all necessary work procedures to avoid damage to existing material assemblies not a part of the work in this Section.</li> <li>The Contractor shall maintain a supply of tarpaulins or other waterproof materials at the site sufficient to cover all exposed areas of adobe in the event of inclement weather.</li> <li>The Contractor shall provide visible barriers and / or warning tape around the perimeter of the work area for visitor protection. Nearby vehicles and adjacent structures shall be protected from damage during the course of the work.</li> <li>The Contractor shall coordinate adobe work with the other trades involved in exterior and interior restoration work including but not limited to masonry, painting, roofing, and window and door repairs.</li> </ol> =PRODUCTS=

HISTORIC ADOBE PROPERTIES
<ol type="A"> <li>Material Makeup of Adobe Brick: Adobes are made of native soil that has sand, silt and clay as the primary components. The proportion of sand, silt, and clay determines the durability, strength, and shrinkage of the bricks. The bricks also gain strength with proper curing and length of drying time. Bricks are allowed to dry for approximately one month. Adobes may also include organic binders such as grass or straw, which can help the bricks to dry more uniformly and is important to note when replacing historic brick. Generally, the clay content of the soil should not exceed 30 percent and the sand content should be greater than 50 percent. <ol> <li>“Ideal” adobe has 70 percent sand, 15 percent silt, and 15 percent clay by weight.</li> <li>Uniform Building Code for new adobes requires 55 to 75 percent sand, 25 to 45 percent fines (silt and clay).</li> </ol> </li> <li>Size: Adobes are made by hand in forms and vary in size. Common brick sizes can range from 4x8x16 inches and weigh 28 pounds, to 5x12x18 inches and weigh 59 pounds.</li> <li>Durability: Adobes are a traditional building material used in the southwest since the sixteenth century and are well suited to arid climates. As the bricks are essentially dried mud and not fired in a kiln like clay bricks, they do not permanently harden. As a result, the adobe bricks remain unstable, are relatively weak, and are susceptible to swelling, shrinking, thermal expansion and contraction, and deterioration. Adobes continually swell and shrink with changes in moisture content, and they disintegrate when saturated in water. The strength of the adobe changes with moisture content; the greater the water content, the weaker the adobe. Adobe can also be affected by rising damp, a process where moisture (and salts) is absorbed from the ground. Salt accumulation contributes to deterioration of the adobe.</li> <li>Mortar: Adobe walls are constructed of adobe bricks laid with mud mortar. The mortar has the same soil composition as the adobe bricks and is usually made from the same material. Likewise, the mortar has the same properties as the adobe bricks. The mortar absorbs moisture and is also susceptible to swelling, shrinking, thermal expansion and contraction, and deterioration.</li> <li>Surface Coatings: Adobe requires regular and frequent maintenance. To protect the unstable and fragile nature of the adobe, traditional surface coatings are generally applied to both the interior and exterior adobe walls. Coatings include: mud plaster; lime plaster; whitewash; and stucco. Coatings applied to exterior adobe provide a renewable surface that helps to prevent surface deterioration.</li> <li>Related Construction Systems: <ol> <li>Building Foundations: Adobe buildings are usually constructed on foundations and rarely over basements or crawl spaces. Foundations are generally large and well constructed to support the weight of the adobe walls. Construction varied according to location and traditional building practices. Early foundations were often constructed of bricks, fieldstones, or cavity walls filled with rubble stone, tile fragments, or seashells.</li> <li>Roofs: Southwest adobe roofs constructed between the 1600s and 1800s were generally flat with low parapet walls. The roofs consisted of wooden poles supported by logs. The logs consisted of either undressed logs (called vigas) or shaped squared timbers, set 23 feet or less on center. These logs were set on the horizontal wooden member at the top of the wall or on decorated blocks (or corbels) set into the wall. The vigas or logs usually projected through the adobe wall, a traditional feature applied in later adobe revival buildings. Poles, 2 inches in diameter, or hand-split planks were placed on the vigas. Sawn boards (like those used for roof sheathing) became available after the arrival of rail transportation and were used on nineteenth- and twentieth-century buildings, as well as replacement materials on older structures. Wooden lath or twigs were applied over the poles and covered with at least six inches of packed adobe earth, which was then coated with adobe mud. The flat roof sloped to funnel the water to drains that projected through the parapet. These drains were made from hollow logs, tile, or sheet metal. During the nineteenth and twentieth centuries, gabled roofs gained popularity. Regional revival or Territorial styles developed with corresponding regional material preferences, such as roof tiles in southern California and metal roofs in New Mexico.</li> <li>Floors: Historically, floors of adobe buildings were installed on the ground with little or no subfloor. Flooring materials included: earth; adobe brick; fired brick; tile; flagstone; and wood.</li> </ol> </li> </ol>

MATERIALS
<ol type="A"> <li>Soil for adobe mud mortar and bricks: The Contractor shall provide soil to match closely the strength, component soil mixture, texture, and color of existing adobe in building walls. <ol> <li>The mix shall approximate the relative sand-silt-clay proportions of the existing adobe within a tolerance of plus or minus 10 percent.</li> <li>The Contractor shall arrange for soil component hydrometer tests and compression tests of representative samples from the historic adobe brick types. The Contractor shall coordinate removal of sample bricks from the building with the Architect. The Contractor shall also arrange for hydrometer and compression tests of new bricks to confirm compatibility.</li> <li>Dried bricks made from such soil shall have a compressive strength similar to that of adobe bricks in the existing building, within a tolerance of plus or minus 100 psi.</li> <li>The color of the new bricks and mortar shall match that of the existing adobe brick colors. The Contractor shall match the historic adobe bricks, NOT brick that may result from poorly matched contemporary repairs.</li> </ol> </li> <li>Methods of material supply: Soil to match historic adobe may be a locally obtained material with no formal, readymade supply or suppliers. <ol> <li>Soil for adobe bricks and mortar may be tested or field matched from local soil samples; method for soil matching is to be determined by the Architect. When soil is field matched, test samples of possible soil matches are taken and placed in a glass jar (mason jar tested) with water to settle for 1 to 2 weeks. The settlement is compared with a similar test conducted on the historic brick, whereby a sample is taken, crushed, and placed in a glass jar with water to settle for 1 to 2 weeks. For commercially available materials, compare any available sieve analysis to that of historic material.</li> <li>Arrangement for the excavation and acquisition of soil and permission to access soil not on the Owner’s property must be obtained by the Contractor with the approval of the Architect. Any additional consultation required in order to acquire the appropriate type of sand is not covered under the terms of this specification and must be completed under IAW applicable laws (NAGPRA, ARPA, NHPA).</li> </ol> </li> <li>Water used in the fabrication of adobe bricks and mortar shall be clean and potable.</li> </ol>

FABRICATION
<ol type="A"> <li>The Contractor shall form soil materials into adobe blocks: <ol> <li>Net size of blocks after drying shall match the dimension of the existing historic bricks. The Contractor shall verify size in field.</li> <li>The Contractor shall form bricks in solid forms using sufficient moisture to form solid compact units without causing excessive shrinkage cracks.</li> <li>Bricks should be dried until they reach a moisture content of less than 20 percent, OR for a minimum of 28 days prior to testing and/or laying. Dry units shall be below 20 percent moisture content before use.</li> <li>Drop Test: Once the adobe bricks are sun-dried, the Contractor shall randomly test blocks for strength and outcome of each batch of brick. This test shall be accomplished by holding brick shoulder height (approximately 5 feet from the ground) and dropping it on its corner. Well-made brick will remain intact; inferior blocks will break upon impact. Do NOT use the inferior adobe bricks.</li> </ol> </li> </ol>

EQUIPMENT
<ol type="A"> <li>Adobe Repair <ol> <li>Saw, chisel, mason’s hammers</li> <li>Trough, wheelbarrow, plastic buckets, hoe, hawk, trowel, burlap (clean, undyed, and unprinted).</li> <li>Natural bristle or nylon brushes (metal bristle brushes are NOT to be used).</li> <li>Trowel, large grout gun</li> </ol> </li> </ol> =EXECUTION=

GENERAL
<ol type="A"> <li>The Contractor shall document existing adobe construction data to include: <ol> <li>Size of adobe brick units.</li> <li>Bonding pattern.</li> <li>Size of mortar joints.</li> <li>Coating material(s).</li> <li>Attachment method (if applicable).</li> </ol> </li> <li>Assessment of Adobe Deterioration. The Contractor shall: <ol> <li>Determine the nature and extent of the deterioration.</li> <li>Identify the source of the problem causing the deterioration. The source causing the deterioration is to be repaired prior to start of the work in this section.</li> <li>Develop rehabilitation and restoration plans for review by the Architect that are sensitive to the integrity of the historic adobe building. Submit a schedule of all work included in this section. Also refer to Section 04290.02, Repair Through Patching, Surface Coatings, and Structural Supports.</li> </ol> </li> <li>Rehabilitation and replacement of adobe building materials shall be done with the same types of materials used originally with the same construction techniques. Building materials should be traditional materials crafted by hand as outlined above. The Contractor shall NOT substitute modern materials or add portland cement or lime to the traditional mud bricks or mortar.</li> <li>Existing wall repair work under this section shall be performed in phases as approved by the Architect. For large wall expanses, work shall be done in phases of 2-foot-wide vertical sections separated by at least 4 feet of wall left undisturbed during that phase. Appropriate shoring and bracing shall be provided during the wall repair work. Demolition and wall repair shall be performed in each phase, with each phase completed before commencing the following phase. No more than one third of a wall area shall be undergoing stabilization or replacement at any given time.</li> <li>All wall repair work under this section shall be undertaken with other Adobe repairs as outlined in Section 04290.02, Repair Through Patching, Surface Coatings, and Structural Supports.</li> <li>Construction of new adobe walls and/or adobe bricks to replace those that are missing shall use techniques, methods and materials as similar as possible to those of the original walls. Reconstruction of wall(s) should 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>Shoring and bracing. The Contractor shall provide sufficient appropriate bracing on both sides of the walls at high and low levels to ensure stability of the walls during repair. The Contractor shall provide bracing diagrams and a safety plan for review by the Architect.</li> </ol>

REPLACEMENT PROCEDURES FOR HISTORIC ADOBE
<ol type="A"> <li>Plaster removal. The Contractor shall remove exterior plaster in areas to be repaired. The Contractor shall: <ol> <li>Sawcut plaster to isolate the sections being repaired. For large areas, the Contractor shall cut and isolate the 2-foot section to be worked on.</li> <li>Remove plaster finish in each section. Breaking up of plaster and concrete shall be done by hand, taking care to minimize damage to the adobe wall behind.</li> <li>Retain exterior plaster finish in sections not in the phase of work undertaken. The Contractor shall NOT remove all plaster at one time from the wall to be repaired.</li> </ol> </li> <li>Patching and Repair of Adobe Brick: see Section 04290.02, Repair Through Patching, Surface Coatings, and Structural Supports.</li> <li>Adobe Brick Unit Replacement: <ol> <li>If a substantial amount of the brick has been destroyed or spalled, the Contractor shall use whole adobe bricks and half-bricks for repairs.</li> <li>The deteriorated adobe bricks shall be scraped out to insert the new bricks, and sections of deteriorated brick shall be removed.</li> <li>If most of the brick is not deteriorated, but losses are greater than ½ inch, then the deteriorated portion may be replaced with a half-brick.</li> <li>The Contractor shall cut back into the deteriorated portions of the brick to achieve a flush fit of the new brick or half-brick.</li> <li>The Contractor shall spray (DO NOT SOAK) the new brick and surrounding area lightly with water to facilitate a better bond. Too much moisture can cause swelling.</li> </ol> </li> <li>Replacing Adobe Mud Mortar: <ol> <li>Match the original material, color, and texture of the adobe mortar. The Contractor shall NOT replace adobe mud mortar with lime mortar or portland cement mortar. It is a common error to assume that mortar hardness or strength is a measure of its suitability in adobe repair or reconstruction. Mortars composed of portland cement or lime do not have the same thermal expansion and contraction of adobe bricks. Portland cement and lime mortars will cause the bricks—the weaker material—to crack, crumble, and eventually disintegrate.</li> <li>Scrape out the deteriorated adobe bricks to insert the new bricks and remove sections of deteriorated brick.</li> <li>The procedure for pointing adobe is similar to pointing masonry joints. The adobe bricks should be sprayed lightly with water to increase the cohesive bond.</li> <li>Trowel adobe mud mortar to fill joints.</li> <li>Allow adobe bricks and mortar to dry in place a minimum of seven (7) days before continuing with the next phase of wall repair. If wet or unusually humid weather is encountered, or if it is evident for any reason that installation is not sufficiently dry, extend drying time accordingly.</li> <li>Protect exposed adobe with tarpaulins or other waterproof material overnight or if precipitation is expected. Do not allow exposed wall surfaces to become saturated.</li> <li>Remove shoring and bracing after wall repairs have been completed.</li> <li>Generally, adobe has an added layer of protection, a surface coating. The Contractor shall test the historic coating to determine its composition and apply new surface coating that matches the original in color, texture, and material composition. The surface coating shall match the existing surface treatment of the adobe brick building. See Section 04290.02, Repair Through Patching, Surface Coatings, and Structural Supports.</li> </ol> </li> </ol>

FINAL REPORT
The Contractor shall: <ol type="A"> <li>Revisit the site with the Architect to compare the finish and color of the repair to see if the desired affect has been achieved after the brick repairs have been executed and new mortar has cured at least 30 days.</li> <li>Document the work and finished product with photographs.</li> <li>Provide a written summary of the project and results upon final inspection and approval. The summary shall outline steps taken or new findings not specified in the initial documentation.</li> </ol>