GPHQ_Addendum 3_0003.pdf

Repair Pemberton Headquarters Roof PAGE 1 of 1

ADDENDUM THREE

ADDENDUM NUMBER THREE

PROJECT:

Repair Pemberton Headquarters Roof, Front Porch and Exterior PMIS: 219142

SITE

1080 Crawford Street Vicksburg, Warren County, Mississippi

OWNER

NPS Interior Regions 1, 2, and 4 West MABO Atlanta Federal Center 1924 Building 100 Alabama Street SW Atlanta Georgia 30303

DESIGNER

Henry H. Lafferty, AIA Joseph K. Oppermann – Architect, P. A.

539 North Trade St.

Winston-Salem, NC 27101

(336) 721-1711

The following is intended to clarify and/or modify the Specifications and Drawings, for the project dated March 18, 2021 entitled: Repair Pemberton Headquarters Roof, Front Porch and Exterior.

I. PRIOR ADDENDA

A. Addendum Number One B. Addendum Number Two

II. PROJECT MANUAL/SPECIFICATIONS

A. Section 04 01 20.91 – Masonry Restoration & Repair: Replace

Included:

Replacement Specification listed above.

END – ADDENDUM THREE

GENERAL PEMBERTON’S HEADQUARTERS VICKSBURG, MS

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SECTION 040120.91 – MASONRY RESTORATION & REPAIR

PART 1 - GENERAL

1.1 RELATED DOCUMENTS

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

B. Section 09 97 26 Cementitious Coatings (Lime-based Stucco).

1.2 SUMMARY

A. The project involves the repair and repointing of brick masonry General Pemberton’s Head-quarters, located at the Vicksburg National Military Park. There may be a variety of mortar types found. Mortar to be repointed has deteriorated due to weathering.

B. Section includes:

1. Removal of all unsound mortar from exterior brick joints.

2. Repointing of exterior brick mortar joints with lime mortar where indicated.

3. Final cleaning.

1.3 REFERENCES

A. Publications listed are part of this specification to extent referenced.

B. Preservation Brief #2: Repointing Mortar Joints in Historic Masonry Buildings, Technical Preservation Services, National Park Service, Washington, DC 1998.

C. Brick Institute of America: Technical Note 1.

D. American Society for Testing and Materials:

ASTM C136/C136M-14 Standard Test Method for Sieve Analysis of Fine and Course Ag-gregates

ASTM C141/C141M-14 Standard Specification for Hydraulic Lime for Structural Purposes ASTM C144-11 Specification for Aggregate for Masonry Mortar

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ASTM C270-140 Specification for Mortar for Unit Masonry ASTM C979-C979 M-16 Standard Specification for Pigments for Integrally Colored Con-crete ASTM C1489-15 Standard Specification for Lime Putty for Structural Purposes

1.4 SUBMITTALS

A. Restoration Program: Submit a written program for each aspect of restoration process, in-cluding protection of surrounding materials on building and site during operations. Describe, in detail, methods and equipment to be used for each aspect of restoration work.

B. Product Data:

1. Hydrated Lime (Type S): Product Data Sheets.

2. Aggregate: Sieve Analysis for job sand.

C. Samples:

1. Submit one cup (8 oz.) sample of aggregate.

2. Submit one 4” x 4” x 3/4" dried mortar sample for each type of mortar specified.

3. Submit reproduction brick masonry materials proposed for use in replacing existing ma-sonry.

a) For each application, provide a minimum of five (5) bricks representing full range of color and texture to be expected in completed work.

D. Manufacturer's Instructions: Submit manufacturer's installation procedures that shall be basis for accepting or rejecting actual installation procedures.

E. Mason’s Qualifications: Submit mason’s qualifications prior to pre-installation conference.

1.5 QUALITY ASSURANCE

A. Qualifications:

1. Raking, repointing, removal, material salvage, and finishing operations shall be per-formed by craftspeople familiar with historic lime mortar formulations, curing conditions and performance characteristics.

2. Only skilled journeymen masons who are familiar and experienced with the materials and methods specified and are familiar with the design requirements shall be used for mason-ry restoration. Masons will be trained or qualified in installation techniques and proce-dures of restoration of historic masonry and will demonstrate experience with a minimum of five (5) historic preservation projects similar in scope to this work.

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3. Contractor will submit qualifications to Contracting Officer. Contraction Officer reserves right to reject masonry restoration technicians not meeting qualifications.

B. Field Samples:

1. Materials and techniques adopted shall do minimal or no damage to masonry substrates while achieving desired results.

2. Test Areas: Locate test areas in unobtrusive locations on representative conditions. Sam-ples shall employ procedures proposed for general restoration.

3. Test are shall be prepared for review by Contracting Officer and/or the Contracting Of-ficer.

4. Repointing test areas shall be prepared in two segments. Each segment shall be approxi-mately 3 courses high by 3 bricks wide. Adjust color and finish of repair mortar as di-rected by Contracting Officer.

b) Demonstrate methods and quality of workmanship for removal of mortar from joints

c) Demonstrate quality of materials and workmanship in pointing mortar joints.

5. Accepted test areas, materials, and procedures shall become standard for quality control of masonry restoration work and shall be left in place for duration of job. Accepted test areas may be incorporated into Work.

a) Test areas turned down by the Owner shall be removed and additional test areas will be prepared, at no additional cost to Owner, until quality of masonry restoration is acceptable to Contracting Officer and Contracting Officer.

6. Field Samples will be completed prior to final acceptance and execution of contract.

Owner reserves the right to terminate Contract should quality of workmanship in field sample(s) not meet approval of Contracting Officer and Owner.

C. Pre-Installation Conference:

1. The owner shall schedule a conference and inspection to be held prior to start of restora-tion work. Conference and inspection shall serve to clarify Contract Documents and res-toration requirements.

2. Conference shall be attended by the General Contractor, the Masonry Contractor and the Contracting Officer. A representative of the AE shall also attend if requested by the Con-tracting Officer.

3. Topics to be discussed at meeting will include:

a) Inspection of existing brickwork and stonework in walls.

d) A review of Contract Documents and accepted submittals shall be made and devia-tions or differences shall be resolved.

e) Review items such as application procedures and sequences. If conflicts exist be-tween what is considered good practice and Contract Documents, these differences shall be defined, resolved, and documented.

f) Review specific problem areas that are to receive special restoration techniques.

g) Establish which areas on Site will be available for use as storage areas and working area.

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1.6 DELIVERY, STORAGE, AND HANDLING

A. Packing, Shipping, Handling, and Unloading: Deliver materials in manufacturer's original unopened packaging with labels intact.

B. Storage and Protection:

1. Store all materials in a clean area, away from construction activities.

2. Stack all materials to prevent water from accumulating on or within materials, using blocking or skids to provide drainage.

3. Cover all materials with tarpaulins or plastic in a manner to provide air circulation and to prevent damage to surfaces.

4. Protect sand from contamination from dirt or other foreign materials.

5. Remove damaged materials from Site.

1.7 PROJECT CONDITIONS

A. Environmental Conditions:

1. Unless cold weather precautions are taken, masonry surfaces shall be repaired or pointed only when air and surface temperatures are above 45° F and are expected to remain so for not less than 48 hours after completion of Work.

2. When air temperatures are above 80° F, Contractor shall take necessary precautions to protect mortar from rapid drying.

3. Keep mortar work damp for no less than 72 hours following placement.

B. Cold Weather Precautions:

1. Comply with following recommendations for cold weather conditions: Brick Institute of America Tech Note 1A.

2. Maintain mortar temperature between 40°F and 120°F. Maintain mixing temperatures within ±10°F of first batch.

3. To assure proper mortar temperatures, heat mixing water or aggregates when air tempera-ture is between 32°F and 40°F. When air temperature is between 25°F and 32°F, heat both water and aggregates.

4. When air temperature is below 20°F, do not install masonry.

5. Do not heat water or sand above 160°F. Do not scorch sand.

PART 2 - PART 2 – PRODUCTS

2.1 MASONRY MATERIALS

A. Replacement Brick:

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1. Reuse existing brick after dismantling masonry walls and piers. Assume 25% replace-ment. New brick shall match original brick in size.

MORTAR

A. Hydrated Lime: Hydrated Lime (Type S)

B. Aggregates:

1. Sand: Natural sands that will produce final mortar colors matching existing adjacent mortar, ASTM C144, clean, washed and free from impurities.

2. Size and Gradation: ASTM C136, natural or manufactured sharp sand with at least four

(4) grades forming a substantial part of the sand and no more than 3% of particles smaller than grade #200. Match sand(s) in existing mortars as approved by Contracting Officer.

3. Color: Match sand(s) in existing mortars as approved by Contracting Officer. Final mor-tar color may be affected by aggregate color.

4. Blend several sands, if necessary, to achieve suitable match.

C. Pigments:

1. The use of pigments is discouraged unless absolutely necessary. Where possible, mortar color shall be adjusted through the selection of aggregate.

2. Iron oxide colorants shall meet the requirements of ASTM C979.

2. Use minimum concentration of colorant as required. Do not exceed 5% of binder weight.

D. Admixtures:

1. No air-entraining admixtures or materials containing air-entraining mixtures shall be used in mortar.

2. No antifreeze compounds or other substances shall be added to mortar.

3. Calcium chloride or admixtures containing chloride ions are not permitted.

E. The use of masonry cement mortars other that as specified herein is prohibited.

2.2 MORTAR MIXES

A. Mortar Mix: Mortar mix designs shall be confirmed by Contracting Officer after inspection of test panels. Bedding mortar shall match pointing mortar.

B. Measurement and Mixing: Measure cementitious materials and sand in a dry condi-tion by volume or equivalent weight. Do not measure by shovel; use known measure.

Mix materials in a clean, mechanical batch mixer.

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1. Mixing Pointing Mortar: Thoroughly mix cementitious materials and sand togeth-er before adding any water. Then mix again adding only enough water to produce a damp, unworkable mix that will retain its form when pressed into a ball. Main-tain mortar in this dampened condition for 15 to 30 minutes. Add remaining water in small portions until mortar reaches desired consistency. Use mortar within one hour of final mixing; do not retemper or use partially hardened material.

C. Mixes: Mix mortar materials in the following proportions:

1. Proportions by volume for natural hydraulic lime (NHL) mortar:

a) Hydrated Lime: 1 part (by volume)

b) Sand: 3 parts (by volume) matched, graded aggregate (adjust quantity of sand as required for workability)

c) Water: To provide workable consistency

2.3 CLEANING MATERIALS

A. Dry cleaning shall be done using stiff, natural bristle brushes and by vacuuming.

B. Water for cleaning shall be potable. The use of water for cleaning shall be minimized to avoid re-distribution of soluble salts.

PART 3 - PART 3 – EXECUTION

3.1 PREPARATION

A. Protection:

1. Protect woodwork, windows, sills, roofs, projections, ground surfaces, and other surfaces from mortar droppings.

B. Brick Removal and Storage:

3. Removal and salvage of brick is anticipated.

C. Joint Raking – Repointing of masonry chimneys where noted on the drawings:

1. Contractor shall use drop cloths to collect all mortar removed from building. Do not per-mit salt-damaged mortar to sit on the adjacent ground. Remove of mortar debris at the end of each work session and dispose off-site.

2. Remove existing mortar to whichever depth is greatest:

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a) 5/8” minimum depth.

b) 2-1/2 times the width of the joint back from the finished face of the brick. (Note: Av-erage width of mortar joints is ±1/2”.)

c) The depth necessary to remove previously installed Portland cement mortar.

d) Until well bonded, cohesive existing lime mortar is encountered.

3. The use of grinders or saws is not permitted.

4. Rake out mortar by hand chisel and mallet.

e) Do not chip, cut, or spall face of brick, or widen joints.

f) The use of a short-stroke pneumatic stone carving chisel will be allowed with ap-proval from Contracting Officer. Chisel width should be no more than half the width of the existing masonry joint.

5. Remove mortar from masonry surfaces within raked-out joints to provide reveals with square backs and to expose masonry for contact with pointing mortar.

6. Remove loose materials with a brush or air pressure.

7. Joint raking operations resulting in damage to masonry will cease immediately until tools, workmen, and methodology can be reviewed and corrective measures taken to ac-ceptance of Contracting Officer and Contracting Officer. Masonry damaged as a result of joint raking procedures will be repaired or replaced at no additional cost to Owner.

D. Cleaning:

1. Prior to installation of new mortar, all masonry surfaces shall be thoroughly cleaned by dry brushing and by vacuuming. Use stiff, natural bristle brushes or nylon brushes.

2. After brushing, thoroughly vacuum all masonry surfaces.

3. The use of water for cleaning shall be minimized, and only as approved by Contracting

Officer.

3.2 INSTALLATION

A. Measuring and Mixing Mortar:

1. Measure the proportions and mix the mortar in accordance with ASTM C 270, unless otherwise directed. Use automatic measuring devices that will consistently maintain the specified proportion within a 5 percentage (plus or minus) tolerance.

4. Mix mortar in a mechanically operated drum-type batch mixer in which water can be ac-curately and uniformly controlled.

5. Mix all dry ingredients for at least 2 minutes, then add water and mix mortar for at least

10 additional minutes. Do not exceed, in volume of mixed material, the manufacturer's rated capacity of mixer. Empty the mixer completely after each batch. Keep mixer and all other equipment clean.

B. Pointing:

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1. Wet joints before pointing, allowing water to soak into surface to prevent free-standing water. Use only enough water to ensure adequate pre-wetting; do not flood joints.

6. Fill joints solidly with pointing mortar. Mortar shall be placed into joints in layers not greater than 3/8”. Fully compact each layer. When each layer is “thumbprint” hard, an-other 3/8” layer shall be placed into joint.

7. Exercise care to fully fill joints to proper depth and finally tool joints at appropriate time to avoid tool burn or slicking. Tool and texture joints to match original appearance of joints. Remove excess mortar from edge of joint by dry brushing.

8. Where existing masonry has worn or rounded edges, slightly recess finished mortar sur-face below face of masonry to avoid widened joints. Refer to detail drawing.

9. On hot, dry days pointing operations will be done in shade only.

3.3 CURING & PROTECTING

A. Protect newly completed mortared masonry against frost and the elements, and cure with wa-ter moisture for a minimum of three (3) days.

B. Hairline cracking within mortar or separation at the joint will be unacceptable.

C. Improperly cured or improperly protected masonry shall be removed and suitably replaced by the Contractor at his expense.

3.4 FINAL CLEANING

A. General:

1. Use dry brush cleaning methods where possible. Follow up dry brushing with wet brush-ing, using minimal amounts of water.

2. Minimize the use of water for cleaning to prevent re-distribution of soluble salts.

3. Do not use pressure washing methods.

4. Do not use pressure or abrasion methods which may cause damage to sealants or pointing.

5. Do not use wire brushes.

END OF SECTION 04 01 20.911

6. Field Samples will be completed prior to final acceptance and execution of contract. Owner reserves the right to terminate Contract should quality of workmanship in field sample(s) not meet approval of Contracting Officer and Owner.

E. The use of masonry cement mortars other that as specified herein is prohibited.