Attachment_1_-_Stucco_Restoration.pdf

SCBL PMIS #315326 09 01 25.91 – 1

PORTLAND CEMENT STUCCO RESTORATION

SECTION 09 01 25.91 - PORTLAND CEMENT STUCCO RESTORATION

PART 1 – GENERAL

1.1 SUMMARY

A. Section Includes:

1. Historic stucco patching that duplicates existing in strength, composition, and workmanship.

B. Related Sections:

1. Section 09 90 00: “Painting and Coating.”

2. Appendix: Stucco and Plaster Report

1.2 SUBMITTALS

A. Where prior approval of cutting and patching is required, submit proposed procedures to Contracting Officer for this work well in advance of time when work will be performed.

1.3 QUALITY ASSURANCE

A. Restoration Specialist: Work shall be performed by a firm having not less than five years of successful experience in comparable stucco restoration and employing personnel skilled in stucco restoration processes and operations indicated.

B. Contractor shall be fully conversant with Secretary of the Interior’s “Standards for the Rehabilitation of Historic Buildings” and attendant preservation briefs associated with stucco restoration.

C. Contractor shall do all cutting and patching of wall surface for removal of certain architectural elements and/or relocation or removal of piping, conduit, electrical boxes, and abandoned pipes.

D. Work Quality Level: Project’s intent is that all existing stucco materials correction and finish Work, and new stucco materials installation and finish Work shall achieve a quality level similar to that exhibited by the existing undisturbed and undamaged stucco.

E. Visual Requirements: Do not cut and patch work exposed on the building’s exterior or in its occupied spaces, in a manner that would, in the Contracting Officer’s opinion, result in lessening the building’s aesthetic qualities.

F. Do not cut and patch work in a manner that would result in substantial visual evidence of cut and patch work.

G. Remove and replace work judged by the Contracting Officer to be cut and patched in a visually unsatisfactory manner.

H. Perform Work in accordance with PCA (Portland Cement Association) Plaster Manual.

I. Mock-Up: Provide an area 24 inches by 24 inches on the retained portion as determined by the

CORfor project standard of repair and finish.

PART 2 - PRODUCTS

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2.1 MATERIALS

A. General:

1. Contractor shall match sample #1 composition and proportions of existing exterior stucco materials, as determined by laboratory test analysis. Ref: Appendix

2. If identical materials are not available, or cannot be used, use materials that match existing adjacent surfaces to fullest extent possible with regard to visual effect.

3. List of products below is to indicate possible products to be used in work, provided they possess like physical and functional characteristics to historic stucco:

B. Hardness: Medium hard.

C. Color: Peach.

D. Aggregate shape: Sub angular.

1. Gradation: Very fine – medium.

E. Fines and sands color: 10YR 9/1.

F. Percentages: 5% lime; 8% fines; 70% sands; 5-16.99% Portland cement.

G. New stucco shall be : 1 part hydrated lime; 1 part Portland cement; 7 parts sand.

H. Water: Clean, fresh, potable and free of matter which can affect plaster.

2.3 ACCESSORIES

A. Lath:

1. Metal Lath: Galvanized steel.

2.4 PLASTER MIXES

A. Mix and proportion plaster in accordance with PCA Plaster Manual.

PART 3 - EXECUTION

3.1 EXAMINATION

A. Verify that surfaces to be cut and patched and conditions under which work is to be performed.

B. If unsafe or unsatisfactory conditions are encountered, take corrective action before proceeding with work.

3.2 PREPARATION

A. Provide temporary support to work to be cut to prevent failure.

B. Provide adequate protection of other work during cutting and patching to prevent damage and from adverse weather exposure. Do not allow any water to enter exterior adobe walls.

C. Cutting and Removal:

1. Use methods that are least likely to damage work to be retained or adjoining work.

2. Use hand or small power tools designed for sawing or grinding, not hammering and chopping where cutting and/or removal is required.

3. Cut through masonry using a cutting machine, such as a carborundum saw or core drill to insure a neat hole. Do not cause vibration or other disturbance that would affect the adobe substrate in

SCBL PMIS #315326 09 01 25.91 – 3

any way.

3.3 INSTALLATION

A. Coordinate plaster patching work with other trades.

B. Patch with seams which are durable and as invisible as possible.

C. Restore exposed finishes of patched areas and where necessary extend finish restoration into retained adjoining work in a manner which will eliminate evidence of patching and refinishing. Match characteristics of historic workmanship.

D. Where patch occurs in a smooth painted surface, extend final paint coat over entire unbroken surface containing patch, after patched area has received prime and base coats.

E. Apply plaster in accordance with manufacturer's instructions.

F. Filling Cracks:

1. Hairline Cracks: Fill with a patching material.

2. Seasonal Reopening Cracks:

a. Widen crack slightly with a sharp, pointed tool such as a crack widener or a triangular can opener.

b. Fill crack with patching material.

3. More Persistent Cracks:

a. Bridge crack with fiberglass mesh tape pressed into patching material.

b. When first application of quick setting joint compound dries, apply a second coat to cover fiberglass mesh tape, feathering it at edges.

c. Apply a third coat to even out surface, followed by light sanding.

d. Clean off area with a damp sponge.

e. After surface is dry, remove any leftover plaster residue or dust.

4. Large Cracks:

a. If cracks are caused by structural movement, repair structural system before repairing plaster.

b. Remove existing plaster on each side of crack to a width of about 6 inches down to lath.

c. Clean out debris.

d. Install metal lath to cleared area, leaving existing metal lath in place.

e. Patch crack with an appropriate plaster in three layers (i.e. base coats and finish coat), G. Patching Holes in Walls:

1. Small Holes (Less Than 4 Inches in Diameter):

a. Trowel a layer of base coat plaster in place and scrape back below level of existing plaster surface.

b. When base coat has dried, apply finish plaster coat to create a smooth, level surface.

H. Larger Holes:

a. For holes where all three coats of plaster are damaged or missing down to metal lath.

b. Clean all old plaster out and re-nail any loose lath.

c. Install expanded metal lath (diamond mesh) by attached to existing metal lath with tie wires and lath nails.

SCBL PMIS #315326 09 01 25.91 – 4

d. Install plaster in three layers over metal lath, lapping each new plaster layer over old plaster so that old and new are evenly joined.

e. In event existing wall is slightly wavy, contour patch to conform to irregularities of existing work.

3.4 PAINTING NEW PLASTER

A. Allow cementations stucco to cure thoroughly before painting.

B. Apply a good alkaline-resistant primer, specially formulated for new plaster.

C. Final finish coats shall be latex paint.

3.5 ADJUSTING AND CLEANING

A. Thoroughly clean areas and adjacent spaces soiled due to work performed or used as access to work.

B. Remove completely paint, plaster debris, oils, putty, and items of similar nature.

C. Thoroughly clean piping, conduit and similar features before painting or other finishing is applied.

END OF SECTION 09 01 25.91