Sealing Or Painting Previously Sand-Blasted Brick Masonry
- CSI Division:
- Division 4- Masonry
- Brick Unit Masonry
- Last Modified:
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Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
THIS PROCEDURE DESCRIBES A REMEDIAL TREATMENT FOR DETERIORATED BRICK THAT SHOULD ONLY BE USED AS A "LAST RESORT". SAND-BLASTED BRICK MASONRY SHOULD BE INSPECTED REGULARLY (ON AN ANNUAL BASIS) FOR SIGNS OF DETERIORATION. IF PROBLEMS PERSIST DESPITE MEASURES TO CONTROL DETERIORATION, THE APPLICATION OF A SEALER OR PAINT MAY BE APPROPRIATE IN ORDER TO ARREST FURTHER DETERIORATION. BEFORE PROCEEDING, SEE 04211-09-S FOR GUIDANCE ON EVALUATING THE CONDITION OF THE BRICK MASONRY AND MORTAR.
A. This procedure includes guidance on sealing sand-blasted brick masonry to prevent excessive water penetration into the units. It contains guidance on applying a siloxane water repellent coating or latex paint to the sand-blasted brick surface. See also 04211-14-R for additional guidance on painting brick.
B. The application of a water repellent or paint serves to protect the brick masonry against liquid water penetration while allowing water vapor to escape from within the brick.
C. The sealing of the outer surface of brick with a water repellent or paint may be necessary only when the exterior skin of the brick has been removed, often the result of sand-blasting.
- Sandblasting is an abrasive method of removing dirt, stains, and paint from the surface of bricks; however, it is not recommended as it also removes much of the outer layer of the brick. Sandblasting also erodes mortar joints.
- By removing the outer layer of the brick surface, sandblasting exposes the inner more porous material to the effects of water penetration and pollutants. This increases the potential of water collecting in the pores, undergoing freeze/thaw cycles, and producing spalls in the brick.
D. Problems with Sealers:
- May trap salt deposits within the brick creating potential for spalling if efflorescence is not removed before sealing.
- May alter color of brick.
- May make repointing or removal of dirt or efflorescence more difficult if surface is not cleaned before sealing.
- See also 07180-01-S for additional information on sealers.
E. Safety Precautions:
- Apply sealer or paint in a well ventilated area.
F. See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO).
G. For general information on the characteristics, uses and problems associated with brick, see 04211-08-S.
1.02 PROJECT/SITE CONDITIONS
A. Environmental Requirements:
- Surface and air temperatures should be no less than 50 degrees F. when applying sealer or paint.
A. Water Repellents (Sealers):
- American Building Restoration 9720 S. 60th Street Franklin, WI 53132 414/761-2440
- Diedrich Chemicals 7373 South 6th Street Oak Creek, WI 53154 414/764-0058 800/323-3565
- Hydrochemical Techniques, Inc. 253 Locust Street Hartford, CT 06114 203/527-6350
- Hydrozo 1001 "Y" Street P.O. Box 80879 Lincoln, NE 68501 402/474-6981
- ProSoCo, Inc. P.O. Box 1578 755 Minnesota Ave. Kansas City, KS 66117 913/281-2700
- Thoro System Products 7800 NW 38th Street Miami, FL 33166 305/592-2081
- Trocal Dynamit Nobel of America 10 Link Drive Rockleigh, NJ 07647 800/631-1668
- V.I.P. Enterprises 9690 NW 41st Street, Ste. 1 Miami, FL 33178 800/327-7479
- Sherwin Williams
NOTE: Chemical products are sometimes sold under a common name. This usually means that the substance is not as pure as the same chemical sold under its chemical name. The grade of purity of common name substances, however, is usually adequate for stain removal work, and these products should be purchased when available, as they tend to be less expensive. Common names are indicated below by an asterisk (*).
A. For Cleaning:
NOTE: THIS CHEMICAL IS BANNED IN SOME STATES SUCH AS CALIFORNIA. REGULATORY INFORMATION AS WELL AS ALTERNATIVE OR EQUIVALENT CHEMICALS MAY BE REQUESTED FROM THE ENVIRONMENTAL PROTECTION AGENCY (EPA) REGIONAL OFFICE AND/OR THE STATE OFFICE OF ENVIRONMENTAL QUALITY.
- Strong base-type powdered cleaning material sold under brand names.
- Other chemical or common names include Sodium Orthophosphate; Tribasic sodium phosphate; Trisodium orthophosphate; TSP*; Phosphate of soda*; (also sold under brand names such as).
- Potential Hazards: CORROSIVE TO FLESH.
- Available from chemical supply house, grocery store or supermarket or hardware store.
- Sodium Hypochlorite (NaOCl):
- An unstable salt produced usually in aqueous solution and used as a bleaching and disinfecting agent.
- Other chemical or common names include Bleaching solution*; Household bleach*; Laundry bleach*; Solution of chlorinated soda*.
- Potential Hazards: CORROSIVE TO FLESH.
- Available from chemical supply house, grocery store or supermarket, hardware store or janitorial supply distributor.
- Detergent such as "Tide", "All" or approved equal.
B. For Sealing:
1. Solvent-based sealer with not less than 5% solids, but preferably more than 7%. Try one of the following or approved equal:
- "Old 200 Hydro-Seal" (American Building Restoration)
- "Diedrich 303-S Siloxseal Siloxane Water Repellent" (Diedrich Chemicals)
- "HT-101 Eon-Clad Water Repellent" (Hydroclean - Hydrochemical Techniques, Inc.)
- "PP/Hydrozo Clear Double 7" (Hydrozo)
- "Tile & Masonry Protector" (ProSoCo, Inc.)
- "ThoroClear 777" (Thoro System Products)
- "Chem-Trete-Bsm" (Trocal)
- "Ombrella Clear No. 9100" (V.I.P. Enterprises)
NOTE: See 07180-01-S "Types of Masonry Water Repellents" for a review of the characteristics of typical sealers.
C. For Painting:
1. Latex (water-thinned emulsion) Paint - either acrylic or vinyl latex suitable for use on brick:
NOTE: DO NOT USE OIL OR EPOXY-BASED PAINT AS THESE ARE NON-POROUS COATINGS AND WILL PREVENT THE MASONRY FROM "BREATHING".
- Should be mildew and alkali-resistant.
- Acrylic latex paints are recommended over vinyl acetate latex paints because the acrylics are more alkali resistant. Many are self-priming so the same paint can be used for both the prime coat and top coat.
- Latex paints can be applied to slightly damp surfaces, though they must be absolutely clean and free of any chalking paint.
- All paint used shall be from the same manufacturer and shall be appropriate for the conditions encountered on the job site.
Cement-based paint for heavily pitted or cracking brick.
2. Masonry Conditioner for coating under latex paint such as "A5V2" (Sherwin Williams), "Wonder Bond 16100" (Devoe), or approved equal.
NOTE: USE SAME MANUFACTURER FOR BOTH LATEX PAINT AND MASONRY CONDITIONER.
- The sealer will prevent the brick from absorbing the water from the latex top coat which would prevent the paint from adhering properly.
- Conditioners/sealers are also alkali-resistant and will prevent adverse chemical reactions from occurring between the masonry and oils in the paint.
3. Mineral Spirits (as recommended by paint manufacturer to thin conditioner):
- A petroleum distillate that is used especially as a paint or varnish thinner.
- Other chemical or common names include Benzine* (not Benzene); Naphtha*; Petroleum spirits*; Solvent naphtha*.
- Potential Hazards: TOXIC AND FLAMMABLE.
- Safety Precautions:
- AVOID REPEATED OR PROLONGED SKIN CONTACT.
- ALWAYS wear rubber gloves when handling mineral spirits.
- If any chemical is splashed onto the skin, wash immediately with soap and water.
- Available from construction specialties distributor, hardware store, paint store, or printer's supply distributor.
D. Clean, potable water
A. Nylon bristle brushes
B. Soft bristle brushes
C. Garden hose
D. Paint rollers
E. Low-pressure spray equipment
F. Plastic bucket
A. Remove all loose and crumbling mortar and/or brick to provide a sound surface.
B. Remove any efflorescence from the surface by dry brushing supplemented, if necessary, with clean, clear water.
C. Remove organic growth from the surface using a weed killer and clean, clear water.
D. Remove mildew and surface dirt:
- Mix 3 oz. trisodium phosphate (TSP), 1 oz. detergent such as "Tide" or "All", 1 qt. 5% sodium hypochlorite (bleach) and 3 qts. warm water.
- Apply solution to the brick surface and scrub with a soft bristle brush.
- Thoroughly rinse the surface with clean, clear water and allow to dry.
E. Repoint or recaulk as required before applying sealer.
NOTE: SEALER OR PAINT MUST BE APPLIED TO A CLEAN SURFACE (SEE SECTION 3.01 PREPARATION ABOVE) TO BE EFFECTIVE.
A. For Sealer Application:
- Apply sealer to a test area in an inconspicuous location.
- Allow to cure for several months; Evaluate performance including color change, water permeability, etc.
- When appropriate sealer is selected, apply sealer by brush or low-pressure spray with a rundown of at least 12 inches. Follow manufacturer's instructions for precautions and special application procedures.
- Apply sealer on dry days; Avoid treating noticeably damp surfaces.
- The transparent sealer or water repellent should penetrate the brick to a depth of 1/8" to 1/2".
- It works by changing the capillary angles of the pores in the face of the brick wall from positive (suction) to negative (repellency).
- Allow to air-dry for at least 6 hours (length of drying time may vary depending on product used).
- Apply a second coat of sealer as in 5. above and allow to dry.
- Reapply sealer every 3-7 years.
B. For Paint Application:
NOTE: THIS METHOD PROVIDES A SURFACE COATING ONLY AND DOES NOT PENETRATE INTO THE BRICK.
- Paint is best applied by brush, though rollers or spray equipment may also be used.
- See also 04211-14-R for guidance on painting brick masonry.
A. Clean brushes and sprayers with white mineral spirits when the work is completed.