REMOVING BIOLOGICAL GROWTH FROM EXTERIOR MASONRY AND STUCCO


PART 1---GENERAL

1.01 SUMMARY

     A.   This procedure includes guidance on removing biological
          growth such as lichens, algae, mold and mildew from
          masonry and stucco.

     B.   Biological growths such as lichens, algae, moss and fungi
          growing on masonry walls is usually an indication that
          there is excess moisture in or around the masonry.  These
          growths should be removed, as they attract moisture to
          the masonry surface and hold it there, which can lead to
          more serious problems.  Lichens and mosses in particular,
          produce oxalic acid which can damage certain types of
          historic masonry.

     C.   See 01100-07-S for general project guidelines to be
          reviewed along with this procedure.  These guidelines
          cover the following sections:

          1.   Safety Precautions

          2.   Historic Structures Precautions

          3.   Submittals

          4.   Quality Assurance

          5.   Delivery, Storage and Handling

          6.   Project/Site Conditions

          7.   Sequencing and Scheduling

          8.   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).


PART 2---PRODUCTS

2.01 MANUFACTURERS

     A.   ProSoCo, Inc.
          P.O. Box 1578
          Kansas City, KS  66117
          913/281-2700

2.02 MATERIALS

     A.   For Removing Mold and Mildew:

          1.   Non-sudsing ammonia or one of the following
               bleaches:

               CAUTION:  DO NOT MIX AMMONIA WITH CHLORINE
               BLEACHES, A POISONOUS GAS WILL RESULT!  DO NOT USE
               BLEACH ON BIRD DROPPINGS.

               Sodium Hypochlorite (NaOCl):

               a.   An unstable salt produced usually in aqueous
                    solution and used as a bleaching and
                    disinfecting agent.

               b.   Other chemical or common names include
                    Bleaching solution*; Household bleach*;
                    Laundry bleach*; Solution of chlorinated
                    soda*.

               c.   Potential Hazards:  CORROSIVE TO FLESH.

               d.   Available from chemical supply house, grocery
                    store or supermarket, hardware store or
                    janitorial supply distributor.

               -OR-

               Hydrogen Peroxide (H202):

               a.   An unstable compound used especially as an
                    oxidizing and bleaching agent, an antiseptic,
                    and a propellant.

               b.   Other chemical or common names include
                    Peroxide of hydrogen*; Solution of hydrogen
                    dioxide*; Superoxol*; (hydrogen peroxide is
                    commonly sold as a 3% solution; Superoxol is a
                    30% solution; Superoxol causes flesh burns; 3%
                    hydrogen peroxide does not).

               c.   Potential Hazards:  TOXIC (when concentrated);
                    CORROSIVE TO FLESH; FLAMMABLE (in high
                    concentration).

               d.   Available from chemical supply house,
                    drugstore, pharmaceutical supply distributor,
                    or hardware store.

               -OR-

               Calcium Hypochlorite (CaCl2O2):

               a.   A white powder used especially as a bleaching
                    agent and disinfectant.

               b.   Other chemical or common names include
                    Chlorinated calcium oxide; Bleaching powder*;
                    Calcium oxymuriate*; Chloride of lime*;
                    Chlorinated lime*; Hypochlorite of lime*;
                    Oxymuriate of lime*.

               c.   Potential Hazards:  CORROSIVE TO FLESH;
                    FLAMMABLE (WHEN IN CONTACT WITH ORGANIC
                    SOLVENTS).

               d.   Available from chemical supply house, dry
                    cleaning supply distributor, drugstore or
                    pharmaceutical supply distributor, janitorial
                    supply distributor, swimming pool supply
                    distributor, or water and sanitation supply
                    distributor.

               -OR-

               Chloramine-T:  Chloramine is any of various
               compounds containing nitrogen and chlorine.

          2.   Trisodium Phosphate:

               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.

               a.   Strong base-type powdered cleaning material
                    sold under brand names.

               b.   Other chemical or common names include Sodium
                    Orthophosphate; Tribasic sodium phosphate;
                    Trisodium orthophosphate; TSP*; Phosphate of
                    soda*; (also sold under brand names such as).

               c.   Potential Hazards:  CORROSIVE TO FLESH.

               d.   Available from chemical supply house, grocery
                    store or supermarket or hardware store.

          3.   Powdered detergent such as "Tide" or approved
               equal.

     B.   Proprietary cleaner such as "Limestone Restorer"
          (ProSoCo, Inc.), or approved equal.

     C.   Clean, potable water

2.03 EQUIPMENT

     A.   Garden hose and nozzle

     B.   Rubber or polyethylene bucket (DO NOT USE A METAL BUCKET
          AS IT MAY REACT WITH THE CHEMICAL CLEANER AND PRODUCE
          TOXIC FUMES)

     C.   Glass or ceramic mixing bowl

     D.   Knife blade

     E.   Stiff, natural bristle brushes (non-metallic)

     F.   Tampico brush, roller or low pressure (50 psi maximum)
          spray such as pneumatic garden sprayer

     G.   Rubber gloves

     H.   Safety glasses


PART 3---EXECUTION

3.01 EXAMINATION

     A.   Determine the source of excessive moisture, i.e. leaky
          downspout, standing water, roof overhang, vegetation,
          etc., and make any necessary repairs before continuing
          with this task.

     B.   Determine the type of stain, i.e. algae and lichens, or
          mold and mildew.

3.02 PREPARATION

     A.   Protection:  

          1.   Provide adequate wash solutions (i.e. water, soap
               and towels) before starting the job.

          2.   Do not spray in the immediate vicinity of
               unprotected people and animals.

3.03 ERECTION, INSTALLATION, APPLICATION

     NOTE:  DO NOT TRY MORE THAN ONE TREATMENT ON A GIVEN AREA
     UNLESS THE CHEMICALS USED FROM PRIOR TREATMENT HAVE BEEN
     WASHED AWAY.

     A.   Removing Lichens and Algae (ONLY):

          1.   Remove as much plant growth as possible using a
               knife blade and stiff bristle brush.

          2.   Water rinse the surface to remove most of the plant
               material.

               a.   If the substrate is sound and dense, use low
                    to medium water pressure (100-400 psi).

               b.   If the masonry is softer, use standard water
                    pressure from the spigot.

          3.   Allow water to soak plant growth for approximately
               30 minutes.

          4.   Gently scrub the surface with a stiff, natural
               bristle brush.

          5.   Thoroughly rinse the surface again with clean,
               clear water at low pressure from a garden hose.  

          NOTE:  DO NOT USE ANY CHEMICALS WITHOUT FIRST CONSULTING
          WITH RHPO.

     B.   Removing Mold and Mildew (ONLY):

          CAUTION:  DO NOT MIX AMMONIA WITH CHLORINE BLEACHES, A
          POISONOUS GAS WILL RESULT!

          1.   Mix the following: 

               3 oz. (2/3 cup) trisodium phosphate (TSP) cleaner 
               1 oz. (1/3 cup) powdered detergent (i.e. Tide) 
               1 qt. 5% sodium hypochlorite bleach (laundry
               bleach)
               3 qts. warm water

               -OR-

               1 part ammonia with 3 parts water

          2.   Apply the solution to the affected area and scrub
               with a medium-hard natural bristle brush.  Keep the
               surface saturated until the stain is bleached,

               CAUTION:  BE SURE TO WEAR RUBBER GLOVES AND SAFETY
               GLASSES WHEN APPLYING THE SOLUTION.

          3.   Thoroughly rinse the surface with clean, clear
               water from a garden hose and allow to dry.

          4.   Repeat the process as necessary to achieve the
               desired level of cleanliness.

     -OR-

     C.   For treating any of the above (lichens, algae, mold or
          mildew), try using a proprietary cleaner such as
          Limestone Restorer (ProSoCo, Inc.), or approved equal.

          1.   Add 1 part Limestone Restorer to 3 parts water and
               mix in a rubber or polyethylene bucket.

          2.   Apply a flood coat of this mixture to the masonry
               using a low pressure spray (approximately 50 psi).

               CAUTION:  DO NOT USE A HIGH PRESSURE SPRAY WHEN
               APPLYING THIS SOLUTION AS THIS MAY CAUSE THE
               SOLUTION TO BE DRIVEN DEEPER INTO THE PORES OF THE
               MASONRY, MAKING REMOVAL OF THE SOLUTION DIFFICULT.


               a.   Begin spraying at the top of the vertical
                    surface and move across horizontally.  Allow
                    100mm rundown.

               b.   Continue the next horizontal pass across the
                    previous run down.

               c.   Allow the solution to remain on the surface
                    approximately 5-30 minutes depending upon the
                    thickness of the growth.

               d.   Gently scrub the surface with a stiff, natural
                    bristle brush.

               e.   Thoroughly rinse the treated area using
                    pressure-applied water (approximately 400 to
                    1500 psi) with a 40-60 degree fan spray or
                    garden hose with nozzle adjusted to a tight
                    stream.  Rinse from the bottom of the treated
                    area to the top. 

               f.   Allow the surface to dry a minimum of 24
                    hours.

                          END OF SECTION