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Historic Preservation - Technical Procedures

Spectitle:

Removing Efflorescence From Plaster

Procedure code:

0920004R

Source:

Mainten, Rpr & Alteration Of Hstrc Bldgs - Gsa/Pbs

Division:

Finishes

Section:

Lath & Plaster

Last Modified:

02/24/2012

Details:

Removing Efflorescence From Plaster



REMOVING EFFLORESCENCE FROM PLASTER


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing
         efflorescence from plaster surfaces.  

         1.   Efflorescence is a condition where white (salt)
              deposits (in the form of a fluffy powder) form on
              the plaster surface.  The formation of salts is
              usually a sign of excessive amounts of moisture in
              the back-up material, such as brick or concrete.  

         2.   Salt deposits on the surface may develop from
              soluble compounds within the adjacent masonry or
              in the soil.  In the presence of water, these
              compounds gradually migrate to the wall surface,
              where they remain when the water evaporates.

         3.   These deposits are generally not harmful to the
              material, just unattractive.  However, they should
              be removed from the surface as soon as possible.

    B.   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 EQUIPMENT

    A.   Clean sponge

    B.   Stiff, fiber bristle brush


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Before proceeding with steps to remove efflorescence,
         examine the plaster and substrate material for
         potential sources of moisture and make repairs as
         required:

         1.   Determine the age of the structure:  Efflorescence
              on older buildings is typically caused by the
              presence of soluble salts in the construction
              combined with moisture.

         2.   Determine the location of the efflorescence:
              Examination may show where the water is entering.

         3.   If possible, examine the condition of the back-up
              material:  

              a.   CAREFULLY EXAMINE the wall for open gaps or
                   cracks in joints and around openings that
                   could allow water to enter the building.  

                   1)   Are joints properly caulked or sealed?  

                   2)   Are flashings and drips in good
                        condition?

                   3)   Are there open or eroded mortar joints
                        in copings or in sills?

              b.   Carefully note the condition and profile of
                   the mortar joints.

              c.   Repair cracks in masonry and/or repoint as
                   necessary before proceeding with the cleaning
                   operations.

         4.   Examine wall sections and details of construction:
              Carefully examine roof and wall junctures and
              flashing details for possible sources of moisture
              entry.

         5.   Examine laboratory test reports on the materials:
              The problem may stem from the composition or
              misuse of the material.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Carefully remove any surface deposits using a stiff
         fiber bristle brush only.

    B.   Wipe the surface with a clean, damp cloth.

    C.   For guidance on cleaning and/or repairing damaged
         plaster, see 09200-01-S, 09210-02-R, 09210-03-R and
         09210-05-R.

                         END OF SECTION