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Historic Preservation - Technical Procedures

Spectitle:

Removing And Replacing Deteriorated Brick Masonry

Procedure code:

0421102R

Source:

Hspg Prepared For Nps - Sero

Division:

Masonry

Section:

Brick Unit Masonry

Last Modified:

02/24/2012

Details:

Removing And Replacing Deteriorated Brick Masonry



REMOVING AND REPLACING DETERIORATED BRICK MASONRY


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing and
         replacing deteriorated brick masonry.  It should be used
         in conjunction with the procedure on repointing historic
         masonry.  For guidance on repointing, see 04520-02-R
         "Repointing Masonry Using Lime Mortar".

    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).

    C.   For general information on the characteristics, uses and
           problems associated with brick, see 04211-08-S.

1.02 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:

         1.   Do not proceed with brick replacement under adverse
              weather conditions, or when temperatures are below
              or above manufacturer's recommended limitations for
              installation;  Proceed with the work only when
              forecasted weather conditions are favorable for
              proper cure.

         2.   Wet Weather:  Do not apply or mix mortar on outside
              surfaces with standing water or outside during
              rain.

         3.   Cold Weather, winter construction is not allowed
              without consent of RHPO;  Winter construction when
              surface temperature of masonry is below 40o F. or
              air temperature is predicted to be below 40o F.
              within 48 hours.  See #6 below.

         4.   Hot Weather:  The surface temperature of the work,
              not the ambient temperature, should not be higher
              than 100o F.; Mortar mixing should be done only in
              the shade; Cover mortar with water-misted burlap in
              hot weather to reduce evaporation; Pointing work
              should be done in the shade;  Work around the
              building during the day so that the fresh work will
              be shielded from direct sunlight to reduce
              evaporation rate.  High temperatures can cause
              flash setting of cements and rapid evaporation of
              water in the mix, leading to lack of development of
              final strength by the cement.

         5.   All materials must be kept above 40o F.

         6.   Special Precautions and Notes:  Do not allow
              masonry to freeze until mortar is thoroughly dry
              and hardening almost complete (approx. three days
              time); The setting of lime mortar is very much
              slower than that of cement mortar because the
              curing requires the absorption of carbon dioxide to
              form hard lime carbonates; It is a very lengthy
              process, so do not expect it to become hard
              immediately, especially at the core of large masses
              of masonry.


PART 2---PRODUCTS


2.01 MATERIALS

    A.   Salvaged Brick:  Approved by RHPO, sound, crack free,
         clean brick without face chips larger than 1/2 inch,
         salvaged from removal of removed face brick work of same
         type.

    B.   Replacement Brick:  Approved by RHPO.

    C.   Brick slips:  Approved by RHPO.

    D.   Mortar to match existing (see 04100-03-S "Preparing Lime
         Mortar for Repointing Masonry").

2.02 EQUIPMENT

    A.   Trowel

    B.   Joint tools

    C.   Chisel

    D.   Hawk

    E.   Hammer

    F.   Stiff bristle brushes


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Deterioration of brick due to moisture is evident as
         spalling, erosion, cracking, peeling paint, and
         deteriorated mortar joints.

    B.   Some causes of brick deterioration include:  a) Rising
         damp, b) the accumulation of dissolved acids carried by
         rainwater and condensation, c) soluble salts
         crystallizing in the pores of the brick face, d)
         alternate freezing and thawing, and e) the accumulation
         of dirt and air-borne particles on the exterior surface.

3.02 PREPARATION

    A.   Surface Preparation:

         1.   Wet brick having absorption rates greater than
              0.025 oz. per sq. inch per minute.

              a.   On the flat side of a brick, deposit water on
                   an area approximately the size of a 25 cent
                   coin.

              b.   If the water disappears in less than 30
                   seconds, wet the bricks.

         2.   Absorptive brick should be thoroughly soaked in the
              pile each afternoon prior to the day they are to be
              used.

         3.   Cover the bricks with tarps or heavy paper to
              prevent evaporation.

         4.   Wet brick as necessary during the day; Sprinkle the
              brick pile with a hose for a period long enough for
              water to run down the side of the pile; Use wetting
              methods which ensure that each masonry unit is
              nearly saturated but surface dry when laid; (DO NOT
              wet stone masonry units).

         5.   Repair flashing if necessary.

         6.   Where fresh masonry joins existing work, clean the
              exposed surface of the set masonry by removing
              loose brick and mortar and wet lightly to obtain
              the best possible bond with the new work.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   Replacing Deteriorated Masonry with Brick slips:  The use
         of brick slips should be limited to replacement of
         individual bricks or to small areas of brickwork.

         NOTE:  Brick slips are brick facings about 1 inch thick.
         They are used when damage to adjacent sound brickwork is
         likely to occur if full-size replacement is attempted.

         1.   Cut out the deteriorated masonry to a regular
              shape.

         2.   Clean the cavity of loose mortar and other debris
              by hand using a chisel and stiff bristle brushes.

         3.   Solidly set the slip in a bed of mortar.

    B.   Replacing Deteriorated Units with Full-Size Bricks:

         1.   Carefully remove deteriorated brick units by hand
              using a hammer and chisel.

         2.   Rebuild back-up and substrate as required to
              replace any unsound material that was removed.  

         3.   Clean the cavity of loose mortar and other debris
              by hand using a chisel and stiff bristle brushes.

         4.   Lightly wet the exposed brick surfaces.


         5.   Lay brick units with completely filled bed and head
              joints; Butter ends with sufficient mortar to fill
              head joints and shove into place.  

              NOTE:  Lay masonry plumb and true following the
              coursing and patterns of the adjacent existing
              sound construction; Level off work at required
              heights and form beds to build-in salvaged or moved
              materials.

         6.   If adjustments are required, remove units, clean
              off mortar and reset in fresh mortar.  

         7.   Blend new work into existing work smoothly with no
              lines of demarcation and no change of pattern or
              coursing.

         8.   Rake all joints in replacement work to receive tuck
              pointing; Joints up to 3/8" in width shall be raked
              to a depth of 1/2"; Joints 3/8" in width shall be
              raked to a depth of 1".

         9.   Brush all excess mortar from the wall surface
              frequently during the work; Protect all existing
              surfaces from mortar dripping and splashing.

3.04 ADJUSTING/CLEANING

    A.   Clean off adjacent surfaces which have been spattered
         during the course of the work.  Rinse immediately with
         clean, clear water.

    B.   Wipe all excess mortar as the work progresses.  Dry brush
         at the end of each day's work.  

    C.   After mortar is thoroughly set and cured, remove loose
         mortar and dirt from new masonry surfaces.

    D.   Wash down the masonry surface with clean, clear water.

                         END OF SECTION