Specification:Removing and replacing deteriorated brick masonry

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=GENERAL=

SUMMARY
 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". 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 Submittals Quality Assurance Delivery, Storage and Handling Project/Site Conditions</li> Sequencing and Scheduling</li> General Protection (Surface and Surrounding)</li> </ol> </li> 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). For general information on the characteristics, uses and problems associated with brick, see 04211-08-S.</li> </ol>

PROJECT/SITE CONDITIONS
<ol type="A"> Environmental Requirements: <ol> 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.</li> Wet Weather: Do not apply or mix mortar on outside surfaces with standing water or outside during rain.</li> 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.</li> 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.</li> All materials must be kept above 40o F.</li> 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.</li> </ol> </li> </ol> =PRODUCTS=

MATERIALS
<ol type="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.</li> Replacement Brick: Approved by RHPO.</li> Brick slips: Approved by RHPO.</li> Mortar to match existing (see 04100-03-S "Preparing Lime Mortar for Repointing Masonry").</li> </ol>

EQUIPMENT
<ol type="A"> Trowel</li> Joint tools</li> <li>Chisel</li> <li>Hawk</li> <li>Hammer</li> <li>Stiff bristle brushes</li> </ol> =EXECUTION=

EXAMINATION
<ol type="A"> <li>Deterioration of brick due to moisture is evident as spalling, erosion, cracking, peeling paint, and deteriorated mortar joints.</li> <li>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.</li>  </ol>

PREPARATION
<ol type="A"> <li>Surface Preparation: <ol> <li>Wet brick having absorption rates greater than 0.025 oz. per sq. inch per minute. <li>On the flat side of a brick, deposit water on an area approximately the size of a 25 cent coin.</li> <li>If the water disappears in less than 30 seconds, wet the bricks.</li> </ol> </li> <li>Absorptive brick should be thoroughly soaked in the pile each afternoon prior to the day they are to be used.</li> <li>Cover the bricks with tarps or heavy paper to prevent evaporation.</li> <li>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).</li> <li>Repair flashing if necessary.</li> <li>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.</li> </ol> </li> </ol>

ERECTION, INSTALLATION, APPLICATION
<ol type="A"> <li>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. <ol>

<li>Cut out the deteriorated masonry to a regular shape.</li> <li>Clean the cavity of loose mortar and other debris by hand using a chisel and stiff bristle brushes.</li> <li>Solidly set the slip in a bed of mortar.</li> </ol> </li> <li>Replacing Deteriorated Units with Full-Size Bricks: <ol> <li>Carefully remove deteriorated brick units by hand using a hammer and chisel.</li> <li>Rebuild back-up and substrate as required to replace any unsound material that was removed.</li> <li>Clean the cavity of loose mortar and other debris by hand using a chisel and stiff bristle brushes.</li> <li>Lightly wet the exposed brick surfaces.</li> <li>Lay brick units with completely filled bed and head joints; Butter ends with sufficient mortar to fill head joints and shove into place.</li>

<li>If adjustments are required, remove units, clean off mortar and reset in fresh mortar.</li> <li>Blend new work into existing work smoothly with no lines of demarcation and no change of pattern or coursing.</li> <li>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".</li> <li>Brush all excess mortar from the wall surface frequently during the work; Protect all existing surfaces from mortar dripping and splashing.</li> </ol> </li> </ol>

ADJUSTING/CLEANING
<ol type="A"> <li>Clean off adjacent surfaces which have been spattered during the course of the work. Rinse immediately with clean, clear water.</li> <li>Wipe all excess mortar as the work progresses. Dry brush at the end of each day's work.</li> <li>After mortar is thoroughly set and cured, remove loose mortar and dirt from new masonry surfaces.</li> <li>Wash down the masonry surface with clean, clear water.</li> </ol>