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Historic Preservation - Technical Procedures

Spectitle:

Repairing Cracks And Checks In Wood Wall Ornament

Procedure code:

0644001R

Source:

Hspg Prepared For Nps - Sero

Division:

Wood And Plastics

Section:

Wood Ornaments

Last Modified:

02/24/2012

Details:

Repairing Cracks And Checks In Wood Wall Ornament



REPAIRING CRACKS AND CHECKS IN WOOD WALL ORNAMENT


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on repairing cracks and
         checks in wood either filling, regluing or using a
         dutchman.

    B.   Cracks and checks in interior wood wall ornament are
         usually caused by uneven shrinkage, impact damage, or
         improperly placed fasteners.

    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).

1.02 DEFINITIONS

    A.   Interior wood wall ornament may include, but not be
         limited to, crown moulding, chair rail, wainscotting,
         base, door and window casings and trim, columns and
         posts, carved relief pieces, and built-in cabinets and
         bookcases.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Wood filler:  Available from hardware store; Tint to
         match existing woodwork.

    B.   Paint and debris remover (paint or chemical):  Available
         from hardware store.

    C.   Wood glue:  Available from hardware store.

    D.   Replacement stock for dutchman:  Available from builder's
         supply store or lumber yard.

    E.   Sandpaper:  No. 3/0 or No. 5/0 garnet paper.

2.02 EQUIPMENT

    A.   Heat gun or plate

    B.   Clamps

    C.   Table saw to cut dutchman shims

    D.   Knife to cut excess shim


PART 3---EXECUTION

3.02 EXAMINATION

    A.   If a check is a result of dried or shrunken end grain, it
         must be filled.

    B.   Checks on the underside of logs with no direct water
         infiltration generally do NOT need filling.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Filling cracks and checks (for small surface cracks up to
         1/2" across):

         1.   Use a proprietary wood filler, or sawdust mixed
              with white glue.  Work into crack so that no gaps
              remain.

         2.   When dry, hand rub filled area with a fine grit
              sandpaper to match surface characteristics and
              level of surrounding surfaces.

         3.   Refinish as required to match remaining ornament.

    B.   Regluing cracks and checks (for larger cracks that
         penetrate into the wood ornament):

         1.   Strip paint and debris from crack area.  Before
              regluing, make sure joint can be forced back
              together.

         2.   Widen joint slightly to get glue in and work joint
              open and closed to spread glue.  

         3.   Clamp joint closed using blocks of wood under
              clamps to protect wood.  Remove all excess glue
              before it dries.

         4.   Let glue dry for 24 hours before removing clamp.

         5.   Refinish as necessary to match surrounding
              ornament.

    C.   Dutchman replacement (for larger cracks that cannot be
         filled or glued):

         1.   Cut long, slender, tapered shims from wood of same
              age, species and grain orientation as piece being
              patched.

         2.   Pre-fit shim into crack.  When shim fits, glue both
              shim and crack surface and remove all excess glue.

         3.   After glue dries, cut shim flush with face of panel
              and refinish as necessary to match remaining
              ornament.

                         END OF SECTION