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Historic Preservation - Technical Procedures

Spectitle:

Repairing Cupped Floorboards

Procedure code:

0956005R

Source:

National Oak Flooring Manufacturer's Association

Division:

Finishes

Section:

Wood Strip Flooring

Last Modified:

06/12/2015

Details:

Repairing Cupped Floorboards



REPAIRING CUPPED FLOORBOARDS


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on repairing cupped
         floorboards.  

    B.   Cupping of hardwood floors is caused by one side of the
         board gaining or losing moisture faster than the other
         side.  Some cupping, especially in wide plank floors, is
         considered normal.  It is usually barely noticeable.
         More severe cupping is of two types:

         1.   Convex cupping ("crowning"):  When the center of
              the board is higher than the edges of the board.

         2.   Concave cupping:  When the edges of the board are
              higher than the center of the board.

    C.   Cupping may result from the inability of moisture to
         evaporate through the boards.  In the case of concave
         cupping, the presence of an impervious surface finish on
         the floor may prohibit the transmission of moisture,
         causing it to build-up on the back side of the board.

    D.   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 REFERENCES

    A.   National Wood Flooring Association
         www.woodfloors.org 

PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Moisture Meters:

         1.   Moisture Register Products Div.
              Aqua Measure Instrument Co.
              www.aquameasure.com 

         2.   Delmhorst Instrument Company
              www.delhorst.com 


         3.   Lignomat USA, Ltd.
              www.ligonomatusa.com 


         4.   Wagner Electronic Inc.
              www.wagnermeters.com 

    B.   Hygrometers and Sling Psychometers:

         1.   Fisher Scientific
              www.fishersci.com 

         2.   Forestry Tools & Supplies 
              www.forestry-suppliers.com

2.02 MATERIALS

    A.   Wood screws

    B.   Soap or paraffin to lubricate screw

    C.   Commercial wood putty

    D.   Headless steel pins

    E.   Wood floor refinishing materials (see 06400-10-R)

    F.   Clean, white towels

    G.   Clean, potable water

2.03 EQUIPMENT

    A.   Moisture meter or sling psychrometer

    B.   Dehumidifier

    C.   Screwdriver

    D.   Hammer

    E.   Floor refinishing equipment (see 06400-10-R)


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   Correct moisture levels by removing the source of excess
         moisture.

         1.   Use a dehumidifier or check outside drainage to see
              that water is draining properly away from the
              building.  

         2.   Regrade if necessary.

    B.   Allow the boards to dry out (this may take several weeks
         or months).  

    C.   Take moisture readings bi-weekly or bi-monthly to
         accurately determine humidity levels.  Use a sling
         psychrometer or digital thermometer hygrometer.

    NOTE:  DO NOT PROCEED WITH ANY REPAIRS UNTIL THE MOISTURE
    READINGS ARE BALANCED BETWEEN THE FACE AND BACK OF THE BOARD
    FOR AT LEAST 30 DAYS.

    NOTE:  FLOORS WITH A SURFACE FINISH WILL DRY OUT MUCH SLOWER
    AS THEY TEND TO RESPOND MUCH SLOWER TO MOISTURE CHANGES IN THE
    ENVIRONMENT.


    D.   If the cupped boards dry out, they should return to their
         normal position.

    E.   If the boards flatten when fully dried, resecure loose
         boards to the subfloor.

         1.   For floors installed using nails:

              a.   Check for loose nails.  These may be quickly
                   located by identifying squeaks in the floor or
                   loose boards.

              b.   Face-nail loose boards or refasten with wood
                   screws.  See also 09560-04-R for guidance on
                   silencing squeaking wood floors.

         2.   For Floors Installed Using Mastic:

              a.   Check adhesion of floorboards to subfloor.
                   Walk across the floor and listen to the sounds
                   made.  If a popping sound is heard, or if the
                   floor sounds hollow when tapped, adhesion is
                   probably lost.

              b.   Remove affected boards.  Some adhesives such
                   as asphalt cut-back mastic can be reactivated
                   by lightly spraying it with kerosene.  Consult
                   manufacturer for recommendations.

                   -OR-

                   Drive headless steel pins through the affected
                   boards and into a wood or concrete subfloor.

    F.   Once the floor and fasteners are secure:

         1.   Fill cracks with commercial wood putty.  See 09560-
              02-R for guidance on repairing small holes and
              cracks in wood floors.

         2.   Reapply surface finish.

              -OR-

              Buff with 00 steel wool, clean and rewax.

              NOTE:  IF A POLYURETHANE FINISH WAS USED, RECOAT
              ONLY IF THE FLOOR HAS NOT BEEN WAXED.

    G.   If the floor remains cupped after drying, it must be
         completely resanded and refinished (see 06400-10-R for
         guidance).

         NOTE:  BE SURE TO FILL CRACKS, CHECK FASTENERS AND MAKE
         ANY REPAIRS BEFORE SANDING.

    H.   A severely warped or buckled floorboard which cannot be
         worked back into place, will have to be replaced, see
         09560-01-R "Replacing Damaged Floorboards" for guidance.

                             END OF SECTION
 


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