Replacing a Damaged Subfloor Under Tongue and Groove Wood Flooring

CSI Division
Division 9 - Finishes
Section
Wood Flooring
Last Modified

Technical Procedures Disclaimer

Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.

Rewrite

We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.

PART 1–GENERAL

1.01 SUMMARY

  1. This specification provides guidance on replacing a damaged subfloor under tongue & groove flooring.

  2. Read “General Project Guidelines” along with this specification. 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). The 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)

PART 2–PRODUCTS

2.01 MATERIALS

  1. Replacement subfloor board.

  2. Nails.

  3. Wood blocking for board support at joist.

  4. Hardwood shims (if required).

  5. Construction grade plywood for complete subfloor replacement (thickness to match existing condition).

2.02 EQUIPMENT

  1. Pry bar.

  2. Wide-blade putty knives.

  3. Carpenter’s nippers to remove nail heads.

  4. Hammer for baseboard and finished floor removal.

  5. Saw to cut damaged subfloor board.

  6. Drill to make pilot hole for saw.

  7. Measurement tools.

PART 3–EXECUTION

3.01 EXAMINATION

  1. Check signs of a decayed subfloor, which include:

    1. Buckling or discoloration of the finished floor.

    2. A spongy texture.

    3. Water stains on the subfloor as seen from the underside.

    4. General dampness.

  2. Probe the wood with an ice pick to determine the existence of rot.

  3. Inspect for signs of insect infestation, such as mold, fungus, bore holes, and sawdust piles.

  4. Documentation: Photograph existing condition of flooring including pattern, etc. for ease of reinstallation.

3.02 PREPARATION

  1. Protection: Adjacent surfaces and permanent equipment must be masked or covered during repair and maintenance. Coverings must be adhered without adhesive tape or nails. Impervious sheeting that produces condensation shall not be used.

  2. Surface Preparation:

    1. NOTE: THE COMPLETE REMOVAL OF THE FINISH FLOOR MATERIAL IS ONLY REQUIRED WITH INTERLOCKING FLOOR ASSEMBLIES SUCH AS TONGUE & GROOVE.

    2. Before replacing the subfloor, carefully remove the baseboard and the finished floor, label and set aside for reinstallation.

      1. As each piece is removed, mark it to identify its original location; during storage, organize by location to ease reinstallation.

      2. Remove shoe molding of baseboard first, using gentle pressure on a pry bar at nail locations. Hold gaps open with blocking as work progresses along the length of each trim piece.

      3. Next, remove baseboard, beginning with top moldings which are often separate from the broad, flat sections. Remove it like the shoe molding, applying pressure only at nail locations until all nails are exposed and the trim pieces can be removed.

      4. To remove nails, pull them out from the back of the board; cut nail heads first, if required.

    3. When removing the floorboards, find the last board that was laid. Remove it and work in reverse of the manner in which the floor was installed.

3.03 ERECTION, INSTALLATION, APPLICATION

  1. Partial subfloor replacement: Cut damaged subfloor board off at nearest joist. Nail block to joist for new board support.

    1. Carefully measure the new board and do a trial fitting. Shim or rip as required to level the new board with the surrounding ones.

    2. Face-nail the new subfloor board to the joist or to the attached support block.

    3. When repair is complete, reinstall finished floor and baseboards to match historic condition.

  2. Full subfloor replacement: If the subfloor warrants complete replacement, consider 1” construction grade plywood. It provides a strong and dimensionally stable subfloor with no squeaks.

 

Print Page
Last updated: Apr 23, 2024
Top