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Historic Preservation - Technical Procedures

Spectitle:

Replacing Wood Treads And Risers

Procedure code:

0643002R

Source:

Hspg Prepared For Nps - Sero

Division:

Wood And Plastics

Section:

Stairwork & Handrails

Last Modified:

10/31/2014

Details:

Replacing Wood Treads And Risers



REPLACING WOOD TREADS AND RISERS


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing and
         replacing damaged wood treads and/or risers.

    B.   Wood stair treads and risers are very susceptible to
         damage because they are constantly exposed to wear.

    C.   Exterior stairs are even more susceptible to damage
         because of exposure to the weather.  Open joints and
         cupping of treads and risers may result from inadequate
         ventilation, preventing the sufficient evaporation of
         moisture.

    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.   Stair/Ramp Covering - Composed of the treads, risers,
         cove molding, nosing (molded or attached), and nosing
         return.  The treads and risers can be connected by a butt
         joint, a rabbet joint, or a tongue-and groove joint.

1.03 SYSTEM DESCRIPTION

    A.   A wood stair covering in proper condition is free from
         decay and is structurally sound.

         1.   The treads and newel must be rigid, the connections
              between all parts must be tight and sound, and all
              trim pieces must be present, undamaged, and adhered
              properly.

         2.   The treads should have a slight descending pitch to
              ensure drainage.  

         3.   The treads should have an integral front nosing.  

         4.   The underside of treads should have a routed drip
              so that water cannot enter the connection between
              tread and riser.  

         5.   The construction should have proper ventilation
              underneath to prevent cupping.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Lumber for replacement risers and treads - treated with
         wood preservative

    B.   Hardwood for wedges

    C.   Wood scrap, same as tread (for assistance in placing
         wedge)

    D.   Nails

    E.   Caulk

    F.   Paint

    G.   Wood glue

2.02 EQUIPMENT

    A.   Hack saw

    B.   Pry bar and putty knives for trim removal

    C.   Utility saw

    D.   Pencil, square, and straight edge for marking

    E.   Hammer and block

    F.   Chisel

    G.   Rooter

    H.   Saw (for wood cuts)

    I.   Drill

    J.   Keyhole saw

    K.   Screwdriver

    L.   Knife to cut wedge excess


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Inspect for paint that is worn, chipped, peeling,
         blistered, or flaking.  

         1.   A proper paint seal is imperative to the protection
              of the wood from decay.  If paint is peeling, decay
              may already be underway.  

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

    B.   Inspect for wear in the surface such as chips or gouges.
         If the wear is minimal, holes can be filled and the
         surface restored.

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

3.02 PREPARATION

    A.   Surface Preparation:

         1.   Waterproof or treat wood with preservative and back
              prime all pieces before installation paying
              particular attention to the end grain.  See
              procedure 06310-01-P for guidance on applying a
              water-repellant preservative.

         2.   To replace damaged wood treads and risers, match
              existing depth.

         3.   Reproduce the joint technique of the original; butt
              joints are easier to repair but dadoed joints are
              stronger and resist movement.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   If underside of tread is salvageable:

         1.   Carefully remove tread and use underside as new top
              surface.

              a.   If tread and riser are butt jointed:

                   1)   Pry off nosing return and cove molding
                        return.

                   2)   Remove balusters by sliding them out of
                        slot in tread and pull down from hole in
                        handrail.

                   3)   Pry off cove molding from under front of
                        tread and carefully begin prying tread
                        from riser below.  Pry only enough to
                        insert utility saw blade.

                   4)   Pry tread from riser below and cut nails
                        with saw.  Pull tread free from above
                        starting at outside edge.

              b.   If tread and riser are dadoed:

                   NOTE:  THE RISER MUST BE SACRIFICED.

                   1)   Drill holes at base of riser above tread
                        and cut along joint with saw blade.

                   2)   Pull tread free from above by starting at
                        outside edge.

                   3)   Cut and properly fit new riser. Glue in
                        new wedge below riser position at inside
                        stringer. Replace riser and toenail into
                        inside stringer from behind.

         2.   Turn tread over and mark 45 degree miter for nosing
              return on outside corner. Measure old baluster
              position and mark inside new miter line. Cut out
              miter and baluster positions.

         3.   Make angled cut at inner corner at new outside edge
              to accommodate angle of stringer.

         4.   Fit scrap, same width and thickness as tread, into
              inside stringer.  Fit new wedge underneath
              accordingly and remove scrap.

         5.   With hammer and block, knock tread with glued inner
              edge into position and nail tread to top of outer
              stringer.

         6.   Replace balusters, nosing return, and cove molding.
              When replacing nosing return, glue only miter and
              adjacent surface to allow for expansion between
              pieces.

    B.   If underside of tread is NOT salvageable:

         1.   Remove nosing return, cove molding, and balusters
              as above.

         2.   Drill starting holes through tread to cut it into
              thirds. Saw across tread in two places; nick
              risers, but, do not damage surface of risers.

         3.   Remove center portion of tread by driving chisel
              into tread over riser to break off nosing of tread.
              Do not damage possible riser tongue. With chisel
              turned sideways, remove remaining tread section.
              Remove protruding nails.

         4.   On new tread, measure old baluster position and
              mark inside new miter line. Cut out miter and
              baluster positions.

         5.   Make angled cut at inner corner at new outside edge
              to accommodate angle of stringer.

         6.   Fit scrap, same width and thickness as tread, into
              inside stringer. Fit new wedge underneath
              accordingly and remove scrap.

         7.   With hammer and block, knock tread with glued inner
              edge into position and nail tread to top of outer
              stringer.

         8.   Replace balusters, nosing return, and cove molding.
              When replacing nosing return, glue only miter and
              adjacent surface to allow for expansion between
              pieces.

    C.   If underside of stair is accessible:

         1.   Remove wedges from tread/stringer and
              riser/stringer connections.

         2.   Remove screws or nails that connect tread to riser.

         3.   With chisel, force riser down from tread.  With
              hammer and block, tap tread back from front.

         4.   Cut and fit new tread or riser to match original in
              size and thickness.  Hold tread and riser together
              temporarily with nail.

         5.   Drive vertical wedge in behind riser at stringer.
              Cut off wedge excess flush with bottom of tread.
              Remove nail.  Drive glue-soaked horizontal wedge in
              below tread.  Chisel off excess wedge flush with
              stringer.

         6.   At 6" from each end, drill pilot holes and drive
              screws through riser above center of tread.

    D.   Additional Instructions for Exterior Stairs:

         1.   Rout a rounded drip edge into the bottom of the
              tread so that water will not enter the joint
              between the tread and the riser below.

         2.   Make the tread nosing integral with the tread.

         3.   Prime all bare wood, using primer compatible with
              top coat.  For redwood or cedar, use a latex primer
              containing a dye reactant.  Prime edges, ends and
              both sides.

              NOTE: Treated lumber containing creosote,
              pentachlorophenol or other oily preservative
              solutions cannot be painted.  Lumber treated with
              waterborne salts can be painted or stained.

         4.   Caulk all joints to seal out moisture.

         5.   Apply top coats of paint compatible with prime
              coat.

3.04 ADJUSTING/CLEANING

    A.   Shrinking may occur within a year.  Repair may involve
         minor filling and repainting.

                         END OF SECTION
 


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