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Historic Preservation - Technical Procedures

Spectitle:

Securing An Exterior Wooden Balustrade

Procedure code:

0643001R

Source:

Hspg Prepared For Nps - Sero

Division:

Wood And Plastics

Section:

Stairwork & Handrails

Last Modified:

11/05/2014

Details:

Securing An Exterior Wooden Balustrade



SECURING AN EXTERIOR WOODEN BALUSTRADE


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on repairing a wooden
         balustrade, including the handrail, the footrail and the
         balusters.

    B.   An exterior wooden balustrade system is particularly
         susceptible to decay for a number of reasons:

         1.   Individual members are usually ornamentally turned
              or carved, exposing a large degree of end grain in
              proportion to the size of the member to wear and
              weather.  

         2.   The handrail takes all the weight from forces
              applied to the balustrade.  It is usually connected
              to a column or post with a butt joint which does
              not allow for the transfer of any load to the
              column and exposes the end grain to weather;
              therefore, making this joint highly prone to
              moisture infiltration and the handrail to decay.  

         3.   Decay in a baluster typically occurs at the joints,
              particularly at the footrail if the top surface of
              the footrail is not sloped to shed water.  

         4.   Decay may also occur in the footrail if the bottom
              surface is too close to the ground.  If the
              footrail is not adequately supported, the entire
              balustrade assembly will sag.

1.02 DEFINITIONS

    A.   Balustrade - The components consist of the handrail,
         footrail and balusters.  The handrail and footrail are
         joined at the ends to a column or post.  The balusters
         are vertical members that connect the rails.

1.03 SYSTEM DESCRIPTION

    A.   A wooden balustrade in proper condition is rigid and free
         from decay. It is designed with sloping surfaces to repel
         water and has properly caulked, tight joints.

1.04 MAINTENANCE

    A.   Periodically (late spring and late fall) inspect and
         clean surfaces.

    B.   Check condition of caulking and replace as necessary.

    C.   Clean with a mild soap and water and scrub with a soft
         bristle brush. Do not allow cleaning solution to remain
         on surface for more than 10 minutes.

    D.   Rinse surface thoroughly with clear water twice. Corners
         should be scrubbed with a tapered-end hand brush or hand
         held mop strands.

    E.   Use sponge along with clean water to rinse. Remove
         streaks with a damp chamois and water.

    F.   Remove mildew, moss, fungal growth, and vegetation with
         a 50/50 mixture liquid bleach and water.  Scrub with a
         natural or nylon bristle brush and rinse thoroughly.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Wood screws

    B.   Galvanized finish nails

    C.   Replacement baluster

    D.   Wood dowels

    E.   Mild soap

    F.   5% liquid bleach solution

    G.   Clean, potable water

2.02 EQUIPMENT

    A.   Ice pick (for determining the presence of decay)

    B.   Waste container

    C.   Corn broom

    D.   Dust pan

    E.   Supply of treated rags

    F.   Wood glue

    G.   Hammer

    H.   Screwdriver

    I.   Drill

    J.   Chisel for mortising

    K.   Wood blocking

    L.   Replacement piece (if needed)

    M.   Two buckets (for extra solution and rinse)

    N.   Two sponges (for solution and rinse)

    O.   Brushes and string mop

    P.   Supply of dry wiping cloths and chamois

    Q.   Broom and garden sprayer


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Regularly inspect for dirt build-up.  Cleaning should be
         done regularly, see Section 1.04 above for maintenance
         guidelines.

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

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

3.02 PREPARATION

    A.   Protection:

         1.   Mask or cover adjacent surfaces and permanent
              equipment during repair and maintenance. Coverings
              must be adhered without adhesive tape or nails.
              Impervious sheeting that produces condensation
              shall not be used.

         2.   Protect landscape work adjacent to or within work
              area. Protect tree trunks with plank barriers. Tie
              up spreading shrubs. Protective covering must allow
              plants to breathe and be removed at end of the work
              day. Scaffolding legs must be placed away from
              plants. Plants cannot be pruned without prior
              approval of historic architect or horticulturist.

         3.   Scaffolding, ladders, and working platforms shall
              not be attached in any way to building. If ladder
              must lean against building, legs shall be covered
              with fabric so as not to mar surface of building.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   Repairing a Handrail - Where the handrail is connected to
         the column with a butt joint, it may be re-attached and
         secured in a series of different ways:

         1.   If wood is still relatively sound:

              a.   Drill pilot holes to avoid splitting the wood
                   when nailing.

              b.   Toenail the handrail back in place.  Use
                   galvanized finish nails because they are more
                   weather resistant and grip the wood better.

                   NOTE:  THIS IS THE LEAST EFFECTIVE METHOD OF
                   ATTACHMENT.

         -OR-

         2.   If enough wood is present to accept a screw,
              toescrew the handrail back in place.  Use a
              galvanized, bronze, or stainless steel screw.
              Countersink it and plug the hole before painting.

              NOTE:  THIS METHOD OF REATTACHMENT IS BETTER THAN
              TOENAILING.  THE SCREW HAS THE ABILITY TO DRAW THE
              MEMBERS TOGETHER AND HOLD THEM THERE.  

         -OR-

         3.   Install a kneelplate to secure the handrail in
              place.

              a.   Cut a kneelplate from extruded angle metal or
                   barstock or purchase as a prefabricated corner
                   brace.  

              b.   Mortise it into the end of the rail.  

              c.   Position it and screw it in place on the post.

              d.   Lower the handrail down over the kneelplate
                   and adhere the kneelplate to the bottom of the
                   rail with a screw.

    B.   Repairing a Loose Baluster:

         NOTE:  BALUSTERS ARE USUALLY SECURED BY TOENAILING.

         1.   Remove nail and secure with a screw.  Countersink
              screw and plug hole.  If baluster can be rotated,
              it can be secured with a dowel screw (threaded at
              both ends).

         2.   If top and bottom of baluster are the same and
              baluster bottom is decayed while the top is sound,
              baluster can be inverted with the appropriate filler to repair the baluster bottom.

         3.   If baluster is ornately carved, try using epoxy
              consolidant.  

              NOTE:  EPOXY CONSOLIDANT SHOULD BE CONSIDERED WHEN
              WORKING WITH HISTORIC MATERIALS SINCE EPOXIES
              ENABLE ONE TO SAVE AS MUCH OF THE ORIGINAL MATERIAL
              AS POSSIBLE.

         4.   If baluster has a square cut end, a replacement can
              be made for the end only and connected to the
              existing baluster with a wood dowel and glue.


         5.   If baluster must be replaced, use wood of the same
              species and age as original if possible.  Replicate
              original exactly and install as original was
              installed.

    C.   Repairing a Footrail:

         1.   If footrail is sound, but sagging, it is probably
              inadequately supported.  

              a.   Support footrail at least every 4 feet.  

                   NOTE: Verify histoic appearance first.  If
                   railing is on a significant elevation, it may
                   not be appropriate to add new support
                   features.  

              b.   Add properly treated blocking as required.
                   Consult historic architect for appropriate
                   blocking type and size.

         2.   If footrail must be replaced, mill new piece with a
              sloped surface to shed water.

              NOTE:  MAKE SURE THAT A CLEARANCE OF 3" TO NOT MORE THAN 4"
              EXISTS BETWEEN FOOTRAIL AND FLOOR.

    D.   If pieces are completely taken apart, backprime all end
         grain surfaces before reinstallation.

    E.   After all reassembly has been completed and all surfaces
         have been sanded ready for repainting, caulk all joints
         with a paintable caulk, i.e., where handrail meets
         support post, top and bottom of balusters at their
         connection with handrail and footrail, and where support
         block of footrail meets the floor.

                         END OF SECTION
 


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