Securing An Exterior Wooden Balustrade

Procedure code:
643001S
Source:
Hspg Prepared For Nps - Sero
Division:
Concrete
Section:
Stairwork & Handrails
Last Modified:
11/05/2014

PART 1---GENERAL

1.01 SUMMARY

  1. This procedure includes guidance on repairing a wooden balustrade, including the handrail, the footrail and the balusters.
  2. 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

  1. 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

  1. 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

  1. Periodically (late spring and late fall) inspect and clean surfaces.
  2. Check condition of caulking and replace as necessary.
  3. 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.
  4. Rinse surface thoroughly with clear water twice. Corners should be scrubbed with a tapered-end hand brush or hand held mop strands.
  5. Use sponge along with clean water to rinse. Remove streaks with a damp chamois and water.
  6. 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

  1. Wood screws
  2. Galvanized finish nails
  3. Replacement baluster
  4. Wood dowels
  5. Mild soap
  6. 5% liquid bleach solution
  7. Clean, potable water

2.02 EQUIPMENT

  1. Ice pick (for determining the presence of decay)
  2. Waste container
  3. Corn broom
  4. Dust pan
  5. Supply of treated rags
  6. Wood glue
  7. Hammer
  8. Screwdriver
  9. Drill
  10. Chisel for mortising
  11. Wood blocking
  12. Replacement piece (if needed)
  13. Two buckets (for extra solution and rinse)
  14. Two sponges (for solution and rinse)
  15. Brushes and string mop
  16. Supply of dry wiping cloths and chamois
  17. Broom and garden sprayer

PART 3---EXECUTION

3.01 EXAMINATION

  1. 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

  1. 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

  1. 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:
      1. Drill pilot holes to avoid splitting the wood when nailing.
      2. 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.
      1. Cut a kneelplate from extruded angle metal or barstock or purchase as a prefabricated corner brace.
      2. Mortise it into the end of the rail.
      3. Position it and screw it in place on the post.
      4. Lower the handrail down over the kneelplate and adhere the kneelplate to the bottom of the rail with a screw.
  2. 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.
  3. Repairing a Footrail:
    1. If footrail is sound, but sagging, it is probably inadequately supported.
      1. 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.
      2. 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.
  4. If pieces are completely taken apart, backprime all end grain surfaces before reinstallation.
  5. 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.
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