Repairing A Wobbly Or Broken Exterior Cast Iron Newel Post

Procedure code:
552301S
Source:
Developed For Hspg (Nps - Sero)
Division:
Metals
Section:
Iron Railings
Last Modified:
11/12/2014


REPAIRING A WOBBLY OR BROKEN EXTERIOR CAST IRON NEWEL POST

REFERENCES:

Margot Gayle, David Look, John Waite. Metals in America's Historic Buildings. Washington,DC: National Park Service, 1995.

L. William Zahner. Architectural Metals. New York: John Wiley & Sons, 1995.

PART 1---GENERAL

1.01 SUMMARY

A. This procedure includes guidance on repairing a wobbly or
broken exterior cast iron newel post. THIS TYPE OF REPAIR
SHOULD BE PERFORMED BY A PROFESSIONAL IRONWORKER.

B. A wobbly newel post may be caused by water from the
setting concrete or stone, improper setting, and/or
joints not caulked.

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).

D. For additional information on the characteristics, uses
and problems associated with cast iron, see 05010-04-S;
for guidance on inspecting cast iron failures, see 05010-01-S.

1.02 DELIVERY, STORAGE, AND HANDLING

A. Storage and Protection:

1. Cast iron railing or balustrade should be stored as
to protect from surface damage at all times,
carefully packed and should remain so from the time
of delivery until set. Keep uninstalled and
unpainted metal materials in a dry, rust-free
storage facility; surfaces to be welded are
generally not primed.

2. Salvaged historic material shall be carefully
packed and stored under cover and in the building
away from working or traffic areas. Mark salvaged
material with the year of removal.


PART 2---PRODUCTS

2.01 MATERIALS

A. Molten lead or lead wool

B. Screws and bolts

C. Wiping cloths

2.02 EQUIPMENT

A. Wire brush - removes rust and flaking metal as well as
loosened paint

B. Eye and skin protection

C. Heavy gloves and protective gear

D. Screwdriver

E. Welding equipment

F. Electric drill

G. Electric grinder


PART 3---EXECUTION

3.01 EXAMINATION

A. Before proceeding with steps to repair cast-iron newel
post, it is important to first determine the cause and
extent of the problem. Determine the age of the
railing/balustrade and examine the condition of the
entire surface. Inspect for:

1. Joints - which are open or misaligned, thus
allowing water into the railing or newel.

2. Parts - which have failed or which are unsecured,
broken, cracked, missing, distorted, or loose
(check screws and bolts).

3. Paint - coating failures such as chips, losses,
peeling, checks, bubbling, and wear.

4. Rust corrosion - caused by moisture including, sea
water and sea air, deicing salts, acids and some
soils.

5. Galvanic corrosion - corrosion caused when iron is
in direct contact with a dissimilar metal and is
wetted by rain, fog, condensation, etc.

6. Determine the source of the moisture which causes
the deterioration.

7. Determine if the railing/balustrade can be
salvaged.

8. Measure the dimensions of the various metal parts
needing replacement.

3.02 ERECTION, INSTALLATION, APPLICATION

A. Repairing A Wobbly Newel Post: This can usually be
repaired on site by a professional or in the shop by an
ironworker.

1. Reset the center rod in the base and weld small
supports at the base of the newel.

2. Drill holes in the masonry step or walk to
correspond with the supports.

3. Pour molten lead into the holes before setting the
newel.

4. Caulk all the joints and prime and paint the entire
assembly. See 05010-13-S and 09900-07-S for
guidance on painting cast iron.

NOTE: IRON THAT IS SET IN CONCRETE OR STONE SHOULD
BE PACKED IN LEAD TO PREVENT THE IRON FROM RUSTING.
LEAD IS SOFT ENOUGH TO STILL ALLOW THE IRON TO
MOVE.

B. Repairing Posts That Are Broken in Half: The posts must
first be internally reinforced with steel pipes.

1. Before attaching the elements, clean the surface of
any traces of dirt, oil/grease stains, peeling
paint, or rust. See 05010-05-R for guidance on
cleaning cast iron.

2. Weld the original elements of the posts back
together, using a professional welder. Grind down
any visible beads of welding material.

NOTE: SUCCESSFUL WELDING OF CAST IRON CAN BE A
RELATIVELY EXPENSIVE OPERATION.

NOTE: WELDING OF CAST IRON IS VERY DIFFICULT TO DO
IN THE FIELD. IT SHOULD BE EXECUTED ONLY BY A
SKILLED WELDER UNDER CAREFUL SUPERVISION.

CAUTION: DURING WELDING THE METAL BECOMES VERY HOT
AND CAN UNDERGO TREMENDOUS THERMAL SHOCK. IT MAY
RECRYSTALLIZE IF EXCESSIVE HEAT IS APPLIED.

a. For large sections, welding should take place
off site. The piece must be removed and
transported to a workshop where it can be
preheated before welding and postheated after
welding to ensure a gradual temperature change
within the metal.

b. Advantages of welding:

1) Arc welding produces a strong, durable
connection and, if properly executed, is
at least as strong as the surrounding
metal.

2) It is faster and less expensive than
threaded connections, which require
drilling a pilot and then tapping to
accommodate screws or bolts.

3) Welding is the most preferred for the
attachment of the decorative castings and
for other non-structural repairs for
economic reasons and because it allows to
preserve the original damaged elements,
which otherwise would have to be
replaced.

c. Disadvantages of welding:

1) In cases where the original attachments
are bolted, the use of this method may
result in internal stresses (welds cannot
move with seasonal expansion/ contraction
cycles) which may in turn lead to further
breaks.

2) Welding may leave a 'bead' along the
surface of the connection which may be
unacceptable in some restoration
projects, even though much of the weld
may later be ground down, depending on
the location and the welding material.

3) Metallic bond (gas) welding is more
reliable than fusion (arc) welding in
repairing large sections of cast iron,
because a lower temperature is used and
heat is applied and removed at a slower
rate.


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