The three Rs – restoration, repair and replication – are equally important in historic metalwork projects, and it takes an expert to know how to proceed
Click here for a list of metalwork repair specialists
By Martha McDonald
Repairing and restoring historic metalwork can be one of the most important parts of an historic preservation or restoration project. Whether it’s wrought iron, cast iron or sheetmetal, the basic approach is to first assess the condition and then move forward with cleaning and repairing it or replicating elements as needed. In all cases, it is recommended that an expert be called in from the beginning because misguided work can damage the historic value of the metalwork.
Doug Bracken, president of Wiemann Ironworks of Tulsa, OK, is a specialist in repairing, replicating and maintaining forged and wrought iron. "My advice is to consult with an experienced metalwork professional and/or an experienced architect or other design professional beforehand if the project involves restoration, reproduction or repair of historically significant metalwork," he says. "Regrettably, many good and well-intentioned metal shops do more harm than good if they
are not given the appropriate guidance in advance."
When repairing the monumental wrought-iron gates, posts and crest originally fabricated in 1928 by Samuel Yellin for the E.W. Marland Mansion in Ponca City, OK, Wiemann Ironworks
of Tulsa, OK, replaced one of the top rails, straightened several other structural members and reproduced some of the decorative cast and forged elements. The gates were sand blasted, epoxy primed and
top coated with a catalyzed urethane.
Bracken cites a case where he was asked to restore driveway gates originally made by Samuel Yellin, a prolific 20th-century ironworker based in Philadelphia. They had been hit by a car and sent to a welding shop for repair. When they were hit again, Wiemann was contacted. "By the time we got them, they had been altered significantly because of the welding repair work performed by the first shop," he says. "Invisible forge welds and amazing mortise-and-tenon joinery were repaired with exposed butt welds, so they no longer had the same kind of aesthetic, the same kind of joinery. Although it is subtle, these kinds of alterations and modifications can’t be reversed easily, so the beauty of the original will be lost for future generations."
When assessing conditions, Bracken says it’s important to clean and strip the metalwork. He looks at the metalwork itself, as well as the joinery and fasteners to see how the metal was attached and recommends pulling the metal out and sandblasting or stripping away the layers of accumulated paint and oxidation. "You need to get back to the base metal before you can make a decision about the work," Bracken says. "Otherwise, it’s basically a guess.
"Metal, like other building products, has a tendency to rot and disintegrate if not properly maintained. More often than not, the horizontal members and connections to the house and posts are most likely to be substantially degraded because they are often exposed to standing water or impossible to maintain," Bracken says. "The vertical members seem to last longer unless they are covered by vines or buried in earth, like the bottom rail of a fence. Sometimes, the paint is the
only thing holding the metalwork together. Sometimes, you will find that what you thought was cast is actually wrought or what you thought was iron is actually bronze. Care must be used in this phase as many of the old layers of paint likely contain lead; therefore, this work should be done by an experienced professional.
"When repairing metalwork," Bracken continues, "choose materials that match the existing in size and shape. Do not substitute tubing for solid bar, replace all of the fasteners and do not put back into service something that serves a life-safety role without being 100% sure it can and will perform. Railings that do not meet current building codes should be replaced, not repaired."
Bracken points out that there’s a difference between historic wrought iron and the alloy that is today commonly called wrought iron. "The contemporary definition of wrought iron is something that is worked by hand, but 99% of the time it is mild steel. We have been using steel for the past 60 or 70 years. If you’re a purist or your particular restoration requires the real pre-1920s wrought iron, you have to get it from scrap yards, or you can still get it from The Real Wrought Iron Co. in the U.K. Most people want the look of the metal and aren’t that particular about the alloy," he adds. "Aluminum can be cost competitive with iron in many cases, and when it’s painted and installed, it is indistinguishable from wrought iron."
When restoring wrought iron of any kind, Bracken says that once it has been stripped and assessed, a primer coat should be put on it as soon as possible. "Don’t let it weather or get exposed to the humidity and moisture in the air," he warns. "Use of a good-quality, rust-inhibitive primer is essential. Then follow that with good-quality top coats of either water-based or oil-based acrylics or urethanes. Mild steel does not weather as well as its predecessor, wrought iron, so
proper application and maintenance of the coatings are essential to extending its useful life. In more extreme environments such as salt air, or where the ironwork is constantly exposed to irrigation sprinklers, additional steps must be used to protect the work."
If the metalwork must be replaced, then the owner and metalworker will decide whether or not to replace it with the same material. "It depends on the job," says Bracken. "I have used cast-aluminum panels to replace cast-iron panels. It is more cost effective, and they are identical and behave the same once they are painted."
As for fasteners, Bracken says he generally uses stainless steel, which is "corrosion resistant and has less galvanic reaction with the stone and other metals. If the metal is anchored right into the stone, however, the old metal and anchoring materials need to be completely removed and reset in place. If you are restoring a balcony," he says, "you certainly won’t use the same fasteners and bolts. It should be attached through the wall and through the framing. Some earlier
attachments are unacceptable by today’s engineering standards."
Originally made of bronze, the Marland crest, along with many of the other decorative collars and bands, were gilded by Wiemann using 23k gold leaf.
Another method of anchoring metalwork is to use epoxies. "A traditional railing was usually set with lead or mortar, but we have replaced lead with pourable anchoring cements and epoxies. A lot of different adhesive epoxies are available for many different applications; many of them were developed for highway construction, but depending on your conditions, such as ocean exposure or constant dampness, some are much better than others," he says.
According to the National Park Service (NPS) Preservation Brief "The Maintenance and Repair of Architectural Cast Iron" by John G. Waite, AIA, with an historical overview by Margot Gayle, "Cast iron is an alloy with a high carbon content (at least 1.7% and usually 3.0% to 3.7%) that makes it more resistant to corrosion than either wrought iron or steel…." It notes that common problems include badly rusted or missing elements, impact damage, structural failures, broken joints,
damage to connections and loss of anchorage in masonry. The report also recommends retaining and repairing historic ironwork rather than replacing it whenever possible.
"Typically, on a residential project, we will look to see what is missing and in what kind of condition the metal is," says Robert Baird, vice president of West Jordan, UT-based Historical Arts & Casting. "Are the components in good enough condition that they can just be cleaned and repainted, or do you need to manufacture new parts? There is always going to be surface rust. We look for issues like broken castings and moisture that has gotten inside and corroded the metal from
the inside out. Most problems occur because of this, so we look for areas of moisture penetration."
The fasteners are another issue. "Cast-iron elements are usually bolted or fastened together," says Baird. "The fasteners will typically rust before the rest of the iron. "If we are restoring cast iron," says Baird, "we sandblast it and prime it within eight hours. If it sits overnight, it is sandblasted again before it’s primed. We use a coating system developed by a company called Tnemec that’s a combination of epoxy and urethane. We start with a primer that’s epoxy and
finish with polyurethane top coats. It’s a very durable system."
Baird notes that a lot of the old castings are full of porosity and holes, so "you have to take time in the painting to make sure you seal up the iron. If moisture gets in those little pits, they just bleed rust. You have to make sure to get an appropriate thickness of the coating to cover the iron."
The NPS report warns against filling "the voids of balusters, newel posts, statuary, and other elements" with concrete, because it promotes further rusting as the concrete cures and shrinks. Small decorative elements that need to be replaced, on the other hand, can be cast from molds and primed in the shop to prevent rust. Often, larger repairs cannot be done on-site, so it is necessary to dismantle the components to take them to the shop. The report stresses that great care
should be taken with the material, as cast iron is brittle, especially in cold weather.
As for substitute materials, the report notes that the most common ones are "aluminum, epoxies, reinforced polyester (fiberglass) and glass fiber-reinforced concrete (GFRC)." It stresses that every effort should be made to use original materials before turning to substitute materials. If they are used, however, each one has different characteristics and should be used accordingly. Aluminum, for example, can be used for ornate decorative elements but may result in galvanic
corrosion if it comes in contact with cast iron. Fiberglass is a lightweight substitute, but it cannot be used for structural elements. Epoxies are suitable for replicating small, ornamental sections of cast iron but, like fiberglass, are not suitable for structural elements. GFRC is lightweight and weather resistant but can cause corrosion to the original cast iron.
"The standard substitute material for cast iron is aluminum," says Baird. "It is lighter and easier to fabricate. There are certain cases when aluminum won’t work. If it’s a structural element, we won’t use aluminum, but if it’s an ornament, aluminum is okay." He adds that in some cases, "you can actually cast the missing pieces off of the existing components." If that won’t work because of the size difference, then new patterns and tooling are required.
Baird points out that historic alloys were a combination of materials. "They were essentially made of iron, but they would smelt whatever they had in the furnace. The metal would really vary. Today, we have more control of the alloy and the typical standard is class 30 gray iron, so you get a better part if it’s replaced."
Sheetmetal experts Heather & Little Limited of Toronto, ON, Canada, offers guidelines for assessing restoration, repair and replication. "When examining a metal restoration project," says Adam Pakvis, project and safety coordinator, "we look at the condition of the metal, how it has reacted with other building elements and what it would take to restore the original condition of the building. Sometimes, the wear and corrosion are so extensive that it is difficult to see what
the original condition was. If there are no clear examples, we will look at photographs or other historic evidence."
The first step is to document where elements are removed from a building, Pakvis says. "We generally take a sample back to our shop for further examination. This gives us a better idea of what it will take to restore the building. From this examination, we determine if repairs can be made or if reproducing the element is more logical."
As with other metals, stripping and cleaning are the next steps. "We strip and clean the metal using different methods to remove corrosion and debris," says Pakvis. "If there is an area that has deteriorated badly, we can form-shape new metal to reinforce the existing element."
Also similar to other metalwork, the decision whether to repair or replace is based on the amount of deterioration. "If the metal is corroded and the edges are separating, it is necessary to replace the elements," Pakvis explains. "However, if the sheetmetal has maintained its integrity and there are only a few problem areas, then we can restore the element by fashioning new pieces."
Replacement carries its own set of issues. "Color matching and attaching to existing elements are two big concerns," he adds. "Attachment is usually done by soldering, being careful not to damage the existing elements." As for color matching, Pakvis says that if allowed to age properly, the elements will eventually blend together. "There are some artificial patinas that speed up the process if time is a factor."
Whether it is cast or wrought iron, a substitute material or sheetmetal, metalwork is an important element of an historic preservation project. It requires a high level of knowledge and understanding of the material, the process and the history of the trade.
Click here for a list of metalwork repair specialists