In rock climbing, “trad” is short for traditional. For climbers the designation of “trad” means purity: no drilling is done, the anchors are set into cracks and rely on the skill of the installer to save them from a fall. In the case of roofing: traditional roofing means no modern solutions like manufactured components, sealants, or other temporary products. When we design a traditional roof, the goal is to make it permanent. A roof should last the entire lifespan of a building. A temporary roof has to be re-roofed multiple times during the life-cycle of the building at considerable cost each time. It is better to invest upfront, and make the roof as durable as the rest of the exterior finishes.
Classically there are a few materials which have proven track records of protecting buildings for multiple centuries: Slate, Tile, and Copper.
Material selection is the easy part. The custom builder, the preservation architect, and the institutional project manager, often wisely selects these materials for historic projects. The problem with selecting these great materials in America: There is no group that juries members who practice the trade, and there is no governing body that sets standards for proper work or curriculum for study. Most of the “new” roofs you see constructed of these great materials are relying on modern (disposable) products to ensure they actually function. Further, there is no legal structure for recourse. If you commission a “historical” roof, and the company selected shows up, does a great job, leaves it looking good (from the ground): this leaves most in the market with the impression they are getting a good service, and a permanent roof. However with properties changing hands so often, the new owner, or the owner in 50 years is going to have a time-bomb on their hands when the temporary sealants, solder and other questionable techniques start to show their inferiority.
This is the status of most homeowners and institutions that have historic roofing, either original or re-commisioned at some point in history; they inherit all the problems and defects caused by poor training, no oversight, and no standards. Many of these defects don’t show up until the poor design has been through many decades of service. In my travels inspecting historic roofs all over the country and the Caribbean, I have seen very few examples of historic work done properly in metal. We did have some great slating traditions that made it over from the old country, and there is a solid heritage in the northeast of very well made slate roofs. This issue was brought to light with Joe Jenkins: in the Slate Roofing Bible. This book is the best source for knowledge on the history of slate roofing and following Joe’s instructions laid out in this reference will produce excellent results.
Where the Slate Roof Bible falls short: is the history and heritage of metal roofing, and the metal flashing associated with most slate and tile roofs.
Our best example and longest surviving specimen of metal roofing is on the palace at Acchen. It is estimated some of these sections date back to the year 800 and are still functioning to this day. The methods those craftsmen used to join the roofing pans together did not include solder. All edges were directly seamed together with a hammer and anvil. For this to happen and still allow for water to flow over the seams, is a process very akin to tailoring, and less to roofing. One standing seam is installed, and then beat down out of the way, then another connecting seam is installed on-top of that laid-down seam. Once the top seam is folded, it is then beat down so the connecting seam can be picked back up and once they are both standing, the un-folded edge can be folded with hammer and anvil to complete the connection. This is a tedious process that requires an experienced hand to keep from cracking the material, or destroying it in the process of seaming. This process, repeated on every seam intersection will allow the whole roof to expand and contract without stressing any individual “pinned” or “glued” detail. The seam holds the sheets together mechanically, and also allows for movement at the bottom of the seam where the sheets are free-floating.
This trade, in the traditional form practiced all over Europe for the last 1200 years never made it to America. The guilds that trained members, protected secrets, and progressed the techniques in the trade were property of their patrons. Guild members were the “exemption class” in feudal times. They were able to move freely and take commissions for building as it was needed, while most citizens were tied to the land they were born on, and the crown they were born under. However they were only allowed to work on guild sanctioned projects, and they of course were tied to the guild for life. Being removed from the guild would be economic suicide for any member or group. As we move into late history, and colonial times the guilds were kept in the home countries, and the members had little incentive to leave their guild for an un-known market in the colonies. The wars and social upheaval of the 18th, and 19th centuries further solidified this split. The colonies developed their own methods, mostly influenced by necessity. Terneplate was available in easily transported boxes similar in size and weight to a bundle of asphalt shingles. This made it a great choice for the early colonial metalworkers. They would join the “plates” together to form a long strip, which would become their roofing pan. This fabrication was usually done on-site, or very close to the final destination of the material. These strips could be rolled up into “coil” and carried onto the roof where the two legs of the pan where formed on the roof. This process is not so different from their guild counterparts in Europe, but the difference has more to do with what happened in the details. The american craftsmen, having no knowledge of the guild secrets or knowledge base, did not have the training to seam edges together on details. What they did have was solder. Anyone performing metal roofing in those times would have supplemented their income with other tin-shop work when there were no roofs to do. They would have already been well versed in tinning, soldering kettles, pots, and any other durable item needed by the town. They applied this tin-shop knowledge improperly to their roofing designs: which started us down a path of soldered roofing elements.
As architectural styles moved into European romantic revival, we see more complicated rooflines that required the knowledge of a guild craftsmen. Since we had none here, and already had a tradition of soldering terneplate and producing “good enough” results, this practice was continued on these more complicated roofs. Any roofer who has worked in an old city will be familiar with tearing this work out, usually as the lowest layer, with other systems added on-top of the original metalwork after it failed. Dead valleys, built-in gutters, and flat sections were treated with this soldered “patchwork” terne almost exclusively.
If the goal of permanent roofing is to last the lifetime of the structure, we can agree that most of these designs; while durable are not permanent. A survey of the “original” roofing stock in any old city will produce a few examples of this original “golden era” terneplate work still functioning. Most of these examples of surviving work are very simple hip or gable roofs, with no or few soldered details. The majority of this work failed, within 100 years or less. As is evidence by a scan of any skyline in historic neighborhoods where most properties are now with asphalt shingles and disposable products.
It didn’t have to be this way though…
We’ve already identified the differences between american tin-shop work and traditional European, guild-influenced metal roofs. The main factor is education of the installer. Guilds were expensive, they required patronage, much like any form of higher learning. The patron invest in the student while they are learning, under the assumption it will pay dividends in the future. This system actually worked for them: cover the expenses of the student while they are learning and once they graduate and start working, you get a much better product. We didn’t have patrons willing to fund schools here, and we had a market that rewarded the “good enough” approach of those who were willing to attempt the work without formal training. We are now holding the bag in the form of deteriorating historic roofs, and a labor force that has no direction on how to rebuild them properly.
There are a number of large roofing companies that specialize in these high-end products, and countless small shops that do slate and copper residentially anywhere where we have a building stock with these original roofs, and the quality of most of this work is measured based on the standards of the american tin-shop approach. Soldering roofing elements is considered workmanlike, commendable even. The same work winning awards and accolades here in the states, if inspected by a guild member would get you thrown out of class.
Of the market leaders surveyed in the midwest: There is an extreme deficiency in the knowledge of solder-less, fully seamed roofing, in keeping with the best standards. This is not really subjective as Europe has a 1200 year tradition of seamed roofing in all weather conditions. They have roofs that are older than our country, still standing, and still giving a return on initial investment. They have also codified the guild system into a modern secondary education program, complete with standards, and a governing body to ensure those licensed to practice metal roofing are getting the proper training, and maintain integrity in design and execution throughout their career.
I’m looking at you: veterans of the industry in America. The ones who’ve won awards doing flat-lock and half-hearted attempts at copperwork. You’ve made a lot of money doing “good enough” roofs, and passing the buck onto this generation. None of this information was readily available and my thesis has developed over 14 years of studying this industry and the history, and what happened to the quality. You wonder why there’s no young folks wanting to enter the trades? There is no incentive without the patronage and education. First step is accepting you have a problem.