When the time is right: Appropriate use of modern materials in a traditional roof system

In my capacity as an historic preservation contractor and consultant, I am often afforded the opportunity to become involved in exciting and challenging projects.  Recently, we were awarded the contract to restore the clay tile roof turrets at the Longy School of Music’s Zabriskie House.  Now a part of Bard College, the Zabriskie House is actually the historic Edwin H. Abbot House with a sympathetically designed addition built in 1969-70.  The deteriorated condition of the turrets, as well as lead-coated copper gutter linings and masonry dormers, had attracted the attention of the Cambridge Historic Commission and a commitment to the proper restoration of these systems was struck between the CHC, building owner and a private donor.

Before I can specify historically appropriate treatments, I need to don my consultant’s cap and dig into the history of a building to best understand its evolution.  Developing the background story will typically answer questions and fill in the blanks when examining traditional building systems.  An 1890 newspaper clipping held by the CHC reports that “[t]he stately home of Mr. Abbot, with its walled-in grounds, on the site of the old Arsenal, promises to be the most costly private dwelling in the city.”  An examination of records held by the Massachusetts Historical Commission and from the Library of Congress’ Historic American Building Survey reveal that the firm of Longfellow, Alden and Harlow designed the Richardsonian Romanesque portion of the building and that Norcross Brothers was the builder of record.

Alexander Wadsworth Longfellow, Jr., was the nephew of the famous poet and an important figure in the architectural history of the United States. After graduating from Harvard in 1876, he studied architecture at the Massachusetts Institute of Technology and the École des Beaux-Arts in Paris, after which he worked as a senior draftsman in Henry Hobson Richardson's office.  After Richardson's death in 1886, Longfellow partnered with Frank Ellis Alden and Alfred Branch Harlow to found the firm of Longfellow, Alden & Harlow.  With offices in Boston and Pittsburgh, the firm designed many important buildings including the Carnegie Library of Pittsburgh and the City Hall in Cambridge, Massachusetts.

Norcross Brothers Contractors and Builders was a prominent nineteenth-century American construction company, especially noted for their work, mostly in stone, for the architectural firms of H.H. Richardson and McKim, Mead & White.  Following the death of Richardson, the brothers became the contractor for many of McKim, Mead & White's projects.  As had been the case with Richardson, much of the value of the Norcross Brothers to architectural firms derived from Orlando Norcross's engineering skill. Though largely self-taught, he had developed the skills needed to solve the vast engineering problems brought to him by his clients. For example, the size of the dome at the Rhode Island Capitol was expanded very late in the design process, perhaps even after construction had begun, so that it would be larger than the one just completed by Cass Gilbert for the Minnesota Capitol.

The Edwin Abbot House is an interesting interpretation of the Richardsonian Romanesque style.  Whereas the great majority of such buildings feature rusticated, pink Milford granite in an ashlar pattern, trimmed with East Longmeadow brownstone, Longfellow created a unique spin for Mr. Abbot.  While trimmed with the brownstone, the field of the walls features coursed Weymouth granite of slightly varying heights.  The motif of orange, brown and golden hues of the stone is continued in the brick wall surrounding the property.  The roof is covered in a flat, square orange-red clay tile.  This is typical of Richardsonian Romanesque buildings which are almost exclusively roofed in clay tile, Monson black slate, Granville, New York, red slate, or some combination thereof.  It should be noted that because their need for stone was outpacing the supply, Norcross Brothers eventually acquired their own quarries in Connecticut, Maine, Massachusetts, New York, and Georgia.

The roof framing system of steel and terra cotta blocks is relatively rare but makes perfect sense when considered in context with what the latest flooring technologies of the era were.  A network of steel beams was bolted together to form the rafters, hips and ridges of the frame. Across each was welded rows of double angle irons (or, inverted T beams.)  Within these channels, in beds of Portland cement, was laid the terra cotta block.  The tile were then fastened directly to the blocks with steel nails.  Because of the ferrous nature of the fasteners, the normal passage of moisture vapor caused the nails to rust and expand slightly, anchoring them securely in place.  Whether this element of the design was intentional or simply fortunate happenstance, the result made for a long-lasting roof.

What doesn’t last forever in traditional roofing systems like slate and clay tile is the sheet metal flashing assemblies.  Over the years there must have been numerous failures which lead to the decision to remove the clay tile from the broad fields of the roof and replace them with red asphalt shingles in the 1980’s.  Confronted with the dilemma of securing the new shingles to the terra cotta substrate, a decision was made to sheath the roof with plywood.  Holes were punched through the blocks and toggles used to fasten it to the roof.  In one area where the asphalt shingles were removed, more than 50% of the plywood exhibited varying degrees of rot due to the normal passage of moisture vapor from the interior spaces.

Fortunately, the turrets had survived the renovations from thirty years before.  A conical turret, in the rear, and an eight-sided hip-roofed turret on the north sided required only repairs which, while extensive, did not require addressing issues with the substrate.  The sixteen-sided turret, on the primary façade of the building, was in poor condition.  Over the years, “repairs” included the use of non-matching tiles, red roofing cement, tar, caulk, and even red slate.  A scaffold was erected to allow safe, unfettered access to the entire turret and the process of removing the tile began.  Care was taken to conserve as many tiles as possible for use in repairing the other two turrets.

The substrate was examined closely and, save for thousands of tiny craters created by the original nails, found to be sound.  A new system for fastening the tiles had to be devised so that they could be attached to the terra cotta blocks. It was critical that the new method allow for the replacement tiles to be securely fastened and resist the damaging forces of escaping moisture vapor.  Cement board, comprised of 90% Portland cement and ground sand, was fastened to the blocks with ceramic-coated masonry screws.  The entire turret was then covered with a self-adhering membrane.  The replacement tiles were carefully matched and sourced from a salvage dealer in Illinois and secured with stainless steel fasteners.  The flat tiles, no longer manufactured new, are referred to as “Cambridge” tiles for their prevalence on the roofs of great homes and institutional buildings in and around Cambridge, Massachusetts.

While I typically advocate for the retainage of all historic fabric when preserving and restoring traditional building systems, there are exceptions.  In the case of the Abbot House roof, we encountered once-modern technologies which pointed us toward contemporary means and methods.  Rusting steel nails in the terra cotta block worked brilliantly for the initial installation but seemed ill-conceived for a second go around.  The use of non-ferrous fasteners and a new substrate that is impervious to moisture infiltration will guarantee the turret’s service life for the next 125 years or more.
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Is Greener Always Better? Problematic Use of Modern Materials in Traditional Building Systems

When new words and terminology enter our vernacular, they often take on a connotation larger and broader than they deserve.  Today, “green” and “sustainable” are synonymous with responsible living and construction, their meanings understood as clearly by an architect or engineer as they are by the lay person.  They are buzz words that make consumers feel good about their purchases; they’re doing their part to protect the environment and help save the world.  But, in certain applications, use of these terms is more than a misnomer; it’s outright false advertising.

Technological advances in building science have allowed for the creation of the most energy efficient systems and materials that the construction industry has ever seen.  With the ever rising cost of every fuel type, energy conservation is always a high priority when planning for and designing buildings.  Buildings, historically, are only as efficient as the technology of the day allowed.  While we may shudder with the chill of a stiff breeze standing by the window in an 1885 Queen Anne Victorian, imagine the relative level of comfort that one of the Pilgrims would have enjoyed in the same situation!

Today’s building designers want to create watertight, airtight structures that use minimal amounts of energy with windows sealed tight and year-round climate control for maximum comfort.  They strive to design an envelope that needs low or no maintenance, fully accepting that building owners will not care for their buildings as a given.  As far as new construction goes, there’s no problem.  In fact, this is good news.  But what happens when the owners of older buildings want to implement these new technologies to increase the efficiency of their buildings?

Older building stock tends to be far less efficient than modern buildings.  Wall systems and joinery, windows and doors—they’re just not as tight.  An unexpected benefit of these inefficiencies is the passive ventilation that occurs, be it laterally through windows, doors and walls, or by the “stack effect” in which warm air rises, bringing vapor with it, escaping through the uninsulated roof system.  Know this: older buildings breath.  Modern building systems are designed so that structures don’t breath and vapor is removed with dehumidifiers or other mechanical forms of ventilation.

In older buildings, solid masonry walls rely on the temperature gradient between interior conditioned spaces and the outside for walls to drain properly.  Insulating these walls stops or mitigates the passage heat through the solid brick masonry.  This slows the drainage/drying process and traps moisture vapor in the wall which, during freeze-thaw cycles, freezes and expands up to 12% in volume.  Oftentimes the result is damage to the wall system of the envelope.  Instead, the focus should be on controlling moisture and preventing it from entering the wall system, both inside and out.

Today, older buildings have kitchens, bathrooms and laundry spaces that they didn’t when first built.  This introduces a significant amount of moisture vapor that may enter the wall system from the interior.  Installation of a vapor barrier will prevent this from occurring without impacting the thermal effect that heated interior spaces have on the exterior walls.  Outside, mortar joints must be kept tight and full.  Penetrations such as window and door jambs must be sealed tight where they abut masonry to prevent water intrusion. 

Roof drainage systems must be functional; gutters protect and shed the walls from runoff and properly placed leaders direct the rainwater away from the building at grade.  It’s also interesting to note that many older masonry buildings have large windows resulting in a high window opening-to-wall surface area ratio.  Improving the efficiency of the fenestration through conservation and repair, as well as the addition of efficient interior or exterior storm windows, will help preserve the historic integrity of the building while also saving on energy costs.

Recently a client contacted me with questions and concerns about insulating his masonry walls.  He was engaged in gutting much of the interior space in his circa 1870 brick townhouse in a National Register historic district in Boston’s South End.  The building department was demanding that he insulate behind the walls in compliance with the International Energy Conservation Code.  When we pointed out that the code specifically exempts buildings on or eligible for inclusion on state or national historic registers, he said it didn’t matter if there was a lot of interior gutting; that was his interpretation of the code.  Only later, when a staff member from the Boston Landmarks Commission intervened, was he straightened out.

Before you breath a sigh of relief, owners may have to prove that their historic projects are worthy of exemptions from the International Energy Conservation Code following changes to the forthcoming 2015 version approved by the International Code Council last year.  The changes were proposed by representatives from the New Buildings Institute, the Natural Resources Defense Council and the Institute for Market Transformation and they remove the exemption language from the code. The group added a requirement that permit applicants file a report with a code official when seeking immunity on specific areas of their project.

Do they sound like groups that know about old buildings?  No, they don’t.  They sound like groups that think LEED certification matters when it comes to old buildings; you know, organizations that don’t think full life cycle analysis matters in “green” building practices.  Why wouldn’t the team include representatives from the Association for Preservation Technology or the Preservation Trades Network?  And, frighteningly, who will train the code official that decides whether a project receives an exemption or not?  The answer is NOBODY.  So guess what happens when you encounter our friend in Boston?

More and more I’m coming to believe that these people actually hate old buildings.  I’ve had arguments with architects and contractors who wanted to spray closed-cell foam insulation between the rafters under slate roofs.  Some specified removing all the slate and covering the roof with an ice and water shield membrane then reinstalling the slate, effectively “sealing” the roof tight.  Besides being an unnecessary, exorbitant extra cost, there’s a big problem with these grand, USGBC-inspired plans:  they actually destroy the materials in a traditional roofing system.

Slate, clay tiles and wood shingles are traditionally fastened to battens, skip sheathing or regular old boards—not plywood, no underlayments.  The roofs are water tight, not air tight and the building breaths through the roof.  Fiberglass insulation can improve energy efficiency and reduce heat loss without preventing the roof from breathing.  Additionally, soffit and ridge ventilation can be added if desired.  Traditional roof materials like slate, clay tile and cedar shingles experience condensation.  The passage of vapor helps dry things out.  When you stop the roof from breathing everything stays wet.

Slate is comprised of thin layers of metamorphic rock that delaminate and fall apart when they are kept damp for months.  Clay tiles, like terra cotta and brick, will disintegrate.  Wood shingles rot.  Steel fasteners will experience corrosion and fail.  This has been the end of many a slate roof; I’ve pulled the slates off the roof and seen it with my own eyes.  Cedar shingle roofs will last five years, max, when installed on a solid roof deck covered in ice and water shield.  The reality is this: greener is not always better, especially when wielded by those unfamiliar with traditional building systems.  “The greenest building is the one already there” is a common expression in the historic preservation world yet it’s never heard in “green building” circles.  Go figure.       

“Nobody is telling me what color I can paint my house!”

The creation of local historic districts, and the subsequent enforcement of historic preservation laws, creates a special set of challenges for preservation planners.  Buildings and structures on the National Register of Historic Places are afforded little—if any—protection against inappropriate alterations or even demolition.  Protection comes on the municipal level when towns and cities adopt a bylaw or ordinance such as MGL Chapter 40C Massachusetts Historic Districts Act or similar statutes in other jurisdictions.  Once a city or town adopts the law they can move toward the creation of local historic districts (LHD) that are governed by an historic district commission (HDC.)

Getting property owners to agree to an LHD is a daunting challenge, no doubt. Culturally, we're programmed to resist and question any infringement of our rights by government, especially the suggestion of someone telling us what we can or cannot do with our property.  And HDCs are government entities telling people what they can and cannot do with their properties.  We cannot ignore that fact—it must be dealt with head on.  There is a statement that could be made to the building owners within proposed LHDs everywhere:  "This isn't about you—we know you'll do the right thing—it’s about what someone else might do some day."  This appeals to the building owner because you're mitigating any concern that the purpose of the LHD is to tell him what he can or can't do. 

And you're planting the seed of concern: "What happens when the people next door sell some day and the new owner wants to do something hideous to the façade of the house?" Or, what happens when the new owner of the charming block of stores next to your business wants to knock it down and build a new Dunkin’ Donuts? Isn't that the purpose anyway, to prevent the wrong thing from happening in the future, not correcting or changing existing conditions?  Theoretically, the building and home owners in these areas like old houses and structures and appreciate the charm and character that they possess.  Hopefully they also understand and appreciate the economic value this adds to properties in their neighborhood.  Build on that. 

Public perception of historic districts and commissions appears to be the greatest hurdle preservation planners have to overcome when creating and overseeing LHDs.  How often have we heard the rally cry, “Nobody is telling me what color I can paint my house!” yet HDCs generally don’t dictate color choices. The best way to counter such myths and misconceptions is through transparency of actions and clear, wide-reaching communication to the public.  The internet is good vehicle for communicating that process.  Every LHD needs design guidelines and the Town of Brookline has an exemplar:

http://www.brooklinema.gov/index.php?option=com_content&view=article&id=342&Itemid=510

The Historical Commission in the Town of Ipswich has a website that should be closely studied:

http://www.historicipswich.org/

The home page of the Ipswich website is a one-stop directory to all of the resources and information that home and building owners need to access.  It is also an engaging site that pulls the viewer in with great pictures and wonderful local history as well as pertinent, contemporary information.  The charm and value of antiquity is present here and viewers are compelled to buy into it.  Increasing public awareness of historic preservation is the best way to increase public appreciation of historic preservation.  Click HERE for an article on this very subject.  Selling people on the importance of historic preservation is critical, as even old home enthusiasts can occasionally be recalcitrant in their support.

Our society is pretty good at accepting the need for zoning laws, permits and building code, but somehow restrictions due to historic preservation send folks over the edge.  Why?  Once a building is protected within an LHD it can’t be inappropriately altered or demolished.  That's the law.  Period. Don't like it? Sell it and move on.  Better yet, why buy a property in an LHD in the first place? The mindset that an owner should be able to do whatever he wants with a building simply because "he owns it" is ridiculous.

Should he be able to hire an unlicensed, uninsured contractor to throw together a set of ramshackle stairs without a permit? Why not? He owns it.  

Should he be able to make changes and alterations that violate code? Why not? He owns it. 

Should he be able to dump toxic waste in the basement? Why not? He owns it. 

Can he pile as many tenants inside as he wants, and provide one crummy toilet and no fire protection? Why not? He owns it.

Just because you own a house or other building doesn’t mean the law be damned, like it or not.  Saying a building owner should be able to do whatever they want with their building is tantamount to saying that one should be able to mistreat a pet--because they own it--or burn money because they can. Anyone who thinks that way shouldn't be allowed to have a pet or doesn't deserve to be rich. Same goes for historically significant buildings. The fact that one fails to recognize, appreciate and respect that significance is neither here nor there. It is illegal to abuse your dog or destroy US currency. And it’s illegal to alter or demolish a building in an LHD without HDC approval.

Photo credits:  Carole Osterink, The Gossips of Rivertown, except the historic photo of the Upper Depot in Hudson, NY, credited to City of Hudson Historian Pat Fenoff and the contemporary image of the same building taken by international photographer Lynn Davis.

When do building materials turn into historic fabric?

Historic fabric is a term used regularly in the historic preservation world but what it is or—better—how it comes to be, receives disproportionately little attention. McGraw-Hill’s Dictionary of Architecture and Construction defines historic fabric as “those portions of a building fabric that are of historic significance.”[1]  This definition implies that materials that are part of a building develop significance, presumably over time and as it relates to the life of the building.  One might also infer from the definition that some parts of a building may not possess historic significance.  What other sources provide a definition for historic fabric?  It would be ideal to point to a definition supplied in the Secretary of the Interior’s Standards for the Treatment of Historic Properties but one does not exist.  Surprised?  There’s no definition of historic fabric in the National Park Service’s Cultural Resources Management Guideline’s glossary either.

The Secretary’s Standards do address significance, however, as it relates to tangible things like cornices and columns and they identify four strategies for effectively dealing with historic buildings: preservation, rehabilitation, restoration, and reconstruction.  The first approach, preservation, is the most desirable and “places a high premium on the retention of all historic fabric through conservation, maintenance and repair.” Further: “It reflects a building's continuum over time, through successive occupancies, and the respectful changes and alterations that are made.”[2] Changes to a building, such as a mansard roof added to an Italianate or so-called Victorian details added to a brick building in the Federal style, are an accepted part of its record and how it’s evolved over time.

However, exactly where and when old alterations or changes to a building develop significance and become historic fabric is not clearly defined for us by the Standards.  And, if “respectful changes and alterations” are to be preserved, why have we decided that the continuum has stopped and we are resistant to additional changes and alterations? Indeed, a great deal of attention has been focused on how to create historically appropriate additions to existing buildings—make it like the original, but easily distinguishable, and smaller in scale. But what about a 1920s rear ell on a Greek Revival? If it looks “right” we want to save it but, if it doesn’t resonate with our collective sense of taste and what we think it should look like—if it doesn’t look “right”—then we’re receptive to wholesale alteration or even demolition.

In my experience as a contractor and consultant I have appeared before numerous historic district commissions throughout New York and New England. This has afforded me the opportunity to listen in as applicants for certificates of appropriateness make their pitch for permission to replace windows, change facades or roofing materials, and otherwise destroy historic fabric. The part I’ve always found most fascinating is when the element or system the applicant wants to demolish is part of the “respectful changes and alterations” that have been made over time. If the alterations are respectful, as the Secretary’s Guidelines indicate, the commission will fight hard to protect them. If not, approval is often swift and paves the way for the demo crew. Does respectful mean it ‘looks right’?

Respectful is a relatively subjective term and, as it applies to a discussion about the value, significance or integrity of an architectural detail, more subjective still. Merriam-Webster defines respectful as “marked by or showing respect or deference.” So, do respectful changes and alterations show deference to the original building? Perhaps not in style (reference the earlier examples of the Italianate and the Federal-style buildings with juxtaposed styles as major alterations) but in the quality of the craftsmanship and the materials used? The dictionary’s definition of deference as “a way of behaving that shows respect for … something” is of little help. Unhelpful, that is, unless we view the term esoterically and, in this context, meaning that the newer work is of a quality and standard worthy of standing beside the original.

That would be a convenient conclusion, if not for the fact that the historic preservation world possesses a general aversion to the idea of altering historic buildings, and this inference would seem to indicate that new alterations and changes can be viewed as acceptable if the quality of work is very high. Returning to the “building's continuum over time” issue, one might think that worthwhile, respectful alterations and changes ceased by the beginning of the twentieth century or perhaps as late as the 1930s when sun porches were vogue additions atop single story bump-outs at the rear of nineteenth century homes. Adding a Second Empire mansard roof to an Italianate, or Victorian details to a brick Georgian, are a clear mishmash of styles that, if proposed today, would be unacceptable.

Is that because the changes, dramatic as they were 150 years ago, are now deemed respectful because they, too, are ancient and reverent? This smacks of Ruskin: “When we build let us think we build forever ... that a time is to come when these stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our fathers did for us.’”[3] There is something special about a hand-planed molding, a carved stone capital, or a centuries-old brick wall—and we treat them with reverence out of respect for the quality of craftsmanship and materials that have endured the test of time. The tangible item that is ancient is automatically awarded respect and shown deference because it is old, and as Ruskin would indicate, becomes sacred. Modifications and alterations to the building, no matter how dramatic they may have been then, are acceptable now and protected.  

Circle back to the earlier question: Exactly when do alterations or changes to a building become historic fabric? Imagine if the owner of the Italianate sought a certificate of appropriateness to remove the mansard roof and restore the building to its original style. His application would undoubtedly be rejected. But what if there was an addition on the side of the building from 1900; would it be considered historic fabric? Why or why not? Since we’re dealing with subjective terms, and varying views, perhaps it depends less on the materials and craftsmanship than one might think. Some historic district commissioners may be patently against demolition and, as such, the “continuum over time … respect for changes” argument is well-suited. Still, even staunch preservationists have a breaking point; some changes must be unacceptable and worthy of the landfill.

Wherever that line lies, on the other side is the place where building materials turn into historic fabric.

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[1] McGraw-Hill. Dictionary of Architecture and Construction, (2003)

[2] Weeks, Kay D., and Grimmer, Anne E. Secretary of the Interior’s Standards for the Treatment of Historic Properties, (1995) 

[3] Ruskin, John. The Seven Lamps of Architecture, (1849)

All photos courtesy Carole Osterink http://gossipsofrivertown.blogspot.com/

Traditional building materials: Still the best choice for #historicpreservation

 

While the internet may be a fantastic tool for sharing information, we must realize that good advice is transmitted as easily as bad.  Consider this recent dialogue from a historic preservation message board in New England.  An architect asked, “Has anyone had experience with use of cellular PVC to ‘replicate’ architectural details on a historic building?”

 
While the respondents were quick to cry nay! for that use, I was surprised by how many suggested that there are permissive uses of PVC composites. In fact, the chairman of a historical commission near Boston indicated that they had adopted a policy of allowing cellular PVC in place of ground-contact lumber (like bottom step risers and porch skirt boards) and rooftop balustrades (if traditional profiles are duplicated) in their local historic districts.

I was shocked.

In the limited instances where wood-meets-earth or the worst precipitation (window sills, balustrades and stair treads), PVC composites may appear to be an attractive alternative. But its use should be considered with caution; new composite risers, fascia plates and sills will not show signs of degradation, but they will conceal what's happening to wooden structural members behind them.  So, when it fails, be prepared for wholesale failure of the system.  ("Gee, the stairs looked great ... who knew the stringers were rotted?")

Like many issues in restoration work, this one can be attributed to a lack of informed sources.  The building owner typically knows only as much as the contractor has told them.  PVC composites are widely available and spend a tremendous amount of money "educating" would-be consumers through marketing. Consider the Secretary of the Interior's position on the subject:

"If repair by stabilization, consolidation, and conservation proves inadequate, the next level of intervention involves the limited replacement in kind of extensively deteriorated or missing parts of features when there are surviving prototypes (for example, brackets, dentils, steps, plaster, or portions of slate or tile roofing). The replacement material needs to match the old both physically and visually, i.e., wood with wood, etc. Thus, with the exception of hidden structural reinforcement and new mechanical system components, substitute materials are not appropriate in the treatment Preservation."[1] (Underlining added for emphasis)  

The use of PVC composites is an attempt to cut corners and remove maintenance and upkeep from the equation.  Consider the use of Spanish cedar, mahogany, oak, and other hardwoods in these limited applications.  You may be surprised how close the price is to the composite materials.

Photo credits:  Three accompanying photos, all courtesy of the author, depicting the finials that will be replicated in the millwork shop for the author’s upcoming project at Historic New England’s ‘Roseland Cottage’ in Woodstock, Connecticut.

 

 

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[1] Standards for Preservation and Guidelines for Preserving Historic Buildings

(http://www.cr.nps.gov/hps/tps/standguide/preserve/preserve_approach.htm)

Be Prepared: Maintenance plans for historic structures

As soon as a building is constructed or rehabilitated, the natural process of deterioration begins.  Preservation has been defined as "the act or process of applying measures necessary to sustain the existing form, integrity, and materials of an historic property. Work, including preliminary measures to protect and stabilize the property, generally focuses upon the on-going maintenance and repair of historic materials and features rather than extensive replacement and new construction."[1]

The most important component of any plan to preserve a historic structure is maintenance.  Regular inspection and maintenance of systems will help preserve the integrity of historic building fabric. If that fabric is maintained, deterioration will be minimized or eliminated. Maintenance is the most cost effective method of extending the service life of a building system.  By logical extension, maintenance is the key to preservation. While the decay of components of the envelope cannot be avoided, neglect can actually cause this process to increase at an exponential rate.  When maintenance has been deferred, and a problem suddenly rears its ugly head, it is not uncommon for the reaction to be swift and inappropriate.  The use of the wrong materials and methods will often cause worse damage to irreplaceable historic building fabric.

When considered in the long term, the cost to maintain historic structures is significantly less than the restoration of historic systems and materials, and it creates far less disruption to building occupants. When a property owner or manager creates a maintenance program for their building, it is strongly recommended that they seek the counsel of a preservation consultant, and/or experienced contractor. The maintenance program should clearly identify and describe courses of action that are specific to the building. Every historic structure, no matter how small, should have a written guide that includes:

·         Lists and schedules for periodic inspections of each system.  These should be set-up in a ‘checklist’ format, to ensure uniformity of procedures over time;

·         Blank elevations of the building to be marked up during inspections and after any work takes place;

·         A full set of actual photographs that comprehensively document the conditions of the entire structure as well as a digital copy of each.  This album will grow over time;

·         An emergency list of contractors who can be called upon in an emergency, especially HVAC, electrician, plumber, and roofer;

·         Individualized procedures for the historically appropriate handling of the individual systems and materials of the building; and,

·         Hard copies of completed reports that document all work and inspections.  Include copies of estimates, contracts, warranty cards, paint colors, mortar recipes, materials sources, and any other information that will be needed by future stewards of the structure.

Maintenance is the most important preservation treatment for extending the life of an historic property.  It will slow the natural process of deterioration and prolong the natural service lives of the historic fabric of the envelope.  A written maintenance plan will help preservation planners organize, schedule inspections, and guide the work necessary to for a historic building. When a property owner or manager creates a maintenance program for their building, it is strongly recommended that they seek the counsel of a preservation consultant, and/or experienced contractor. The maintenance program should clearly identify and describe courses of action that are specific to the building. When the full life cycle of a building is considered, there is no smarter money spent than on maintenance.

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[1] National Park Service, Nationwide Programmatic Agreement Toolkit for  Section 106 of the National Historic Preservation Act, glossary of terms
 

Appropriate Roofing Material Choices for Historic Structures

Selecting a historically appropriate roofing material is often restrictive as a simple matter of economy. Not everyone can afford a new slate roof. But individually landmarked structures and those in local historic districts are often monitored by historic district commissions (HDCs) that often require property owners to replace in-kind or with an otherwise historically appropriate material.  While the preference is typically “replacement in kind,” an intelligent argument for an alternative can often be made.  The HDC can consider other materials that were available at the time of construction, as well as what buildings of similar style in the community have on their roofs. A Queen Anne may have started with a polychromatic Vermont slate roof, but the commission can consider that nearby Queen Annes have monochromatic Monson slate or even cedar shingles. A Greek Revival may have a silver-coated tin roof, but few would argue with a homeowner willing to replace with copper standing seam. This blog article will look at several American building styles and the materials used to roof them.

 

Colonial Styles, 1620 to 1780

From the New England Salt Box to the Dutch vernacular homes of upstate New York, the earliest structures in the American colonies were roofed with wood shingles. It is a myth that they were covered with hand-split shakes, because these do not hold up well, rotting and failing in just a few years; ask anyone who has made the mistake of using them. Wood shingles were easily made by planing down the shakes to a uniform thickness for ease of installation.  In the Northeast, Eastern White Cedar was the typical material used, while cypress was often used in the South. Western Red Cedar was not used much in the eastern U.S. until after the 1850s and should not be considered appropriate on a circa-1820, Federal-style structure in Connecticut. Eastern White Cedar, however, rarely lasts longer than ten years in a roofing application. Instead, preservation architects now specify Alaskan Yellow Cedar. Predominantly distributed from British Columbia, this dense wood is favored because of its longevity and because it develops a silvery patina, like Eastern White, within one year.

Federal and Neoclassical Styles, 1780 to 1820

 

Many of these buildings have low-sloped roofs and are often obstructed by a balustrade that runs across the top of the eaves. In congested, urban environments the roof may not even be visible from the street. This raises the obvious question: What needs to be done when an element of the exterior is not within the street view? Most HDCs use that standard question to limit their purview over a proposed alteration.   If your roof falls into this category, then you should pick the most enduring and sustainable material you can afford. These structures were not often originally covered in slate, although many are today. Original roofs were wooden shingles, less than ideal on a roof with a shallow pitch. In some limited instances, standing-seam or flat-lock seamed roofs are seen on these building styles. To find out what’s appropriate, check out roofs on structures of the same style in your neighborhood and neighboring communities.

Greek Revival, 1820 to 1850

This style also features a low-sloped roof, typically 4:12. While the original roof material may have been wooden shingles, many in the Northeast were long ago replaced by a more sustainable material. Flat-lock tin or terne-coated steel were typical from the late 1800s on. Many have standing-seam roofing, although this system tends to be less conducive to the many and varied changes in the roof plane that multiple roofs and additions create.  Because many of these structures also have box gutters at the eaves, keep in mind that re-lining these systems is costly and will need to tie in to the new roof material. It is not uncommon for an affordable membrane (like EPDM or TPO) to be used on the majority of the roof and a costlier, appropriate material (like copper) to cover the visible, projecting “porch” roof

Gothic Revival, 1840 to 1860

While many of these structures were initially covered with wooden shingles, many had decorative styles and patterns. This was also a popular style when the slate industry in Vermont, Pennsylvania and Virginia started to produce roofing slate in such quantities that it could be realistically specified as a material choice. The influence of architect Frank Furness and others shone through, as polychromatic slate patterns adorned the Gothic “cottages” of Alexander Jackson Davis, Andrew Jackson Downing and their many disciples. In the South and in the Mid-Atlantic states, standing-seam roofing is quite common. Again, check out roofs on buildings of the same style in your neighborhood and neighboring communities. What’s appropriate?

Italianate, 1845 to 1875

While many Italianates have out-of-sight, low-sloped roofs that an HDC will not be concerned about, many of the “villa” variety have gables and other roof planes that are visible from the street. Like those on Greek Revivals, these roofs were often clad in flat-lock seamed or standing-seam sheet metal. In later years, many were re-roofed with clay tiles. Note that the advent of this new material correlates with the growth of the Ludowici firm in Chicago in the 1880s. The HDC will likely require replacement in-kind to create the original look, although there may be some leeway with respect to the material itself. After all, it’s all about keeping up appearances.

Second Empire, 1855 to 1880

The mansard roof is the character-defining feature of this style. A mansard is essentially a hipped gambrel. The lower roof, between the eaves and upper cornice, is most often covered in slate. More often than not, these parts of the roof can be restored and do not need to be replaced. If they do need replacement, be prepared to face an HDC that’s going to want it done in-kind. Keep in mind that these structures almost always have (or had) a built-in gutter at the eaves.
The sheet-metal linings fail, and replacement is expensive – especially if they failed long ago and wood rot has resulted from the neglect. The upper roof typically ranges from flat to a low-sloped 4:12 pitch. Once the roof becomes visible from the street, the material choice becomes important, and the same argument applied to Greek Revival and Italianate styles holds true here.

Queen Anne, 1880 to 1910

Severe recessions in the U.S. during the 1870s stymied new construction. By the time the economy rebounded, the Queen Anne had replaced the Second Empire as the popular style of choice. Improvements in rail service, as well as material fabrication and production, were game changers. Architects and builders roofed these Victorians with various slate colors, cedar shingles, and flat-lock and standing-seam copper, along with different colors and shapes of clay tiles. And, often, these buildings have combinations of roofing materials and styles.

Unfortunately, many HDCs allow building owners to replace original roof fabric with so-called “architectural shingles.” These shingles were created to replicate wood shingle (or shake) roofs in an economical way. It is a fallacy that they are an appropriate alternative to slate; in fact, three-tab shingles look more like slate than architectural shingles do. Before you replace your entire roof, consider that it may only be the flashings that need replacement.