Built-in gutters may be the most complicated system in the building envelope, yet they are also the most elusive when you start searching for information on them. Sometimes called Yankee gutters, box gutters or even Philadelphia gutters, it’s no wonder they remain a mystery to many. Built-in gutter systems are actually part of the cornice structure and drain through internal or external leaders. They are not readily visible from the ground, further lending to the mystery of their design and function. Because they are integrated into the structure, built-in gutter linings that fail will cause extensive damage to the cornice and, in some cases, interior of the structure.
|A plate from a Victorian era pattern book depicting built-in gutters as part of a mansard roof system. Source: Miller, Charles. Architecture: Designs for Street Fronts, Suburban Houses, and Cottages. Toledo: S. Bailey & Eager, Publishers, 1868.|
|A detail from the same pattern book.|
Rebuilding the framework will be necessary if built-in gutter linings are not maintained. Photo from author.
Careful inspection by a competent roofer is critical to the longevity and success of the system. He will look for defects such as localized damage due to fallen limbs or other debris; cracks from expansion and contraction at joints or folds; or pinholes from corrosion. Roofing tar and other bituminous compounds should never be used to parch, repair or coat gutter linings. It makes the condition of the gutter indeterminable, corrodes metal linings, will crack and fail quickly, and cannot be removed without destroying the lining. Ice damming is not uncommon in the winter but should not be removed with sharp tools for obvious reasons.
Restoring built-in gutters
Restoration of long-neglected built-in gutter systems that leak and have caused decay in the cornice and roof structure is often complicated and can be costly. But once the work is completed, a regularly maintained, well-detailed system can last 60 to 100 years or more, depending on the life of the metal lining. A preservation architect or consultant should inspect the building, propose treatment options, develop working drawings and specifications, and supervise bidding and construction. Temporary protection and permanent repairs should be performed by a roofer experienced in this specialty on historic buildings.
Gutter lining sections are seamed, riveted and soldered in a proper application. Photo from author
"We encourage restoration of historic built-in gutter systems," says Michael Devonshire, a building conservator and principal at Jan Hird Pokorny Associates in NYC. "The use of modern building materials as an adjunct to traditional materials boosts longevity." Devonshire describes the typical steps involved with a built-in gutter restoration:
- Strip off old gutter lining and two feet of the above roof cladding;
Where rafter ends or lookouts are rotted, install sisters (new rafter ends adjacent to old ones) or scarf in new wood and sisters; Replace old wooden gutter bottom with kiln-dried-after-treatment (KDAT) plywood treated for resistance to decay, minimal expansion and contraction, and increased longevity, sloping bottom toward outlet;
- Install gutter lining: an elastomeric ice-and-water shield on the bottom (not always required); building felt; a slip-sheet of rosin paper; and copper on top (16 or 20 ounce, depending on the dimensions of the gutter);
- Install on the roof decking above the gutter two feet of elastomeric ice-and-water shield (or copper flashing) and roof cladding over it; and,
- Repair or replace cornice moldings and interior structural elements as needed.
The Copper Development Authority and SMACNA recommend the use of copper sheet metal because of its workability and durability in a roofing application. Indeed, many linings have lasted one hundred years or more. Lead coated copper and tin/zinc alloy coated copper may also be specified for a variety of largely unsubstantiated reasons and mere speculation. Aesthetically, however, the water staining caused by sheet copper can be minimized or controlled by using one of these alternative materials. Gutter linings are sometimes replaced with EPDM rubber or similar membranes because of a perceived cost factor. While there will be initial savings, the linings will need to be replaced more often and—ultimately—cost more in the long run.
Lead coated copper is an acceptable material for the gutter linings. Photo from author
If not, what affect will the water have on the exterior of the building? How will the envelope be impacted? What problems could this cause in the basement or—worse—the foundation? Once these questions are realistically answered, the preservation of the built-in gutter system seems more attractive, if not a necessity. An architect or preservation consultant whose practice focuses on historic structure envelope should be consulted before any such alteration is undertaken.
|Detail of built-in gutters at the Olana State Historic Site in Hudson, NY. Photo from the Historic American Building Survey|