Capitol Hill Restoration Society

New and Existing Roof Issues – Preservation Cafe

Posted on March 7th, 2016

Local Contractor Gary Barnhart discussed structure, maintenance and replacement of roofs, Thursday, March 17, 2016.

Capitol Hill is a neighborhood with very unique roof systems. The majority of structures built in the United States for housing have pitched roof with inexpensive asphalt shingles. However, here on Capitol Hill, roofs are generally many decades old and use flat roof systems.  In this neighborhood, the type of materials and systems vary widely in that each type of roof has its own comparative advantages and disadvantages. As well, each system has different requirements for maintenance and maintenance challenges.

Gary Barnhart, general contractor and owner of GL Barnhart Construction addressed many of the most common issues related to new roof decisions and information to consider when choosing new roof systems.  A Capitol Hill resident, Mr. Barnhart previously trained as a construction inspector before starting his firm in 1997. Today, the company focuses on modern renovations, historic restorations, and construction work in the Capitol Hill area.

The presentation, titled “New and Existing Roof Issues,” focused on the unique flat roofs found on Capitol Hill.  The majority of housing in the US incorporate pitched roofs, but due to the dense rowhouses found on the Hill, flat roof systems are the norm.  The discussion addressed many of the most common issues related to flat roofs: the membrane materials and their constructions.  .

Roof issues discussed by Gary included:

  • Most existing historical roofs are “built-up roof” systems, compromising of multiple layers of hot asphalt covered by a ballast of pebbles/gravel.  These systems were easy to install and maintain, but are now harder to repair as skilled labor is in short supply due to the popularity of more modern membrane systems.
  • Torch-down systems: these single-ply systems are the modern equivalent of the more traditional built-up roof systems.  The rolls are installed with a hot torch, making their installation problematic if the installer is not familiar with the equipment or best recommended practices.  Be sure to check your home insurance policy to see if they cover fire damage due to torch-down installations.
  • EPDM (ethylene propylene diene monomer) are synthetic rubber, single-ply roof systems.  The membrane is adhered to the roof sheathing via a chemical process (no open flames needed).  Since this material comes in wide 10’-0” sheets and is hard to patch with new seams, this membrane is better suited for commercial applications and not small rowhomes where there are many penetrations through the roof (skylights, vents, chimneys).
  • TPO (thermoplastic polyolefin) roofs are also single ply systems, but they are better suited to rowhouses.  The material is easier to patch and cut around penetrations than EPDM systems.  It is also a very durable membrane, resistant to much tearing and punctures.  The material comes standard in a white color, which will help reflect sunlight and reduce internal energy gains in the hot summer season.
  • Metal roofs: copper and aluminum standing-seam roofs are recommended materials, especially for homes in the historic district where the roof is visible from the street.
  • Slate roofs are found at most mansard roofs. These will last 50-100 years if properly installed and maintained.
  • Maintenance of any existing or roof system is key to its longevity.  Yearly inspections of transitions in materials and at intersections with walls and gutters will help keep a roof functioning well.

Happy to answer any renovation questions, Gary can be reached at 202.569.8471 or