Today we’re starting a multi-part series discussing rake boards and fascia boards. Rake boards and fascia boards are perimeter elements in roof framing and finished trim carpentry. Technically, in typical stick frame construction, there will be a subfascia installed below the area of the fascia board, but in historic construction common in Washington, DC, the subfascia was often omitted. Most people are not aware of that, but unfortunately we often find that condition once the original or previous fascia board rots to the point that it must be replaced entirely. By the way, as a point of better or best practice in restoration construction, it’s worth noting that big box stores like the notorious ones here in DC will often sell finger-joint wood as exterior trim boards, and while this might be technically permissible, those boards do not hold up in exterior applications nearly as well as historic single source boards and or synthetic materials.
Rake boards are installed along the sloped edges of a gable roof, providing a finished look and protecting the roof’s edge from weather damage. Fascia boards run horizontally along the lower edge of the roof, covering the ends of roof rafters and supporting the lower edge of roof tiles or shingles and or metal terminations in the low-slope or flat roofing so common in Washington, DC. Both boards are typically made from wood, PVC, or composite materials. They are installed at these locations to enhance the roof’s aesthetic appeal, protect the underlying structure from moisture and pests, and provide a mounting point for gutters and other roof accessories.
The picture below shows an image of a roof curb, before it is overlaid with a single ply membrane for flashing. This particular curb could be used for a variety of different elements but in this case it’s going to be used for a large skylight. This picture, before it is overlaid with TPO membrane, is interesting because without the roofing material on top of the curb it looks very similar to a rooftop rake or fascia board termination. Rake and fascia board terminations are used to span the gap between the roof system itself and the vertical walls of the exterior of the building but they’re also important because the drip edge or gravel stop which actually terminates the roof membrane must be set against something solid which has a relatively straight or planar surface. Here, in this example you can see why the same principles apply both between a roof termination and a skylight mounting, in this unique particular circumstance. In this case, the skylight will be set to mount with its rim around the curb and this wooden material becomes both the surface which the rim will set against and also the substrate to which the frame of the skylight will be fastened.
The next picture below shows an aluminum coping mounted at the top of an exterior wall. At the top of this wall, the horizontal or low-slope roof system joins the top of the parapet where it is covered with an aluminum coping. Rake boards will often be installed along the edge of a parapet. In most cases the parapet wall will be built with a degree of angle or slope to follow the angle or slope of the roof below. Normally, that slope was built into the brick envelope and shell of the building because it saves cost to build a slope, particularly where the wall will not be visually exposed to the public, as is the case in most side to side connected row buildings. Here though, this particular wall is a bit of an anomaly because it is exposed, although an adjacent building is built against a lower part of the wall, the upper part of the wall rises above that adjacent building.
There is a very interesting hodgepodge or quilt work style tapestry of elements, regarding the different materials, conditions, and finishes on this exposed portion of the wall.
To the left, a portion of the building is clad with a severely rusted oxidized metal panel, like a type of metal siding. This particular type of panel was installed many decades ago without having been there to witness it ourselves, we can tell from the visually identifiable signs today that this particular installation is old. It’s severely rusted, and in the regular construction building material market, metal panels like this, for this particular type of installation purpose are not really available today. Also, in today’s Construction Supply market, Ferris metal panels are rarely sold for the purpose of building cladding. There are exceptions of corten steel or metals that are intended to oxidize for a visual effect but will specifically self-stabilize after surface rust, to avoid accelerated deterioration. This panel though, by comparison is actually very old.
You can see that same wall from a slightly different angle in the next picture below. Often in our blog and on our website we talk about the problems associated with omitting rooftop chimney flue caps. In the picture below you can see that there is a historic brick chimney with separate terracotta tile flues being used at the chimney at the exposed outside wall of this building.
The area on the outside of the rooftop, just below the parapet coping, has been repointed, it’s likely at this area there were specific issues of water entry. The area below the reported area has a much darker almost black color. That area has been coated with an asphaltic type of pitch, which in the middle of the 20th century was used in some cases as a type of makeshift damp proofing. Damp proofing and Waterproofing are sort of similar but unlike waterproofing damp proofing doesn’t actually have the ability to fully stop water entry, it merely deters water entry to an extent. Prior to the advent of thermoset materials and polymer based synthetic waterproofing materials, bitumen or asphaltic type pitch damp proofing was used somewhat extensively for attempts at foundation sealing.
In an upcoming article, here on our site, we’ll take another look at this building and the HVAC systems at an adjacent rooftop with a spider-like span of metal ductwork exposed to the elements above the roof. We’ll talk about some of the inherent problems that come with fully exposed ductwork systems on rooftops.
We recommend every building owner in DC who values the longevity of their roof (and their investments) and building use a contractor who values the simple and important principles of proper roof construction like Dupont Roofing DC. Learn more about our company and the proper techniques of working with roofing on historic buildings in Washington DC here on our blog at DupontRoofingDC.com, and you can call us at (202) 840-8698 and email us at dupontroofingdc@gmail.com.
