Difference Between Rake Boards And Fascia Boards
In our last two articles, we looked at counterflashing and how this type of termination is used to shield a flat roof from water entry at certain types of roof edges such as chimney base flashings. Today we start a two-part series examining the use and function of a similar but distinct type of roof termination, found at rake boards and fascia boards. Rake boards are generally found at the top of a gable roof, and they are also found, in some cases, at flat roofs.
Particularly, rake boards are used at parts of a roof where there is at least some low slope running, in most cases, towards the rear of the roof at a positive or downward grade. In contrast, fascia boards are installed at the top of walls, just like rake boards, but at the horizontally flat (or close to flat) wall tops. Although there is different nomenclature used to describe these two different types of boards, they actually work in a very similar functional way. More often though, the fascia board is a location where the roof terminates by using a drip edge. and most commonly the rake board is terminated with the roof ending in a gravel stop. The difference between a gravel stop and a drip edge is that the gravel stop goes upwards in a triangular shape before coming back down to cover over both the edge of the roof and the top of a rake board.
If you look closely through the trees, at the back of the roofs, in the picture below, you can see that almost every adjacent house goes back farther or less far than the adjacent house. at every one of these differing dimensions or depths of the roof of adjacent properties, the exposed edge or side of the longer projecting roof must be terminated and treated. In almost all of those cases, a rake board is installed at the top of the wall and a gravel stop is installed on top of that rake board to terminate the flat roof membrane. In contrast though, the rearmost wall of each of those buildings, in almost all cases, has a fascia board installed at the top of the wall. Both fascia boards and rake boards have functional purposes, mainly to attach or fasten the terminating metals, but more importantly, in the case of a rear fascia board, at the determination, the fascia board also is responsible for holding the weight of the gutter at the rear of most row home roofs.
The rowhomes in the picture above have projections at the rearmost rooms but those rearmost rooms are really old sleeping porches that have been converted, in some cases, to interior Space. Across America and much of the world, interior space has become increasingly valuable, particularly in expensive cities like Washington DC. Here, the vast majority of houses, have interior space that is worth well over $500 per square foot. Those old porches, become significantly more valuable when they are converted into interior space, so the conversion has a high ROI. Technically though those rear porches were not originally part of the building footprint and even today, as you can see in the picture above, those rear rooms walls do not extend all the way down to the ground, in many cases.
The buildings shown in the picture below though have a similar but also very different type of layout because they have long rear ells. Rear ells are parts of buildings or the configuration of the exterior of the building which allows a long side of joined row homes to be exposed to the exterior. This was of functional importance, many decades ago when mechanical systems of today were not available to provide exhaust and ventilation. Long rear ells of this type also allowed fenestration and outdoor light to come farther into the interior space of the building. Here though, you can see, based just on the roof alone, it looks like the rear roof, at the lower part of the picture is actually a separate building, but it’s actually the same building. Since, in this case, the neighboring buildings have a similar repeating layout, the roof at the lower part of the picture has a long open edge where it is terminated on both sides of the roof system on the right hand side, there is a long gutter. This gutter collects water and conveys it away from the roof system. on the left side there is a fascia board, similar to but different than a rake board. That portion of the roof runs almost horizontal. In most cases, such as in the example above at the higher roof, at the top of the picture, the roof goes from a higher elevation in the front to a lower elevation in the back.
The next article is the second part in this series and we will look at other examples of rake boards and fascia boards, and we will also take a look at some of the maintenance and upkeep requirements for gutters and or terminating metals where plant debris and or growth can get into gutters and or behind faces and rake boards to cause problems in the building systems.
Smart and proactive replacement, construction, upkeep and maintenance of low slope roof and mansard roof systems requires an enthusiastic interest and understanding of historical methodologies, waterproofing principles, and building science. Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building.
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