Deck Rebuild Project: Transforming Your Outdoor Space
Recently, we got to take a look at a deck under construction with a CMU (block) foundation. This type of configuration and type of construction layout is not very common but once in a while we’ll see it in places like city areas with historic buildings like Washington DC. It’s rare to see it out in the country lands outside of Washington DC. But it has a purpose and it can actually be useful. In this case, this deck is a hodgepodge of elements that were built decades ago and are now being rebuilt into a very nice deck.
This particular deck is being built with a wider stair than most. Generally, stairways to access the rear of the deck are limited to a dimension relatively close to the minimum code requirement, but in this case they have almost doubled that amount of space which makes for a much more ample and convenient approach to the deck from the backyard and vice versa. That simply feels more comfortable and is a nice convenience to add to a deck as it opens up to become a joint space between the exterior of the house and the backyard.
In this case, the stairway is built with four stringers. A stair stringer is one of the sloped boards that support the steps of a staircase. In the case of this exterior deck, the stringers are placed along the sides and sometimes in the middle to carry the weight of the treads (the horizontal part you step on). In this example, there are four stringers: two on the outside and two evenly spaced in the middle to provide extra support. In total this makes for three cavities and there are subframing boards installed between each of the stringer cavities. Those sub framing boards will support composite deck boards once the remainder of the framing is complete
In Washington, DC, the minimum required width for a stairway serving a deck is 36 inches or 3 feet wide, per the International Residential Code, which D.C. follows through adoption. This space is deemed to be enough that the stairs are considered to be wide enough for safe use.
Interestingly, but not necessarily surprising, the building code does not specify a fixed distance for the maximum allowance in the range of total width of the stairway. General construction guidelines recommend that stringers should be spaced no more than 16 inches apart on center when using typical decking materials like composite wood, to properly support the treads. Composite wood has less intrinsic rigidity than most natural woods and can even begin to sag over the time as the years go by. In this particular case, a subframing board has been installed directly below the location of the deck board to provide additional rigidity and support.
Many of the relevant codes can be found in the IRC Section R311.7 for stairways and general stair construction. This particular section of the building code can be somewhat complicated because there are requirements for all types of different aspects of the stairway construction. Some of the elements included in this section include the spacing we discussed, but also elements of the stair tread depth, and stair riser height constraints,
The next picture below looks a little bit closer at the 4×4 posts installed around the perimeter of the stairway and the deck itself. These particular posts will be used to connect the guardrails and handrails which will provide a degree of safety to prevent falling off the edge of the deck and the associated stairway. The building code also has several requirements for the installation of guardrails and handrails. Often the terms guardrail and handrail are used interchangeably, but from the eyes of the building code there is a distinction and a difference.
One of the main distinctions is that a guardrail does not have any requirement for a graspable element. In other words, in the case of a handrail, which generally runs a long down the sides of a set of steps or stairway, there is a requirement in the building code that requires a guardrail has a graspable area which people can use to secure or stabilize themselves as they walk up or down the stairway. In the building code, there are limits to the size, shape, height, and distance of this handrail from the wall and or adjacent framing.
In an upcoming blog article, we’ll talk more about the space underneath of the deck and the potentially use and options for storage.
Use a contractor who understands and cares about doing things right. Dupont Decks and Patios is the premier deck and patio contractor in the Washington DC metro area. Always, feel free to reach out to us here at Dupont Decks and Patios. We are happy to help with almost all steps of the deck building and design process. Let us know about your ideas and talk to us if you have questions about possibilities. You can call us at (202) 774-9128. You can find us online at https://dupontdeckspatiosdc.com and you can email us there as well at https://dupontdeckspatiosdc.com/contact-us
