Located at the very top of roofing systems, ridge boards appear as the main framing members at the peak of a roof. Since the rafters and other roof framing sections below are attached to the ridge board, you might wonder if it supports structural weight. So, is it load-bearing?
Ridge boards are not load-bearing. They essentially provide a surface on which common rafters and as well as other types of rafters used in hip roof construction can lean against. They are not, however, designed to bear any structural weight and are typically thin, as little as 1 inch (25 mm) nominally in thickness.
Often times ridge boards are confused with ridge beams, which are structurally load-bearing. Keep reading as we’ll take a look at whether ridge boards are necessary and how it differs from a ridge beam.
What Does Load-Bearing Mean?
First, let’s take a look at what the term load-bearing implies. A load-bearing structure is an active structural element in a building. Load-bearing refers to a vertical transfer of weight or “load” from either structural or non-structural elements above to the structural element below down to the building foundation.
While it is true that a ridge board is subjected to horizontal loads from the sides where the attached rafters are resting against it, the weight is not being supported by the ridge board in a vertical direction. What’s more, the weight of the roof is not transferred down from the ridge board to any element below.
Another way to think of this is if you were to remove the ridge board, could the rafters attach directly to one another and still provide the same level of roof support? They certainly could, which then brings up another question. Do you actually need a ridge board?
Is a ridge board necessary?
While not structurally required, a ridge board is helpful in providing a surface onto which roof rafters can be attached. This makes installing the rafters much easier and can speed up the framing of the roof. It also offers a compressive surface onto which the rafters can rest.
Codes, such as the International Residential Code (IRC) specify the use of either ridge boards or rafters that are directly connected to one another with a gusset plate as a tie (Section R802.3). This implies that they (ridge boards) are optional since rafters can be joined directly.
While the IRC does not specifically require ridge boards, the code does require ridge beams on roofs that are less than 3 in 12 in slope (25-percent slope). Ridge boards, on the other hand, can only be used on their own for roofs with a slope of 3 in 12 or greater.
The reason for this is that ridge beams have the ability to carry roof loads down to the foundation along posts or the gable end wall. A more tilted roof (steeper pitch), in contrast, will naturally transfer the weight of the roof towards the lower ends of the rafters and to the top of the sidewalls below.
Are Ridge Boards and Ridge Beams the Same?
Ridge boards and ridge beams are often confused with one another. They are not the same thing, however. While they are both located at the peak of the roof, a ridge beam is a structural member that provides load-bearing support for the roof, while a ridge board does not as discussed previously.
Ridge boards and ridge beams can be used in combination. In this type of setup, the ridge beam is placed underneath the ridge board to provide structural support. It’s important to keep in mind that it is the ridge beam that is providing the load-bearing capacity.
This combination provides both the connection benefits of a ridge board with the structural benefits of a ridge beam. This can be a good solution for roofs that have a slope that is less than 25-percent (3 in 12).
How to Attach Rafters to Ridge Boards
Rafters are sloped structural roof beams that attach with the ridge board at the peak of the roof and with the top walls down below. Rafters are typically nailed directly to the ridge board at an angle (called toenailing). This can either be done manually or by using a nail gun.
An alternate way of attaching the rafters to the ridge board is by using metal fasteners such as Simpson Strong-Tie. However, these connectors work best with ridge beams that are 2-inches or more in thickness, so they will not work with thinner ridge boards.
Ridge Board Size and Material
Ridge boards are typically made from conventional lumber. Typical sizes include 1×8 and 2×8 or larger. The IRC (Section R802.3) states that the minimum nominal width for a ridge board is 1-inch (25mm). Additionally, the depth needs to be at least as much as the depth of the cut end of the rafter.
Common lumber species used for ridge boards are similar to those used in general framing. They include Douglas fir, hemlock fir, Southern pine, spruce pine. On the other hand, ridge beams often include engineered woods such as glue-laminated timber (glu-lam) and laminated veneer lumber (LVL). Structural steel is sometime used as well.
Ridge boards are not load-bearing, but they serve a very important function in that they provide a surface on which rafters can lean against. They are not, however, designed to bear any structural weight and are typically thin, about 1-inch (25 mm) minimum in thickness.
Rafters can be attached directly to the ridge board using nails or metal fasteners. Nailing can be done either manually or by using a nail gun and driving the nails at an angle, a method referred to as “toenailing” in framing construction. Metal fasteners are less commonly used, but an option nonetheless, in particular when connecting to a ridge beam.
The advantage of using ridge boards is the ease with which rafters can be attached using conventional methods (i.e., nailing them directly). While not required, since the code allows for direct fastening of the rafters to one another, the use of ridge boards helps make roof framing easier and more expeditious.
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