Understanding Type lll Framing Of Exterior Walls In Mid-Rise Construction Projects

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Before we discuss Type lll framing, let’s answer one question: What is meant by “Type III construction”? Also referred to as a brick and joist structure by some individuals, this type of constructed building has the following characteristics:

  • Walls are masonry-bearing
  • Structural framework, floors, and roof are made of some type of combustible material such as wood.

Example: A concrete block building that has wood floor and roof trusses.

Framing Exterior Walls

Mid-rise, wood framed construction projects have been and still are increasing in popularity. With this increase comes numerous queries – one of which being the following: At the floor intersection, what’s the best way to frame the exterior wall?

These mid-rise buildings are classified as Type III construction due, in part, to the number of stories and their size. Where floor framing and wall framing are concerned, the requirements by the IBC (International Building Code) are clear. Where the wall and floor framing intersect, however, clarity is not particularly provided.

Let’s take a brief, general look at several types of framing.

Common Platform

A challenge is presented when platform framing is desired. The challenge? Find a rim board that won’t shrink to less than the height of the joists, is of compatible height, and maintains its ability to transfer both lateral and vertical loads.


To properly detail the walls and floor intersection, what options exist for specifiers? The walls can be framed taller, instead of platform framing, and joists can hang from a ledger attached to the wall or from the top plate. However, to the framing and design, this option can add time and costs. The reason? Namely, the need for additional shear wall length, taller studs, eccentric loads, blocking, connections, and joist hangers.

I-Joist Framing – Platform Framing

For the rim board material, engineered wood lumber (structural composite lumber, I-joists) is used for platform framing using engineered wood I-joists to frame the floor. Both at the time of installation and throughout the structure’s lifetime, this helps to ensure dimensional compatibility with the I-joists. Due to increased shrinkage and initial differences in depth, glulam beams and sawn lumber are not typically suitable alternatives here.

Sawn Lumber Framing – Platform Framing

To transfer lateral and vertical walls through a structure, a rim board is required for this type of platform framing. By building department officials and specifiers, it is usually considered a structural element of the wall framing. What does that mean for Type III construction projects? For these buildings – with wood framed exterior walls – at the exterior wall, the rim board must be wood that is classified as FRT (fire retardant treated).

Work with US Framing for Type III Framing

Are you in charge of a mid-rise construction project? As you can see by the above information, framing can be involved, technical, and must be done right. If you’re in search of a company that is reliable, experienced, and knows all the ins and outs regarding type III framing and construction, look no further than US Framing. When you engage our services, we’ll be with you every step of the way to answer all your questions.

We have framed a vast array of buildings including student housing, hotels, apartments, etc. since our start up in the 90s. Please feel free to contact us for a quote or more information.

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