Type V Wood Frame Construction

• This manual chapter provides general information about Type V wood frame building construction classification.
• Each member is responsible for exercising appropriate control in the implementation of this directive, as dictated by their rank.

General Information

• In Type V construction, all major structural components can be made of combustible materials.
• The basic construction method involves using a wood frame for primary structural support.
• Many Type V structures need to have a 1-hour fire resistance for their structural components.
• Plaster or fire-rated gypsum board provides protection for combustible frame members.
• Types of frame buildings include Balloon Frame, Platform Frame, Post and Beam, Log, and also Plank and Beam.
• Modern wood-frame buildings often use "light-frame construction," introduced in the US in the 1830s.
• Type V buildings can use solid beam or lightweight building components.
• Light-frame construction uses smaller studs, joists, and rafters, eliminating heavy posts and beams so buildings go up faster and cheaper.
• A key difference between Ordinary and Frame construction is that frame construction uses wood for exterior bearing walls.

Balloon Frame

• A continuous wall stud is used from the lowest level through the roof area.
• The void space is interconnected between the floor joist at each level of the building with the wall void spaces.
• Fire stopping is rare, making the entire void space within the building one large interconnected area.

Platform Frame

• It is the most common type of new frame construction
• Starts at the lowest level with floor joists and flooring installed at the foundation.
• Side walls are erected on the floor
• Floor joists and flooring for the floor above are set onto the studs after they are raised.

Post and Beam

• Uses posts as vertical members and beams as horizontal ones.
• Rigid joints connect the posts and beams to support the structure.
• Posts support the walls instead of wall studs.
• Typically associated with commercial buildings initially, it's now used in renovated private homes.

Plank and Beam

• Similar to post and beam.
• Uses beams of significant size covered with thick planks or laminated boards.
• Popular for churches, skating rinks, and buildings needing a large, clear span without center supports.
• Beams are often boards laminated for increased size.
• Integrated structure uses tongue and groove planks at least two inches thick.
• Interior of the plank can serve as a finished surface.
• These structures present a high fire load because flammable interior finishes allow rapid fire spread.

Walls

• Bearing walls support the structure and can be any exterior wall depending on the layout.
• Load-bearing walls typically use 2"x6" studs set 16-24" on center.
• Interior studs usually use 2"x4" lumber set 16"-24" on center.
• Interior walls must act as bearing walls if spans exceed 20 feet.
• Interior walls can be left exposed in small buildings like garages or sheds.
• Most interior walls use OSB, plywood, gypsum board, or plaster for better appearance, thermal insulation, and fire resistance.
• Sheathing, building wrap, and foam insulation are typically between interior/exterior walls for resistance to environmental conditions and pests.
• Exterior veneered walls add an attractive material layer.
• Voids between the veneer and building wrap can allow fire to spread.
• Veneer provides little structural support but can add thermal insulation.
• Various sidings like vinyl, wood, aluminum, stucco, or asphalt provide the exterior finish.
• Sidings can be combustible or non-combustible, offering weather protection and aesthetic appeal.

Roofs/Floors

• Frame buildings have roof and floor joists sitting on or in exterior bearing walls.
• Lightweight trusses, laminated wood, glulam beams, and wooden I-beams can span wider areas.
• Floor and roof systems can consist of structural composite lumber, laminated veneer lumber, plywood, oriented strand board, particleboard, and composite panels.
• In lightweight wood frame construction, truss roof or floor depends on every component and connection.
• Losing a member or connector can cause the whole system to fall.
• Trusses are lighter and cheaper but have less material to burn, leading to faster failure in fire.
• Connectors like gusset plates, staple plates, pins, and through bolts can conduct heat inside, speeding up destruction.

Strengths

• Type V buildings are easy to breach for access, ventilation, or escape.
• Type V buildings are also resistant to collapse from earthquakes due to being lightweight and flexible.
• Collapse debris is light and manageable
• Most structures don't exceed three stories.
• Newer building codes require fire blocking in high hazard areas.
• Newer building codes also require fire blocking around ductwork and piping.
• Newer building codes also require fire blocking between cornices of two-family dwellings.

Weaknesses

• A key problem is the presence of extensive concealed void spaces, allowing fire to spread within buildings.
• A Type V building can be totally involved and destroyed in a fire because of inherent combustibility.
• Type V structures are prone to fire spreading from the outside, rapid flame spread inside, water damage, and total collapse.
• An involved wood-frame building can threaten nearby structures.
• Building codes restrict the maximum allowable heights and areas.
• In void spaces, rapid failure of the structural is anticipated when framing members are exposed to fire.
• Fire can easily travel the vertical cavity into floor joists and the attic in balloon framing if fire starts/enters the stud space.
• Fire can spread parallel and perpendicular to truss joists where they are used in floor construction, making it hard to determine the fire's full extent.
• Subflooring typically consists of OSB or plywood in residential construction, with carpet or tile, that can fail within minutes when exposed to fire.
• Another concern is the possible existence of an unfinished ceiling over a basement space, where fire stopping or other barriers may not be intact.