Structure—Know the Minimums
But Go Beyond Them!

Building codes are the minimum standard for safety and habitability of a structure,
but not the standard for savvy builders who build quality structures.

Solid structural design requires an understanding of the complex of forces that a structural assembly must be designed to resist.  Beams, columns and walls carry each load down to the ground.  Acting as a unit instead of a collection of isolated components that the wind can pick off one by one, these various systems interacting together are necessary to keep a building upright and make it stronger. Lumber sizes, the diameter and length of nails and structural screws, and other bracing requirements are determined by the structural demands of the building.

Structure nears completion on  the Building Savvy Idea Home in Dallas’ Midway Hollow.

Plywood and OSB panels are recognized by the building code for their strength and performance in wall construction and their code-compliant nail base for attaching brick ties, siding and trim.  Combining advanced framing methods and the use of raised-heel trusses with continuous wood panel sheathing provides increased structural support and multiple other advantages.

Much of the focus by building codes and building code inspectors is on preventing water from penetrating a home to cause structural damage and a potentially toxic indoor air environment.  Exterior cladding is essentially the first line of defense against water penetration and should be designed to work in tandem with underlying vapor-permeable water-resistive barrier (WRB) materials that repel and drain water to keep the structure dry and while allowing any water that does get in from rain or condensation to effectively dry.  Installation requirements and vital air spaces are specified either via manufacturer’s instructions or building code.

Applying WRBs from the bottom up allows subsequent layers overlap the layer below to create a proper drainage plan.  To maintain continuity of the barrier, metal or adhesive flashings must also be properly overlapped or sealed around wall openings and over adjacent enclosures and should divert water away from the wall or toward a WRB-protected area.

Foam sheathing products which are foil-faced with rigid polyisocyanurate are another process for creating the drainage plane when used in conjunction with the proper tape to seal the joints.  Some experts recommend applying the foam with shiplap joints at the vertical seams and a black poly strip as a Z-flashing at horizontal joints.

While pre-formed flashing can be an efficient choice, metal coil flashing which is malleable is used to form-fit spaces around windowsills, fascia and door casings.  Once again, the order and process of applying the flashing is important; install first to the underside of a windowsill or door then to the sides so that both sides overlap the bottom. Pan flashing on top of the drainage plane further assures against leakage within the factory-built window assembly itself. W flashing for inside corners and J flashing where siding meets trim or stone are the norm.

Wall and roof connection joints are the weakest link of any building. Chapter 15 of the IRC provides standards for roof assemblies including nailing requirements for attachment of the roof.  Connectors, often referred to as “hurricane clips” or “hurricane straps” are required by code in some areas and used as a best practice in others to attach roof framing members to the supporting wall top plates. Weather-protection includes ice barrier membrane requirements under eaves, valleys and crickets. Some of the membranes are coated with felt paper or synthetic underlayment, serving as a bond break for the shingles. The minimum required overlap for shingles, to prevent water from wicking underneath and fasteners from corroding, sometimes varies with the slope of the roof.

Framing structures, cladding and roof shingles are regulated not only by building codes that ensure structural integrity but also those related to the control and integration of fire safe design and fire prevention. The IRC requires that residential floors be covered with a 1/2-inch gypsum wallboard membrane, a 5/8-inch wood structural panel membrane or the equivalent on the underside of the floor framing member.  In response, truss manufacturers now feature a proprietary coating that enhances the joist’s fire resistance and enables the floor assembly to meet the new membrane requirements.  Roof shingles may also be required to meet a Class A or B fire rating classification per local building codes.

The bottom line: Framing inspectors look at the plans and check the work completed, often considering not only if the structure complies with the building code but also if it follows current best practices.

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