As the housing market continues its path to recovery, certain mistakes when using engineered wood products (EWP) are becoming more common.
Best Practices for Quality Framing
A house's frame is its skeleton. The frame not only provides the structure and shape of the home, but it also affects the quality of the mechanicals, interior finishes and exterior finishes. Problems resulting from a poor framing job usually don't have quick, easy solutions. With so much riding on the quality of the framing, it's critical that home builders take quality assurance into their own...
|Beams carry weight across spans that are too long for joists, I-joists or floor trusses to carry.|
A house's frame is its skeleton. The frame not only provides the structure and shape of the home, but it also affects the quality of the mechanicals, interior finishes and exterior finishes. Problems resulting from a poor framing job usually don't have quick, easy solutions.
With so much riding on the quality of the framing, it's critical that home builders take quality assurance into their own hands. Because of the way their companies are structured, Giant home builders rely heavily on framing contractors to provide a structurally sound, high-quality framing system.
"In general, building inspectors look for code compliance, but not necessarily for construction quality," says Bruce Dickson, Building Services Project Manager for IBACOS, where he specializes in field assessments in construction quality for home builders. "It's up to your construction team to make sure that every home is framed per the plans and specifications and lives up to the quality standards of your company."
A framing system that meets building code has achieved the minimal requirements dictated by law, but code doesn't require builders to ensure certain quality factors. "For example, even if the framing job meets code, if the joists are poorly installed, they can cause cosmetic problems, such as visible ridges in the flooring. Bowed wall studs can make the drywall uneven. Misaligned roof trusses can make the exterior roofing uneven," says Dickson.
Do your site superintendents know how to ensure that a particular system in your homes, such as the framing, meets high standards of quality? One best practice for your team to follow is to take a process-driven approach to all stages of construction.
|Sill plates provide a mouting surface for the floor structure.|
Understand how the floor system is designed to work
All of the framing components work together to provide a stable floor system. It's hard to ensure quality without understanding how the floor system is designed to work. Your site superintendents should understand the basic concepts behind building a structurally sound floor system.
• Floors Carry Weight. Picture a small kid balancing on one leg atop an aluminum soda can. The lightweight soda can is actually able to hold up under the kid's weight. But if someone comes by and dents the aluminum can even slightly, the can will be crushed under the weight, sending the kid tumbling to the floor.
An aluminum soda can is able to support a surprising amount of weight. "That's because its symmetrical shape transfers that weight down to the floor. Using this same principle of weight transfer, a floor system remains stable under the weight of grand pianos, marble bathtubs, refrigerators and large house parties. If even one element of the floor framing system is missing or is poorly installed, the floor's stability is compromised," Dickson explains. That's not to say that the entire floor will buckle as easily as an aluminum soda can, but missing or misaligned framing components can lead to performance issues that your customers will notice.
All of your site superintendents should understand how the floor system is designed to carry and transfer weight downward to the ground supporting the home. Even if the floor system is designed to be structurally sound, if it isn't installed per the design specifications, it might not perform as expected. It's possible that the floor will squeak in places when the homeowner walks across it. Clearly, a squeaking floor won't make customers happy. Construction quality details like this one are directly related to customer satisfaction.
|Cantilevers are part of the floor system that project out from the structure of the home.|
• To Build a Stable Floor. The weight of the home and its contents puts what's known as a load on the floor system. In a structurally sound floor system, floor beams and joists transfer loads downward to the ground supporting the home.
When the homeowner walks across the floor, the joists deflect, or bend slightly. Joists that deflect too much will make the floor feel bouncy or spongy when the homeowner walks across it. Per most codes, the floor joists shouldn't deflect more than 1/2 inch every 15 feet of span. But higher quality designs actually limit deflection to 1/2 inch every 20 feet of span, because that level of deflection is too small for homeowners to notice.
There are three ways to build a floor system: using dimensional-lumber joists, using I-joists and using floor trusses. Each of these three methods has special installation issues. Your site superintendents should be familiar with these issues so they can avoid installation errors during floor construction.
|Rough openings are created to accommodate interior items such as chimney boxes and stair cases.|
- Dimensional Lumber Joists. Dimensional-lumber joists have to be doubled or tripled to carry loads under key areas such as exterior walls, the ends of roof trusses and heavy fixtures, such as bathtubs. The site superintendent should check these areas to make sure the joists are doubled or tripled per the plans and specifications.
- I-Joists. I-joists are unstable until all bracing and subflooring have been installed. The site superintendent should make sure the I-joists are stabilized during installation.
- Floor Trusses. Floor trusses are designed to be part of an integrated floor system. The site superintendent has to confirm that the right hardware, such as strongbacks, ribbon boards and blocking, have been installed correctly to unify the trusses into a strong, stable floor system.
Each stage of construction, from the foundation to the drywall, has key issues that affect quality. Here are some of the key quality issues your site superintendents should confirm when they're checking floor systems.
- Make Sure the Beams are Installed Correctly. Your site superintendents should check the beams to ensure that they've been installed to transfer loads properly and provide a stable, comfortable, and attractive floor.
- Confirm that the sill plates are properly anchored to the foundation. Superintendents should also check the sill plates that anchor the floor system to the foundation. Sill plates must be manufactured from pressure-treated lumber to protect them from contact with moisture and termites.
Currently, two preservatives are used in pressure-treated sill plates: ACQ (Alkaline Copper Quaternary) and borate. ACQ-treated sill plates corrode some types of fasteners. Stainless steel or G-85 galvanized fasteners must be used with ACQ-treated sill plates. If the wrong fasteners are used with ACQ-treated sill plates, they will corrode, weakening the connection. Eventually, the connection could fail. If borate-treated sill plates are used, special fasteners aren't required.
- Ensure that the dimensional-lumber joists, I-joists or floor trusses will transfer loads properly and provide a stable, comfortable walking surface. Dimensional-lumber floor joists have to be doubled or tripled in critical areas to transfer the weight of the home to the beams, columns, load-bearing walls and other major supports. I-joists and floor trusses have to be installed per a layout specifically engineered for the home. Your site superintendents need to know the basic installation requirements of each type of floor system. With this knowledge, they can check joist, I-joist and floor truss layouts to ensure quality construction.
- Check the cantilevers and rough openings to confirm that they've been constructed per the plans. Cantilevers and rough openings place extra stress on the floor system. A cantilever is a part of the floor system that projects out from the structure of the home, such as an overhang above a porch. A cantilevered joist is supported at only one end. The amount of load a cantilever can carry depends on whether it's constructed with dimensional-lumber joists, I-joists, or floor trusses, and on whether or not the cantilever is carrying a load from above.
To create a rough opening for a staircase or chimney box, the framing members are spaced farther apart. These framing members are designed to be strong enough to compensate for the larger space between them. Joist hangers are installed to bear and transfer the stress placed on the framing members at the rough opening.
Your site superintendents should confirm that all cantilevers and openings are constructed per the plans and specifications.
- Make sure the joist hangers are installed correctly. Joist hangers ensure accurate nailing and reduce the amount of settling at connections. They allow framing members to be installed more quickly, and are easier for local code officials to inspect. Your site superintendents should be making sure that their framing crews use the proper size joist hangers and that every nail hole is filled. It's also important that the hangers be aligned properly. Otherwise, the joists will be misaligned, and the sheathing, flooring, and drywall will show these irregularities on the interior. Also, it will be difficult to hang drywall evenly against the hangers.
- Ensure that the subfloor panels are installed correctly and are fastened securely to the floor system. Local codes determine the minimum fastening requirements. However, the manufacturer might recommend a more stringent fastening schedule, which your superintendents should follow. Subflooring manufacturers typically recommend a combination of fastening and gluing to provide a stable, comfortable floor. The site superintendent should confirm that the subfloor doesn't bounce or squeak.
Even though your customers can't see the framing system, they can experience the problems that result from poorly installed framing, like squeaky floors and uneven drywall. Each stage of construction involves potential problems that your construction teams can prevent by following a process-driven approach. Don't risk your customers' satisfaction. Be sure your site superintendents follow a process-driven approach to all stages of construction. Make sure they understand how each system in the home works, the different ways to implement the system, and the key issues that affect quality in that system.