Build a Better Performing Floor for Less
By Tim Powell
Whether building starter homes, mid-price residences or high-end custom homes, managing costs is critical at every step. At the same time, cut too many corners and you’ll end up with unhappy customers.
For structural framing in the floor, there’s an easy way to reduce material costs while maintaining or even improving performance. In essence, using fewer materials overall, yet creating a more solid-feeling floor.
The key is to look at the floor framing as a system – joists and floor panels - are designed and installed to work together. These elements can be sized and spaced in numerous ways that effect the finished floor’s feel and cost. Often, though, such decisions are made based solely on previous experience or regional traditions. The result can be a structurally sound, code compliant floor, but one that feels softer than preferred, has squeaks or costs more than it should by not optimizing materials.
With readily available design and evaluation tools, builders can consider multiple floor framing plans and pick the best one for their needs before construction begins. In affordable homes, a builder may choose a lower-cost floor option designed to code requirements, but may want a more solid floor in higher-end homes. Within the same home, the owners may be fine with a basic floor system in the office or other low-use rooms, while desiring a higher rating in living rooms and kitchens where traffic and visitors are more frequent. Whatever type of floor is needed, design and evaluation tools can help balance floor performance with costs.
One such tool available to builders through dealers is iLevel Javelin® design software. Designers can use the program to analyze various options for joist size, spacing and span, along with floor panel thickness, to help target floor performance to its intended use. Built into the software is the TJ-Pro™ Rating system, which provides a single rating number for each floor or framing area in a home which indicates how most users will perceive the floor’s feel. The software provides a detailed framing plan that shows the precise location and size of all structural materials, along with a material list. This helps avoid unnecessary material and labor costs inherent with overbuilding or from ordering too many materials.
A specific floor system solution that works well in many applications is to use thicker floor panels in conjunction with wider joist spacing. For example, builders may be able to substitute 7/8” iLevel® Edge Gold™ OSB panels for 22/32” OSB panels and increase joist spacing from 16” on-center to 19.2”. Such floor systems usually have a higher TJ-Pro Rating because the thicker panels are stiffer and better dampen vibration despite the wider joist spacing.
While 7/8” panels cost more, the total floor framing cost is often less because fewer floor joists are needed. Thicker panels also can help reduce the risk of callbacks by better resisting edge swell if the subfloor gets wet during construction – which can lead to buckling in hardwood floors. As with all structural framing, it is important to confirm that local codes allow wider joist spacing in conjunction with thicker panels.
Beyond the joists and panels, rim board selection also plays an important role in the cost versus performance equation of a floor system. Rim board provides attachment points for joists and floor sheathing and helps carry and transfer vertical and lateral loads. To do this properly, it must be the same depth as the joists. Because dimension lumber rim typically shrinks and does not match the depth of the wood I-joists it is not recommend for use with I-joists. As an alternative, many builders use LSL rim board. Products like Trus Joist® TimberStrand® LSL rim board match the depths of TJI®-joists and are dimensionally stable, strong, consistent and resist warping and twisting. The result is a floor that’s more likely to remain quieter and more firm well after installation.
Getting started with designing and building floors as an integrated system is easy. Your building material dealer or manufacturer can assist with information on the latest products and construction methods, as well as design tools and performance ratings. Some also have on-staff engineers who can work with you to help ensure a cost-effective, quality floor.
Tim Powell, is a National Accounts Manager for iLevel by Weyerhaeuser. iLevel offers a range of residential, multi-family and light construction structural framing materials, technical support and software, including TJI® joists, iLevel Edge Gold™ panels, TimberStrand® LSL, Parallam® PSL and iLevel Premium® Joists. www.iLevel.com, 888-453-8358