Engineered Wood: A Perfect Fit for Urban Infill

Infill builders can reduce material and labor costs with engineered wood products

by Scott Lockyear

Many architects and builders are finding that engineered wood is ideally suited to today’s urban infill projects. It’s material that offers outstanding structural performance, design flexibility, and an environmentally friendly low-carbon footprint. Additionally, engineered wood can be used in multi-story infill projects at a fraction of the cost of concrete/steel construction.

Engineered wood is a great fit for both single-family infill projects and two popular types of multifamily infill builds: wrap-around and podium. A wrap-around design consists of a central parking structure surrounded by multiple stories of wood-framed units. A podium design provides retail services or parking at ground level by building five stories of wood frame over two levels of concrete podium.

Designers are increasingly turning to engineered wood to meet a variety of objectives in urban infill construction: meeting stringent fire codes, achieving higher load/span and shear values, protecting the environment, and reducing construction costs.

Foulger-Pratt, one of the largest infill apartment developers in the Washington, D.C. area, is planning three large projects that will be constructed with wood rather than concrete. Foulger-Pratt estimates that it costs about $70,000 more per unit to build with concrete than with wood.

“Single-family infill jobs involve different detailing issues than single-family homes in the suburbs,” says Brian McNertney, AIA, senior vice president of Toll Architecture in the Dallas area. “Examples would be rooftop decks over living spaces, and shear design gets harder because homes are narrower with fewer walls.”

The Value of Versatility

Infill builders can often streamline purchasing when they choose an engineered wood product. For example, LP® FlameBlock® Fire-Rated OSB Sheathing can be used in both exterior and interior load-bearing wall assemblies, plus roof deck applications. Using this product in exterior wall assemblies helps meet rigorous fire codes and will eliminate the need for a layer of gypsum in certain designs. It also meets the demands of higher shear when Struc 1rated LP FlameBlock sheathing panels are used. Using LP FlameBlock sheathing in interior demising walls of townhomes, as a substitute for gypsum panels in shaft wall liner designs, eliminates the need for additional components like C and H channels, H studs, and breakaway clips while contributing to an assembly that exceeds code requirements for minimizing sound transmission. LP FlameBlock sheathing rated wall assemblies have been tested and rated from Sound Transmission Class (STC) at rates as high as 62. Further, when used in roof deck applications, LP FlameBlock sheathing also delivers a higher load/span rating than Fire Retardant Treated (FRT) plywood at the same thickness.

Let’s take a closer look at the many benefits of engineered wood in infill construction:

Reducing Material and Labor Costs

Construction crews at RT Framing in Denver recently used fire-rated OSB sheathing to reduce costs in a Type III seven-story multifamily project in the city’s Belleview Station neighborhood. “I decided to use fire-rated OSB not just for the labor-saving aspect, but for the means and methods,” says Russell Beilby, RT Framing vice president. “Putting on one sheet of gypsum is simple because you can lean through the studs. It’s the second sheet that causes difficulty on the higher stories because you have to rent equipment like cherry pickers and boom lifts, which can run about $6,000 per month. I chose the fire-rated OSB because there would be no need for a second layer of gypsum.”

“One thing we like about LP FlameBlock sheathing is that one trade can install both the sheathing and fire separation, not the usual two trades,” says Toll Architecture’s McNertney.

Installation Simplicity

For infill projects ranging from single family and townhomes to Type III multifamily, wall assemblies that incorporate fire-rated OSB offer time-saving installation ease. The UL U349 exterior wall assembly eliminates the need for a layer of gypsum – and the UL U350 interior wall assembly is lighter and easier to install than shaft wall liner. Contractors can even have panelizers build these wall assemblies in a factory and ship them to the jobsite.

Some engineered wood trim products (like LP® SmartSide® Trim) come in lengths up to 16 feet for potentially fewer seams and faster installation compared to many other trim options. The product also comes in a variety of width sizes. With a range of widths to choose from, installers may save time as they do not have to cut custom width sizes as frequently on the jobsite.

Higher Density at a Lower Cost

As our cities grow rapidly, it’s imperative for builders to find ways to increase downtown density in a cost-effective way. That’s why so many infill developers and designers are taking a fresh look at engineered wood solutions.

Every new wood-framed wrap-around and podium multifamily project—and every innovative single-family infill job—helps eliminate the need for more greenfield developments far away from the city center. Engineered wood is playing a pivotal role in making our metropolitan areas more vibrant and environmentally responsible.

Scott Lockyear, PE, is AEC National Sales Manager at Louisiana-Pacific Corporation. With over 10 years in the engineered wood industry, he has held many roles, including the Technical Director at WoodWorks and Technical Manager at Weyerhaeuser. In his current role as National Sales Manager – AEC with LP Building Products, Scott specializes in the design of wood framed structures, helping the commercial and multifamily design community in solving their design hurdles.