Kiln Dried and Engineered Lumber in Panelization - For Builder Architect Magazine

In the production of quality wall and floor panels, selection of the proper raw material is critical.

The single greatest impediment to achieving a quality finished wood frame structure is the high moisture content and lack of consistent shape of the green lumber normally used in site framing. This lack of consistent lumber ensures a sill plate that does not provide a level base for floors and walls, makes it difficult to achieve a quality result when plumbing and squaring your walls, and requires door and window shimming. These problems are made even worse as the wood dries over time, changing shape, causing nails to pop, corners to crack, walls to bow and windows to leak.

In addition, the change from arsenic impregnated to copper impregnated Sill Plate now requires use of Hot Dip Galvanized fasteners, anchor bolts, hold downs and straps to combat the corrosiveness of the copper. According to the Simpson Strong-tie Technical paper T-PTWOOD06, the new copper process has a corrosion rating of over 3x, a significant increase over the ratings on previous methods of pressure treating wood, and one that demands more expensive hangers, fasteners and hardware.

In order to address the above problems, automate the manufacture process and to provide the superior quality that can be realized with manufactured panels, leading Panelization Firms use Kiln Dried (KD) lumber for framing lumber and have dramatically expanded the use of Engineered Lumber in their products.

KD lumber comes in exact dimensions, ensuring level, unbowed walls and greater quality delivered with no change in shape or form after the walls are placed. All lumber is #2 or better with no Standard or No-Grade lumber in use at all. When used in longer wall panels, up to 27’, the used of KD and of automation delivers a machine produced product that requires no on site adjustment. In fact, with a wall of this size normally site framed in three separate sections, with each section plumbed separately, the ability to place and plumb only one machine trued wall, delivers vastly superior quality at greater speed.

In many areas, the use of Engineered Lumber also greatly improves quality and performance. In floor panels, the use of I-Joist and Tongue and Groove (T&G) sheathing allows for longer spans and greater open space in the structure, while delivering minimal deflection and no squeaks. The Weyerhaeuser Silent Floor Systems, when properly utilized by a floor panel manufactured, provides a warranty that is passed all the way through to the Home Buyer (see www.ilevel.com for details).

To address the new wall Sill Plate requirement for Hot Dip fasteners, hardware and imbedded items, smart panel manufactures are using a Zinc-Borate treated LSL (Laminated S_ Lumber) Sill Plate. The use of this Engineered Product insured a straight, level and square base for the walls, but does not require any specially treated fasteners, hardware or imbedded items, dramatically lowering those related costs. Additionally, pneumatic (collated nail gun) fasteners can be used. A few leading panel firms are also experimenting with the use of LSL studs for window and door sub-components. As the Engineered Lumber does not expand, contract or change shape, window and door openings remain at the exact desired dimensions and no shims are required. Windows don’t leak from expansion and contraction of the wood cripples, trimmers and sills. Doors continue to open and close properly as well. Finally, the use of LSL lumber ensures better quality balloon framed walls, though these panels are typically only 10’ wide rather than the 27’ wide standard wall panels.

How are leading panel firms able to afford to use more expensive material like KD and Engineered Lumber, while still being cost effective? Efficient operators of wall and floor panel lines generate dramatically less waste than job-site framing does; 3-5% compared to 18-22%. This fact, combined with the very large amounts of lumber purchased (5-10,000,000 board feet annually) at one site, by panel manufacturers, provides lumber costs that are significantly lower than that available on the jobsite. This advantage allows quality panel firms to use higher quality KD and Engineered products to deliver quality at a cost that is lower then the less precise site built competition.

Be sure any panel firm you are considering uses KD lumber at a minimum and as much Engineered Lumber as possible, to ensure you receive the best possible product on your jobsite. Quality In, Quality Out.