Uploaded June 2020 | Updated September 2026, 2 hours ago
Mega Build Playlist: bit.ly/2zFd35V
Our Mega Build Project House has 12 foot ceilings throughout most of the ground floor—and some very large rooms with enormous uninterrupted spans—(up to 44 feet in one area). This created some very interesting structural considerations when we designed the second floor support system.
To achieve that, we’ve gone with a fully integrated floor framing system from Willamette Industries. This floor framing system utilizes various engineered wood products. For the sub-floor, we used 1 1/8” tongue-and-groove plywood decking from Willamette, which we glued, nailed, then screwed to the supporting I-joists.
ENGINEERED WOOD PRODUCTS IN THE FLOORING SYSTEM.
Engineered wood is made when trees are harvested then chopped up into smaller pieces. Those pieces are then reassembled into whatever forms and dimensions are needed to accomplish the desired structural task.
When engineered wood was invented in the late 1800’s, builders were no longer limited to having to find trees that had grown to the dimensions they needed in order to build huge structures. If big square sheets of wood are needed, then the wood components can be assembled, or “engineered”, to manufacture plywood or OSB. If gigantic support beams are needed, then smaller 2 x 4 or 2 x 6 boards can be glued together and laminated to create “glulam” beams, and so on.
I-joists are the horizontal support members that span the distance between load-bearing walls. They’re called “I-joists” because they look like the capital letter “I” when viewed from the end, just like steel I-beams. Engineered wood I-joists are strong, stable and versatile, and for this reason are finding heavy use in residential and light commercial construction. They are an alternative to traditional “sawn” lumber support members that generally come in 2”x 8”, 2” x 10” and 2” x 12” dimensions. In a house this size, with big rooms, large open spaces and large spans between load-bearing walls, engineered wood I-joists are an ideal solution because they generally perform better than beams sawn from raw lumber in supporting a floor—they won’t warp or bend to make the floor squeak the way raw lumber can. They’re engineered to be longer, stronger and straighter than sawn lumber.
Engineered wood I-joists are dried in a kiln to remove the moisture that can compromise the performance of conventional millled lumber. These joists are bone-dry. However, if engineered wood is exposed to moisture over time, it will “grow” as it absorbs that moisture and this can seriously impair performance. Therefore, it is essential to take steps to avoid trapping moisture in areas where engineered wood is used.
Glulam Beams
Glued laminated lumber is an engineered wood product composed of wood laminations, or “lams” that are bonded together “glued” with strong, waterproof adhesives. A glulam beam looks like a bunch of 2 X 4’s or 2 X 6’s glued together into one massive beam. Individual “lams” are typically two inches or less in thickness. Pound for pound, a glulam beam is stronger than steel.
Laminated Veneer Lumber (LVL)
Laminated Veneer Lumber (LVL) is made by layering dried and graded wood veneers with waterproof adhesive into solid blocks of material. These blocks are called “billets”. The flanges on I-joists are LVL billets. LVL billets are excellent support members because the grain of each layer runs in the same direction, which greatly increases the structural strength of the beam when it is either face or edge-loaded.
In the Mega Build, we have installed massive LVL billets as structural floor supports in place of I-joists beneath sections that bear more of a load than a typical I-joist can handle.
Environmental factors
As is the case with most engineered wood products, LVL billets have a consistent moisture content, meaning they resist warping, splitting and shrinking. In addition, LVL billets, like most engineered wood products, are manufactured to disperse wood's natural defects, such as knots. This dispersal of defects greatly minimizes the effect of naturally-occurring flaws on performance and stability.
Rim Board
The APA Performance Rated Rim Board used in the Project House is placed around the outside, or the “rim” of the flooring system. The rim board is an integral structural component that transfers both lateral and vertical-bearing forces. The rim board must evenly match the depth of the framing members—an important consideration, since conventional solid sawn lumber typically does not match the new generation of wood I-joists.
Plywood is sometimes called “the original engineered wood product”. The Egyptians were using plywood in furniture as far back as 1300 B.C. Egyptian mummies were sometimes buried in coffins made of plywood. The art of “veneering”--slicing wood into thin sheets and gluing them together--was used by the Chinese, Romans, Greeks and Renaissance-era Europeans to create exceptionally beautiful furniture.
Mega Build Playlist: bit.ly/2zFd35V
Our Mega Build Project House has 12 foot ceilings throughout most of the ground floor—and some very large rooms with enormous uninterrupted spans—(up to 44 feet in one area). This created some very interesting structural considerations when we designed the second floor support system.
To achieve that, we’ve gone with a fully integrated floor framing system from Willamette Industries. This floor framing system utilizes various engineered wood products. For the sub-floor, we used 1 1/8” tongue-and-groove plywood decking from Willamette, which we glued, nailed, then screwed to the supporting I-joists.
ENGINEERED WOOD PRODUCTS IN THE FLOORING SYSTEM.
Engineered wood is made when trees are harvested then chopped up into smaller pieces. Those pieces are then reassembled into whatever forms and dimensions are needed to accomplish the desired structural task.
When engineered wood was invented in the late 1800’s, builders were no longer limited to having to find trees that had grown to the dimensions they needed in order to build huge structures. If big square sheets of wood are needed, then the wood components can be assembled, or “engineered”, to manufacture plywood or OSB. If gigantic support beams are needed, then smaller 2 x 4 or 2 x 6 boards can be glued together and laminated to create “glulam” beams, and so on.
I-joists are the horizontal support members that span the distance between load-bearing walls. They’re called “I-joists” because they look like the capital letter “I” when viewed from the end, just like steel I-beams. Engineered wood I-joists are strong, stable and versatile, and for this reason are finding heavy use in residential and light commercial construction. They are an alternative to traditional “sawn” lumber support members that generally come in 2”x 8”, 2” x 10” and 2” x 12” dimensions. In a house this size, with big rooms, large open spaces and large spans between load-bearing walls, engineered wood I-joists are an ideal solution because they generally perform better than beams sawn from raw lumber in supporting a floor—they won’t warp or bend to make the floor squeak the way raw lumber can. They’re engineered to be longer, stronger and straighter than sawn lumber.
Engineered wood I-joists are dried in a kiln to remove the moisture that can compromise the performance of conventional millled lumber. These joists are bone-dry. However, if engineered wood is exposed to moisture over time, it will “grow” as it absorbs that moisture and this can seriously impair performance. Therefore, it is essential to take steps to avoid trapping moisture in areas where engineered wood is used.
Glulam Beams
Glued laminated lumber is an engineered wood product composed of wood laminations, or “lams” that are bonded together “glued” with strong, waterproof adhesives. A glulam beam looks like a bunch of 2 X 4’s or 2 X 6’s glued together into one massive beam. Individual “lams” are typically two inches or less in thickness. Pound for pound, a glulam beam is stronger than steel.
Laminated Veneer Lumber (LVL)
Laminated Veneer Lumber (LVL) is made by layering dried and graded wood veneers with waterproof adhesive into solid blocks of material. These blocks are called “billets”. The flanges on I-joists are LVL billets. LVL billets are excellent support members because the grain of each layer runs in the same direction, which greatly increases the structural strength of the beam when it is either face or edge-loaded.
In the Mega Build, we have installed massive LVL billets as structural floor supports in place of I-joists beneath sections that bear more of a load than a typical I-joist can handle.
Environmental factors
As is the case with most engineered wood products, LVL billets have a consistent moisture content, meaning they resist warping, splitting and shrinking. In addition, LVL billets, like most engineered wood products, are manufactured to disperse wood's natural defects, such as knots. This dispersal of defects greatly minimizes the effect of naturally-occurring flaws on performance and stability.
Rim Board
The APA Performance Rated Rim Board used in the Project House is placed around the outside, or the “rim” of the flooring system. The rim board is an integral structural component that transfers both lateral and vertical-bearing forces. The rim board must evenly match the depth of the framing members—an important consideration, since conventional solid sawn lumber typically does not match the new generation of wood I-joists.
Plywood is sometimes called “the original engineered wood product”. The Egyptians were using plywood in furniture as far back as 1300 B.C. Egyptian mummies were sometimes buried in coffins made of plywood. The art of “veneering”--slicing wood into thin sheets and gluing them together--was used by the Chinese, Romans, Greeks and Renaissance-era Europeans to create exceptionally beautiful furniture.
