Mid-rise wood framed walls, floors and roofs is increasing in popularity. 5 story wood framed housing construction is being used on top of multi-level non-combustible platforms, resulting in hybrid structures of 7 stories total+/-.
Rand Soellner AIA/NCARB, HOME ARCHITECTS TM recently took an online course from McGraw-Hill (Architectural Record magazine) entitled: Multi-Story Wood Construction. The subtitle is: “A cost-effective and sustainable solution for today’s changing housing market.” Karin Tetlow was the author.
Multi-Story Residential Wood Framing
What was remarkable about this course was the fact that residential wood construction has typically been thought to be limited to 2 to 3 stories. The point of this course is that with certain creative and legal code applications, this limit can be expanded. For instance, the IBC (International Building Code) classifies construction into 5 types. Types I & II are typically non-combustible, such as for high-rise steel and concrete buildings. Type III permits wood and non-combustible materials and Type IV and V are allowed to use wood and other combustibles, per regulations.
Code Issues for Wood Framed Multi-Level Buildings
Multi-level residential wood construction typically will be within Type III and Type V. Type IV is thicker timber construction, which is also part of Rand Soellner’s typical designs. Each Type of construction has a sub-type A and B which relates to degrees of fire-resistance. A is more demanding. When projects get into larger sizes, Type IIIA is often used these days, which calls for substantial fire-proofing of the wood and utilization of Fire Treated Wood for structural load bearing elements such as 2-hour rated exterior bearing walls.
Often, a cast-in-place concrete parking garage of multi-levels provide a totally fireproof concrete “podium” with a thick top concrete slab offering at least a 3 hour horizontal fire separation, which allows the wood framed structure on top of it to be considered as a separate building for the purposes of area calculations, fire walls, number of stories allowed per code and construction type (which has much to do with the materials).
There is much more having to do with open space around such hybrid commercial buildings, fire sprinklers and creative detailing for gypsum board fire rating of walls and floors between tenants and levels and components.
World’s Largest Shake Table Test of Wood Framing
However, one of the most interesting items for the purposed of this website, is the fact that wood framing up to 6 stories, without any other platform, podium or other construction type was tested on the World’s largest seismic test “shake table” in Japan. Some people might have expected such a thing as 6-story tall wood framed walls, floors and roofs to fall apart like a house of cards. Not so.
Click here to see this amazing “shake test”—> Earthquake test of mid-rise wood framing .
This huge shake table is located in Miki City, Japan at the “E-Defense” “NIED” (National Research Institute for Earth Science and Disaster Prevention.)
David Rosowsky, Engineer, Texas A & M University, and John van de Lindt, Engineer, of Colorado State University administered the engineering, prefabrication, shipping and re-construction of the test structure, which on the YouTube video link (above) appears to be perhaps 54′ tall (6 stories) x perhaps 50’+/- wide x 36’+/-.
Engineer Rosowsky stated that “the detailing that we’ve incorporated into the structure is not difficult, it’s not especially expensive; it’s just an engineered system. And we can certainly put this into all of our structures built in high seismic regions and expect that these structures will perform well in earthquakes and that lives can be saved.”
The Shake table is a huge apparatus that has enormous pistons supporting it, that can move the table in multiple directions at the same time (up, down, sideways), to properly simulate a real earthquake. For this particular test, the scale was a 7.5 earthquake. This is a once in 2,500 year predicted event. Engineer John van de Lindt said that this is an extremely violent earthquake that is Much Stronger than what we design for in the United States at this time.
Keys Holding Together Multi-Story Wood Structures
The Simpson company, who fabricates steel assemblies for reinforcing homes and other wood structures, provided the “Hold Down” attachment clips that are bolted to the sides of “studpacks” on each wall level, in addition to the vertical threaded rods that are combined together to yield the effect of one, long, continuous steel rod, “holding down” the wood structure from the top floor, all the way down and into its foundation. This is the key element that holds wood frame buildings together during an earthquake event, according to Engineer van de Lindt. “This prevents the over-turning of the entire building,” he said. Additional wood framed shear walls were also involved, using wood studs and what appeared to be plywood or OSB (Oriented Strand Board).
The test results revealed that there was no significant structural damage to the building and only minor damage to the interior gypsum board finishes. This led the engineers to conclude that perhaps even 8 story tall wood framed structures might be possible, if properly braced.
Click here to go to Home Architect—> Contact Us .
The above testing was funded by the US National Science Foundation’s Network for Earthquake Engineering Simulation.
Your Next House Should Have These Earthquake Resistive Features
The reason that Rand Soellner and his company, Home Architect, PLLC is posting this article is to help his clients and other people who are planning new homes to please consider installation of wood shear walls and steel hold-downs per manufacturer’s and engineer’s guidelines, to help your new house resist earthquakes no matter where they might be located. For instance, one of Soellner’s projects was in a characteristically minor earthquake zone in Virginia, which did not legally require ANY earthquake provisions whatsoever. However, Soellner did provide his normal hold-downs and lateral shear walls, as he believes this is prudent. This home, like many of Soellner’s had 2 main levels, and some of his projects feature 3 levels of wood framing. Shortly thereafter, that area of Virginia experienced a 5.9 earthquake. This only goes to show you that you can’t be too careful. An ounce of prevention can keep away a pound of cure and keep you and your loved ones literally Alive. Be safe, not sorry: hire a real architect to design your next custom house.
What you probably do not know: building codes do NOT always require earthquake precautions, even though you may reside in a location that can experience light to moderate earthquakes. And, there is No guarantee from your local building department that the massive rock plates on which our continent sit, might decide to slip more than local recorded geologic history (only the last 100 to 200 years?) in your region of the USA or World may have noted (the last 100 to 200 years of relatively light seismic activity is No guarantee that a severe earthquake could not occur tomorrow and a couple of hundred years is only the blink of an eye in geological action terms: for instance, the last time the Yellowstone mega-volcano erupted was about 70,000 years ago, but that’s no guarantee that it won’t blow again tomorrow). If you live in a mountainous region south of historic glaciers, there is a reason those mountain are there: hint: seismic activity: translation: earthquakes! So, regardless of the lack of building code requirements, you would do well to help your new home protect itself by having your architect install at least some precautionary good design practice details to resist at least some seismic action.
Rand Soellner, AIA/NCARB: 1-828-269-9046
tags: custom, wood framing, cashiers, chicago, atlanta, los angeles, canada, buenos aires, russia, aspen, boulder, jackson hole