Earthquake Defense mechanical connections require a lot of planning.
With the 2007 CBC codes addressing Earthquake Defense more progressively, we’re feeling more like Carpenters of Steel than carpenters of wood! The amount of steel in new buildings in California for seismic structural engineering is changing the way carpenters frame. For production framing here in California, we used to use the words “blow and go” a lot. But those days are over. Now all anyone talks about is “mechanical connections.”
There was a time when all a carpenter needed was a set of nail bags, a Skill saw, a 100-ft. cord, and a couple of hand saws. Top carpenters showed up with a cats paw! All of that stuff fit easily into the trunk of a VW Bug. Trust me, I know. But framing today is completely different.
As you can see from this partial list of the structural hardware in the 5,600-Sq. Ft. residential building we’re currently working on, framing today is more about mechanical connections than pulling out your hammer and banging together walls and rafters.
- 900+ A35 Anchor Clips
- 400+ LTP4 Lateral Tie Plates
- 130+ Hold-Downs
- 12 HFX Hardy Fames
- 500+ Straps
- 2 Steel Moment Frames
- 2 Bent Steel Rafters
According to the 2007 CBC codes, “Any change in the plane of the structural frame has to have a mechanical connection.” The mechanical connection could be something as simple as an A35 anchor clip attaching the frieze blocks to the top plates, or HDU hold-downs for uplift. The A35 anchor clip isn’t new to framing in the United States, but with 500+ A35 anchor clips in most residential buildings, it’s no longer a simple installation. When A35 clips are required 4.5 in. O.C., most of the time we set our joist beams and joist rim, and install the A35 anchor clips before the TJI joists are installed. Yes, the A35 anchor clips are touching each other at 4.5 in. O.C.
If we install the TJI joist first, then we use a palm nailer to install the nails in the A35s. We buy boxes of Simpson A35s like we used to buy 6-packs of beer. We were always running out of beer, and now we’re always running out of Simpson A35s!
All beams must have a mechanical connection to the top plates. Toe-nailing beams down to wall top plates is no longer allowed. Since every beam has a mechanical connection to the top plates, we often use a router to dado out either the bottom of the beam or the top of the top plates, especially when the mechanical connection is an MST strap positioned horizontally for a drag strap.
The tools we use today are mind-boggling. I never would have imagined it twenty years ago. Now, instead of one saw, we carry three or four—with left-hand and right-hand saws for cutting rafters, Big Foot saws, and chippers (see below). And we even carry routers! For framing! It used to take 3-4 weeks—TOPS—to frame a house. Now it takes a year.
The templates we use for routing the MST straps are made out of 1/2-in. or 3/4-in. plywood with 1x2s attached with screws. The template width between the 1x2s is the width of the router plus the width of the MST straps.
|MST60 strap dadoed into top plates. With the MST strap dadoed into the beam or top plates, the beam sits flat on the plates.|
I live thirty miles from Simpson headquarters. Lately, I’ve given some thought to moving farther away. It seems the closer you get to Simpson, the more hardware you have to put in a building.
We use a lot of hold-downs for mechanical connections to prevent beam uplift.
The PHD2 5/8-in. all-thread hold-down rod is drilled through the 6×12 header, and a 3 1/2-in. x 3 1/2-in. x 5/16-in. plate washer is installed on the bottom of the 6×12 header.
We use a Protool drill guide—with an 18-in. Wood Owl Ultra Smooth Tri-cut Ship Augers bit—to drill double stacked 4×8 truss rafters, as well as drilling out the holes for the PHD hold-down all-thread rods through 6×12 headers.
A lot of planning is required for the 50 hold-downs that are in this basement slab (see photo, left). About 30 of these hold-downs are for the uplift mechanical connections at the ends of the basement shear walls. The other 20 hold-downs are for post-to-beam uplift mechanical connections that transfer up to the roof sheathing for the continuous load path.
Before we start any job, we spend a lot of time looking at the plans for the continuous load paths that require uplift mechanical connections. A lot of the connections—per the structural engineering drawings—are un-constructable. If we see any un-constructable uplift mechanical connections, we send an RFI to the structural engineer. Or we send the structural engineer a replacement drawing or suggestion. The structural engineer then responds with a “no objection” or “objection” to our replacement suggestion…and the job or delay goes on….
When we have to epoxy in new hold-down all-thread rods, we use a rebar-cutter SDS drill bit—Bosch or Relton—to drill/cut through the rebar with our Bosch or Hilti rotary hammer. The hold-down all-thread rods require precise placement in the concrete slab, so we use an SDS drill bit—which is 1/8-in. wider than the all-thread rod—and drill the hole until we hit the rebar in the concrete. Then we switch bits, and drill with the rebar cutter until we’ve cut through the rebar. We finish off the hold-down hole with the standard SDS drill bit. Per the 2007 CBC, all epoxy hold-downs must be inspected by a special inspector. The new hole for the epoxy must be brushed out, then blown out with an air nozzle that reaches all the way to the bottom of the hole, and brushed out again, and then blown out again with an air nozzle.
|A lot of these mechanical uplift connections are side by side! The MST72 and HDQ8 have a 6x post below each of them. At the bottom of the post, another hold-down secures the 6x to the basement slab.|
|There are 5 hold-downs in this picture! And no, I didn’t mock this up as a joke. The two HDQ8 hold-downs at the end of this shear wall are for the shear wall connections. The other three HDU4 hold-downs are for post-to-beam uplift connections.|
Sometimes there is more metal in the walls than wood! So we don’t have to cut studs loose, we install all the hold-downs as we frame the walls.
When we’re not planning out the location of the uplift connections—which transfer load from the basement slab up through the roof sheathing—we’re installing horizontal collector straps. A chipper that I used for cutting rafter seat cuts in the ’70s and ’80s is now used to cut dadoes in the subfloor for these straps.
All these dadoes consume a lot of subfloor thickness. The plans called for 3/4-in. subfloor—imagine what would be left! I up-sized the subfloor to 1 1/8 in., so our flush-cut CMST14s would not weaken the plywood subfloor.
On steel I-beams, it’s the carpenter’s job to layout all of the mechanical connections, like these HFX Hardy Frames with 1 1/8-in. all-thread rods, and the location of the web stiffeners on each side of the 1 1/8-in. all-thread rods, too (below).
When framing with this much steel, it’s important to keep an eye on Moisture Content. That’s something no framer in the ’70s or ’80s thought much about. Code requires that all the lumber be dried to at least 19%, but even that wet, it shrinks. And steel doesn’t. Keep in mind, we have to put 6x material for nailers on the I-beams, so excessive shrinkage can cause major problems in floors and walls (bumps and high spots in floors, cracks in walls, etc.). Luckily, on this building, it sat for so long that most of it was dry. Which also gave us a chance to go back and tighten all the bolts. Think about that. What happens when the frame is completed and dried in before you have an opportunity to tighten the bolts?
A lot of planning and calculations went into making this 67.5° roof axis point work (below). The 7:12 to 26:12 roof axis points were tough enough to calculate, let alone the 67.5° 26:13 pitch-bent steel hip rafter!
In the photo to the right, Erik is drilling 11/16-in. holes in the 1/2-in. steel plate using the Hougen Portable Magnetic Drill. After that, the 1/2-in. thick steel plate is bolted to the concrete wall, and an ECQ column cap base is welded to the plate for the joist beam uplift connection.
The first time I drilled holes in steel I-Beams back in the ’70s, it took about an hour to drill an 11/16-in. hole for the 5/8-in. bolt or all-thread rod—that was using a standard twist-drill bit. With the Hougen Portable Magnetic Drill, it only takes about 1 or 2 minutes per hole. There are two switches on the tool, one for the magnet and one for the motor. First, you position the drill bit on the hole, then you switch on the electromagnet. After that, running the tool is like operating a drill press—you just crank the bit into the steel.
We had a job in SF 1 1/2 years ago where I spent $700 for drill bits to drill a-holes through the I-beams so we could attach backing. With the magnetic drill, and using Annular Cutters, I can drill 100+ holes, instead of the 2 or 3 that you get out of a twist-drill bit.
All of the roof beams have a mechanical connection to either the walls below, or the joist beams below. “Mechanical connection” translates to mechanical fasteners, like bolts, base caps, straps, or hold-downs. Any change in the plane of the structural frame has to have a mechanical connection, which includes every common rafter and hip rafter. No more toe-nailing rafters to the ridge beams!
After we install the fascia, we re-check the building with Stabila levels, so we know where we need to add more structural hardware.
When I first saw the plans for this building, I thought it was going to be a lot of fun, but the structural steel took all the joy out of it. On the main house, we had to first install the 26/12 rafters, then sheet the roof, then cut the radius rafter tails, and scribe the bottom side so it laid on top of the roof sheathing. Finally, we had to cut a hole through the sheathing so we could put an MSTI26 from the rafter tail across the rafter. And that was for every single rafter on the main house—200 radius rafter tails, and every one had an MSTi26 strap.
Sometimes I worry about installing all those straps. With all the engineered walls we build into homes, it’s no surprise that the other trades get us into trouble. One time, the heating and air guys came in and butchered a shear wall—they notched out the top plate. The engineer required us to install a 6-ft. long 1/4-in. x 4-in.-wide steel strap, with 16d nails 1-in. on center! I said to the engineer: “Hey, we’re just going to split out all the wood! What’s the point?” His answer: “Okay, then pre-drill the holes.”
|Just when you think you’re done with all of the mechanical connections, you have to screw the siding and trim to steel Hardy Frames!|
“Blow and Go” = Fun
Mechanical Connections = Frustration and a lot of un-constructable engineering.
Sim Ayers is the owner of SBE Builders, a commercial and residential framing company, located in the San Francisco Bay Area, which was established in 1988. He uses empirical knowledge, gained by means of observation, experience or experiment, to frame buildings from the ground line (Z1), to roof axis (A1), to the bring-back line for scribing (B1).
Sim is a second generation carpenter. He is passing on the family tradition to his two sons Brian and Erik. As a typical California production roof cutter and stacker in the 1970s and 1980s, Sim keeps a sharp eye out for new information on roof framing geometry, or for writing online scripts that use a tetrahedron to show the relationship of geometric framing angles for use with the carpenter’s steel framing square. His online tools can be found on the web at www.sbebuilders.com/tools.
Great article. A few of questions:
1. I see your chipper is set to a depth of 1/4″. Is the router in Figure 3 set to the same depth?
2. In Figure 9, why are the upside-down hold-downs not in contact with the top plates?
3. Where are you getting PHD hold-downs? Simpson discontinued them last year.
Charles, the router depth for the collector straps is closer to an 1/8″. In the two photos of the hold-downs, you can see that there are 5 hold-downs at the bottom plate. HDQ8’s at the ends of the shear wall for racking and uplift. The three hold-downs in the middle of the bottom plate, attached to 4×6 post, are for uplift only. The hold-downs that are not touching the top plates of the shear wall are for the continous load path to the roof for uplift only. These three continous load paths to the roof have a total of 15 hold-downs that tranfer thru each floor level for the beam uplift at the roof plate line.
Even thru the PDH series hold-downs are being replaced by the HDU series hold-downs, I ordered 3 boxes of the PHD5 holdowns. We can still get them eaisly. I even talked with the Simpson engineers at a trade show and told them that that can’t discontinue the PHD5 hold-downds. I needed 5 kips of uplift at most of the beams and the HDU5 is to tall for the 11 7/8″ TJI joist.
Great article!! What a story and 1/2. Construction sure has changed, and in a pretty short time span.
Thank you for contributing to TiC! The magazine wouldn’t be much without contributions from readers/authors like you.
Wow that chipper thing looks good, what is it like a circular saw with a dado set fitted to it ? never seen anything like that here.
Chris, yes it is a 7 1/4″ Skill saw with a custom arbor and guard attached to it. Skill made a 12″ dado saw in the 60’s and 70’s, but it only had a 2″ set of dado blades. In the late 70’s most of the production roof cutters had custom 3 1/2″ wide dado saws made. Then we switched over to custom made swing tables in the early 80’s.
I enjoyed the article—well done in my opinion.
I recall building a number of buildings around Cal-State Northridge Univ—must have been in the 1970s. Even then we had hundreds of holdowns and drag strips with so many bolts that the top plates would split.
I do have some questions:
1. Can a building be built too solid—too rigid? The old, flexible, single story tract home will rock and roll in an earthquake, but seldom collapse.
2. Who needs a 5,600 sq. ft. house these days?
3. Is the bumper sticker: “Live simply that others may simply live” just that—a bumper sticker?
Thanks again for your article. Larry Haun
Larry, it’s funny that you should mention Cal-State Northridge Univ. It was in the early 70’s around Cal-State Hayward on top of a hill on the earthquake fault line that I installed my first A35 clip. I remember using those short baby teo nails to install the A35 clips and beating your fingers to death, because the nails were so small. With both of us being/been production roof cutters here in California in the 70’s and 80’s we must have had a lot of the same framing experinces. Class of 69…
1#. I don’t know about the track homes you built in the 70’s, but if I remember correctly the track homes I worked in the 60’s and 70’s only had 1/2″ anchor bolts 6′ O.C. and I don’t have any faith in 1/2″ anchor bolts in a 7.0 or higher earthquake after seeing all the houses fall off their foundations in the 1964 earthquake in Alaska.
2#. Dr. Dumas needs a 5600 sqft house.
3#.Live simply that others may simply live…as long as you have fun living simply.
Thanks for the reply. Yes, I have seen houses scoot off their foundations because of 1/2 in. bolts spaced 6 ft. o.c. But they didn’t collapse and kill anyone.
Simple houses, even if they are not fun, seem to be safer.
Have you by chance checked out Swisscell on Google? These paper houses sound pretty good to me. Forget the steel if what they say about them is true.
Take care–Larry Haun
While reading this I found myself wondering if wood frame construction, a strong and inexpensive method, has finally met it’s match in the seismic requirements. Wouldn’t it be simpler to build this some other way? maybe completely from steel? but then you’d have to ultrasound every member! argh!
How on earth did you manage to locate all the hold down locations when laying out the foundation? I remember reading somewhere of a system used in commercial work that uses modern surveying equipment (sat based?) to layout locations in multi story buildings. supposedly was very accurate and payed for itself ($20k?) quickly. It must have been in JLC paper or online where I saw that.
Also cool info on your website, now I just need a 20 or so hours to try and figure out if I can use it, then a lifetime of figuring out the individual concepts!
Rodger, Dick Seibert has a project that I’m going to frame for him later this year and after seeing all the Simpson hardware I installed on the Woodside project he eliminated all of the shear walls and had the structural engineer use steel I-Beams everywhere. So the building structure is completely steel.
I remember reading the article in JLC about the modern surveying equipment and thinking it was was pretty usefull. But I just laid out 1×6’s for the location of the walls in the basment and then laid out the hold-down locations. Out of the 50 hold-downs in the basement I only had to epoxy in 2 new all thread rods for the hold-downs. The hard part wasn’t laying out the hold-down locations in the basement, it was making sure the hold-down locations in the basement formed a continous load path to the structural roof beams.
From the article: “All these dadoes consume a lot of subfloor thickness. The plans called for 3/4-in. subfloor—imagine what would be left! I up-sized the subfloor to 1 1/8 in., so our flush-cut CMST14s would not weaken the plywood subfloor.”
No wonder California is in such financial trouble. Do you guys just lay down and play dead? Look at the quote. Then think about this – all of this is being dictated by architects, engineers, and bureaucrats, a TOTALLY unworthy lot ( to keep the language clean ).
Who decided to up-size the sub-floor? A CARPENTER! ‘Nuff said.
Consider this quote: ‘The engineer required us to install a 6-ft. long 1/4-in. x 4-in.-wide steel strap, with 16d nails 1-in. on center! I said to the engineer: “Hey, we’re just going to split out all the wood! What’s the point?” His answer: “Okay, then pre-drill the holes.”’
Like drilling that many holes won’t weaken the wood? Gimme a break.
Morse, last night I heard the Simpson StrongTie jets fly over my house. They must be on their way to the Washington DC area after the earthquake in Maryland last night. To lobby congress to pass stronger earthquake defense engineering for the entire nation. We the people of California do here by release all of our engineers to serve the rest of the nation for better or worse.
Sim, what an interesting article, I really enjoyed reading it. Isn’t it amazing how a few changes in building code can increase costs exponentially?
Great website too, ever thought of writing a book?
Sim, I’m a joiner in England and was sent this article by Larry Schweitzer (Nebraska), who I met via the WoodWeb forum. I will NEVER complain about the Building Regulations in the UK ever again! How the hell do you guys stay sane?!
Great work though.
Sim, this is the saw article.
[file]http://www.thisiscarpentry.com/wp-content/uploads/2010/07/circular saw safety.pdf[/file]w
Where were you when I needed you? I have fought framers and concrete men my whole construction career. As a hands on foreman with extensive knowledge of metal framing, wood framing, and metal building construction, the “We’ll do it our way” became predominant twenty years ago.
The very first thing I learned as a superintendent was to be PERSONALLY involved in all of the building anchors. I would draw all of the anchor locations, give my signed drawings to the framer and concrete foremen, and I would be there when the trades installed them. I even gave specific directions to the framers as to which end of a wall to begin their framing centers. All for naught. Unfortunately, a superintendent cannot be at all places at once. I did two projects in CA. There, I’ve had the “top-of-the-line” framers cut off my HD anchor bolts, my sill anchor bolts, and my PA straps because it didn’t conform to their framing desires…all without consulting me. Yes, they paid for the epoxied anchor replacements (with the structural engineer present), but did not pay for the time lost. In addition, I had the “politically correct” inspectors on the job that had never driven a nail, some barely spoke English, and all were schooled in the UBC which, as you know, are the MINIMAL ACCEPTABLE STANDARDS of construction. I was “red-tagged” for using 4X6s instead of 4X4s, sheathing copper lines that penetrated concrete, and denied the use of pre-treating for termites.
Prior to construction, I asked the L.A. County Inspection Dept. the following:
1. Why do I have all of these HDs, anchor bolts, and all-threads up to the roof line?
Answer: “Well, you’re within four miles of the San Andreas Fault Line and you need this so that, in case of an earthquake, the building will sway with the movement without collapsing.”
2. Okay, with that in mind, why do I have all of these plywood and sheetrock sheer-walls on the exterior and interior of the homes?
Answer: “Well, you’re within four miles of the San Andreas Fault Line and you need this so that, in case of an earthquake, the building will be rigid enough to with-stand an earthquake and not collapse.
Your article was fascinating and informative AND a good confirmation of why I have refused any more supervisory work in your state.
Dave, We the people of California do here by release all of our engineers and “top-of-the-line” framers to serve the rest of the nation and the UK for better or worse.
I’ve laid-out all of the anchor bolts and hold-down bolts on all of my jobs for the last 15 years. I don’t truss anyone to lay out anchor bolts and hold-down bolts. Especilly,concrete workers and “top-of-the-line” framers.
I just sent out 2 rough frame bids today. 600 sqft guest house, structural hardware price of $19,000.00. 2700 sqft house, structural hardware price of $27,000.00.
That’s $46,000.00 for jet fuel for Simpson Strontie, so they can visit all of the states that don’t require all the different structural hardware they manufacture.
I thought I was reading an article from Scientific American. I’m left thinking that I’m glad this old dog lives & works in Maine & not California. Way out of my league… Very interesting though. Thanks for a an informative read.
For me, Roger poses the big takeaway question from Sim’s article.
In the late eighties, an LA County building inspector insisted that I use three toe-nails to attach the 4″ of 2×8 floor joist bearing on the mud sill of a small addition. Presumably, if one 16d nail provides 10,000 lbs of shear, THREE nails will provide 30,000 lbs. When you consider that the rim joist is attached to floor joist with three through-nails already, you may as well be nailing a paintbrush to it.
I read Larry’s “The Very Efficient Carpenter” and for a while had great fun framing the projects I would be doing finish on. (Larry, I wish I had taken your advice about wearing long-sleeve shirts!) I have long since figured out that it’s not all about me and my fun, but I’ve also come to believe that most of this “earthquake-proofing” is driven by the insurance companies’ misguided belief that these building requirements will save them money in the event of a major quake.
As Larry has pointed out, single-story wood frame houses are resilient and by a very large majority withstand earthquakes very well, even with decades-old regional building practices.
I have lived in the San Fernando Valley for more than fifty years, through both of the Valley’s large quakes, and none of my pre-1960 (one-story) homes have received more than superficial damage.
In my experience, the homes and apartment buildings that took the biggest hits were of the 70’s and 80’s “post and beam” variety, the two-story ones with vaulted ceilings and heavy tile roofs, built like a houses of cards. They were just just bad buildings. A few were condemned, but with the exception of a couple of poorly-built apartment buildings, none came down.
In my opinion, in the next big quake, which could be very much larger than the ones I’ve experienced, even the “heroically-engineered” homes will sustain damage and due to the complexity of their design will be more expensive to repair and of coarse, to replace.
The human toll, in addition to the usual culprits, un-reinforced masonry and falling building facades, will mostly be from falling fixtures and furniture, things un-addressed in building codes.
Perhaps structural wood framing will be limited to single-story and traditional-hybrid (triangles and shear-walls) two story buildings. Everything else will be steel with wood in-fill.
While framing in Calif., I came to a personal conclusion that you can actually build houses that are too rigid. I say personal because of my own experience and observation. I am not an engineer.
I had an article published in Fine Homebuilding Magazine on earthquake damage after the Northridge quake. I checked on many of the houses and apartments that we had framed. Shear walls nailed 2 in. o.c. with 10d commons were often split apart because there was no give for them to rock and roll. They rocked and split.
Yes, wearing long sleeve shirts out in the hot sun can help keep us skin cancer free.
Check out http://www.swisscell.com. I would be interested in what you think about this type of construction.
I had some trouble with your link, but a Google search got me to a couple of sites presenting swisscell.
I have samples of a similar product from a manufacturer who touted one of its’ uses as floor panels in aircraft construction. I was interested in using it as a floor for a trailer I was planning.
After a decent search of their site, the joinery process remains a mystery. It is versatile stuff, apparently able to take a wide variety of veneers. It’s light weight has great appeal to me.
I’ve always questioned the building industries’ insistence on using some of the heaviest materials imaginable when there are so many advantages to using lightweight materials. Solid MDF doors? sheetROCK? The cost savings in shipping and handling and the costs associated with the physical toll on construction workers alone argue for a change in how we build.
The biggest concern from my finish carpenter’s perspective is that what I’ve loved most about buildings is their different historical and regional vernacular styles. I’d hate to see building materials dictate a world of those Swiss-designed houses.
By the way, the roof framing of that house is truly beautiful. Kudos to the carpenters.
Great,great article. I am humbled by what so many of you have to deal with
I kind of agree that if you have to do this much hybrid framing with steel… maybe the whole thing needs to be re-thought. Seems to me lumber, engineered or not, is no longer the best material for the job. Issue #1 -splitting out the wood and therefore compromising its integrity because of the ridiculous number of fasteners required for strapping and shear panels (pre-drill 1″oc holes..yuh
…. and #2, the “what if we dried-in before we could tighten the bolts” issue. There’s no way in hell all those connections are going to stay on spec for more than a year or two, no matter what you do, dried in or not.
We used to have that problem with all-steel bolted red-iron structures for commercial buildings. We’d actually go back in a year and not a single bolt would be on-spec., with whole building swaying in the breeze. Some nuts so loose you could spin them off without tools… fasteners that were all torqued at the time the building was constructed. I can’t imagine the impact on wood-to-steel connections. All that engineering down the tubes… why don’t they (the specifying engineers) get that? It’s borderline silliness… engineering that is so critical with no tolerance, being imposed on materials that are impossible to make comply over time. The absolute best of intentions, but that’s what paved the road to hell. Time to look into reliable monolithic structures. Maybe something like ICFs properly reinforced – maybe with new admixtures and reinforcing techniques – Still a PITA, but once it’s poured and cured, it’s not going to change. Or, follow the commercial world with big iron riveted and welded, with non-structural closures just hanging off of the super-structure.
Joe- I really do suspect that the regulations would change with real-world testing. I doubt (actually, I know) that Simpson builds houses and then takes them apart 5-10 years later. They rely on testing (in house and out-of-house) to generate the data, but none of that reliably can mimic 10 years away.
I think there’s a section in “the Japanese House” where they talk about looking at traditional Japanese house construction and why it tended to do very well in earthquakes (but not so great in fires) was because of how the joinery allowed the house to move, rather than stay rigid. Some of that data went to changing the design of very large buildings away from looking for absolute rigidity to a certain amount of elasticity.
Fascinating article. Appears one needs a PhD to be a framer in CA these days or at least to run a framing company. I am having trouble picturing the nightmare that estimating a complex project like this must entail. Quite a number for “contingency” I would think – somewhere in the neighborhood of 2X everything else I priced out would make me feel more comfortable. Just the minimal amount of hardware here on the east coast is tough to keep track of. Wow!
I very much enjoyed you’re article. I hadn’t realized that things had gotten so out out hand. There is an interesting passage in Sam Nakashima’s book “Soul Of A Tree” where he goes on a full page rant about framing hardware. At the time I first read the book, I thought, yeah, but we need to provide safety and affordibility. In retrospect, he was probably correct, although not in the way he envisioned.
I too am a long time Ca. builder (son of an architect, started “helping” as a child, built spec, “blow and go”, class of 69-etc.etc.). I started with steel framing (just tin can studs) for chimneys after the 94 quake. Over time I have come to prefer steel framing for a number of reasons, such as: doesn’t burn, doesn’t rot, and termites won’t eat it. If I were able to build a home for myself, there would be zero wood involved (though I now spend most of my time in a woodshop) besides all of the interior finishes, which is what we primarily experience anyway. I find that most of the difficulties we face with the massive amounts of framing hardware can be traced to trying to build a fish with wings-a mutant love child of a fir tree and a steel beam. I am convinced that the solution is to eliminate ALL lumber in the structual portion of the building. Obviously, this a very old idea, albeit limited (primarily) to high rise construction-but it works, to well over 100 stories! If the design is coherent, a series of moment frames can be shop built with final assembly and series connections done on site. At that point the seismic integrity and load bearing requirements of the structure are complete and you’re a carpenter again, installing infill and partion walls but with different saw blades and a screw gun instead of a hammer, plus the studs are way lighter than the soggy junk currently for sale in my area. Also, you won’t have to pull string and rectify framing in order to get straight drywall and the plumber and electrician will be ever so happy using the standard clips and grommets and provided holes instead of repeatedly drilling and fastening their pipe/tube/flex and cables. The difficulties that remain are related to the horizontal portions of the structure. They have long been solved in regards to the thousands of high rise buildings that spread like a disease across all our cities, but the adaptation of steel pan and light weight concrete to smaller buildings is uncommon (although I (we) have done it) There is no inherent problem with this method of construction, as witnessed by the millions of acres of floor space built since the 1930’s without any lumber whatsoever. Your residntial inspector may initially get the vapors, but if he talks to his boss and looks at the 20 story bank/hospital, whatever, across the street he should calm down soon enough.
Thanks for your article,
Guess with all that steel the home owners insurance rate goes down,because all of this is to save the insurance industry so they don’t have to pay.On the East coast we have the the “GET THE LEAD OUT”Great article
I don’t agree with that, really. The structure can be wood beams- the problem is really that the structural steel is largely an attempt to create structures that aren’t designed for the materials, to provide security that the structure will stand even if built by unskilled workers, and to meet insurance company hopes for absolute profits.
I’m betting Sim or Larry or many of the skilled carpenters could build a house with no structural steel that would stand up as well as the same house built to the tee with structural hardware by the current industry standard carpenters. Of course, rational design would be important.
One more post. I, of course, witnessed the trtansition from no metal connectors to thousands. The first houses we built in the San Fernando Valley (1950)didn’t even have foundation anchor bolts.
Part of the reason, I think, that more and more steel was added to building (besides making houses more stable) had to do with building departments not wanting to be liable for what happened to houses they OKed. So they turned most of their worries over to engineers who stamped their OK on the plans. Once the engineers got hold of a good thing (along with Simpson Strong-Tie) metal started appearing on jobs by the truckload.
Does that make sense to you. Larry
What Larry said sounds entirely credible to me. Then again, 1950 is quite some years before I was born. Further, I could just not resist to reply to this great man, even though he is no longer with us (rest in peace, Larry).
Sim, would it be out of place to worry that corporate lobbying is affecting building code?
I’m originally from Holland where they often use pile driven foundations. Living in Texas and having worked in construction here (finish) I have seen my share of cracked concrete slab foundations that could surely have been avoided. A lot of buildings here when considered structurally would be considered more shed-like when compared to Dutch standards and would surely not pass inspection there. It does strike me that California has much stricter code and code enforcement than Texas does.
Although I have no expertise in structural design it would appear to me that the main safety issues regarding earthquakes would need to start with the foundation of a building. When you make an entire structure rigid, but a big earthquake hits, it will shake the entire structure and the stresses will come to a crescendo in the weakest parts of the building (or the parts that ‘give’). This is why I was interested in the concept of “seismic isolators” as tested by Stanford for residential buildings. Those isolators allow a structure to rock back and forth during an earthquake whilst maintaining most of the structure’s structural coherency.
As Larry mentioned in an earlier post, he witnessed some houses coming off their foundations but otherwise stay relatively unharmed. It is basically describing what happened to the homes tested with those seismic isolators, except that with the traditional bolt-down methods the structure had no dish shaped centering pads to center itself back again using gravity. It simple slid off the foundation one direction or another.
However, there may be some limitations to the types of buildings that could be built using the isolators method.
I just got permits for a two story 19’x20′ in Southern California and also is in the new “wind calcs area”. It has 16 pages of engineering and is being built with two strong walls at the portal and standard shear walls with HD2’s and HD4’s, nothing new, Having dealt with some engineers with the response of what have you been smoking, find a better engineer, the solutions are not black and white but gray.
Don, like I said before “We the people of California do here by release all of our engineers to serve the rest of the nation for better or worse.” No matter what the’ve been smoking.
Like you, I have been framing in Calif and Arizona since 1974. I built about 60 of the very complex structures in the Oakland Hills after the 91 fire.
Becoming more and more frustrated with the ‘SIMPSON’ solution to everything, I decided to adopt the new, modern form of framing of light gauge steel. See my site http://www.vitruvianbuilt.com to learn more.
Duane Heil, president
This is great but not all building codes require this, for example Sonoma county building codes hardly requires any steel connectors for residential construction and I’m sure a lot of other counties don’t require it either, maybe its just for comercial buildings.