Tag Archives: truss bracing

How Far West, A Two-Story Winery, and Truss Bracing

Today’s PGB answers questions about how far west we service, if building a two-story pole barn for a winery is possible, and lateral truss bracing.

Post Frame HomeDEAR POLE BARN GURU: I’m curious how far west you service? I’m in WA state and am having a hard time finding anyone that makes kits similar to  https://www.hansenpolebuildings.com/pole-barn-prices/ out here. At this point it’s just research. Thanks JON in WASHINGTON

DEAR JON: In the United States we service as far West as Cape Wrangell, Alaska and Ka’ena Point, Oahu, Hawaii. We have actually provided more post frame building kit packages in your state, than any other!

 

DEAR POLE BARN GURU: Hey guys, I’m starting a winery in eastern PA and I was wondering if you dealt with two story barns? I want my tasting room above the actual wine making room and I also want a deck off the back of the tasting room that overlooks the winery. I’m solely looking for pricing right now.

Thanks JEREMY in PENNSYLVANIA

About Hansen BuildingsDEAR JEREMY: Thank you for your interest in a new Hansen Pole Building. We seemingly are designing and provide multi-story post frame building kit packages nearly every day, so yes – we deal with two story barns. We can also provide structural portions of your deck either post supported, or cantilevered depending upon your needs and budget. Unless you have developed a fairly close approximation of what your building should ultimately be like, and are planning upon beginning construction soon, all pricing is going to give you is a guesstimate. Material prices fluctuate so greatly, you could find yourself 25-30% short on funds with an extensive time delay.

 

DEAR POLE BARN GURU: Are the boards (2/4 or possibly even a 1/4) that lay across the bottom of the trusses there for a structure reason are they there to aide in the building phase of the pole building (gable style – no poles in the middle of the building) . KATHI in HARTLEY

 

DEAR KATHI: Those boards you are mentioning are typically part of a permanent lateral bracing system designed by your RDP (Registered Design Professional – architect or engineer) who is esponsible for doing a structural analysis and providing sealed plans for your building. They are essential for truss stability and improperly (or missing) design and/or installation of these braces can result in significant problems up to and including catastrophic failure.

For further reading on this subject, please see: https://www.hansenpolebuildings.com/2013/10/bottom-chord-bracing/

 

 

 

Who is Responsible for Design of Permanent Truss Bracing?

Who is Responsible for Design of Permanent Truss Bracing?

This article was triggered by an email questioning truss bracing from Hansen Pole Buildings’ client JASON in WELLINGTON who writes:
“My inspector is telling me that the truss documents take precedence over the building plans. I told them the building plan has the x bracing and the t-bracing. He didn’t care. He wants all the shown bracing from the truss documents. I am not sure what to do. I think the inspector is being ridiculous.”

In my humble opinion this inspector has an absolutely incorrect opinion. Included in Hansen Pole Buildings’ Construction Manual are engineer sealed letters from two significantly large truss plate manufacturing firms, clarifying who has responsibility for design of Permanent Truss Bracing. These companies typically supply engineer sealed drawings for metal plate connected wood trusses (MPCWT) manufactured by purchasers of their truss plates. Copies of these letters should be provided to this inspector.
Inspector can also be given this link (to ANSI/TPI 1-2014): https://static1.squarespace.com/static/53442b51e4b072e71999c8c5/t/56d9d1038259b560ad3a0821/1457115397817/ANSI_TPI+1-2014StdONLY-WEB_WP.pdf

Included in ANSI/TPI 1-2014 (incorporated by title in Building Codes) are:

In Section 2.2 DEFINITIONS

Building Designer: Owner of the Building or the Person that contacts with the Owner for the design of the Building Structural System and/or who is responsible for the preparation of the Construction Documents. When mandated by the Legal Requirements, the Building Designer shall be a Registered Design Professional.”

Permanent Building Stability Bracing: Lateral force resisting system for the Building that resists forces from gravity, wind, seismic and/or other loads.

Permanent Individual Truss Member Restraint: Restraint that is used to prevent local buckling of an individual Truss chord or Web member due to the axial forces in the individual Truss member.

Registered Design Professional: Architect or engineer, who is licensed to practice their respective design profession as defined by the Legal Requirements of the Jurisdiction in which the Building is to be constructed.”

And be pointed to Section 2.3.2 Requirements of the Building Designer

Section 2.3.2.3 Review Submittal Packages:The Building Designer shall review the Truss Submittal Package for compatibility with the Building design. All such submittals shall include a notation indicating that they have been reviewed and whether or not they have been found to be in general conformance with the design of the Building.

(Author’s note – General Note 9, Sheet S-0 of Registered Design Professional sealed plans provided to client, specifically addresses Section 2.3.2.3 above.)

Section 2.3.2.4(c) All anchorage design and connections to the Structural Elements and the Permanent Building Stability Bracing required to resist uplift, gravity, and lateral loads.

Section 2.3.3 Requirements for the Permanent Member Restraint/Bracing of Truss Systems.

Section 2.3.3.1 Method of Restraint. The method of Permanent Individual Truss Member Restraint/Bracing and the method of anchoring or restraining to prevent lateral movement of all Truss members acting together as a system shall be accomplished by:

Section 2.3.3.1.3 Project Specific Design. A project specific Truss member permanent Lateral Restraint/bracing design for the roof or floor Framing Structural System shall be permitted to be specified by the Building Designer or any Registered Design Professional.

Building Officials and inspectors have a veritable mountain of materials referenced by Building Codes. Tremendous volume of these references becomes more than any one person (or small group of persons) can possibly know completely contents of all. It would be unrealistic to expect otherwise.

80 Foot Span Wood Trusses

Setting 80 Foot Span Wood Trusses

Here is the question asked by CHAD in EVANSVILLE:

“What is the best way to hang an 80′ wooden truss? The company I work for is building 80×120 pole barn for one of our customers. The trusses are kicking our butt.”

Before you even think about getting started, you will want to read this article: https://www.hansenpolebuildings.com/2013/12/wide-span-trusses/.

My first adventure in setting 80 span metal connector plated wood roof trusses was on a horse riding arena for Percy Freeman in Oregon. You can read about the misadventures here: https://www.hansenpolebuildings.com/2014/03/wide-span-trusses-2/, as it was quite a saga!

I have learned a lot since Mr. Freeman’s building and would approach the solution much differently today than 30 years ago.

In your case, I would imagine you are placing the 80 foot trusses either every two or four feet on top of truss carriers. You will want to fully concrete encase the embedded corner and endwall columns, so there is an adequately stable foundation. Firmly brace the endwall columns, to prevent (as much as possible) and sway in the lengthwise direction of the building.

I’d look at bringing a large crane in, so at least 12 feet of roof could be fully assembled on the ground (or at least to the point of being ready to insulate and steel the roof. Install all required permanent bracing along the bottom chords and webs of the trusses. I would also X brace in line with each endwall column, from bottom chord of the endwall truss to top chord of the truss at 12 feet and from the bottom chord of the truss at 12 feet back to the top chord of the end truss. Confirm all trusses are plumb before attachment of the X bracing. If the individual member of the X braces cannot be nailed directly to truss vertical webbing, they need to be connected together where they cross. If this is the case, to prevent buckling in the narrow direction, install one member with the narrow face towards the ground, the other with the wide face towards the ground.

Next install bracing across the upper side truss bottom chords in a zigzag fashion, beginning at the corners of the building. These will be left permanently. Repeat this across the tops of the purlins, however these will be removed prior to installation of the roof insulation and steel roofing.

Raise the entire section into place and install the first few panels of roof steel. This section will give a steady anchorage point for the installation of subsequent trusses, either in sections or individually. Make sure to brace off each truss or section of trusses as they are installed.

The Registered Design Professional contracted for the design and inspection of the temporary and permanent bracing systems may desire additional bracing beyond the above. However I would look upon this as a minimum for successful and safe installation.

Prefabricated Roof Trusses Part Two

Prefabricated Roof Trusses – They can Make You or Break You

In yesterday’s blog, Mike the Pole Barn Guru started to share some secrets which should both increase your bottom line as well as allow you to sleep soundly at night.

A short recap here, for the full account, read Part One posted yesterday, May 25th.

A case in point, not too many years ago, we provided the post frame building kit package for the Nature Center at the Cheyenne Mountain Zoo in Colorado Springs, Colorado. The Building Department gave the ground snow load as 27 psf (pounds per square foot), yet wanted 40 psf as the roof snow load. When our engineer called the Building Department to discuss this, the explanation given was, “The snow is just different here!”

Moving on to “the rest of the story” on prefabricated roof trusses.

Truss design programs calculate the roof snow load using Pg as the basis and multiplying it by several factors. This is the formula for the relationship between the ground snow load and the roof snow load adjusted for slope or Ps: Ps = 0.7 X Cs X Ce X Ct X I X Pg.

All of these factors should be clearly outlined on any set of plans being submitted for a structural plan check to a building department. If not, or there is some doubt, the engineer of record for the building should be consulted to make a written determination.

Cs is the sloped roof factor. Metal roofs are assumed to be slippery surfaces unless the presence of snow guards or other obstructions prevent snow from sliding. It is calculated based upon whether the roof is warm or cold, the nature of the roofing material, and the slope of the roof. With heated, steeply sloped and/or slippery roofs, these reductions can be significant.

The Exposure Factor (Ce), is most often 1.0, but can vary from 0.7 to 1.2 and can make a huge difference in both truss design and price.

The Thermal Factor (Ct) for heated buildings will be 1.0 or 1.1. However, most post frame buildings are not heated year round, and if so the factor should be 1.2.

Most truss manufacturers assume a Risk Category II (shown as “Is” or “Importance” factors on truss design drawings). Many post frame buildings will not result in the loss of human life in the event of a failure, given they are used for agriculture or storage and are Risk Category I. This alone can reduce the roof snow load by 20 percent as compared to residential, office or manufacturing type structures!

Will the building be in an area with little or no snowfall? Don’t forget area reductions. If the truss span times the truss spacing is over 200 square feet, a reduction is in order. This calculated value can reduce the roof live load (Lr) to as little as 12 psf.

Further, if Lr is greater than Ps (sloped roof snow load), the Duration of Load for roof loads is now 1.25, instead of the 1.15 typical default value.

What can you do? Make sure the values of Pg, Cs, Ce, Ct and I as shown on the plans, are provided to the truss manufacturer and are reflected on the drawings you will be asked to sign off on.

One other important thing to look for – the “fine print” on the truss drawings should state the trusses are designed for an unbalanced snow load (think drifting). Some truss manufacturers will ignore this crucial component of design, in order to reduce their truss price.

Now, let’s save you some money.

Truss bracing is important, and when neglected can result in catastrophic failures. When overdone, it can kill a building budget in materials and labor.

The truss company will produce preliminary drawings and ask you to “sign off” on them, prior to production. Look at the interior members (webs) which require lateral bracing. These are most typically longer webs which are in compression. Often bracing to web members can be reduced or eliminated by asking the truss designer to switch the direction these long webs run, which will place them in tension. Increasing the size and/or grade of the web can also help. These changes are generally less expensive than the cost of the added bracing.

Lateral bracing needs can also be reduced by using trusses which are physically doubled – installed face-to-face without blocking in between. If your standard building design is for single trusses every four feet placed on a truss carrier spanning eight feet between columns, consider going to a double truss every eight feet, which eliminates the need for truss carriers. Why would this reduce bracing? Because the double truss is now a three inch wide member, instead of 1-1/2 inches, for the most part cutting bracing needs in one-half.

Using trusses spaced over ten feet apart? The truss drawings probably show lateral bracing as a single 2x spanning from truss to truss. Any truss braces spanning over ten feet should be done as “T” or “L” braces, otherwise they can fail in weak axis bending (the skinny direction) under a load.

Learning to read and understand the information on truss drawings is crucial to the success of your business. Don’t make the assumption the truss company is going to be right. If there is something on a truss drawing which is unclear, ask the truss provider to explain it – in layperson’s terms. And, if you still have any doubts, ask your RDP.

Construction Safety Trajedy

Sometimes Things Go Tragically Wrong

Construction safety is nothing to overlook. Even the most experienced among us can make errors (read a very personal story here: https://www.hansenpolebuildings.com/2011/07/dont-take-a-fall/)

Tuesday, September 8, 2015 an under construction building in Queenstown, Maryland had some challenges. Here is the story:

“Two construction workers were flown to the University of Maryland Shock Trauma Center in Baltimore for treatment after a building they were working on in Queenstown collapsed Tuesday, Sept. 8.

barn collapse The Queen Anne’s County Sheriff’s Office, Queenstown Volunteer Fire Department, Queen Anne’s County Emergency Medical Services and Maryland State Police MedEvac responded Tuesday afternoon to 201 Overlook Drive, where the floor gave way in a pole barn-type structure under construction, according to the sheriff’s office. Five construction workers fell through the floor to the ground, police said.

Police said the structure is believed to be intended for personal use as a barn in a residential area.

 In addition to the two workers flown to Shock Trauma, a third worker was taken by ambulance to University of Maryland Shore Medical Center in Easton. The other two workers refused treatment, the sheriff’s office said.

 Maryland Occupational Safety and Health also responded. The scene was made safe by the county contractual building inspector, police said.

 The cause of the accident and the names of those involved were not released on Tuesday evening.”

To set the record straight, this particular building, while it may be a barn, is not a post frame (pole) type structure. The building framework is stick frame (stud walls) built upon a poured concrete foundation wall.

What happened here?

I spent a fair amount of my life in the metal connector plated prefabricated wood roof truss industry. Generally, if a truss is going to fail it is due to improper, or a lack of, truss bracing.

(Read more here: https://www.hansenpolebuildings.com/2014/12/temporary-truss-bracing/)

Looking at the photos of this building, nowhere is any diagonal or X bracing evident which would have prevented the trusses from toppling over given the least amount of wind or vibration. I am frankly amazed they were able to get all of the trusses up and in place before the collapse.  The best I can see on the photos is minimal blocking between the trusses, which is totally inadequate given the height and weight of the trusses.

Don’t become the next tragedy we read about on the internet. Be safe, be smart, and use sound construction safety practices. And finally, follow sound building principles, thoroughly bracing as you go!

Pole Building Truss Framing

My Truss Framing Does Not Match the Plans

Every good set of pole building plans should have at least one page upon which is drawn a “cut through” view or cross section of the building. To read about what should be depicted on this page: https://www.hansenpolebuildings.com/blog/2011/10/pole-building-plans-101-interior-section-elevation/ or actually view an example at: https://www.hansenpolebuildings.com/sample-plans.htm.

sample building plansOne of the features of this page, for buildings utilizing prefabricated roof trusses, is a generic representation of the roof trusses. The trusses will be shown accurately for span (the length of the truss from outside of column to outside of column) as well as roof slope. Any lateral (the length direction of the building – perpendicular to the trusses) permanent bracing for the truss top chords (the roof purlins) as well as the bottom chords which are required by the Engineer of Record, will also be depicted on this drawing.

As the person doing the drafting is not privy to the final trusses drawings, provided by the roof truss fabricator, at the time the plans are drawn, truss members on the plans will not resemble those of the actual delivered trusses.

What things might be different? Everything!

The sizes of any and all members could very well be different than drawn. As well, the configuration (or pattern) of interior truss members (webs) will most likely not even be close.

Do not fret – they are not meant to be a match.

An often confusing part of the sealed truss drawings from the manufacturer, may be what is shown as top chord bracing. Many times what appears on the drawings as a 2×4 placed flat over the top of the truss, is merely the truss engineer’s showing the recommendation for the truss to be braced. The Engineer of Record is responsible for permanent truss bracing design, which is typically accomplished by the roof purlins being placed on edge between the trusses.

Breathe deep, exhale completely and move forward following the truss framing installation instructions, and everything will be just fine!

Barn Collapse!

This story appeared in the Windsor, Ontario, Canada Star June 27, 2013:  

“Firefighters had to use a metal cutter and giant airbags Wednesday to rescue a man trapped under a barn collapse.

“Upon our arrival, there was one person that was trapped underneath the trusses,” said Essex Fire Chief Ed Pillon.”He was conscious, alert, but his lower extremities were pinned underneath some roof trusses with his legs embedded in the ground.”

One man suffered a broken ankle in the collapse. Another had a broken leg. A third man also working at the site wasn’t hurt.

Emergency crews responded shortly after 11 a.m. to the large property on County Road 12 in Essex. Pillon said the call was for a barn collapse with one person trapped.

He said firefighters lifted the debris off the trapped man using airbags and a metal-cutting saw, then slid him onto a backboard.

barn collapse“A second person managed to jump out of the way,” said Pillon. “He had injuries also but he wasn’t trapped.” Sgt. Dave Dibbley with Essex County OPP said the trio was putting roof trusses on a new barn.

“There were three of them on the trusses trying to stabilize them and straighten them out after putting them up,” said Dibbley.

“While they were doing that, about 10 of the trusses came down and brought all three of the guys down.””

Prefabricated wood roof trusses can be great and wonderful things, they allow for buildings to be constructed affordably, with spans which could not have been imagined before their advent.

The pole building pictured above, uses widely spaced trusses, set on top of headers (also known as truss carriers). As constructed in this case, none of the trusses appear to be directly connected to the columns – which could possibly have prevented the barn collapse and injuries from occurring. This is just one of the many reasons my personal preference for post frame construction is to use two ply trusses, spaced 10 to 14 feet on center and directly connected to the bearing columns.

What do I mean by directly connected?

First a notch is cut into the columns where the trusses can sit within this notch for full bearing. Second, secure the trusses with bolts or LegerLoks®. Don’t get in a hurry to get all the trusses up before bracing them. The quickest and easiest way is to start putting purlins as well as all permanent and lateral and X bracing in as you get each truss up.  Put in the bottommost purlins, the ridge purlins (tightening the bays as you go) and at least every other purlin in between as your “temporary” bracing for the roof. This type of assembly and connection greatly reduces the probability of toppling.

The Wood Truss Council of America (www.woodtruss.com) and the Truss Plate Institute (www.tpinst.org) have produced a document BCSI-B10 for “Post Frame Truss Installation and Bracing”.

From the NDS (National Design Specification for Wood Construction):   

“The erection of wood trusses is inherently dangerous and requires, above all, careful planning and communication between the erection contractor and the installation crew. Construction accidents can happen, but planning the actions of all construction personnel involved beforehand greatly reduces the probability of an accident.

 The wood truss industry provides several recommendations to help the contractor use safe practices during the truss installation. These recommendations should accompany the truss drawings and truss placement plan that are submitted to the contractor for approval and use during construction. However, the contractor has the ultimate responsibility for job site safety.”

 That, my friends, needs to reign supreme in any construction project: jobsite safety.  ‘Nuff said.

Engineered Buildings Part II: Continuous Lateral Restraint Systems

As I said yesterday, a properly engineered building is a fully engineered building.  Either it is engineered, or it is not.  I have been appalled to hear what clients feel are reputable companies tell me they sell buildings at a much lesser price if the client does not require sealed plans.  My question to them was pointed. “You design them the same, though, right?”  Their answer was the one which left me with a sick feeling in my gut, “well….” they hesitated, clearly not liking being put on the spot, “they are engineered to be stout.”  Pushing the issue I innocently mimicked, “stout?”  Again their hesitancy said “guilty as charged” all over their answer, “Yes….well…they are built to what our engineers feel are robust.”  Excuse me but….”stout”?  “Robust?”  This is where all I can think of to say to clients is, “Buyer Beware”!

To continue from yesterday…

Many wide width buildings have seriously under-designed interior columns, especially those using columns which are nail-laminated (several 2x plies nailed together). Other major deficiencies include no accounting for additional loads induced by drifting snow and improper truss web bracing. With respect to the latter, roof trusses utilizing continuous lateral restraint  systems to brace longer compressive web members, may be improperly installed and often fail to include diagonal bracing to prevent bracing shifting. This can result in web buckling and subsequent truss failure.

From my view, the more major concern is not improperly installed continuous lateral restraint systems in these buildings, but using them to begin with on the web portion of the truss. In my opinion buildings with trusses over 2 foot on-center should have T- or L-bracing to all long compression webs. Use by builders of continuous lateral restraint systems (rather than L- or T-bracing) results from truss designs produced with software developed for residential buildings. Using L- and/or T-bracing saves lumber and provides greater stability, braces are easier to install (they can be attached on the ground) and do not cause progressive collapses.

With a continuous lateral restraint system, when one truss fails, the lateral restraint attached to that truss pulls on similarly buckled truss webs located on each side of the failed truss. The truss on one side of the failed truss is helped by this action and does not fail (as its bowed compressive web is somewhat straightened out).

Meanwhile the truss on the other side of the failed truss becomes more compromised as its buckled web is pulled further out of alignment. This almost always snaps the web of this truss, resulting in its collapse. The second truss collapse brings down the next truss in a similar fashion. Like dominoes, trusses continue to fail until there are no more trusses to pull down. This entire failure process explains why this failure type is characterized by a partial roof collapse ending at a wall.

It is quite apparent, to me, a vast majority of building purchasers are under the impression they have purchased a properly engineered building, when in fact they have not. In some cases, these clients are intentionally misled which is highly unethical if not criminal.

Frequently trusses are quoted with a “balanced design snow load” which was used as an input to a truss design program by a local lumber yard employee. Given this number, a builder or building owner assumes they are getting a fully engineered building. This could not be further from the truth. Trusses so designed seldom account for all loads to which trusses are subjected, nor do they account for the exact manner in which trusses will be connected to other components, receive loads from other components, and/or be braced by other components. Furthermore, a truss is only one element in an extensive building system and each of these elements must be properly engineered with special attention given to unique interactions between elements.

Back in the day, when I ran my own truss plant besides having a pole building construction business, we quoted trusses without consideration for unbalanced snow load – meaning snow drifting. The Building Codes in use at the time did not address it as an issue and the available computer design programs just didn’t have the capabilities.
So if you as a building designer or truss supplier are trying to “cheap out” when folks don’t know the difference, failure to follow building codes designed to save lives (human and otherwise) is at the least shoddy design work and could be criminally negligent. Wider span trusses in snow country will be more costly, however cutting corners at the risk of property, animals or human lives, is just not worth the risk.