Tag Archives: truss installation

Long Span Truss Storage

Site Storage Guidance for Long-Span Trusses

Originally published byConstruction Magazine Network(link is external) — February 3, 2021

The following article was produced and published by the source linked to above, who is solely responsible for its content. The Pole Barn Guru blog is publishing this story to raise awareness of information publicly available online and does not verify the accuracy of the author’s claims. As a consequence, The Pole Barn Guru cannot vouch for the validity of any facts, claims or opinions made in the article.

Editor’s Note: The article below is the second in a ten-part SBCA series on long-span truss installation guidance specific to the post-frame industry, all of which will be published in Frame Building News.

By Sean Shields, With Contributions by Jim Vogt, P.E.

When handled and installed properly, metal plate-connected wood trusses are incredibly effective at spanning long distances while efficiently resisting intended design loads (gravity, snow, wind, etc.). The proper handling of trusses prior to their installation is very important, because significant damage may occur to wood members, plates, and joints when a truss bends out of plane—and this can affect their long-term performance (see Truss Techniques, Part 1(link is external) in the November 2020 issue of Frame Building News(link is external) for greater detail). 

Correct installation is also vital. We’ll explore some best practices for common installation challenges in future installments of this series, but it’s important to address two additional topics prior to installation. One is long-span truss handling equipment, which we will tackle in the next article, and the other is truss storage on the job site.

Location, Location, Location

One of the most important factors in a successful truss installation, particularly in relation to long-span trusses, is choosing the most appropriate storage and staging location. Why? First, the location where the trusses are stored on the job site impacts the extent to which the trusses need to be handled. If you will be using a crane, the trusses should be stored and staged close enough to the building being erected that they only need to be lifted once, as they are set in place.

Requiring trusses to be double-picked (or hoisted twice) compounds the chances that the trusses may become damaged or installed out of order (or in the wrong orientation). The reason for this is because trusses are typically bundled in the order in which they are meant to be installed. Lifting and restacking bundles of trusses either reverses the intended order or requires the trusses to be scattered individually, increasing the opportunity for installation errors. Not to mention that double-picking will likely also increase the amount of time it takes to install the trusses, which in turn puts pressure on the framers to make up that time in other areas (often resulting in them pressing through other important aspects of the installation process). 

If tele-handlers or other mobile equipment is used to move the trusses, the larger the distance between where the trusses are stored and staged and the new building, the more opportunities there are for damage as the equipment maneuvers over the rough terrain on the job site.

Prepare a Way

For these reasons, it is beneficial to choose a storage and staging location for the trusses early on in the site preparation process. While there may not always be a lot of flexibility or options when it comes to truss storage on the job site, it’s important to consider several factors when weighing the best possible location.

As the first section of this article points out, proximity to the installation area is likely the most important factor to prioritize. To the greatest extent possible, the trusses should also be placed in an area that does not obstruct normal traffic flow on the job site. Creating an obstacle on the job site increases the opportunity for other equipment and materials to come in contact with the trusses, potentially causing expensive damage. 

Many times, long-span trusses need to be prepped prior to installation. Ensuring there is sufficient room around each truss to mark purlin locations on the top chords and/or affix T- and L-web reinforcement can speed up the process and make life a lot easier for everyone involved in the installation process.

SBCA’s Building Component Safety Information (BCSI) handbook states in the B1 section (www.sbcindustry.com/b1(link is external)): “Trusses may be unloaded directly on the ground at the time of delivery or stored temporarily in contact with the ground after delivery. If trusses are to be stored horizontally for more than one week, place blocking of sufficient height beneath the stack of trusses on 8′ to 10′ intervals (or as required) to minimize lateral bending and to lessen moisture gain from the ground.”

While the trusses can be stored directly on the ground, minimizing lateral bending is key. This means that the site chosen for truss storage and staging needs to either be level, or blocking need to be placed on the ground ahead of time to create a level bearing area for the trusses while they are stored. Moisture gain also needs to be minimized. This means the storage area should be reasonably dry and preferably in an area that will not collect water in the event of a rainstorm.

The B1 section further states: “Trusses stored for more than one week shall be protected from the environment in a manner that provides adequate ventilation of the trusses. If tarpaulins or other protective covers are used, the ends shall be left open for ventilation. Tight-fitting coverings are not recommended, since they can trap moisture.” Excessive dirt and/or moisture gain can impact both truss installation and long-term truss performance, so it is a best practice to protect trusses from both while they are stored on the job site.

Communication Is Key

Of course, all the site preparation and planning done ahead of time goes to waste if it isn’t communicated effectively to the person delivering the trusses. In most cases, the individual delivering the trusses has never been to the job site before they show up. It may or may not be clear to them where traffic naturally flows throughout the job site. It may also be unclear where rainwater is most likely to collect, creating troublesome puddles and mud. They are also unlikely to know the equipment that will be used to handle trusses on the job site or the hoisting radius of the crane being used to set the trusses in place. Finally, they will not know how long the trusses will need to be stored prior to installation.

In short, it should not be left to the person delivering the trusses to choose where they should be stored and staged on the job site. The earlier in the process the truss storage site is chosen, the easier it is to not only flow the rest of the job site around it (e.g., not storing other building materials in the same location that will then need to be moved upon the truss delivery), but also communicate that location to the person delivering the trusses.

While a phone call ahead of delivery will likely suffice in some instances, there are several other best practices that can be employed to ensure there isn’t any confusion at the time of delivery. The easiest, when possible, is to take one or more photos of the job site and send them to the driver ahead of time. Outlining the area with a few stakes or marking spray paint on the ground can also ensure the trusses are placed as close as possible to the predetermined spot. A quick sketch of the job site, with the truss storage area clearly marked, can also be photographed and sent ahead of time.

The Bottom Line

A little forethought about the best location to store trusses on the job site can have a significant impact on not only how well their installation goes, but how well they perform over the long term. Having a solid storage plan is good. Communicating it effectively to the person delivering the trusses ahead of time makes the plan even better.

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.

Truss Manufacturers Educate for Safety

Most every truss company makes sure every jobsite delivery includes a packet of BSCI (Business Social Compliance Initiative) standards. Usually all truss drawings are included in this packet, with a large orange warning sheet in the cover asking installers to ‘Read the Safety Documents’. Frequently the information is in a big zip-lock bag so it has to be opened in order to get the truss drawings out. It is a way to educate truss installers and to warn them not to become too complacent about their work.

Education from the truss companies isn’t just for builders.  And it’s really not enough. The Hansen Buildings Construction Guide (furnished online to every purchaser) includes an entire chapter titled, “Roof Truss Legalese”. Proper truss handling and bracing, both temporary and permanent are covered, in detail.

The information provided includes specific information for builders of pole buildings. It can be very dangerous setting trusses, especially very large agricultural trusses and church trusses. These are the most common failures.

There are various reasons for building collapses. For pole buildings, it can be due to large spans and wide spacing of trusses. Most pole buildings are engineered with trusses 10 to 14 foot on center, and in some cases even wider. The average house span is 30 to 32 feet. The average pole barn truss span is 50 or 60 feet, so it’s twice as long. Because they’re so far apart, bracing these trusses (especially during assembly) becomes crucial.

The last couple of winters have brought heavy snowfalls to the Midwest which have caused more agricultural roof collapses. People often want to save money and they ask truss suppliers to build their projects with the minimum amount of loading possible. Many times they will ask for no ceiling load because it’s “just going to be a storage shed”. These requests can lead to trouble down the road. Originally it’s “just going to be a storage shed”, but then later it is turned into a shop with a ceiling and lights, or they will add feed equipment for animals. The trusses were not designed for these loads. Add a heavy snowfall, and disaster strikes.

Professional builders may know the pros and cons of good truss installation, but sadly, do not often follow them. Many pole barns, as well as church buildings, are not always built by experienced builders. Those without experience tend to read and follow all of the instructions, rather than just thinking they know the best way.

Ag buildings are many times built by farmers. Sometimes they’re using a tractor with a bucket to lift the trusses into place. They don’t have the proper lifting equipment. They’ll use a chain to pick trusses up right from the center. There are two things wrong with this: one, they damaged the connector plate in the center of the truss; and two, the truss is not designed to be picked up this way. A huge stress load is placed on the middle of the truss which can start to pull the connector plates or the joints apart.

On the other hand, church buildings are sometimes built by volunteers. Maybe it’s a guy who builds houses or garages for a living, and comes and volunteers to put it up, but they’ve never handled anything this large before. They’re not using the proper equipment.  Using a spreader bar to lift and hold the trusses works to distribute the weight to not just one, but several points.  Long span trusses tend to fold in half because the excessive weight on the outside ends of the truss.  This creates a hinge affect in the center.  Even in a slight wind there’s a lot more danger involved.

Some experienced contractors don’t take common safety precautions into account, such as adequate fall protection. Lots of guys climb around in trusses, basically working unprotected greater than 6 feet off the ground. This happens probably more so in ag buildings, because they tend to be in more rural areas where they’re not so much under the watchful eye of OSHA (Occupational Safety & Health Administration).

With modern agricultural buildings often larger than in the past, and farmers doing fewer DIY projects, there’s little excuse for proper loading and installation requirements to not be followed by today’s builders. They have better access to information than ever before. Sadly, frequently seen, are attempts at bypassing safety for the sake of cost. There is no cost savings large enough, to be worth endangering a human life.