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Building Your Own Pole Barn Trusses

Wants to Build His Own Pole Barn Trusses

Reader DANIEL in HAMPSHIRE writes:

“Good evening, I was wondering if I could ask for your help? I have a question regarding truss designs and truss spacing. I’m building a pole barn (50ft wide x 112ft long x 12ft tall). Prices of pole barn kits have skyrocketed just as much as steel buildings. Building this size 3 years ago would have cost a third of the price today. I’m building an indoor fish farm. If you like to know more of my back story you can visit www.steelheadsprings.com I don’t want to waste your time reading it here. I spent years collecting investors and putting up my whole life and it turned out its not enough. However, I found a solution, I must build it myself, I must build everything myself. I have good support here however I don’t have a specialist. Every time I speak to an engineer, they tell me it can’t be done. Right now my problem is trusses. Locally, each 3-ply 6x6x14 post columns retails anywhere between 400 and 500 dollars. I laminated mine for just under a $100. Steel brackets to mount said post columns into concrete with hardware retails around $125 each, I sourced a local shop to build mine for $40 each. Steel sheathing for walls and roof was sourced from social media from an out of business contractor for .30$ on the dollar. Currently trusses are outrageously priced! The few local places are pricing them anywhere between $600 and $900 for the 40-footer and between $800 and $1300 for the 50-footer. One building needs 15 trusses and another two need 8 trusses each. Prices just keep going up, so I’m forced to build the trusses myself. So, I turned to the web. I’ve been educating myself on designs and ideal styles that would suit my buildings.  Already have the concrete columns pored. Pillars are 18-inch diameter and 50-inch deep. Brackets are already installed at 8ft on center. I would like to use the saddle style truss and wedge it at the top. I have 20 inches of middle board notched out to accommodate a saddle truss. I want a 4/12 pitch with 8ft o.c. truss spacing and 2ft o.c. purlin spacing. Because I’m going 8ft o.c. truss spacing I must install the purlins upright on its edge. This works perfectly because it gives me plenty of room for insulation to be installed flush with the steel. I have no overhangs and my heel is 10″. I found a company on the web (medeek designs). They design the geometry of the trusses. I basically plug in the lumber and the software does the rest. It designs the truss and with a simple click of the mouse I can get exact dimensions of my tc, bc and the webbing. However, it does not explain what size of lumber I should use to achieve the desired clear span goal. I must go to an online retailer and look up a truss and copy their design to plug in the information. I need your help; my land is in an unincorporated county which basically allows me to do anything that I want. I just must follow simple rules with foundation and snow/wind loads. Top Chord live load is 30psf, Top Chord dead load is 7psf, Bottom Chord live load is zero and Bottom Chord dead load is 10psf. I chose 12ft height because it is just tall enough for my needs and it’s sturdy enough for the wind and snow loads. I almost built 4-ply columns, but I decided to go with three because I would obtain the same rigidity with girts spacing of 24-inches instead of 36-inches. I built a 20-ton gusset plate press, and I used the software to build a sample truss. I tested it to the best of my abilities, and it stood its ground. I watched a few videos where some people installed wooden “gusset” plates as additional support over the steel plates. Some even used glue. I know that I want to over engineer this truss to make sure it stands the time. It leaves a good story for the upcoming generations about how we built this from the ground up. I still recall hearing stories from my grandfather and father how they both built their homes. I will attach a few pictures of the drawings that I have. Both 50-foot and 40-foot trusses should be double fink as this truss is rated for 40-60ft clear span. I was going to use 2×8 for both top chords and bottom chords with 2×4 for the webbing. The 40-footer truss isn’t the problem because the truss only has one cut in the bottom chord at the 20ft mid-point. The 50-footer truss is the big issue. If we assume that 2×8 lumber is strong enough for the construction, where should the bottom chord be spliced/connected as my common sense calls for a one 20ft middle section and two 15ft outer sections. If that is ok, what about the top chord, where should the 20ft board be extended? I’m so sorry for taking so much of your time, I hope this is enough information and I hope it makes sense. Can you please help? Thank you.” 

Mike the Pole Barn Guru:

Let’s start with the disclaimer at www.medeek.com:

The truss designs produced herein are for initial design and estimating purposes only. The calculations and drawings presented do not constitute a fully engineered truss design. The truss manufacturer will calculate final loads, metal plate sizing, member sizing, webs and chord deflections based on local climatic and/or seismic conditions. Wood truss construction drawings shall be prepared by a registered and licensed engineer as per IRC 2012 Sec. R802.10.2 and designed according to the minimum requirements of ANSI/TPI 1-2007. The truss designs and calculations provided by this online tool are for educational and illustrative purposes only. Medeek Design assumes no liability or loss for any designs presented and does not guarantee fitness for use.

Moving forward, Building Codes and ANSI/TPI have had several changes since Medeek put this information out. Most jurisdictions are using 2018 or 2021 versions of Codes and ANSI/TPI 1-2016.

I have previously opined in regards to site built trusses: https://www.hansenpolebuildings.com/2018/12/site-built-roof-trusses/

I spent two decades in management or owning prefabricated metal connector plated wood truss plants. In my humble opinion – attempting to fabricate your own trusses of this magnitude is a foolhardy endeavor, for a plethora of reasons:

1) You want to build trusses only from a fully engineered design, specifying dimensions, grades and species of all wood members, as well as detailing dimensions of all connections. Besides dead and snow loads, design wind speed and exposure need to also be considered. Do NOT try to copy someone’s online design, as it is likely to prove inadequate.

2) It is unlikely you will be able to obtain lumber graded higher than #2, without a special order. A 40 or 50 foot clear span truss with your specified loads is going to need some high grade lumber for chords – expect to see MSR or MEL lumber (read more here: https://www.hansenpolebuildings.com/2012/12/machine-graded-lumber/).

3) You will be unable to purchase steel connector plates of sufficient size and thickness to connect members. This leaves you with having to invest in Struct 1 rated plywood to cut into gussets.

4) Should you have a failure from building your own trusses without an engineered design, your insurance company can easily get themselves out of having to pay your claim.

Per your statement, “I know that I want to over engineer this truss to make sure it stands the time.”

Do yourself a favor and find a way to invest in prefabricated trusses. It will give you peace-of-mind you will not get otherwise.

This entry was posted in Pole Barn Planning, Trusses, Professional Engineer, Pole Barn Questions, Pole Barn Design, About The Pole Barn Guru, Constructing a Pole Building and tagged , , , , , , , , , , , , on by .

Help Me Insulate My Pole Building

This story is sad, to me. As post frame building “experts” we (an industry collective we) owe it to our clients to educate them at design phase to avoid a situation such as reader ERIC in SPOKANE VALLEY has become happily (or maybe less happy) involved in.

Eric writes:

“I want to start insulating my pole building. 30x40x16, roof layers are metal, synthetic underlayment, osb, 2×8 purlins. My question is, can I leave an air gap between roof and insulation, as I plan on using R19 batting and covering with facing. Has an open ridge vent. Thank you.”

Mike the Pole Barn Guru responds:

Placing batts between purlins is probably not a Top Twenty best answer for several reasons:

If you do not completely fill purlin cavities, Code requires airflow from eave to ridge over top of the insulation. You have no way to achieve this without a major remodel. You don’t even want to go there.

Getting a perfectly sealed vapor barrier under purlins would be nearly impossible to achieve.

You would have to seal the ridge vent (it isn’t working anyhow, because your building does not have an air intake from enclosed vented soffits).

While installing a flat ceiling at truss bottom chord height might appear to be a quick solution, it also is fraught with some perils:

Trusses are probably not designed to support a ceiling load. It might be possible to obtain an engineered repair from the company who produced your building’s trusses.

Ventilation system would need to be addressed for newly created dead attic space.

Closed cell spray foam insulation would need to be added in the area closest to eave sidewalls.

Weighing what you have to start with, my recommendation is to spray three inches of closed cell foam insulation below your roof sheathing. This will provide a greater R value than R19 batts and provides a vapor barrier. You will need to seal off the ridge (foam installer may be able to just spray foam underside).

Also, I notice in your photo what appears to be a total absence of truss web and bottom chord bracing. I’d have to have a copy of your building’s sealed plans, a truss drawing and some more photos to truly discern.

How Could This Have Been Avoided?

Whoever provided this post frame building should have been asking some important questions:

Will you, or anyone who might own this building in future years ever want to climate control (heat, cool or both)?

If yes, what method of roof insulation is being considered? I like insulation over a flat level ceiling personally, as I then no longer pay to heat or cool the attic area. In order to do this right, energy heels (https://www.hansenpolebuildings.com/2012/07/raised-heel-trusses/) should be utilized. It also means having adequate attic insulation with soffit vents as intakes and ridge vents as exhaust.

It all could have been so much simpler.

 

This entry was posted in Ventilation, Building Interior, Insulation, Pole Barn Questions, Pole Barn Design, Pole Barn Planning, Trusses and tagged , , , , on by .

Temporary Truss Bracing

The Importance of Temporary Truss Bracing

Back in my early days in the prefabricated metal connector plated truss industry, one of my clients was the congregations of a church along Highway 95 in Hayden, Idaho. The project was for an entirely new building, with the work being done by primarily volunteer help, under the supervision of a carpenter with more decades of experience under his belt than even my Father or my five Uncles.

The design called for a large central clearspan comprised of low slope trusses with a raised heel. (For more reading on raised heel trusses: https://www.hansenpolebuildings.com/blog/2012/07/raised-heel-trusses/)

Surrounding this on three sides were areas with monoslope (sloping in one direction away from the main span) trusses, which were placed first.

Once the walls for the central portion were framed, the supervisor called for delivery of the main span. As the trusses were very large, they paid extra for our crane truck to individually place the trusses (good idea). All of this was accomplished on a chilly windless day in mid-January, without a hitch. Our crane truck had hardly completed the 15 minute drive from the building site back to our manufacturing plant, when we got “the call”…..the roof had collapsed!!

I high-tailed it out to the church, to find the experienced carpenter shaking his head. The rear of this set of trusses had been braced against the previously framed roof behind, with temporary truss bracing. Before putting permanent bracing in place, the contractor had removed the temporary bracing. He said he knew it was in trouble the moment he pulled out the last nail, and in the blink of an eye, it was scrambled trusses on the ground!

From the pole building photos attached from a recent project (not the church), it is impossible for me to determine if the trusses and their attached purlins were in place or being placed when things went bad. What I can tell is this – there is no bracing of any sort to be found in this assembly which would have kept it from racking or toppling. The temporary truss bracing is AWOL.

What would have helped to prevent this pain?

X BracingAn X Brace, or braces, between the top chord of one pair of trusses and the bottom chord of the other pair would have prevented toppling (the larger the span, the greater the need for more than a single X). Also, temporarily nailing some of the wall girts to the tops of the roof purlins in diagonal fashion would have prevented the assembly from racking.

The Wood Truss Council of America (WTCA) www.WoodTruss.com and the Truss Plate Institute (TPI) www.tpinst.org have prepared a summary sheet BCSI-B10 “Post Frame Truss Installation and Bracing”, which is included in the Hansen Pole Buildings’ Installation Manual, and should be provided to anyone who is assembling a pole building using prefabricated wood roof trusses.

Trusses are very, very strong when properly installed and braced in the vertical direction for which they were designed. By using care and caution, during handling and installation, they will perform admirably for generations.

This entry was posted in Trusses and tagged , , , , , on by .

Dear Pole Barn Guru: What is the Proper Wind Shear Bracing?

New!  The Pole Barn Guru’s mailbox is overflowing with questions.  Due to high demand, he is answering questions on Saturdays as well as Mondays.

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday or Saturday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

Dear Pole Barn Guru: What is the proper wind sheer bracing for a 60’W x 80’L by 20’H monitor pole barn with a 20′ center aisle and a second story? The raised center portion has 20 foot walls, then another 6 feet to the center at the ridge.

The 2 sheds on either side are 10′ at the edge and intersect the center at about 15′. The entire structure is made of poles on 20′ centers, Lvl beams and ladder trusses for floor and trussed roofs. It is unprotected from the wind. We are in central Texas. TEETERING IN TEXAS

DEAR TEETERING: This is why it is such an excellent idea to order complete pole building packages from a company who can run all of these calculations accurately in advance. Then buildings are designed to resist the proper loads, including wind shear, without having to search for solutions in the middle of the game.

Provided all of the columns are adequately sized and embedded …..

Steel roofing should be 3′ width, minimum 29 gauge, with high ribs every 9″, attached to 2x purlins on edge spaced no more than 28″ o.c. Roofing should attach to purlins with #12 x 1-1/2″ diaphragm screws at 9″ o.c. at each purlin. At eave and top edges of panels place screws on each side of every high rib.

Provided you attach the endwall steel the same as the roof steel, you should be able to have up to 19 lineal feet of openings on each endwall without further reinforcement.

All of this should be reviewed by a Registered Design Professional (RDP – engineer or architect) for structural adequacy.

DEAR POLE BARN GURU:  Is it possible to get a quote to have it assembled? MINDFUL IN MORRIS

DEAR MORRIS: We are not contractors, however fair market value for labor is typically about 50% of materials costs.

I recommend placing an ad on Craigslist under “labor gigs” such as:

Contractor needed to assemble pole building kit package on my clear level site in Morris County. 24’x40’x14′ includes 12″ overhangs, a 12’x12′ overhead door, entry door and wainscot. I will provide all materials except for nail gun nails. Willing to pay $4000-5000 depending upon experience and references.

DEAR POLE BARN GURU: I have a metal building constructed of 2×4 square tubing and 4×4 metal posts. 3″ × 1.5″ c purlin is welded with the c side down spanning across my 2×4 square tubing roof beams. I have a metal roof screwed to the c purlin. The building wraps around an existing building and looks like an L from a top view and has a 2 on 12 shed roof with a hip. The building is “stand alone” and attached to the other structure only with a side wall transition piece. The metal roof slides under the eve of the other structure with the side wall transition on top. I also used the vented enclosure under the sidewall transition for ventilation. I also have a ridge vent at the hip with the vented enclosure under the hip cap. I have a 12″ soffit around the outside perimeter of the metal structure with soffit vents every 5 ft. I have a 4 ft cedar picket half wall around the outside perimeter with the remaining height of the wall in screens….basically a screened in party room but I plan on switching out the screens for heavy plastic sheeting in the winter. I have a hot tub inside and I want to insulate the roof and install a ceiling. 1st question: do I have to install a vapor barrier IF I am using 3/8 marine plywood for the ceiling and the attic side of the sheathing is covered in heavy vinyl….sheathing was once election signs. I am attaching the ceiling directly to the bottom of the 2×4 roof beams following the slope of the 2 on 12 pitch.

2nd question…..because I only have the 4″ depth of the 2×4 sq tubing + 1.5″ depth of the c purlin = 5.5″ total for insulation AND vent space, how would you insulate? Spray foam is too expensive for me. I want to reduce the radiant heat in the summer and I am concerned with the humidity from the hot tub especially in the winter. Any help would be greatly appreciated. TOASTY IN TEXAS

DEAR TOASTY: My guess is you are going to be creating an inadequately ventilated dead attic space. You need to have 1/150th of the “foot print” of your space, as ventilation, equally divided between the eaves and the ridge. In your case, you have no ability to adequately vent the high side of your roof, as it abuts another building.

Even though the best solution might well be to tear everything down and construct a new building, chances are you would not look favorably financially upon it as the end all.

Probably your best bet is to install an A1V reflective radiant barrier beneath the roof purlins (https://www.buyreflectiveinsulation.com) with the reflective side up. Make sure every seam is tightly sealed. This should help reduce the thermal gain in the summer. If you are going to create a dead attic space between a ceiling and the reflective radiant barrier – powered attic vents in each end could be a good investment.

As for humidity from your hot tub, install air inlet vents near the floor and exhaust vents near the ceiling line. You may also need to have one or more powered vents in the walls of this area.

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Dear Pole Barn Guru: Why Do I Need Truss Web Bracing?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU:  Hello,

I came across the link below while investigating Pole Barn House kits, but since we don’t want a concrete slab, I was wondering about how the poles work in conjunction with a crawl space.

https://www.hansenpolebuildings.com/blog/2013/03/crawl-space/

GNASHING IN NASHVILLE

DEAR GNASHING: The easiest (and most affordable) way to create a crawl space is to construct in typical pole building style, with an elevated wood floor.  This now creates a crawl space which can either have an insulated perimeter, or the floor may be insulated leaving an unconditioned area.  A far more expensive route would be to pour a continuous footing and foundation, mounting the columns to poured-in-place brackets on top of the foundation walls.  We’ve done them both ways, so it’s client’s preference.

DEAR POLE BARN GURU: I’ve hired a contractor to assemble a Hansen Pole Building kit package for me. He says he is short on trims to cover the fascias. As he was explaining to me, is that the triangle cut part of the end needs to be covered by the ‘L’ trim. Does that make sense? It does to me looking at it, but hard to write out! WRUNG OUT IN WASHINGTON

DEAR WRUNG: Your building requires 30’3” of trim to cover each fascia, when installed to match the instructions provided in our Construction Guide. A total of 63 feet was shipped to your building site, so there was plenty provided.

It appears, what has happened, is your installers have made an assumption of how to correctly apply the trims, rather than having thoroughly reviewed the directions provided. Failure to follow the step-by-step detailed instructions does occur every once in a while. Hopefully your project is not past the point of no return (where trim was improperly used).

DEAR POLE BARN GURU: What is the purpose of bracing the webs of roof trusses? Why do some webs need braces while others don’t? MYSTIFIED IN MISSISSIPPI
DEAR MYSTIFIED: The internal members of roof trusses are referred to as webs. The permanent braces sometimes required on roof truss webs are called continuous lateral braces, or CLBs. They’re typically required on a web which is in compression. The truss web bracing is intended to keep the truss web from buckling in the weak (skinny) direction.

To explain why they’re sometimes necessary, imagine pushing down on a yardstick which extends vertically to the floor from the palm of your hand. It doesn’t take much pressure for the yardstick to buckle.

Now imagine taking your other hand and restraining the yardstick halfway up from the floor. If you press down now, it takes a lot more pressure to make the yardstick buckle. In effect, you’ve added a CLB to the yardstick.

The web of a truss is much like a yardstick. It can withstand a certain amount of compression without bracing. The amount of compression a web can withstand depends partly on its size, species, and grade. But the biggest factor in determining truss web bracing requirements is the overall length of the web.

In some cases, webs can require two rows of bracing rather than one. This design is most often seen in very tall trusses.

Single trusses are only 1-1/2 inches wide and require far more web bracing than does a double truss system, where the two individual trusses are nailed directly together so as to form a three inch width member. Doubling the thickness makes the webs twice as stiff against buckling.

If one CLB is required on a web, it should be roughly in the center of the web. If two CLBs are called for, they should be at one-third points on the web.

Continuous lateral bracing won’t do any good if it’s not anchored to something solid. The CLB will just transfer the buckling, and the whole set of webs will buckle in the same direction. Typically, CLBs are anchored with diagonal braces to rigid points such as the top chords of trusses, or to a building endwall.

In pole buildings, it is not uncommon to have trusses spaced eight feet or more apart. CLBs begin to become impractical, as they eventually become so long they will buckle between the trusses. In no case should a single 2x (1-1/2 inch wide) CLB used with a length over 10’.

So how to apply truss web bracing of widely spaced trusses? By applying a 1×4 or larger brace to the top or bottom (if two CLBs are required, to both top and bottom) of the web needing to be braced, for at least 90% of the length! These braces act as a strongback, restraining the web from buckling in the weak direction. The braces should be attached with 10d common nails, placed at a spacing as recommended by the RDP (Registered Design Professional – engineer or architect) for the project.

To determine if you need CLBs, look at the drawings accompanying the trusses; they should have the locations of any CLBs on them. Many truss manufacturers also put tags on webs which require braces. For more information on trusses, visit the Wood Truss Council of America’s Web site at: www.sbcindustry.com

This entry was posted in Pole Barn Questions and tagged , , , , , , , on by .
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