Tag Archives: bottom chord dead load

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.

Materials for Girts, a Raised Floor, Truss Loads

This week the Pole Barn Guru answers reader questions about girt material choices for a 60’x120′ shed, Mike’s thoughts on a raised floor to compensate for a 7% grade change, and if some 4′ oc trusses can handle the load of a heater.

DEAR POLE BARN GURU: I plan on putting up a 60′ x 120′ post frame shed. I’m going to run my 6×6 posts at 8′ o.c. can I use all 8′ 2×6 material for the girts or should I have some 16′ material staggered in with the 8′ material? Will that increase the strength or do you think it would be similar? Thanks guru! JASON in NEW HOLSTEIN

DEAR JASON: Depending upon eave height, design snow and wind loads and wind exposure 6×6 may be inadequate to carry imposed loads. Using 16′ external girt material will be slightly stiffer against wind loads perpendicular to girt and will deflect slightly less. They will not impact overall building strength. Depending upon spacing, grade and species of 2×6, and again design wind speed and wind exposure, they may also prove to be inadequate.

Personally, I would look at using glu-laminated columns every 12′, double trusses directly aligned with columns and 2×6 bookshelf style wall girts. This will result in fewer holes to dig and fewer pieces to have to handle and install. It also allows for wider sidewall door openings, without requiring large headers.

 

DEAR POLE BARN GURU: I’m building a home on land that is at a 7% grade from top to bottom. I was thinking about doing a raised floor/crawlspace with the back aligned closer to grade and the front more elevated. What are your thoughts on this idea, and elevated floor pole buildings generally? I assume you would support the floor with piers instead of spanning entirely? Thanks! MATTHEW in HOUSTON

DEAR MATTHEW: Having built for myself an elevated floor post frame building (I had 14 feet of grade change in 24 feet), I feel as though they are a great solution. Unless you had enough grade change to practically utilize space below, I would use interior columns to reduce spans of beams and joists – little, short columns being far less expensive than large multiple ply beams and large dimension floor joists. My knees also prefer to live on wood, rather than concrete – making this a double win.

 

DEAR POLE BARN GURU: Hot Dawg™ heater…..just built a 40×30 pole barn. 4/12 roof, trusses are 4′ apart, wanting to hang a 80kbtu heater from trusses, with steel channels being suspended from two trusses. Will trusses handle the weight? Thank you. SHARKBITE

DEAR SHARKBITE: In order to determine if your trusses can handle weight of this unit, you would need to look at your engineer sealed roof truss drawings. If Bottom Chord Dead Load (often shown as BCDL) is less than five (5) psf (pounds per square foot) then probably not. Ideally, reach out to whomever fabricated your trusses. Give them weight of your unit, where you propose to hang it, as well as if you have a ceiling and insulation and they can give you a definitive thumbs up or down.

Where We Ship, Raising Walls, and Bottom Chord Dead Loads

This week the Pole Barn Guru answers reader questions about where we ship, whether or not trying to raise pre-assembled walls is a good idea, and the use of double or single trusses when applying drywall.

DEAR POLE BARN GURU: Where do you guys ship? Nationwide? SUZANNE in BROOKSVILLE

DEAR SUZANNE: Hansen Pole Buildings is America’s leader in providing fully engineered, 100% custom designed, post frame building and barndominium kits, with multiple buildings in all 50 states. Your deliveries come from one or more of our thousands of shipping locations across the country (minimizing delivery costs) – so chances are excellent we are ‘close’ to you (as well as supporting your local economy)!

 

DEAR POLE BARN GURU: Hi. I love your blog. Planning a 30x60x12 pole barn for workshop and RV storage. A 20 year framer friend is planning to help with (do most of ) the building. He suggested partially assembling walls (3 poles/30’ ) on the ground, then raising to vertical, lowering into holes with already poured footers, then proceeding to brace/collar/backfill/girt. In my extensive research on your blog and the rest of the internet, I have not seen this technique mentioned. Possible? Or bad idea? Would greatly appreciate your thoughts. TIM in BUENA VISTA

DEAR TIM: Thank you for your kind words, they are greatly appreciated.

While what your framer friend proposes is possible, it is unlikely to be easier, practical, or yield a better result. In order to work, poured footers would need to be all at exactly same depth below grade and top of footing perfectly level. Any variation from this would throw off your partially assembled wall. Even if exact depth is to be thrown out and up or down was to be compensated by shooting depths with a transit and adjusting splash plank location accordingly, it would still be reliant upon tops of footings roughly three feet in ground being level.

Even should all these manipulations be done successfully, it would result in having to utilize some significant lifting equipment to raise trusses, as opposed to being able entire bays straight up columns with truss winch boxes, as pre-installed wall girts would preclude this. https://www.hansenpolebuildings.com/2019/11/winch-boxes-episode-v/
My encouragement would be to continue tried and true assembly methods as outlined in our Construction Manual.

 

DEAR POLE BARN GURU: Do I need double trusses if a single truss is manufactured to handle the weight of both the roof and inside ceiling?

I’m looking to get some trusses ordered for a 40×60 pole barn but am having a hard time with the bottom chord dead load as I plan on hanging sheetrock. The prebuilt trusses available are only rated at 1psf on the bottom chord, but by doubling them would I be able to hang sheetrock? If not, I’ll need custom ordered trusses, but those are rated for the full weight and I’m not sure if I still need to double them at that point.

Thanks REID

Installing a ceilingDEAR REID: While you do not necessarily “need” double trusses, there are some structural advantages to double trusses and they typically require far less bracing (read more about double trusses here: https://www.hansenpolebuildings.com/2018/09/true-double-trusses/).

Whether using a single or double truss system, you will need to order custom trusses rated specifically to carry weight of sheetrock – most usually with a 10 psf (pounds per square foot) bottom chord dead load.

 

 

Insulating an Existing Pole Barn

Insulating an Existing Pole Barn When Things Started Wrong

Reader TOM writes:

“Mike,  I have an existing pole barn (6×6 post with 2’ on center girts ) that has a 4” concrete floor with 10 mil plastic under it. The side walls have 1” XPS insulation on the outside of girt then steel siding with no wrap or barrier. My thought is put Tyvek on inside of girt ( facing same direction as if on outside application ) then put inch and a half XPS DOW insulation against that ( because there’s two bunks already there) then 2×4 frame with batten insulation between them, then 6mil or heavier vapor barrier then OSB. The floor has PEX tubing in it but not hooked up. Is this a proper install?  Also I will have to have an engineer check the BCDL as I want to put OSB on the ceiling but would like to know how to insulate the ceiling. There is a one foot fully vented overhang with a ridge vent also. Thank You for the info in advance. 

Mike the Pole Barn Guru advises:

I am concerned about your building having an inch of XPS insulation between girts and siding. This allows screw shanks to flex, potentially creating slotting under screw heads and excessive deformation can result in your building cladding’s shear strength being compromised and (under extreme circumstances) racking enough to create a failure. I would feel much more comfortable if you were to add 7/16″ OSB or 1/2″ CDX plywood to the inside of girts in bays on each side of corner columns from splash plank to eave girt.

Moving forward….

Your external XPS is now acting as a vapor barrier (or close to it). Any exposed to inside seams should be taped. Do not put Tyvek on the inside of the girts, as this would allow any moisture in assembly to be trapped between it and XPS. Unless you already own a pile of 1-1/2″ Dow insulation, skip it and instead fill the balance of the wall cavity with rock wool or stone wool unfaced batts. Do not place a vapor barrier on the inside or seal OSB on the inside of the wall. Walls will now ‘dry’ to inside.

Provided your trusses are capable of supporting a ceiling, blow in fiberglass above your ceiling finish of choice. Make sure to allow at least an inch of air space above insulation at eaves so you get proper air intake from vented soffits. Unless you are very close to Canada and have at least 8000 heating degree days, do not add a vapor barrier at ceiling level.

Stamped Plans, Bottom Chord Loads, and Spray Foam Options

This Monday the Pole Barn Guru answers reader questions about engineer stamped plans,  hanging sheetrock of OSB from truss bottom chords, and the best choice for spray foam insulation in a post frame building.

DEAR POLE BARN GURU: Are your drawings engineer stamped to meet local municipality requirements? ERIK in LAS VEGAS

Engineer sealed pole barnDEAR ERIK: Yes, our structural plans, sealed by our independent third-party engineers are designed to meet or exceed loading requirements for each individual building’s jurisdiction. We have provided several buildings in Clark County, including the giraffe barn at your Lion Habitat Ranch in Henderson. We do always have our clients verify load conditions with their Building Department prior to ordering. This will give you an idea of what will be on form to be completed: https://www.hansenpolebuildings.com/2020/08/building-department-checklist-part-i/.

 

DEAR POLE BARN GURU: Can I hang 7/16″ osb or 5/8″ sheetrock from my pole barn style garage with 4′ on center trusses with a 2×4 bottom chord & 2×6 top chord & a 28′ span? I have thought of running 2×4’s perpendicular to the trusses but am concerned about all the weight. Any thoughts or ideas for me? DAVID in HELENA

DEAR DAVID: If your building’s roof trusses have been designed for at least a five psf (pounds per square foot) bottom chord load (often shown as BCDL on engineered truss drawings) then they could support weight of either 7/16″ OSB or 5/8″ sheetrock. Neither product is designed to span greater than two feet, so you would have to add framing between trusses to adequately support.

This circumstance is why all Hansen Pole Buildings prefabricated wood roof trusses spanning 40 feet or less are designed with a minimum BCDL of five psf or more – just an added service for our clients who decide to add a ceiling later on.

 

DEAR POLE BARN GURU: I have read many, many of your replies pertaining to the multitude of insulation questions to try and find a scientific and experience answer to an insulation quandary my daughter will experience in a matter of days. I am very familiar with & proficient in stick build & the associated vapor & breathing issues in that form of home building. However, the post & frame discipline is different & yet has some similarities in physics. My daughter & son-in-law are already in contact to have 4″-5″ of “open-cell” spray foam for insulation for walls & roof. I completely understand house wrap, condensation etc….my question is this. Should Tyvek be used between the metal sheathing (siding) & the open- cell or not? The trusses are spaced 2ft o.c. & 2×4 purlins are laid flat 2ft. o.c. then standard girt spacing, etc. on walls. I just want to make sure I provide my daughter with the correct answer so as her family can live in their home with the concern. I thank you for your time and expertise. NICK in MORRIS

DEAR NICK: Luckily physics remains same from stick built to post frame!

For walls – my preference would be two inches of closed cell sprayed directly to wall steel, then fill balance of wall cavity with unfaced insulation of your choice. Fiberglass would be least expensive for this, although open cell spray foam or BIBs are options (I have done BIBs personally and think it is great).

For roof – if attic space is to be conditioned and there is no other provision for condensation control, I would start with two inches of closed cell directly to roof steel and then open cell to it to desired R value. If attic space is to be ventilated and insulation placed at ceiling level, if no condensation control do closed cell again, then blow in insulation at ceiling level. This will require adequate eave and ridge ventilation.

 

Overhead Doors and Eave Height

Putting a 14 Foot Tall Overhead Door in a Short Eave Height…

I’ve been doing post frame buildings now for a couple of years. Okay, maybe a couple of couple of years, as in 37 (ouch, am I seriously this old?). I’ve learned a certain amount of clients (and builders) are seemingly dimensionally challenged when it comes to fitting overhead doors into buildings. Quote request, after quote request has come across my desk, for the overhead door height and the building eave height to be the same!

Newer readers might want to review how eave height is measured on post frame buildings: https://www.hansenpolebuildings.com/2015/02/eave-height-2/.

Hansen Pole Buildings’ Designer Doug posed this question of me earlier today, which came from a client of his:

“Do you offer a vaulted bottom chord that would allow us to lower the sidewall height and keep 15’6” at the 14’ overhead door?”

And Doug added…..

“My instinct and experience says we need minimum 2’ especially with a 14’ high door but it never hurts to ask.” (This would be needing two feet of eave height greater than the overhead door height)

The building in question has a 40 foot wide endwall. With placement of the overhead door at the center of the endwall, here is my answer to Doug:

The bottom side of the top jamb will be at 14’2.5″ above grade, 15″ to clear = 15’5.5″. Door is 12′ wide, so allow an extra 6″ of width for the tracks. This means at 13’6″ from the sidewall, you need to have 15’5.5″ above grade. With a standard gabled roof and 2×6 top chord on the trusses, the door just fits.

If the scissor truss bottom chord was a 1/12 slope, the eave height could be lowered to 14’10.5″; 2/12 13’9″; 3/12 12’7.5″.

 

 

Now the kicker – with scissor trusses, your client had better drive straight into the building and not want to park close to one of the sidewalls, because those trusses make a nasty slapping sound when they get hit, right before the roof caves in.

Because the scissor trusses are going to require adding to the exterior slope of the building, the overall building height is going to be the same or more, and scissor trusses are more expensive than standard trusses – probably making the entire project more expensive, with less net interior clear space throughout the building.

Can he do it? Sure. Is it practical or safe? Probably not.

Will My Trusses Hold Added Ceiling Dead Load?

Understanding the Needs of Load Bearing Finish

I sadly hear this story all too often. A brand new post frame building which quite possibly will not meet the load needs of the owner due to lack of due diligence upon the part of whomever sold the building. Here is the story and my response:

DEAR POLE BARN GURU: I have a newly constructed 30 x 40 pole barn, truss spacing 8′ o.c., 2×6. 5 PSF. I am wondering if I can cap the ceiling and insulate without over loading the bottom chord? Recommended material used for this? In laymen’s term how do I determine how much dead weight can be applied to bottom chord? At the time of construction I did not understand the load bearing needs of interior finish. Thank you – JUSTIN in MONROE

Dear Justin: Yours is one of the two most frequent issues following completion of a new post frame building, the other being insulating. Most post frame builders and building suppliers are afraid to have this discussion with potential new building owners – for fear the increase in price will scare them off! In my humble opinion, part of delivering “The Ultimate Post Frame Building Experience” is to discuss important issues such as this with clients BEFORE the building design process gets too far down the line. Shame on whomever you invested hard earned dollars with for not having had this discussion with you.

You should have been furnished with engineer sealed truss drawings for your building. If you were not, call whomever you purchased the building from, and request them. On the truss drawing will be a section which outlines all of the live and dead loads which the trusses are designed to support. If the number next to BCDL (Bottom Chord Dead Load) is less than five psf (pounds per square foot) then the trusses and the building are not designed to support a ceiling.

Take heart, if the design BCDL happens to be less than five, you can contact the truss manufacturer and for a nominal fee they can usually (especially with smaller truss spans like yours) get an engineered repair (or fix) to upgrade the trusses to support the load of the ceiling. This is never as inexpensive as having it done right to start with.

In order to install a ceiling in your building, you will need to ventilate the dead attic space you will be creating. More reading on ventilation is available here: https://www.hansenpolebuildings.com/2014/02/pole-building-ventilation/

Once past the truss loading and ventilation stages, the adequacy of the footings for the building columns to handle the extra load could pose a challenge – IF your new building was not designed to support a ceiling load to begin with. You should consult with the engineer of record who sealed the plans for your building, to verify the ability of the footing to properly transfer the loads from your building to the supporting soils. If you are unable to contact him or her, a competent engineer should be contacted to confirm what you have works, or to design a repair if not. Don’t overlook this step, or assume what you have will handle the load – we all know what assuming ends up causing – nothing but grief and having a column settle due to the added weight is not a problem you want to have to solve.

Ceiling joists will need to be installed between the bottom chord of the trusses. To support 5/8″ gypsum drywall, #2 (not standard & better) grade 2×4 or 2×6 can be placed 24 inches on center supported at each end with 2×4 joist hangers.

Planning a new post frame building? If you feel you or anyone after you who uses your new building will ever have the desire to install a ceiling (trust me – it happens a lot), at the very least have the trusses designed to support a ceiling load, as well as make provisions for adequate ventilation. The headache you solve, may very well be your own!