Tag Archives: trusses

Building Your Own Gambrel Barn Wood Roof Trusses

Gambrel style rooflines are often enticing, they offer the feeling (however not the reality) of getting added space for free. Building your own gambrel barn trusses might appear on the surface like a way to make this even a greater savings.

This was prompted by an inquiry from reader DON in WAYNE. Don writes:

“I am building a 24 ft. wide x 40 ft. length barn. I am going to build a gambrel truss with 2×8 and with 4 ft. wide gussets. How far apart should I space them using purlins and should I use 2×4 or 2×6 purlins. I was thinking of going 4’ wide with the trusses and using 2×4 spaced 2 ft. wide for the purlins.”

Mistake number one is even considering building your own trusses, on site, unless you are constructing them from drawings designed and sealed by a Registered Design Professional (RDP – licensed architect or engineer). Chances are way too good (100% guaranteed) you are dooming your building (and possibly its occupants) to failure. In all seriousness, prefabricated steel connector plated wood trusses are the only way to go – you will save money in the long run and you will be able to sleep soundly at night.

Your second mistake is in trying to be your own building engineer. If it was my own building (depending upon the design wind and snow loads), I would probably be using a single truss on each endwall and double (two ply) trusses every ten feet, bearing directly upon the columns. In my humble opinion this will give you the safest end resultant as the trusses can be notched into the columns and not possibly slide down the columns (or have a questionable connection to a header or truss carrier). You can then utilize 2×6 (or 2×8 depending upon loads) roof purlins on edge to support the roofing.

Your idea of using 2×4 (I am guessing flat over the tops of the trusses) every two feet and spanning four feet will not work unless you have the availability of lumber graded higher than the Standard and Construction material from your local lumber yard.

To avoid making crucial mistakes, which could waste your hard earned money, I would recommend you invest in a fully engineered post frame building kit package.

 

 

A Stone Base Floor? Trusses vs Rafters, and Entry Door Install

DEAR POLE BARN GURU: I have a 40 x 24 pole barn with a 4 inch stone base floor. Can I place 2×4 grid framing 24 in on center with 3/4 inch T&G 4 x 8 sheets for light weight shop usage? No vehicles. JEFF in SYCAMORE

DEAR JEFF: Some ifs – if your site is drained so as to not have excess moisture beneath the building, if the subgrade is thoroughly compacted and if you have a well-sealed vapor barrier underneath, then it might work. Be prepared for the possibility of frost heaving. Both the framing and the sheathing should be pressure preservative treated to a minimum UC-4B level to prevent possible deterioration.

 

craigslist pole barnDEAR POLE BARN GURU: You compare scissor trusses to conventional trusses, but I see nothing about using beams instead. I’m aware of only one post frame supplier that provides beam systems in lieu of trusses. Are there any down sides to using beams and avoiding trusses all together? RACHEL in ST. LOUIS

DEAR RACHEL: My only guess would be you mean rafters, not beams. Or it could be your intent is a ridge beam supporting rafters. In any case, the answer is going to come down to time, money and reliability. If an alternate system to prefabricated wood roof trusses is to be used, it should most certainly be a design which has been thoroughly reviewed and sealed by a Registered Professional Engineer. Obviously prefabricated wood roof trusses are most highly prevalent because they offer the advantages without the expense of time and labor.

DEAR POLE BARN GURU: Can I install a 36″ steel entrance door before the exterior girts are applied? DONAVON in EAGLE GROVE

DEAR DONAVON: In most cases, the columns on one or both sides of the entry door are trimmed off above the door and supported by a wall girt which runs between two roof supporting columns. If your particular application has framing on both sides of the door which is attached to the roof system, then it would probably be possible to install the entry door prior to the wall girts. I am not seeing any apparent advantage to doing so and it would add to the possibility of inadvertent damage to the door.

 

“My Guy Says… Materials… Design…”

“My Guy Says….. Materials… Design…”

Title inspired by our Wizardress of all things materials – Justine!

I’ve now been in the post frame industry for nearly 38 years, the majority of them spent providing complete building kit packages, most often to do-it-yourselfers. Some new building owners happen to hire contractors to erect some or all of their building packages for them. It is from this last group where I get the infamous report of…..

“My Guy Says….”

This is actually construction short speak for, “We have really screwed something up here, not quite sure what it is, but it must be someone’s fault other than ours even though we have not truly looked at the engineered building plans, or bothered to open your Construction Manual”.

Here is an actual example.
The building in question happens to be 36 feet in width, and 28 feet deep. It has a single prefabricated metal connector plated wood roof truss on each endwall, and a double truss nine feet from each endwall. Roof purlins for the building are on edge joist hung to the top chords of the double trusses and running over the top of the end trusses in order to support a 12 inch endwall overhang.
Sound simple?
Please read on….

Client: “We have an issue with the purlin/joist hangers.  We appear to be 24 short of the LU-26, but we have 28 of the ESR2523 (H1) hangers.  My guys say the H1 hangers don’t work for mounting to the trusses. I’ve included a picture of the two hangers; the one with the square mounting plate is the H1.”

Hansen Pole Buildings Technical Support: “The purlins go OVER the end trusses and use the H-1 hanger there. Please refer to Detail 9/S-4 of plans.”

Client: “Yes, thanks. We did find that detail.  I went ahead and purchased the missing hangers at Menards.”

Tech Support: “Doing a manual count, we come up with 60 LU26 and 28 H-1 needed, which actually provides 2 extra LU26. If you were not short shipped, the concern is your guys may have done something which is going to cause future challenges. Other than at the double trusses, there should be no other LU26 used on the building.”

Client: “We found them… They were installed on the end trusses. OOPS”

Fiberglass Panels, Accurate Info, and Truss Bracing!

DEAR POLE BARN GURU: I have four skylights with old fiberglass panels that are in need of being replaced. I doubt the design of the panel can be matched easily but am wondering if I send you a piece of it if it can be. I understand the way to go is with a polycarbonate, not fiberglass, panel. Thanks DAVE in BAY

DEAR DAVE: As you are finding out, skylights are problematic. Here is some extended reading on why: http://www.hansenpolebuildings.com/2012/01/skylights/.

If indeed you determine the only solution is to replace fiberglass panels with polycarbonate (me, I would replace them with steel panels and be done with the future headache) I would recommend a visit to the ProDesk at your local The Home Depot® as they can order in most anything and it usually comes in freight free, which can prove to be a significant savings.

DEAR POLE BARN GURU: I am buying a building immediately but your website is too intrusive to shop, so I will not be using you. I, like many others, do not like the setup for quotes because in most cases you turn into used car salesmen. BRAD in KNOXVILLE

DEAR BRAD: Thank you very much for your input. In order to be able to provide accurate pricing and design advice to our clients, we do need to gather some basic information. Things like where is your new post frame building to be constructed (so we get the correct climactic loading conditions), as well as how do we best reach you to discuss your proposed project. We get several hundred new inquiries each day, seven days a week, and frankly you are the first to voice an opinion as to our website being intrusive. If you have constructive solutions as to how we can best glean the information needed to be able to best provide our services, without coming across as being ‘intrusive’ we would welcome your input, as we always strive to improve.

Our Building Designers are highly trained professionals whose mission is to assist our clients in the quest for the ideal dream building which melds imagination, budget and available space. Post frame buildings are highly involved, engineered structures, which ideally require a fair amount of interaction between us and the client to arrive at the best design solution. We do not “sell” anything to anyone – we provide the assistance to our clients, as well as the education which enables our clients to invest in The Ultimate Post Frame Building Experience™, should they decide we are the best fit. Most of our clients have spent hours perusing the thousand plus pages of free information on our website and have decided they are going to own a new Hansen Pole Building long before they ever request a quote.

 

DEAR POLE BARN GURU: Question about my plans. On the drawings, my purlin spacing is noted as 31” OC. On the truss drawing, I see that it says the bracing for the top chord is 24” OC. Am I reading this correctly? 

It states: 

(Switched from sheeted: Spacing > 2-0-0).

and then below it talks about the Bottom Chord: Rigid ceiling directly applied or 6-9-13 oc bracing. What does that mean?

Thanks! DAN in QUAKERTOWN

DEAR DAN: Truss drawings are designed without any knowledge of how a particular building is constructed, or what the final bracing system for the entire structure is – the permanent bracing design is left to the engineer of record (see General Safety Notes #2).

You will note the top chord bracing says 2-0-0 purlins then says the maximum spacing is 4-7-0 (least of the three drawings). The 31″ spacing on the plans is far less than the 55″ maximum.

Bottom chord bracing is a function of a maximum L/d (length divided by depth) ratio of L/80 for members in tension (truss bottom chords are in tension as they are preventing the walls of the building from going out). The width of a single 2x member is 1.5″ X 80 = 120″ maximum for a single width 2x member. You will note on the endwalls of the building there is a 2×4 nailed to the face of the bottom chord of the truss. This now makes the member three inches in width so technically it could be braced once every 240″ (or 20 feet). The same goes for the interior double trusses, the three inch width member is good up to 20 feet without being braced laterally.

 

 

Roof Trusses? Contractor Reviews, and Insulation Installation!

DEAR POLE BARN GURU: I would like to rip off my current roof of trusses that are made of 2x4s 2 feet on center with new one of mono-pitched trusses that are every 4-ft or less on center. The roofing material on top of the new trusses would be a SIP panel of some sort. The unfinished ceiling would be the bottom of the SIP panel. The house would have exposed trusses to create a loftier feel as the ceilings are currently too low. (house is 28 ft wide by 30 feet long)

Is this something that you can help with — the design & manufacture of the trusses/roof?

Thanks! NATHAN in KIRKLAND

DEAR NATHAN: Your Building Department is going to require engineer sealed plans in order to issue a building permit for your project. As such, your best bet is to hire a local engineer who is experienced in wood frame construction to provide your plans. They should come out to your house and do a thorough investigation into the adequacy of the structure to support the loads.

Some thoughts to consider – SIPs are going to prove to be very expensive. You could create a more spacious feel by constructing a knee wall on top of one of the existing walls, then use I joists or parallel chord trusses – either of which can be insulated between to give an adequate R value.

DEAR POLE BARN GURU: How can I find independent customer reviews in Washington state for Pride in Construction. GINGER in TACOMA

DEAR GINGER: Getting independent customer reviews on any building contractor anywhere is a challenge, as most builders do not construct enough buildings to develop much of a track record either good or bad.

Here are the seven steps to not getting yourself burned by any contractor, follow these: http://www.hansenpolebuildings.com/2013/07/contractor-6/ and require a performance bond and you will greatly limit your risk of not getting the finished product you expected. Here is Performance Bond information: http://www.hansenpolebuildings.com/2012/07/contractor-bonding/.

 

DEAR POLE BARN GURU: I will be installing insulation under the steel roof.  Are staple guns the best choice for temporary stabilization until the roof is added?  What length staples?  Which gauge staples?  Narrow?  Electric, air or grip staple gun?  Recommendations?  I will be using metal tape to join each roll of insulation side-by-side.

Trying not to re-invent the wheel, that’s why I went Hansen of course. RALPH in KENNEWICK

DEAR RALPH: From Chapter 14 of the Hansen Pole Buildings’ Installation Guide: Using a minimum 5/16” galvanized staple, staple through insulation to eave purlin top. As an alternative to staples, 1” galvanized roofing nails (with the big plastic washers) also work well.

These fasteners are only going to be needed long enough to get a sheet of steel on top of them, so there is no occasion to get fancy at this juncture. I’ve found a tack hammer to be more than adequate.

Keep in mind, the one edge of each roll of A1V insulation has a pull strip on it, with adhesive under the pull strip. This eliminates the need to use rolls of tape to adjoin each piece of insulation.

 

Builder Shaming

The Builder Knows More Than We do…. After Hansen 18k Plus Buildings

Very few things in life frighten me. Among them are heights (growing up in a family of framing contractors and having vertigo issues were not a good mix) and builders who tell me, “I can build anything”.

This last one usually sets off the alarm bells in my head which I interpret this to mean, “I won’t read your plans or follow your instructions, but when things go sideways – I will be blaming you for it”.

Now my lovely bride tells me I can be a bit harsh when it comes to writing about builders whose competency skills I may find to be ‘challenging’. I’ve written previously about the phenomena which a few of these folks are afflicted with (and I would encourage you, gentle reader to delve further into the subject by reading: http://www.hansenpolebuildings.com/2015/01/dunning-kruger-effect/).

For your reading pleasure I will share with you, in its unedited glory, a recently received email from a builder:

“Building one now and plans for trusses were wrong. I explained to the guy that I knew exactly what needed to be done to fix it. He didn’t seem to be interested in what I thought. Mind you I have 14 years of full time framing experience (new construction) condos and custom homes.  Done a bunch of remodeling also worked on bridges for 4 years, framing also, bridge end post forming, radius walls framed and poured etc etc. I’ve been in the field for 21 years. Anyway blah blah. Guy from Hansen wants to have the drawing done and wants me to look at it and go by it. Haha. I already no what needs to done!  I’m in the field building the thing, I no the material list!  Now the material comes for the new facia and the new WRONG drawing of the soffit support, and 2 by 8, which we didn’t need but since they shorted us on 2by 4 we used. The WRONG drip edge piece came but we are using that also. He’s now going to eat the 5 1/2″ facia metal because of the WRONG drip edge piece sent, he has to buy bigger facia pieces. I guess what I’m trying to say, is that, if you had listened to the licensed builder that has framed miles and miles of buildings in the first place. I could’ve easily put a material list together, showed you the cost, ordered it locally and probably saved you money on the material, and us the headache of dealing with wrong stuff. By the way The soffit nailer doesn’t change from the original height in the drawing. It still tucks in exactly 3 1/2″ with the 18 degreee bevel. The only measurement that changes with the 2 by 8 truss is the 16’5. The only thing it changes is the size of the facia.”

Construction ManualFeel free to ponder this over your New Year’s Holiday weekend. Next Tuesday, I will dive into….the rest of the story!

Be safe, don’t party and drive, and I will catch you in 2017!

Pole Barn Design for Free

Please Structurally Design My Pole Barn for Free

This is one of those POLE BARN GURU questions which results with a lengthy enough answer I feel I must devote a whole column to it.

DEAR POLE BARN GURU: Could you please help clarify, for a 40 ft. wide x 64 ft. long x 15 ft. high Pole Barn Building,

What size & kind of posts are needed?
How you would recommend connecting posts to trusses?
Footer depth & construction?
Lateral Wind bracing & Uplift measures?

Would greatly appreciate hearing your recommendations.  Thank you! EILEEN in CENTERBURG

DEAR EILEEN: What you are asking for is to have a building engineered, without knowing the parameters the building is being engineered for.

Without the knowledge of your wind loads (including exposure), snow and seismic loads, any answers I would give to you for your pole barn design would most likely be incorrect.

post-frame-construction-150x150Post frame buildings also work as a system, so individual components or connections might possibly be adequate, however the entire building fails due to a weak link. This is why I always, always (did I say always) recommend ONLY to invest in a building which is designed by a registered design professional (RDP – engineer or architect) – especially for your particular site.

Some general answers to your questions (answered as if I was going to build this building for myself):

Posts

I would use true glu-laminated columns (not nailed up columns), as they have a high strength to weight ratio, are lighter to work with and tend to be less prone to warp and twist.

Trusses

The post to truss connection would have double trusses set into a notch cut into the top of the column. This prevents the trusses from being able to “slide” down the column in the event of a high snow load. To avoid uplift challenges, the trusses can be bolted or a combination of threaded hardened nails and bolts could be used. In high uplift situations, appropriately sized Simpson HST brackets may prove to be the best design solution.

Footer

Footer depth and construction – the holes need to extend at least below the frost line, and I tend to use 40 inches as a minimum depth into undisturbed soil. The columns should be floated eight inches above the bottom of the hole then no less than a total depth of 16 inches of premix concrete poured into the hole. The diameter of the holes will depend upon the loads being placed upon them, as well as the assumed bearing strength of the soil at the site.

Do not attempt to use concrete “cookies” – http://www.hansenpolebuildings.com/2012/08/hurl-yourconcrete-cookies/ or bags of sackcrete – http://www.hansenpolebuildings.com/2012/11/concrete/
Siding

Provided there are not excessive door openings in endwalls, in most cases the utilization of the proper screw for attachment of steel to framing the steel skin should be able to adequately transfer the imposed loads:                                           (http://www.hansenpolebuildings.com/2012/08/this-is-a-test-steel-strength/

Bracing

Here is some reading on bracing which you might find helpful: http://www.hansenpolebuildings.com/2016/03/diagonal-bracing/ and http://www.hansenpolebuildings.com/2012/01/post-frame-construction-knee-braces/

Good luck with your pole barn design.

Mike the Pole Barn Guru

Adding Steel Ceiling Liner Panels

I Want to Add a Steel Ceiling

This must be my week for receipt of good questions which require lengthy answers in order to do justice to the subject. Here is another one:

liner-steelDEAR POLE BARN GURU: I have a 42 x 60 with insulation in walls and roof, 26 gauge metal, wood trusses, 10 feet o.c. with 2 x 6 purlins. I do furniture and cabinet work and love the insulation but would like to add the white metal ceiling, to help with the heating, cooling, and lighting. Can I add trusses in between existing ones, and build them underneath the purlins? If so can the white metal span 5 feet for a metal ceiling? CHARLES IN BUTLER

DEAR CHARLES: I would begin by examining the truss engineering – if the bottom chord of the trusses is designed for an adequate dead load (oftentimes this will appear as BCDL on the drawings) of five psf (pounds per square foot) or more, then the trusses are probably capable of handling the added weight of the ceiling plus applicable framing.

If the truss drawings are not available, look for the manufacturer’s stamp on the trusses, it should be on the bottom chord and will give the manufacturer’s name as well as the load the trusses were designed to support.

Not having to add more trusses will be the far most economical and practical design solution.

In the event the trusses are not designed to support the weight of the ceiling, I’d recommend asking the truss manufacturer for a “repair” to upgrade the trusses to be able to support the added weight. If you are unable to contact the manufacturer, a registered professional engineer who is competent in truss design and repair should be consulted to design an engineered repair for you.

Once the load carrying capacity has been determined to be adequate, ceiling joists can be placed at five foot on center between the trusses (using joist hangers), so the liner panels can be screwed directly to them.

Could you add another truss between each of the existing ones? Sure, but it is not probably going to prove to be an easy task as they will need to be maneuvered into place. The ends of each new truss are also going to have to be supported by a structural header placed between the sidewall columns and adequately attached to support the weight.  The design of these headers and their connections should also be done by an engineer.

If the purlins are joist hung between the existing trusses, the new trusses will have to be manufactured so as to afford you the ability to have the bottom chords of the trusses all at the same height. This may not be possible.

Steel ceiling liner panels should be able to span five feet, without significant deflection issues making them appear unsightly.

In addition, Here are some thoughts about the use of steel liner panels for ceilings: http://www.hansenpolebuildings.com/2013/08/steel-liner-panels/

Good luck! And let me know how everything turned out for you!

Carport Attachment: Part II

We Don’t Always Do Things Perfect, But We Do Listen Part II

Last summer Hansen Pole Buildings Supplied a pole building kit package to a client who experienced a few challenges and took the time to address them.

Here is a portion of the email I was responding to:
“On the design flaws, and other issues, here is what I have experienced.

If you just joined in this blog – read yesterday’s blog for Part I in a 4 part series from a client who experienced some construction challenges…

“2-Carport attachment.

My plans have a 12 foot carport section on the front.  The engineering on this section is very confusing.  The plans state that the double truss system is supposed to be used but, the outside truss is supposed to lowered by roughly 6 inches to make room for the purlins to travel over the top of it.
With this system there is no double truss.  There is one truss that is supporting the load of two sections of roofing.  To further complicate the matter, the trusses that were engineered and supplied were constructed with 2 X 6’s.  What does this do, well, when I lowered the outside truss 6 inches there is absolutely NOTHING to attach that truss to the other truss.  A few spots of webbing is it.  This seems like a totally weak link in the system and I cannot figure out why this was done this way.
It seems to me that you would have run a normal double truss and then nailed a siding backer onto the outside truss for tin placement.  This dropped truss created other issues as well.
When placing the X bracing for the carport as well as the first bay in, the X is placed at 2 different locations on the bottom attachment.  On the carport section the X bracing is attached to the outside dropped truss, 6 inches below the other truss.  On first interior bay the X is attached to the upper truss.  The two braces are not pushing on each other.  And, I have no idea how I am going to place the tin on this section because I have a 2X4 10 inches above my garage door.  Am I supposed to cut around the 2X4 and try and figure out how to make it work?”

carportMy response: Actually in the hundreds of buildings we have provided with carports, you are quite honestly the first person who has ever brought forth any of these issues as being challenges. Your bringing this to our attention is greatly appreciated.

With Hansen Buildings knowing the carport to enclosed portion the trusses were not going to be at the same height (per the plans), the trusses for your building were ordered and designed to work with a single truss placed every six feet (the worst case scenario).

One truss does not support two sections of roofing, as the end of the purlins in the direction of the carport rests on top of the top chord of the lowered truss. Each truss at this juncture is supporting six feet of roof, just as it was designed to be.

Your recommendation of keeping both of these trusses at the same height and having a siding backing nailed to the face will be taken under serious advisement. The challenge will be, in many instances, the wall columns in this area are 4×6, oriented with the wide face against the wind. In those circumstances, it would be impossible to notch three inches into a 3-1/2” thick column. We are in the process of discussing with our engineers turning the corner and endwall columns 90 degrees to be able to notch in the two trusses, as you suggest. Because we do so many different applications, we need to see if this will cause other challenges.

The idea of the X braces is not to push against each other – it is to create a rigid brace frame which is restrained against buckling in both directions and transfers load into the roof diaphragm. There is no structural reason for them to be at the same height.

Install the steel siding on this wall first, then the X brace. A small slot can be created, using a punch, to slide the Simpson LSTA12 bracket through for attachment.

“3-Girt Spacing

The girt spacing is an interesting way to save a few hundred bucks, probably not mine.  The plans call for the girts to be about 40 inches on center.  I know this is not exact but close enough.  This is the absolute maximum allowed by the tin specs, I know because I called and spoke with the engineer.  Common practice is girts places 2 feet on center.  It does not take a rocket scientist to know that when those girts are placed in a funky location, like 40″ OC, you cannot hang insulation, drywall or anything else without a bunch of waste or owner supplied materials.  I chose to purchase my own 2X6’s to build the thing at 24″OC.  It cost me a whopping $250 for the lumber and a bunch of headache every place else.  I now need to order more screws because I do not have enough for attachment.  You would think that for $25,000 it could be done right without cutting corners.”

My response: There exists no “common practice” for the spacing of wall girts, other than what is needed to support the given load conditions.  Your building, with the loads imposed on it – came out to what we designed, 37-5/8″ spacing.

This is not about “cutting corners”, as with any structural member of a post frame building, the wall girts are located and spaced to carry the loads (in this case wind) being placed upon them, without added pieces being placed “just because”.

The information provided by you, in your request for your initial quote, indicated: “insulation_options: cold”, which precluded us from knowing your intention was to insulate the walls of your building. This is just one of the many reasons why we have each of our clients review and approve their building plans online prior to materials being ordered. At time of review you could have asked why the girts were spaced at 37-5/8” on the plans, or requested any spacing you desired, which would have gotten you not only the extra lumber, but also the screws. There is no indication in the notes in our records your intentions of insulating the building at a future date, or even of it having been discussed.

As for the spanning capabilities of the steel – your building’s steel roofing and siding is Imperial Rib® manufactured by American Building Components. In looking at the span tables for this product, for 29 gauge over three spans (crossing three or more framing members) and spanning 3.5 feet (42 inches), the allowable minimum loads in pounds per square foot (psf) are 54 for positive wind force and 53 for negative wind force. The formula to convert wind speed in mph (miles per hour) to force is Speed^2 X .00256 = psf, so force to speed is the square root of psf divided by .00256, or 143 miles per hour. AS the design load for your building is 100 mph, it doesn’t appear “This is the absolute maximum allowed by the tin specs”. I’d be happy to supply a copy of the chart, should you desire.

Tomorrow’s part III of a 4 part answer from Mike the Pole Barn Guru to a challenged client deals with ceiling loaded trusses. See you then

Pole Building Trusses

Pole Building Roof System – Dressed Up!!

For years I sat in church on Sunday mornings with my children and admired the magnificent trusses which supported the roof. Built from glulams with the joints connected with bolted steel brackets – they were nothing short of fabulous. To me (coming from a background of construction and prefabricated roof truss manufacturing), I believe I had a special attraction to them more than just the average parishioner.

Truss-FramingAs pole buildings have gravitated from the farms of the 1950’s into the mainstream of popular construction, their owners have been looking for more appeal than what was offered by the average tractor shed.

The aesthetics of massive exposed trusses somehow is appealing to many of us. By using glulaminated timbers to fabricate them, the members have very few flaws and can be readily finished to highlight the natural beauty of the wood.

By using prefabricated metal plate connected wood scissors trusses, the structure of the roof surface can be readily supported. These trusses may have conventional “heels” (the point where the top and bottom chords meet) and an exterior slope which is greater than the interior slope. By use of a raised heel, the bottom chord slope can be increased to give a more dramatic look, as well as creating a deeper insulation cavity.

Ceiling finishes are then often tongue and groove two or three inch thick material. Depending upon the spacing of the trusses, often no other bottom chord framing is required for their support.

Non-load carrying glulam trusses can be placed directly below the decking to give the impressive look, without sacrificing any of the “pretty” parts of the truss – as this work is being done by the hidden trusses above the decking.

Whether office space, a church, great room or man cave – if you want to “knock the socks” off your guests or clients, this one offers some distinct possibilities

Dear Guru: Can My Pole Barn Trusses Handle a Ceiling Load?

DEAR POLE BARN GURU: I have a question regarding truss loads, specifically ceiling loads, for a pole barn.  I know you have touched on this before, but I was hoping for a little more detail.

I recently purchased a property that came with an existing pole barn, and other than a few material ratings I cannot find any data on the trusses (no manufacturer tags, etc).  The building is 32×48, and the trusses 4/12 pitch with 2×6 top cord, and 2×4 bottom cord and webbing, on 4′ centers.  I want to add a steel ceiling, plus insulation and lighting. By my math I am looking at a dead load of 2-3 lb/sq ft, including the weight of the bottom cord of the trusses.

I have done a lot of research on the subject, and it seems that it is common in pole buildings to have trusses spaced much wider than 4′ (8’+ seems common).  Is the tighter spacing a indication that these trusses should support a 2-3 lb/sq ft dead load for ceiling and insulation?  If you were specing trusses for my requirements, how would you design them?  If these trusses are not sufficient, what sort of reinforcement would be required?

One of the only bits of data I have been able to find is this page http://www.pole-barn.info/gable-roof-trusses.html, where toward the bottom it lists a 30′ span with the same lumber sizes as my trusses.  While it says “no ceiling” it also lists a bottom cord dead load of 5 lb/sq ft, which would be plenty for what I have planned. BAFFLED IN BOZEMAN

DEAR BAFFLED: The spacing of the roof trusses has no influence upon their load carrying capacity. In reality, trusses spaced 12 feet on center could easily have a greater ceiling load carrying capacity than ones placed even every two feet!

As a starting point, you should assume the trusses are NOT designed to support dead load weight of anything other than the trusses themselves, required bracing and minimal wiring and lighting.

The size and or grade of the truss chords as well as the webs and their quantity, and the size of the roof truss plates may not be adequate to carry the weight of the ceiling load. It’s not as easy as just knowing the size or spacing of each part, but rather it’s more of how all the parts function together in any configuration.  In other words, it’s a formula with many parts which change the final answer of “yes” or “no”.

The only safe way to make sure your new ceiling doesn’t end up on the floor with the rest of the roof following it, would be to hire an engineer to confirm the trusses are adequate to support the ceiling load, and to design a repair for them, if necessary.

DEAR POLE BARN GURU: We are builders, putting up a Hansen Pole Building currently. It is large enough so the main clearspan building and attached shed had to be shown on two different pages of the blueprints. Anyhow, we made a mistake on setting the poles. Where we are looking at the 4 posts going across up by the “matchline”  we have the left sidewall posts set correctly but the 2 main building posts and the right side shed post are set incorrectly. We ran a string line but the workers ended up setting those 3 posts on the other side of the string line.

I am wondering if there is an easier solution than pulling out the posts. We have a lot of concrete in the holes and it would be hard to get them out. Could we fir out the left sidewall posts and go out and buy longer purlins? ERRANT

DEAR ERRANT: While this doesn’t happen often, you are not the only person to have this problem. In this particular case, you are constructing an engineer certified post frame building, which means any deviation from the plans is going to have to be approved by the engineer. This is going to mean time delays and the expense of paying the engineer.

Even if it was not an engineered building, using purlins for a span which is now 5-1/2 inches greater could overstress the purlins in bending. While 5-1/2 inches may not sound like much, in the design calculations for the purlins, the span is squared.

I’ve had to pull out concreted in columns before, and it isn’t fun. Best method I found was to use a backhoe or loader, wrap a chain around the column and lift it out. Fairly fresh concrete can be chipped away from the column and the process of setting the three columns can begin again.

I’m sorry I don’t have an easier solution, but you will be much happier with the outcome if you do reset the posts. And all in all, it may end up being far less expensive as well, in both time and materials.  As I said, I’ve done this myself, so I am right there with you.  The good news is, once you reset the posts, just knowing you have things all “in order” will make the project run smoothly from here on out

 

 

 

Permanent Truss Bracing

I have to give a lot of credit to Building Department plan checkers and field inspectors. They have to know a lot of stuff, about a myriad of different areas of construction. Even one who is an expert at what is written in the Building Code itself, would be only fluent in a small portion of what it takes to construct a Code conforming building, as the Building Codes now reference a litany of other publications and documents. Think of it as being similar to the IRS income tax code.

Puts it into perspective, doesn’t it?

truss bracingPrefabricated roof truss drawings (provided by the roof truss manufacturers) give the recommendation for how the truss designer feels the trusses should be braced, however the ultimate design of the truss bracing system, is the responsibility of the building designer (registered design professional – engineer or architect).

Recently one of our clients advised our office of the request, from their building inspector, for an email or letter from the engineer of record on their new Hansen post frame building. The request was in regards to the truss bracing system designed by the engineer superseding the bracing shown on the roof truss drawings.

Although the following may sound like it is in a foreign language, on the first page of the engineered building plans is a series of “General Notes”. Note 9 says:

“PER ANSI/TPI 1-2007 SECTION 2.3.2.3 TRUSS SUBMITTALS HAVE BEEN REVIEWED AND ARE FOUND TO BE IN GENERAL CONFORMANCE WITH THE DESIGN OF THE BUILDING. THE PERMANENT LATERAL BRACING HEREIN MEETS THE REQUIREMENTS OF ANSI/TPI 1-2007 SECTION 2.3.3.2”

ANSI/TPI 1-2007 pretty much lays out who does what and how. Here are some relevant excerpts:

2.3.2.5 Responsibility Exemptions.
The Registered Design Professional for the Building is responsible for items listed in 2.3.2, and is not responsible for the requirements of other parties specified outside of Section 2.3.2.

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:

2.3.3.2 Method Specified by any Registered Design Professional.

The method of Permanent Individual Truss Member Restraint and Diagonal Bracing for the Truss Top Chord, Bottom Chord, and Web members shall be permitted to be specified by any Registered Design Professional.

On this particular project, general note 9 covered the permanent lateral truss bracing system and is sealed by the Engineer of Record. This makes the request for an Email or letter from the engineer to cover the same topic redundant, as well as an unneeded expense to the building owners (engineers do not just do work for free).

Potentially, the building inspector could decide to alter the truss bracing system designed by the Engineer of Record, however this opens up an entirely new can of worms. In making an alteration, the inspector could be in violation of the laws which govern engineers, as well as placing the jurisdiction in a liability situation should a failure occur.

History of Pole Buildings Part I- back to the cave man!

While many old barns exist, it was not until the last century that pole barns developed, first as farm buildings. The following is excerpted from the National Frame Builder’s Association website:  www.nfba.org:

The post-frame industry has grown steadily in North America, gaining more and more widespread application in the past 100 years. Yet, many people still wonder, “What is post-frame construction?”

Post-frame buildings are structurally efficient buildings composed primarily of:  trusses, purlins, girts, bracing and sheathing. The primary element of the design incorporates square posts or wood columns, which are typically embedded in the ground or surface-mounted to a concrete or masonry foundation.

The post-frame building concept is not new. Many pre-historic peoples throughout the world used posts embedded in the ground to fashion sturdy structures for residences and other uses. For centuries, buildings along shorelines and in low-lying areas have been built on poles to elevate the structures above the guideline and/or water hazard. In rural areas, poles were used to erect sheds or temporary structures in 19th-century America. In all these cases, the limited life-span of poles in contact with the ground made them unsuitable for use longer than a few years, except in very dry areas or when rot-resistant strains of wood were used.

However, two significant technological developments in the twentieth century allowed the post-frame building to develop into a viable, long-lived structural system. First, pressure-treated materials that provided excellent durability, particularly poles that were initially developed for the electrical industry, became available for the construction of buildings. Secondly, large, lightweight metal sheeting was produced that could span supports spaced several feet apart. What remained was for builders to optimally use the advantageous features of these two materials in what is now known as the post-frame or laminated column building.

The availability of pressure-treated wood permitted the replacement of a continuous concrete foundation in conventional buildings with a vertical structural member that carried the live roof and dead building loads directly to the ground below the frost line.

The availability of lightweight, formed, metal roofing material permitted the use of spaced roof decking. The strength of the roofing materials resulted in a significant portion of the lateral building loads being transmitted to the end walls, to reduce the load on the supporting posts. The availability of trusses for a wide variety of spans further enhances and aides in the development of the post-frame building. Whereas trusses in conventional light-frame buildings are generally spaced 2-ft. or less on-center on stud walls, trusses became readily available that permitted truss spacing of anywhere from 4 to 12 ft. in post-frame construction. Each of these features contributed to the evolution of the modern post-frame building and its increasing popularity.

Stay tuned for tomorrow’s Blog- Part Two of The History of Pole Buildings.   You will find out who is really responsible for getting the pole barn design started, and why it was so important in the 1930’s.