Tag Archives: purlins

What Kind of Trusses Are Pictured?

What Kind of Trusses Are Pictured?

This question was posed by Hansen Pole Buildings’ Designer Doug. Photo isn’t of a Hansen Pole Building, probably raising questions in Doug’s mind as it looks rather foreign.

Only actual trusses in photo are in raised center portion of this monitor style building. Interior trusses were probably sold to building owner as being “double trusses”. In actuality this system has only a single truss placed upon each side of columns. These trusses, even though only inches apart, do not load share. They are only as strong as weakest individual truss. Between trusses, sticking up beyond top of top chords are paddle blocks (read about paddle blocks here: https://www.hansenpolebuildings.com/2012/05/paddle-blocks/) to attach roof purlins.

Monitor wings (or side sheds/lean-tos) have rafters placed each side of columns with paddle blocks as well. Second floor (aka loft) extends out into wing areas, although quickly loses functionality as headroom decreases close to eaves.

More headroom could have been garnered throughout entire second floor had trusses and rafters been positioned to allow roof purlins to joist hang into their sides. When placed as “top running” purlins, interior clear height decreases by purlin thickness. Positioning of roof trusses as lowered, below purlins causes builder to have to frame outriggers (or tails) above truss in order to support sidewall overhangs. Each paddle block makes for a purlin stagger and eliminates one’s ability to predrill roof steel panels. This adds to possibilities of roof leaks being created by each stagger point.

Other concerns exist in this photo. Where roof purlins overhang single end truss, attachment has been made with yet another set of paddle blocks. With an assumption overhangs will be enclosed, this allows for outside air to enter in spaces created between purlins. This decreases efficiency of dead attic space airflow from eaves to ridge.

Solid blocking should be placed between end overhanging purlins to provide continuity of a load path from roof diaphragm to ground. As being built, load path has been divided.

Perimeter beams in this photo show to be inset between the columns. My curiosity wonders how they adequately attach? Your guess is as good as mine.

 

Installing Joist Hangers

Installing Joist Hangers on Opposite Sides of a Double Truss

My friend and loyal reader LONNIE in COLORADO SPRINGS is one Hansen Pole Buildings’ client who truly puts thought into the assembly of his new post frame building.

Lonnie writes:

“I’ve been pondering and pondering this and I may have a solution that I want to run by you. I’m considering buying a Bostitch F21PL framing nailer to use on the project and mainly because it includes a metal connector tip that will allow it to drive the 3” nails through the hangers for the purlins. What I was thinking of doing is to frame each truss bay using 2@ 1 1/2” 10d nails (always making sure to use the same 2 holes for each hanger… i.e. upper left and lower right) to build each bay on the ground. After raising the truss bays, go back and attach the double trusses together and at the same time finish the hangers with two 3” 10d nails in the empty hanger holes. The only concern I had was that the 3” nails would be driven opposing the 1.5” nails on the opposite truss hanger. However, since the nails would be driven point to point I think the odds of the 3” driving the opposing 1.5” out would be very slim. 

Do you think that mix of 1.5” and 3” nails for the connectors would be sufficient or should I really consider just temporarily attach the hangers and replace the temporary attachment with the 3” nails? If that is the case, is there an issue driving 3” nails basically tip to tip through the hangers?

Mike the Pole Barn Guru writes:

Your mix of nails will be more than adequate, as the load carrying capacity of the hanger is greater than the ability of the roof purlin to carry a load. In simple terms – the hanger and its fasteners are not the weak link in the system. Also – if you take two hangers and place them back to back, you will notice the holes do not all line up – whether the variability is accidental or purposeful, I do not know, however it further reduces the probability of nails from opposite directions exactly hitting each other tip-to-tip.

A caution – situations involving a differentiation from what is shown on the actual engineer sealed plans should always be verified for structural adequacy prior to implementation.

 

Extreme Efforts to Add Post Frame to House

Extreme Efforts to Match Post Frame to House

Reader JOSH from POST FALLS and I have previously communicated. He is doing what I refer to a piecemealing – putting together his own building by making repeated trips to the local lumber yard (learn more about piecemealing here: https://www.hansenpolebuildings.com/2014/03/diy-pole-building/.

Josh’s new post frame garage is adjacent to his home and he wants things to match up.

Josh writes:Construction Manual

“Thanks so much for your offer for help. The knowledge of other people’s questions on your site is a great resource. I’ll buy my next pole structure kit from you for sure.

Quick question. I have an 18″ overhang with 2×8 purlins and truss top members. My pole garage is next to my house and will be matching the exterior of the house. The varge rafter and fascia on the house are 2×6.  It looks like I can just trim the bottom off on the fascia side, but what is the recommended way to match the gable end to the house if the purlins on the garage are 2×8 instead of 2×6?

Also are the varge rafter and the facscia both 1×6? or 2×6?

P.S. I noticed you used grok in one of your answers to a question. Haha, first use of grok in a non-technical setting I’ve seen. You must have a technical background.”

Mike the Pole Barn Guru Writes:

My mission is to be informative and entertaining – if grok got a chuckle from you, then all is good! I also try to throw out some occasional words most people do not use every day, with the hopes it will expand the vocabulary of some.

Unless your pole garage is attached to your house, frankly no one except you or I would ever notice the fascias are not the same dimension. People just are not finely attuned to details such as these. If it is really important to you, you could cut the overhanging portion of the purlins down to 5-1/2″ by ripping a chunk off from the overhanging portion, without it negatively affecting the structural ability of the purlins to carry the load. Your Building Department may require a letter from the engineer who designed your building on this one, however.

I would go with two inch nominal material for both the varges and fascias – they will be far straighter and will tend not to wave as much between supports.

 

 

Roofing Before Siding

Roofing Before Siding

If I am not mistaken, somewhere in the not too distant past I have expounded upon how I know a particular builder is or was a stick frame builder. How can I tell? The giveaway is they feel compelled to build the walls before the roof. I’ve listened to many experienced post frame builders in my career, as well as having constructed a few (hundred)post frame buildings myself.
The verdict – for best results, frame the roof and install the roofing prior to any wall framing being done.

Why?

First point is, if by some odd chance the columns at the base of the building are not exactly where they ought to be, the roof can easily be squared up still. It is relatively easy to move the tops of columns which are not framed to or sided. This allows for the column tops to be placed where they should have been at grade level.

Secondly, all of the roof purlins in interior bays can be precut to exactly the same length (in most cases), or at the very least an entire bay can be done at a time. If the column spacing varied between sidewalls and columns tops were not where they should have been, it would take custom cutting to length every roof purlin all of the way across the building. Neither fun, nor time efficient.

Third, without siding installed, it is relatively easy to square up each roof plane to make installing the roofing as painless as possible. Once either the steel roofing or roof sheathing with shingles is installed, the roof planes will be affixed where they should be.

Fourth, much easier to drive a pre-mix concrete truck around the perimeter of the building and chute the concrete in for a slab on grade floor. No framing or siding to get in the way, only widely spaced columns.

Am sure there are more reasons than just these, however the factors stated should be enough to convince any builder (or DIYer) to give it a try and see if in the end, the result isn’t far happier

Rehashing Eave Height

Rehashing Eave Height

Eave height on post frame buildings seems to be a challenge for some folks. At Hansen Pole Buildings, we do make some efforts to see to it our clients (or more often the builders some of them hire), actually build to the correct height.

How important is it to get this correct? After having a solid foundation, this would probably be number two on the list.

My long term readers are going to begin having drool run out the corners of their mouths quickly, as I have harped (oops – expounded) upon the subject frequently in the past.
Today’s lesson is due to one of our clients who is currently erecting his pole barn. This particular building has overhangs on the gabled endwalls, fashioned by lowering the end truss by the thickness of the roof purlins. This allows for the purlins to run over the top of the purlins to support the overhang. It makes for one sturdy overhang which isn’t going to sag.

The question?

“Where it says lower end truss by 7 inches and 5/8 of an inch? Can you please confirm this? Doesn’t this mean the eave will be lower than 12 feet?”

Mike the Pole Barn Guru Responds:

Our client was spot on with how far to lower the trusses on the end of his building.
Today’s answer on eave height lies with some extended light reading, enjoy: https://www.hansenpolebuildings.com/2015/02/eave-height-2/

Save Me, My Trusses Do Not Fit!

Here is a case where investing in a post frame building kit from people who have actually constructed buildings is a huge asset (am surmising this is not the case, since this person sent the Hansen Pole Buildings Technical Support email address a plea for help).
Reader James writes: “I have a 24 x 60 pole barn. I pulled my outside dimensions from outside of skirt board now on my trusses are an inch and a half long on each side how can I fix this?”

Dear James ~

Since I do not know who supplied your post frame building kit package, I will have to do some guessing as to how your post frame building was designed. Typically questions like this can be answered by whomever provided your plans and materials – and if it is an engineered building, the building engineer should be consulted as well.

A quick solve for anywhere in the country and any method of construction – to the eave outside of all corner and sidewall columns, attach a pressure preservative treated 2×6 from grade, up to the level of the trusses. In most cases two 10d galvanized common nails spaced every nine inches will be an adequate connection. As these 2×6 will be in contact with the ground, they should probably be treated to at least a UC-4B standard. Your building’s skirt board and any other exterior mounted framing can now be attached to the face of these 2×6. Using this method allows for siding to be installed normally, without any undue compensations to get it to lay out properly.

Another possibility – provided the heel plates of the prefabricated light gauge metal connector plated trusses are not in the way, you could cut 1-1/2″ off of the end of each truss, making them 29’9″ to match the width of your building from outside of column, to outside of column. In no case cut through a steel truss plate.

Or, (in cases with recessed or joist hung purlins) attach the eave girts between the overhanging 1-1/2″ of each truss. The end connections end up being a bit trickier here as it requires nailing through the end of the truss, into the end grain of the eave girt.

With stacked purlins, the eave girt can be nailed to the outside face of the columns above the truss.

If the chosen path is any of the last three choices, when the endwall steel is placed, start the first panel of steel 3/4 inch PAST the corner of the building. The corner trim will cover this and it eliminates having to do a lengthwise rip on the last sheet of steel on the opposite corner.

Mike the Pole Barn Guru

Purlin Questions for the Engineering Department: Building Disaster Part IV

Purlin Questions for the Engineering Department

For those readers just joining us, go back to Tuesday through Friday’s blogs to catch up to the following story…

Our client (after discussing possible corrections with one or more builders) poses this:

“I have two questions I’d like to ask of the engineering dept.

1.) Is there an acceptable way to inset the grade boards to be flush with the posts? Perhaps with hangers? If so, it would mean the wall girts would not have to be furred out.

2.) Would building frames for the end wall overhangs, and attaching them to the end trussses a viable option? Or do they feel like the end trusses would need to be lowered so the purlins can be extended?

I don’t know all of the terminology. Hopefully the above makes sense.

Thank you.”

Any proposed “solution” at this point is only a suggestion for discussion. A revised set of drawings should be produced and sealed by the engineer of record to incorporate the ultimately agreed upon repair fix.

Answers…

(1) Place a UC4B Pressure Treated 4×4 block at least 7-1/4″ long on each side of the column at the level where the 2×8 skirt board would attach. Use 3- 5″ Ledgerlocks to attach block to column. Pre-drill for them and stagger to avoid splitting. Drive 6-10d common nails through skirt board into 4×4 block. Cut ends of 4×4 block and 2×8 skirt board to be painted liberally with Copper Napthenate. Place (2) Simpson Strong-Tie LSTA12 straps across each column to tie from one skirt board to the next. Any 10d nails driven through the LSTA12 into the 2×8 PT and block would count towards the total of six.

(2) Building a “ladder” floating in space is far from an ideal solution. If they opt for this, I would want to see an LSTA24 on top of each purlin split 50/50 between blocking in the ladder and the purlin behind the truss, with 10d nails in each hole. Ladder would need to be built of 2×6 and also nailed through the 2×6 on the building side of the ladder, into the top chord of the end truss with 2-10d @ 12″ o.c.

Ultimately repairs can be simple, difficult, low cost or spendy. In the end the least expensive solution for question number one will be to furr out the girts by nailing a 2×4 flat across the columns at each wall girt. Fairly easy to accomplish and not overly expensive in time or materials.

The right way to do number two is to remove all of the purlins from the end bay, take down the end truss, cut the notches into the columns to support it (as detailed in the plans) at the correct height, and properly place the truss. This will entail the purchase of longer purlins, however it will give a much better end result.

And this my friends, is the end to my story about a building “gone wrong”.

There ARE some truly excellent builders: Hansen Building Disaster Part II

There ARE some truly excellent builders…

This just isn’t one of them.

In our last episode, the ‘builder’ had botched the shearwalls. A minor issue compared to what comes next.

This building was designed to have enclosed overhangs on all four sides.  On the endwalls the roof purlins project over the top of the end truss to support the overhang.

I said, “the purlins project over the top of the end truss to support the overhang”.

Obviously this escaped said “builder” as he cut off all of the purlins and fit them nicely behind the end truss.

The end truss was to have been lowered so the purlins could go over the top of it. The distance to lower the end truss is only spelled out twice on the plans, so it could easily have been missed. Well, maybe not easily. There is also a detail on page four of the engineered plans at 1-1/2” per foot which shows exactly this circumstance.

If this wasn’t enough, an entire chapter for the Hansen Pole Buildings’ Construction Manual is devoted to this overhang sequence!

But wait – there is more.

And it gets even (if this is possible) worse!

See the pretty truss on the end of the building? Not only is it 5-13/16” too high, it is designed to be placed into notches cut into each of the end and corner columns.

The lack of adequate bearing on these columns is a huge structural challenge, as under a load there is little to keep the truss from wanting to slide down the face of the column except nails.

When end trusses are properly notched in, there is 2×4 siding backing placed flat on the face of the bottom and top chords of the truss. A horizontal 2×4 is to be placed at mid height of the truss to attach the siding to, so it is not over spanning the capabilities of the siding.

The siding backing on the bottom chord of the truss also serves as bracing to create a three inch thick member, reducing the chances of the end truss bottom chord buckling under extreme loading conditions.

Stay tuned to this channel – the fun is not over yet!

Post Frame Building Clients Can Be So Fun

Post Frame Building Clients Can Be So Fun!

In providing “The Ultimate Post Frame Building Experience”™ Hansen Pole Buildings is not selling buildings to anyone – we are providing a service. If there is such a thing as a past life or lives, I must have been some sort of instructor in a past life. I am so enjoying our clients who want to know about their buildings, how they work and how to get the ultimate strength results from the new post frame building kit packages. These are the clients whom I know will easily construct a finished building with far better workmanship than they could ever pay a builder to do.

One of my current favorites is a Mr. W. I have never had the privilege of meeting him in person, we have not even spoken on the phone. However we’ve had some super email interactions. I could be mistaken, but he seems like the type of person with whom I could sit for hours and discuss buildings over cold adult beverages.

I’d like to share with you a recent exchange between us:
Ralph wrote:

“Thanks for the excellent information! Very encouraging to have these pesky issues put to bed.
I have Joist Hanger questions on the LU28’s that hold the 2×8 Purlins:

1. I assume I will nail perpendicular through the holes? Not angled like the LUS style hangers?
2. 8 nails into the truss? Use all the holes?
a. Double truss should I use 10d x 3” common HDG? Or just use 10d x 1-1/2” joist nails always?
b. Won’t nails into hanger on opposite side hit these nails or cause problems if using 10d x 3”?
c. Single truss should I use 10d x 1-1/2” joist nails?
3. 6 nails into the purlin? Use all the holes?
Use 10d x 1-1/2” joist nails?
4. All the purlins are under compression except at the single truss ends. Should I use SDS screws on the hanger-to-truss ends? The sheet metal will eventually provide the compression needed I’m sure.

Thanks,
Ralph”

To which I replied:
“Mr. W. ~

Thank you for your kind words.

When using engineered hangers, always nail in the direction of the holes (if no “bubble”, so the hangar nailing area is flat, nail straight in). Always nail through every hole which will allow for the fastener to have tips into wood without causing undue splitting. In most instances, only a portion of the holes actually need nails to be adequate to support the appropriate loading conditions, however having open nail holes tends to become problematic to field inspectors and we prefer safety over remorse.

In double trusses use three inch nails, if you place two hangers back to back, you will notice the holes in the flanges do not align with each other for this very reason. Single trusses – use 10d x 1-1/2″ nails. While the nails will prove to be adequate, SD screws (in my humble opinion) are a superior fastener and I encourage their use whenever possible and practical.”

Kindest Regards,

Mike the Pole Barn Guru

For related reading:
Simpson Strong-Tie® hangers:

https://www.hansenpolebuildings.com/2013/08/simpson/

and

https://www.hansenpolebuildings.com/2016/02/hang-those-joist-hangers/

Strong-Drive® Screws (aka SD screws):

https://www.hansenpolebuildings.com/2017/03/simpson-drive-screws/

Joist Hanger nails:

https://www.hansenpolebuildings.com/2013/01/tico-10d-common-nails/

A Serious Case of Roof Steel Leaks

This is one of those “Dear Pole Barn Guru” letters which I feel bad for the client in having to answer. The client has paid good money to have his new post frame building constructed, only to have installer challenges render the end result as far less than ideal.

For your reading pleasure:

DEAR POLE BARN GURU: The Hansen pole barn kit I bought has 26 gauge steel roofing put on twice by a licensed contractor that still leaks profusely. A licensed roofer suggested 50 year shingles. Will the trusses bear the weight of a wooden deck and shingles? What’s the expected life span/warranty on your 26 gauge steel roofing from ABC in SLC? TOM in SHERIDAN

DEAR TOM: I’ve had seen the photos of your roof from the inside, as near as I can tell, the roof purlins were not originally set in a straight line from one end of the building, to the other. It then appears the roof steel was predrilled, causing a plethora of screws to miss the purlins as installation progressed from the end towards the middle. The only real solutions are to add lots of framing under all of the holes (so every screw goes straight into the underlying framing) or to remove the roofing, align the purlins and then install new steel over them. If the roof plane is square, the purlins are placed in straight rows and the roof steel is predrilled to properly match the purlin spacing, there is no reason it should leak – other than plain installer error. Placing screws through holes at an angle, or using caulking is not an adequate repair.

As with most post frame (pole) buildings, the roof has been designed to support the weight of the trusses, roof purlins, minimal roof insulation (to prevent condensation) and the roof steel. In order to support OSB or plywood and shingles, at a minimum the roof would need to have been designed for a 7 psf (pounds per square foot) dead load, rather than 3.3 psf. It might be possible to get an engineered repair to the trusses to increase the load carrying capacity, but it is unlikely it would be an easy, or inexpensive, fix.

The steel warranty information is available on our website at:

https://www.hansenpolebuildings.com/pole-building-faqs/product-warranties/

In your climate, properly installed, your steel roof should last longer than either you or I.

On a side note – a “50 year” shingle typically has a very rapid decline in what percentage of replacement material (no labor) is covered. Here is the true story of shingle warranties:

https://www.hansenpolebuildings.com/2015/03/shingle-warranties/

Termites and Pole Barns

A Buggy Situation

A client writes to Justine (the Hansen Pole Buildings’ Order Fulfillment goddess) this week:

termites“I was hoping to get some advice.  I’m still working on the building having just completed rafter placement and was starting to pull apart the two bundles of lumber for the purlins.  When I started pulling boards out of the bundle I noticed some surface damage that just kept getting worse as I sent through the stack of lumber.  Toward the center there was a large amount of termites, see pictures.  The odd thing was it only affected the stack of 2X6X10′ boards, the other bundle of lumber, sitting right next to it was untouched.  This is really unusual for our area where summers are hot 90-100° with very low humidity <15-20% making termites a very rare issue.  The lumber was stored as instructed in your manual but now we have a probably 1/2 of the 2X6X10′ boards that are damaged significantly.  Since termites are not a large problem in this area and all of the infestation was in the center of a stack of very wet wood (not from any rain or external water) and there was no damage to the stack sitting next to it, I suspect it came with termites but of course I can’t prove that so as disappointed as I am let me get on to the request for advice.  These boards are primarily used for the purlins and horizontal siding support around the outside of the building.  I know the purlins are structural and need to be 100% clean wood, but is some level of damage acceptable for the horizontal boards between the posts?  If so, how much, or is any penetration by the termites into the wood render it unusable? “ 

Personally, I feel bad for the client, however he did take delivery of the materials back in April and on May 3 he wrote to Justine:

“I have all of the material and all is in good shape.  Thank you for all of your support”

On one hand client has received everything in good order, on the other hand nearly four months later there are some challenges. It is possible the lumber was shipped buggy – wildly random things do happen. It is also possible the material got wet in the spring and the heat from the 90-100 degree summer days caused the relative humidity in the center of the unit to increase as the unit was likely paper wrapped. In either case, it ended up as the perfect breeding ground for pesky little critters.

The lumber grading rules are fairly generous about allowable defects, so some of the damaged materials may be able to be used.

Here was Justine’s response (spot on by the way):

lumber damage“We would happy to provide some advice for this situation. Let me first say this is why we stress so much to inspect and inventory wood as they arrive up front. You are probably correct in your conclusion they came with the mites in the bundle. If the bundle would have been opened then we could have probably avoided your current situation.

To answer your question, yes there are some level of acceptable defects in lumber. Keep in mind the wall girts are just as crucial as the roof purlins in supporting the loads of your building.

You can read about these allowable lumber defects on our blog: https://www.hansenpolebuildings.com/2013/12/lumber-defects/


I would generally apply some common sense on how I use certain boards and which ones I decide not to use. I would say first take the boards you deem usable but in the worst shape in locations which don’t provide as much structural value like in blocking locations. For girts and purlins they don’t need to be perfect but anything meeting the allowable defect rules it will work for those locations but I would try to keep the better boards for those two locations. Anything which does not meet the minimum requirements will have to be replaced.”

Moral of the story – regardless of whom you buy your building from, or where the lumber came from, inspect it thoroughly at time of delivery for defects as well as surprises. This allows for anything out of the ordinary to be taken care of promptly, before feelings get hurt. And, always try to use materials as expediently as possible, the sooner they become part of your new post frame building, the happier they will be.

What does 2×6 Lumber Weigh?

Is 2×6 lumber heavy?

ScaleThis is actually fairly important, not just to determine how many boards can be toted around a jobsite by one person, but also in calculating the dead loads which must be carried by structural members such as roof trusses and rafters.

Like most things played around with by engineers, and other people with too much time on their hands, there is a formula to calculate this (please feel free to scream in anguish now):

62.4 X [ G / (1 + G X 0.009) X (m.c.)] X [1 + m.c./100]

Whoo Hoo!! If this isn’t fun…..like watching paint dry?!

Seriously, it is not so tough. G is the value of the Specific Gravity of a known species of lumber. In the U.S. the most popular choices for framing lumber are Southern Pine (G=0.55), Douglas Fir-Larch (G=0.50), Hem-Fir (G=0.43) and Spruce-Pine-Fir (G=0.42).

The moisture content of the lumber is expressed as the “m.c.” above. Lumber stamped as “dry” has a maximum moisture content of 19%.

Picking Dry Hem-Fir and filling the appropriate blanks into the formula gives, 62.4 * [.43 / (1 + .43(0.009)(.19)] * [ 1 + (.19/100)] = 26.86 pcf (pounds per cubic foot).  So a 12 inch cube of dry Hem-Fir should weigh 26.86 pounds.

A cubic foot has 1728 cubic inches (ci). 2×6 has finished dimensions of 1-1/2 inches by 5-1/2”, or 99 ci in lineal a foot. Taking the weight calculated above (26.86 pcf) dividing by 1728 and multiplying by 99, gives the weight of a foot of Hem-Fir 2×6 as 1.539 pounds (lbs).

Want to pack around 12 foot long 2×6 lumber? In Hem-Fir, it will weigh 18.466 lbs.

Think of dead loads as the weights of materials which are permanent. In the case of a typical pole barn roof, purlins will always be there supporting the roof sheathing.

If purlins are placed two foot on center, up the slope (or run) of the roof, the dead load attributed to the purlins can be determined by dividing the weight per lineal foot (1.539 lbs calculated above) by the spacing of the purlin (in feet) divided by the cosine of the roof slope. In this case, it is roughly 0.81 psf (pounds per square foot).

Not a lot of weight, but it still must be accounted for. As well, 60% of dead load weight can also be used to counteract the forces of uplift.

So much for the math lesson of the day.

Now, aren’t you glad you asked?

Purlins: Missing Screws

Just in case I have never mentioned how much I appreciate the questions posed to me by Bob, one of the Hansen Pole Buildings’ Designers, I will do so here.

Bob writes,

I got into a discussion with a gentleman in Kansas that liked our design approach (post spacing, double interior trusses, purlins on edge, etc.) but has no faith at all that he or his crew would hit all of the purlins on edge with the roofing screws.  We discussed pre-drilling and I had him off the ledge, but when the discussion of book shelf girts came up, he started breathing hard again.  Now I’m pretty sure book shelf girts is the only option these days for any pole barn, but it seems I’m dealing with a client that is afraid of pre-drilling and his ability to square his roof and building.

One of your blogs describes the simple fix for a missed hole (“Either push the underlying purlin up towards the peak of the roof, or push it down towards the eave line until the pre-drilled hole aligns with the center of the purlin.”) but I’m having trouble imagining being able to push a purlin that is in place that far.  And if a purlin is pushed into position as described, what happens upon release?  Maybe this is a situation that I could appreciate more with personal experience, but I’m not getting there with my imagination alone… and as a result I won’t be terribly convincing that it’s really that easy.”

The beauty of pre-drilling pilot holes for roof and wall screws is perfectly straight lines. Straight screw lines are truly a thing of beauty – there are few things in life as pleasing as looking across a wall or roof and seeing the screws lined up like soldiers.

In an ideal world, every piece of lumber would be absolutely perfectly straight, and remain this way forever. Lumber, even though it is produced in a factory (a sawmill), is organic – it really wants to return to its nature as a tree. This means it wants to warp, twist, cup, crook or otherwise deflect.

The wonderful thing about lumber is it will flex a long way in the weak (1-1/2” narrow direction). This is exactly why wall girts placed flat on the outside of columns rarely meet the requirements of the codes – they deflect too far!

With both ends of a roof purlin restrained by an engineered joist hanger, or wall girts restrained at each end by solid blocking, the only portion of the framing which will be a potential for a “shiner” is as the girt or purlin approaches the middle of the span.

In the Hansen Buildings product guide (downloadable free on our website), is a photo of my feet (seriously) – as I stand on a 2×6 laid flat (I am standing on the wide 5-1/2 inch face. The 12 foot long 2×6 probably bends close to six inches at the center!

Whilst Bob (and his client) may be concerned about the ability to move purlins or girts up or down, the reality is – wood is forgiving, it can be moved remarkably easily to where it should have been had we been living in the previously mentioned ideal world.

And remember, steel roofing and siding functions much like very strong, very thin plywood. Once the screws are in place, the strength of the screws and the rigidity of the steel will easily hold everything where it ought to be.

FOOTNOTE: (Added by JAHansen, Mike’s wife) – Coming into the pole building business over a dozen years ago, knowing absolutely nothing about lumber, steel and the like, I can certainly identify with the skeptical client.  When you haven’t experienced the ease of building with lumber, 1-1/2” sounds pretty small to “hit” with a screw!

However, I can testify as a true novice at building, Mike’s words are straight as an arrow.  I’ve personally assisted on half a dozen buildings over the past years, and I can say almost every time there was a purlin or girt that looked like the screws were going to “miss” – especially on the wall girts where the weight of the wood sometimes caused the center to droop down an inch or more.  The holes near the ends were not a question for putting the screws into the wood. Because they are near the ends, the holes were “right on”.  We made sure on the center of each purlin or girt to use a block of wood as a support (wall girts) or in case of the roof purlins a “lever” to push the center into alignment.  It’s much easier than it sounds, and yes, the screws were dead on.

Thousands of pole buildings have been built, with no leaking roofs.  That should be solid proof, but if you still have doubts – go watch a pole building being constructed.  Seeing is believing.