Tag Archives: roof purlins

NEW Hansen Pole Buildings Roof Purlins and Connections

NEW Hansen Pole Buildings Roof Purlins and Connections

Hansen Pole Buildings has always utilized what is known as recessed roof purlins, where purlins are placed between roof truss top chords.

Top of roof purlins and top of trusses are at same height and purlins were connected with typical standard joist hangers. This resulted in clients (or their building erectors) having to carefully place joist hangers to keep purlins from being too high, or too low in relationship to their respective trusses. Adding to this complexity, joist hangers were to be attached to double trusses with 10d common nails (.148” diameter x 3” long).

We wanted to make this into an easy connection, so now are providing a Simpson Strong-Tie PFDS26B (for 2×6 roof purlins) or PFDS28B (for 2×8 roof purlins). This part easily slides into place over a pair of trusses, automatically establishing proper purlin height. It fastens to truss pairs with SD9212 screws – three each side for 2×6, four each side for 2×8. These screws also are used to pair truss top chords, where previously two or three 10d common nails were required, usually roughly every eight or nine inches. SDWS9212 screws are also used to attach hangers to purlins, rather than 10d x 1-1/2” joist hanger nails.

Roof purlins were previously evenly spaced, resulting in some challenging measurements. We now have standardized spacing to fall so measures are evenly divisible into eight (8) feet. Examples are 32”, 24”, 19.2”, 16” all of which are keyed to markings on tape measures.

By again utilizing high strength msr lumber for roof purlins, spans previously needing to be 2×8, or in some cases even 2×10, can be done with 2×6 lumber.

We have even made it easy to quickly identify lumber to be used as roof purlins – one end will arrive spray painted PURPLE for ‘field’ purlins and PINK for purlins in high load areas – such as drifting near ridge in snow country. If you (or your erector) need to trim a board, please trim unpainted end, as this makes it easy for you (if you hired a builder) or an inspector, to quickly identify wood as being properly utilized!

We have improved speed and accuracy of installation, reduced dead weight of roof system and increased system strength and reliability!


I mentioned how double truss top chords are usually nailed together with lots of nails. Well, we are now connecting truss webs and bottom chords with Simpson SDWS16300 structural screws – spaced much further apart than nails were. Fewer and stronger fasteners!

Call 1.866.200.9657 TODAY to participate in “The Ultimate Post-Frame Building Experience”.

And, don’t forget to watch for our next article!

Roof Purlins for a U.K. Pole Barn

Roof Purlins for a U.K. Pole Barn

Reader KEN in CHERTSEY, U.K. writes: “With 10.8′ truss spacing @ 19.64° slope and 39″ purlin spacing, would 2″ x 6″ purlins (on edge) be sufficient for steel clad roof unlikely to ever see more than 4″ snow for more than a few days?”

I don’t often get to answer questions posed from outside North America. I toured England and Scotland for 23 days in 1997, however sadly did not get south of London. Not knowing what species of lumber you are using, calculations below are based upon weakest of common North American framing lumber – Southern Yellow Pine (SYP) with a Fb (fiberstress in bending) value of 1000 psi (pounds per square inch), equal to 6.89 N/mm2. This would fall between your common designations of C16 (5.3 N/mm2) and C24 (7.5 N/mm2). The following describes 2×6 SYP #2 purlins spanning a 10.8′ bay, with an on-center spacing of 39″ (sf).

Purlins are recessed between rafters with their top edges flush with rafter top edges. Purlins are mounted to rafters with Simpson Strong-Tie LU-26 joist hangers at both ends.

Effective simple beam span length (le) will be taken as 126.6″.

Applied loads

Dead load, D

Dpurlin: dead load from weight of purlin itself
Dpurlin = purlin density × ((b × d × le) / (sf × l))
Purlin density found via NDS Supplement 2015 Section 3.1.3:

density = 62.4 × (G / (1 + (G × 0.009 × moisture content))) × (1 + (moisture content / 100)) moisture content = 19%
density = 62.4 × (0.55 / (1 + (0.55 × 0.009 × 0.19))) × (1 + (0.19 / 100)) density = 34.56 pcf
Dpurlin = 34.56 pcf × ( ( 1.5″ × 5.5″ × 126.6″ ) / ( 39″ × 129.6″ ) ) × 1/12 in/ft
Dpurlin = 0.599 psf

Roof designed for 29g corrugated steel
Dead load from weight of steel (Dsteel) based on values from the American Building Components catalogue:
Dsteel = 0.63 psf

D: dead load
D = Dpurlin + Dsteel
D = 0.599 psf + 0.63 psf
D = 1.229 psf

Project load to a vector acting perpendicular to the roof plane:
D = D × cos(Θ)
D = 1.221 psf × cos(0.343)
D = 1.157 psf

A conversion from psf to psi will be made for ease of calculation:
D = 1.157 psf × 1/144 psi/psf
D = 0.008 psi

Roof live load, Lr

L: roof live load
Lr = 19.717 psf (this is minimum roof load allowed by our IBC code)

Project load to a vector acting perpendicular to the roof plane:
Lr = Lr × cos(Θ) × cos(Θ)
Lr = 19.717 psf × cos(0.343) × cos(0.343)
Lr = 17.489 psf

A conversion from psf to psi will be made for ease of calculation:
Lr = 17.489 psf × 1/144 psi/psf
Lr = 0.121 psi

Bending test (fb / Fb′ ≤ 1.0)

Fb: allowable bending pressure
Fb′ = Fb × CD × CM × Ct × CL × CF × Cfu × Ci × Cr
CL = 1
CM = 1 because purlins are protected from moisture by roof
Ct = 1 NDS 2.3.3
CF = 1 NDS Supplement
Ci = 1 NDS 4.3.8
Cr = 1 NDS 4.3.9

S: section modulus
S = (b × d2) / 6
S = (1.5″ × (5.5″)2) / 6
S = 7.563 in3

w: pounds force exerted per linear inch of beam length
M: maximum moment
fb: maximum bending stress

Dead + Lr

CD = 1.25
Cfu = 1 Fb′ = 1000 psi × 1.25 × 1 × 1 × 1 × 1 × 1 × 1 × 1
Fb′ = 1250 psi

w = (D + Lr) × sf
w = 0.129 psi × 39″
w = 5.031 pli

M = (w × l2) / 8
M = ( 5.031 pli × (126.5″)2 ) / 8
M = 10063 in-lbs

fb = M / S
fb = 10063 in-lbs / 7.563 in3
fb = 1330.7 psi

fb / Fb′ ≤ 1.0
1330.7 psi / 1250 psi > 1.0
1.065 > 1.0

So, our Fb = 1250 example would not be adequate

To use C16 2×6 spacing would need to be reduced to 27″ on center; C24 2×6 could be used by reducing spacing to 38″ on center.

Sheathing Under Portion of Steel Roof

Sheathing Under Portion of Steel Roof

Loyal and very kind reader JOSEPH in LaPORTE writes:

“Good afternoon, let me start off by saying that I’m extremely appreciative of your content. The reason for my email is that I’ve been contracted to build several 30x180x9 post frame buildings and my plans are calling for 5/8” OSB for the center 60’ of the buildings. Do you have a diagram that shows how to “lower” the purlins 5/8’s to reduce the transition? Thank you in advance.”

Thank you very much for your kind words.

Cases such as yours should always (but rarely are) specified by your building’s Engineer of Record on sealed building plans, but somehow rarely are. Our third-party engineers take it upon themselves to actually account for situations such as these and don’t just leave it up to contractor’s whims to resolve.

Your solution is actually fairly simple – in areas with OSB order trusses with standard 1/4″ heel cuts (vertical ‘butt cut’ on end of bottom chords). For areas without OSB have heel cuts increased by thickness of OSB (in this instance heel cut would be 7/8″). This will allow for all truss carriers to be set to same height and result in a smooth roof plane.

As you have trusses on top of truss carriers, where your transition in heel heights occurs, attach a 2×4 ledger alongside top chord of first 7/8″ heel cut truss (at extreme edges of OSB sheathed area) to support ends of 2×4 purlins laid flatwise.

Somewhat unrelated to your question – I can only assume OSB has been added due to buildings being very long and narrow (aspect ratio is 6:1). If this is indeed your situation, then steel roofing by itself is unlikely to be able to carry applied shear loads. However, greatest shear is at each endwall, not at center of roof. I would have expected to see a need for OSB closest to each end, rather than in center 1/3rd. You might want to point this out to buildings’ engineer as (given information at hand) it could prove to be a serious design flaw and could potentially result in a failure situation under extreme wind loads.

Properly Insulating Between Roof Purlins

Properly Insulating Between Roof Purlins

Reader SAM in MATTAWAN writes:

Hi, I have a wood framed pole barn that is fairly unique in design and doesn’t have any “attic” space. It’s very similar to what a steel building would be. There are 2×8 roof purlins to support OSB sheathing. My question is regarding ceiling/ roof insulation and venting. I will be doing a shingle roof and vinyl siding. Since there is no attic space, are ridge and eave vents still required? And what would be recommended for insulation? Spray foam would probably be ideal, but more than likely out of budget. Would fiberglass batts be ok to use right up against roof OSB? Thanks.”

According to Martin Holladay (Green Building Advisor):

Experts usually advise builders that you can’t install fiberglass insulation directly against the underside of roof sheathing. If you want to install fiberglass between your rafters, you have two basic choices: either include a ventilation channel between the top of the fiberglass insulation and the underside of the roof sheathing, or install enough rigid foam above the roof sheathing to keep the roof sheathing above the dew point during the winter. These rules were developed to prevent damp roof sheathing.”

With post frame construction ‘purlins’ would replace ‘rafters’ above.

You have some options….

Per IRC R806.5 (4) In Climate Zones 5, 6, 7 and 8, any air-impermeable insulation shall be a Class II vapor retarder, or shall have a Class II vapor retarder coating or covering in direct contact with the underside of the insulation.

IRC R806.5 (5.1.1) Where only air-impermeable insulation is provided, it shall be applied in direct contact with the underside of the structural roof sheathing.

My note – this would be closed cell spray foam

IRC R806.5 (5.1.2) Where air-permeable insulation is installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing in accordance with the R-values in Table R806.5 for condensation control.

My note – Van Buren county is in Climate Zone 5A. IRC Table R806.5 requires a minimum of R-20 for your Climate Zone. This would require R-20 rigid insulation boards on top of your roof OSB, you could then use your choice of batt insulations between purlins.

IRC R806.5 (5.1.3) Where both air-impermeable insulation and air-permeable insulation are provided, the air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing in accordance with item 5.1.1 and shall be in accordance with the R-values in Table R806.5 for condensation control. The air-permeable insulation shall be installed directly under the air-permeable insulation.

My note – this would require R-20 (roughly 3 inches) of closed cell spray foam applied directly to the underside of your OSB sheathing, with a balance of insulation (either batts or open cell spray foam) applied directly below between purlins.

In summary – do not vent your eaves and ridge, and fiberglass batts between roof purlins may not be used directly below roof sheathing without either R-20 insulation directly above or below roof deck.

Through Screw Steel Roof Leaks

Through Screw Steel Roof Leaks

Reader DEBRA in KERSEY writes:

“20 years ago my husband Jim and I bought a 40×60 pole barn and it’s been wonderful except for the leaks in the roof. After reading some of your online articles about roof leaks, I wanted to get in touch with you and see if any materials had improved since 2004. Jim wants to reseal with sealant every screw in roofing so I want to make sure we know if there are any upgraded materials you are selling for your older building kits that might help with this issue. Jim is now 77 and I really don’t want him up on that roof for this job and am hoping you have an alternate idea for me Looking forward to hearing from you.”

Properly installed, through screwed steel roofing, with correct screws, on a fully engineered post frame (pole barn) building should never pose a leaking challenge.
Mike the Pole Barn Guru says:
Let’s look at why buildings leak.

If leaks are discovered immediately following construction completion they are most often from:

Roof steel lapped in wrong direction (three-quarter lap goes OVER full lap – even “professional” builders make this error)

Screws not properly being seated (under driven or driven at an angle allowing water to seep in around shank of screw, or over driven crushing gasket under screw head)

Screws missing roof purlins (most often due to roof steel not being pre-drilled, or purlins not being adjusted to straight during installation)

No provision to control condensation (this is most often seen in Spring and Fall when dew points are higher than ambient air temperatures). This truly is not a leak, but feels like one. It can be solved by application of two inches of closed cell spray foam to the underside of roof steel.

Closures missing from beneath the ridge cap.

Leaks over time:

Improper screw patterns (screws must be placed into each roof purlin, at the side of steel ribs away from overlap then every nine inches. At eave and ridge, screws must be each side of each high rib)

Screws were placed in high ribs, rather than in flats (it is impossible to perfectly seat every screw into crowns of high ribs. Even using a screw gun with a clutch, variations in stiffness of roof purlins cause screws to not all be identically driven. As wind cycles into your building roof, shank of screws in void between crown of high ribs and purlins will flex slightly and over time cause slotting around shanks)

Inadequate screw diameters – we subjected a full scale roof to cyclical loads, to failure. We found industry standard #10 screws in areas of high shear loads (at eave and ridge) began slotting below fastener heads. When slots became long enough, roof leaked.

Screws without EPDM gaskets below grommets – most screws have neoprene rubber gaskets. Neoprene is not UV resistant and will deteriorate in a matter of very few years.

Poor screw coatings – cheap screws have only minimal electroplated galvanization. Once this wears through, screws will rust and decay quickly.

There is no sealant capable of adequately solving individual roof leaks beyond just a very short term. I have tried it myself and it is not an approved method of correcting leaks endorsed by any steel roll former. There are roofing coating systems advertising their ability to completely seal entire roofs. I have never used one, so cannot speak to their effectiveness, durability or how they look.

Without knowing more about your building’s leak specifics (where does it leak, when does it leak, how long has it leaked) it is difficult to recommend a possible solution or solutions. In most cases, provided ridge closures are intact and not decayed, if screws were placed in flats – replacing all screws with larger diameter, longer screws, powder coated with EPDM gaskets can resolve leak issues.

Snow Load, Clear Span Scissor Trusses, and a Window Replacement

This Wednesday the Pole Barn Guru answers reader questions about whether or not a 30 year old building correct snow load, the possibility of clear spanning scissor trusses to eighty feet, and assistance with the replacement (or repair) of a window in a Hansen Building from 2014.

DEAR POLE BARN GURU: How do I figure out the snow load rating for my Morton barn since it is 30 years old and it has poles, trusses and purlins. The purlins are 2 x 8 and 20″ on center with 36 of them over 50 feet and 6 trusses nine feet tall and spanning 50 feet in length and 8 feet apart. Is the rating more than 55psf or not? MARK in PORTVILLE

DEAR MARK: Your roof purlins appear to be adequate to support this type of a snow load. As to trusses, I would reach out to Morton Buildings with your site address and they should be able to pull up truss drawings for your building. If not, you would need to retain services of a Registered Professional Engineer who could do an actual inspection of your trusses and run calculations to determine exactly their capacity.


DEAR POLE BARN GURU: Can you 80 foot clear span scissor truss on a 14-16 foot eave? Commercial shop use. Northern Indiana. ANDREW in AVILLA

DEAR ANDREW: Can and should are not often same.

Yes, an 80 foot clearspan scissor truss can be done, expect it to be either designed with a flat top and a peak “cap” or to be parallel chord with a deep heel and joined together onsite at center. It will prove to be far more economical to utilize flat bottom chord trusses with a taller eave height – this would also allow for full height interior clearance from wall-to-wall. One of our Building Designers will be reaching out to you to further discuss your building needs.


DEAR POLE BARN GURU: I built my Hansen monitor pole barn in 2014. It took this long but a nasty storm broke out my window in the upper floor of the building. What’s the best way to replace a window and frame in a metal sided building. Do I need to remove the surrounding ribbed sheet metal panels and are there any tricks to that? With an eight-year-old build should I use new screws as the gaskets might be dried out from baking on the southern facing wall? Any methods you can suggest to get me going are appreciated. Thanks DAVE in FERNLEY

DEAR DAVE: Unless your window’s vinyl frame was actually damaged, in most instances a glass company can do a repair of just broken glazed portions. I would suggest a call to Capital Glass in Reno (775)324-6688 as this appears to be in their wheelhouse and they service Fernley.

Rarely does glass repair require steel panels to be removed. In an unusual case where there is no alternative, and steel must be taken off, your siding screws have EPDM gaskets. These are UV resistant and have a manufacturer’s warranty they will outlast your steel siding.

Should you have some photos of your completed building, we would greatly appreciate your sharing them with us.


Basic Stats for Post Frame Home Floor Plans

Basic Stats for Post Frame Home Floor Plans

If there is a single commonality among us humans it is this – we are dimensionally challenged. This situation is even more so crucial when it comes to planning your new post frame home.

Here are a few tips to help you out:


Measure from the pressure treated splash plank bottom, to intersection roofing underside at sidewall columns. This is not to be confused with ceiling height (also known as interior clear height).


For discussion’s sake (and as most post frame homes are concrete slab on grade), set a “zero point” at exterior grade (pressure treated splash plank bottom), slab top will be at +3.5 inches.

To create eight foot finished ceilings requires 8’ 1-1/8” (allows for 5/8” sheetrock on ceilings). This puts us at 8’ 4-5/8”.

Now allow for roof system thickness. With recessed (joist hung between trusses) roof purlins, 6-1/16″ for truss heel height with 2×6 top chord at 4/12 slope (provided you are using closed cell spray foam insulation between purlins).  Minimum eave height would then be 8’ 10-11/16”. If using blown-in insulation truss heel height should be insulation R value divided by 3 plus 2″ to allow plenty of eave to ridge air flow above insulation.

What about two floors?

In order to be able to run utilities (e.g. plumbing and ductwork) through second floor supports, I highly recommend 4” x 2” prefabricated wood floor trusses. Generally truss depth will be about an inch for every clear span foot with a 12 inch minimum.  Adding an arbitrarily chosen 16” deep floor truss and 8’ ceiling on second floor to example in previous paragraph puts eave height at 18’ 4-9/16”.

Stairs challenge even many experienced builders. Finished width must be no less than three feet (if planning allows, four feet is so much nicer), allow for drywall on each side when determining interior framing of stair opening width. In most jurisdictions maximum tread rise is 7-3/4” and minimum run is 10”. In above example, second floor top is 9’ 5-7/8”, so stairs would need at least 14 treads, taking up at least 140” (11’ 8”) horizontally. At stair top and bottom a space, in travel direction, equal to stair width must be provided. Headroom along every point of finished stairs must be no less than 6’8”.


Different providers measure their building footprints differently – some use wall girt outside at ‘call out’ while others use column outside and are three inches greater in width and length, this will need to be accounted for in room dimensions.

Exterior walls with bookshelf girts will be wall column thickness plus 1-1/2” for girts protruding outside of columns. With 3 or 4 ply 2×6 glulams or 6×6 columns allow 7-1/4” plus interior sheetrock thickness. Interior 2×4 walls with ½” sheetrock on each side end up 4-1/2” thick.


Below are popular post frame home rooms and their average square footage, in three categories (listed as small/medium/large):

Entry Foyer (65/89/138)
Kitchen (193/275/423)
Walk-In Kitchen Pantry (17/31/51)
Great Room (487/481/680)
Dining (148/196/281)
Living (256/319/393)
Family (311/355/503)
Recreation (216/384/540)
Entertainment/Media (140/192/280)
Master Bedroom (231/271/411)
Master Bathroom (115/144/210)
Secondary Bedrooms (130/139/178)
Other Bathrooms (93/146/313)
Laundry (67/87/145)
Utility/Mud Room (30/48/80)

Always allow adequate space for hallways (same minimum width rules apply as stairs).

Roof Purlins for a Bar Joisted Lean-To

Roof Purlins for a Bar Joisted Lean-to

Reader JIM in MOORESBURG writes:

“First, I have spent the last 3 hours reading around your site and am impressed. I appreciate the manner you answer questions on your site”, respectful and factual with no hint of disrespect (even if deserved) in your replies. Professional and well done! Second…My question is about correct purlin sizing/spacing on a lean-to shed roof 48ft long 25ft deep with 12ft bar joist spacing spanned by these purlins. (this is an open front machine shed). I wish to size for the snow load that occurs here (mountains of East Tennessee!) about once every 15 yrs which is 2 ft of snow. Purlins will be bolted into “U” shaped brackets welded to the tops of the bar joist similar to the design used on many kit pole barn metal trusses. My attempt to calculate purlin size/spacing results in using 2x8x12′ purlins at 24″ spacing but too many assumptions on my part to be comfortable yet other detail…Bar joists attached to post (in ground) adjacent to an existing wood barn. Roof Metal is Type “R” deep rib. Yes…this is DIY with materials from my surplus pile:) thanks.”

Thank you for your kind words. Our eldest son and his lovely bride lived in Maryville for many years, so I know where you are and have driven in your area.

Two feet of snow should give roughly a 25 psf ground snow load (https://www.hansenpolebuildings.com/calculating-loads/). Without an engineer’s review, your attempt at calculations look as though they should be plenty adequate – PROVIDED:

Roof slope of existing wood barn and lean-to are the same and in the same roof plane.

Otherwise you will have either an accumulation of snow at a steeper-to-flatter roof plane, a slide off load, or drifting to account for. If any of these are your case, then you should contract a Registered Professional Engineer for an accurate structural design. Any of these situations could easily cause an overload of your bar joists as well and should be validated.

Don’t Let Valleys Get You Down

When it comes to post frame barndominiums, rooflines run from simple gabled roofs, to complex designs including hips, valleys, reverse gables, etc. Basically, if you can imagine it, post frame can provide a design solution.

Loyal reader (and my Facebook friend) RUSS in PIPERSVILLE writes:

“Hello Mike. As we get a little further along with our design I would like to ask for your opinion. I read in past blog topics that you don’t recommend designing roofs with valleys when going metal over purlins. Our current plan has a large reverse gable on the front of the house covering the entry and porch and our utility mechanical room is a reverse gable room attached at the rear. All roofs are 6/12 pitch. I’m a bit worried about getting the details right. Is it that difficult to install the metal roof correctly over purlins, or should I just consider installing solid sheathing with metal over? Perhaps forego the metal and return to wood deck and shingles? Tom Z. has been a help in explaining how the gables must be framed but I must confess that the details don’t leave me all warm and fuzzy about the roof construction. Any insight you can offer is always appreciated.”

Mike the Pole Barn Guru says:
If I led you to believe I have issues with valleys on steel roofing over purlins I somehow took you astray.

In order to have a successful valley, these steps are followed:

Main roof is framed up, including purlins across area where reverse gable will intersect. 2×12 blocking is then placed between main roof purlins, centered on what will eventually be the middle of the valley. This provides a landing point for intersecting roof purlins from reverse gable (next to be installed). Once these purlins are in place, any reflective radiant barrier (RRB) is installed (I prefer using roof steel with Integral Condensation Control to a RRB). Valley flashing is then installed. We furnish Emseal® self-expanding foam closures to seal between valley flashing and roof steel, following slope of valley flashing. Roof steel is then applied and you are buttoned up tight.

Most challenging parts of assembly are cutting intersecting roof purlins (besides cut being at a 26.6 degree angle along wide face of purlin, cut also needs to be done at 26.6 degrees from perpendicular to compensate for slope of intersecting purlins from vertical) and cutting roof steel at valley to end up with a nice straight line up valley. Neither one is actually beyond most people’s abilities.

There really is no structural advantage to solid sheeting your roof and even the best of shingles have a very poor warranty and I cannot, in all good conscience recommend them as a practical design solution.

For extended reading on Emseal® closures: https://www.hansenpolebuildings.com/2016/03/emseal-self-expanding-sealant-tape-closures/

Temporary Client Insanity – Truss Problems?

Temporary Client Insanity – Truss Problems? 

Long ago someone told me during the course of any construction project there comes a time when every client goes absolutely bat-pooh crazy. Personally, even knowing what I know, I am guilty of freaking out and having had a case of temporary client insanity during our own remodel and construction projects for our home.

For hyperventilation they have people breath from a brown paper bag, in my case – perhaps a plastic bag over my head and tied tightly about my neck would have been more appropriate.

Below I will share a client’s concerns. He remained much calmer (totally appreciated) during this process than I might have. He wrote to Justine (Hansen Pole Buildings’ Master of All Things Trusses):

“Justine, one more thing, the top chords of the trusses show 2×8 and the trusses were delivered with a 2×6 top chord, so all the bracing (purlins) will be hanging down. This roof is going to be insulated.

Also, the double trusses are not fastened together and I think I should have more than 1 set of scissored trusses.”

Our Technical Support response:

Building plans are drafted prior to receipt of truss drawings, so trusses as drawn on your plans are merely a depiction of what they may look like. Top and bottom chords as well as internal diagonal webs may be entirely different. The roof slopes will be accurate. Your building’s roof purlins certainly may hang below roof truss top chords, as this has no bearing upon your ability to insulate (please refer to Figure 9-5 of your Hansen Pole Buildings’ Construction Manual). As your roof has a Reflective Radiant Barrier, if you intend to use batt insulation between purlins, make sure to use unfaced insulation without a vapor barrier on underside, otherwise moisture can become trapped between two vapor barriers. This can lead to ineffective damp insulation as well as potential mold and mildew issues.

Per change order #3 your building is to have standard trusses in front 24 feet and a vaulted ceiling in rear 24 feet. With a pair of scissor trusses at 12 feet in front of rear endwall, this allows for the rear 24 feet to be vaulted and front 24 feet to have a level bottom chord.

Truss assembly people are not carpenters – and rarely do truss manufacturing facilities even have nail guns. It also avoids nail wounds from inexperienced or inappropriate use. As an example – back in 1979, I was shopping for a new employer designing and selling trusses. I interviewed with Tilden Truss, near Seattle. They used air guns firing a “T” staple to initially set steel truss plates. Their fabrication shop ceiling was covered with hundreds (if not thousands) of these “T” staples!

You will find it much easier to maneuver single trusses around your building site, than twice as heavy double trusses.

Please feel free to address any building assembly concerns to TechSupport@HansenPoleBuildings.com.

Another crisis averted.

The Ultimate Post Frame Building Experience

Hansen Pole Buildings is on a mission to provide “The Ultimate Post Frame Building Experience™”. (Read about “The Ultimate Post Frame Building Experience™” here: https://www.hansenpolebuildings.com/2016/06/ultimate-post-frame-experience/) In doing so, we often make what I will refer to as ‘tweaks’ to make not only our clients’ experiences better, but also their new post frame buildings better.

About Hansen BuildingsWe look for trends in questions asked by owners of existing pole barns – usually not even those we provided! There are a couple of these our team has decided to address and we have so far done a very poor job of letting our clients know we have done so.

Lesser of these items are folks who decide, for whatever reason, they would like to add either plywood or OSB between their new post frame building’s roof purlins and roof steel (https://www.hansenpolebuildings.com/2017/03/osb-steel-roofing-pole-buildings/).

Near universally pole barn builders and kit suppliers (as well as most truss manufacturers) have designed trusses with barely enough load capacity to meet minimums. In most instances, actual weight of materials (dead load) of roof truss top chords is around 2.5 psf (pounds per square foot). This is enough to account for truss weight, roof purlins, some sort of reflective radiant barrier or other minimal condensation control, as well as light gauge steel roofing. We have been using 3.3 psf just to give a little extra cushion (roughly 1/3rd more capacity).

½-inch plywood and 7/16-inch OSB both weigh 46 to 48 pounds per four foot by eight foot sheet or 1.5 psf. In order to account for possibilities of someone wanting to add one of these sheathings during building assembly, Hansen Pole Buildings has opted to increase our design top chord dead load to five psf for clearspan trusses up to and including 40 feet. This is DOUBLE minimum requirements.

Tomorrow, I will share with you a solution to an all too frequent challenge.

Stay tuned……

Dancing With the Posts

Reality television watchers have suffered through 384 episodes of the ABC networks, Dancing with the Stars hosted by Tom Bergeron since 2005. On occasion, it seems some of our clients (or much more often their builders) have done some posts (as opposed to pole) dancing when placing columns for their new building. A certain amount of randomization can be accommodated, as found in this real life scenario:

Our client contacted his Hansen Pole Buildings’ Designer Rick recently, with this information:

“(name withheld) has a question about what to do with the bottoms of his posts being off and how it will affect his roof purlins. 

He sent this diagram showing how his posts are off: 

pole layout

Red circle is 3 inches off 

Blue circle is 1 ½ inches off 

The question is, does he just set the tops of his columns where they are supposed to be, or does he add a 2×6 to the side of one post?”

From front to back on the left side of the building the now poured into concrete column spacing is: 120”, 144”, 144”, 144”, 119.5”. Other than the rear bay being ½” short, it is spot on.

Now, for the right side – 117”, 145.5”, 144”, 144”, 121.75”. Those of you who pulled out your calculators already know the right side is ¾” longer than the left, as well as the columns not aligning.

In the most typical (as it allows for least cost, fewest holes to be dug and more long term design flexibility) Hansen Pole Buildings construction, double trusses are notched into the sidewall columns and 2x purlins are joist hung on edge between them. For ease of construction and builder sanity, it is ideal for the purlins in each bay to be able to be cut to the same length.

There is a solution, which I passed along:

“Construction Tolerances Standard for Post-Frame Buildings” allows for columns to be 1% out of plumb, which on a 16′ eave would be 1.92″.

He certainly wants to have trusses placed on columns so as to be able to cut all of the purlins to the same length in each bay.

Working from bottom of page up –

First pair up page (diagram sent by client) – tip left column forward (down page) 1-1/2″, right rear (up page) 1-1/2″

Next three on left tip forward 1-1/2″

Rear – left corner tip outward (back) 1/2″ right corner tip forward 1/4″

The posts will easily flex this far, so it shouldn’t be a huge issue.

This is just one of many reasons why post frame building roofs should be framed (as well as sheathed) prior to any wall framing being done. In the event the walls would have been framed prior to this, solving the challenge would have proven to be difficult, at best.

Thankfully, we have a very astute client who contacted our Technical Support Department for assistance as soon as they were aware of something gone awry.

Dear Pole Barn Guru: Toe Nail Purlins or use Hangers?

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

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU:It looks like your double truss system uses hangers between the trusses rather than the boards running on top of the trusses.

When I see these used on decks it sometimes looks like the nails that are toe-nailed into the connectors don’t do anything as they are at the very end of the board. The board splits or chips out.

Have I just seen it done improperly or perhaps I’ve seen the wrong types of hangers or nails being used?

I’m guessing you’ve seen your fair share of improperly installed connectors so I’m looking forward to what you have to say.


DEAR NOVICE: The Hansen Pole Buildings double truss system (as well as the special requests we get for widely spaced single trusses) do utilize engineered steel connectors to attach the roof purlins to the sides of the trusses.

As an experiment, I looked today at the hundreds of hangers we have installed on a 42’ x 120’ self storage building being constructed for Eric (one of the Hansen Pole Buildings owners). All of the hangers for the project are manufactured by Simpson Strong-Tie:


The hangers installed are their LU26, LU28 and H1 brackets.

The roof purlins being nailed into are kiln dried 2×6 and 2×8 of Douglas Fir (DFir) and SPF (Canadian Spruce-Pine-Fir). All of the nails used in the hangers are joist hanger nails (#10 x 1-1/2” long) which are designed specifically for use in engineered metal connectors.


I was unable to find a single case on Eric’s large building with hundreds of joist hangers where the nails contributed to an end split in a purlin or a portion of the roof purlin being split away.

I do have some theories as to what may be the cause of what you have seen on decks.

Theory #1 – other than a few specially designed brackets, joist hangers are designed for the nails to be installed at right angles to the wood. Toe-nailing (driving the nails in at an angle) could be responsible for splits.

Theory #2 – in your part of the country, the vast majority of lumber used for decks is pressure preservative treated Southern Yellow Pine (SYP). It could very well be the SYP lumber is more susceptible to splitting than the species of wood provided for use in the building we are currently constructing.

Simpson Strong-Tie produces millions upon millions of engineered steel connectors every year – if there existing an inordinate (or any) number of failures due to the use of their products, they would be on top of making changes in the design to prevent them.

Me – if my choice is to nail a purlin over the top of the truss (which in the great majority of cases does not calculate out to be adequate structurally) or to use an engineered connector – the connector is going to win every single time.

DEAR POLE BARN GURU: I am currently assembling a Hansen Pole Building kit package. The building has a transition in roof slope from a steeper slope in the enclosed area, to a flatter slope in the open attached side shed.

In following the instructions in your Construction Guide, I note the solid wall between the enclosed and open portions is to have the wall framed and wall steel installed prior to placement of the roof steel.

My questions are these – I’m running the J trim at the top eave girt between the enclosed wall and shed.  Do I need to flow around the shed rafters with the J trim? Will I be able to square the roof if I put the wall steel on? STUMPED

DEAR STUMPED: Yes – the J Trim goes around the rafters which project through the wall. And as long as this wall is plumb before installing the wall steel, it will not interfere with being able to square up the roof.

The Great Purlins Caper

Here is the scene….

roof framing plansOur client has ordered a pole building kit package which is designed around sidewall columns spaced every 14’. For those who care, the building has a design roof snow load of 30 psf (pounds per square foot) and the actual roof dead load carried by the roof purlins (including the purlins themselves) is 1.626 psf. Our engineer designs a roof system with a pair of trusses at each sidewall column, and 2×8 #2 roof purlins joist hung between the trusses and placed 24 inches on center. The engineer prints off two sets of plans and supporting calculations, places his seal and signature on them, and sends them off to our client.

The client submits his plans and obtains a permit to build, which he proceeds to do.

Once under construction, the client sends this email to our office:

“My planning department made a notation on my plans that the roof purlins on the 14′ bays either need to be 16″ on center or use MSR 1450 rated lumber. The plans call out purlins 24″ on center and I don’t believe the wood I was shipped is rated MSR 1450. What is the resolution to this issue?”

The real issue, in my perhaps narrow mind, is a plans checker with perhaps limited ability to perform structural calculations, has made edits to an engineer sealed plan. Effectively, and probably unknowingly, this person has made themselves into the EOR (engineer of record) for this project, putting themselves and their Building Department into a potential position of liability should the building happen to fail structurally.

I wrote at length about this very issue earlier this year: https://www.hansenpolebuildings.com/blog/2013/07/building-official/

A couple of things to know about engineers (a broad generality of course) – their time does not come free, and they can get pretty bent out of shape when someone other than a Registered Design Professional questions their work.  After all, they spent considerable time and money getting their degree to be the “professional” assuming liability for every set of plans they seal.

In order to expedite a solution and keep the peace, I make a call to the plans checker. In the call I discover they have used 10 psf for the dead load on the roof purlins…..over six times the actual load! This sort of dead load would be much more appropriate for a building sheathed with OSB (oriented strand board) or plywood, with a shingled roof!

After a quick and happy conversation, the plans checker and I are now buddies, the crises is averted and the client is out building away on his building, using the plans as designed by the engineer.