Tag Archives: exposure c

HELP I Didn’t Do Enough Research on Deflection

HELP I Didn’t Do Enough Research

Reader JORDAN writes:

“Unfortunately I didn’t do enough research before building a post frame building. I’m running into a lot of deflection on the gable end of a 48x72x16’ high building. I made my own laminated columns out of 4 ply 2×6 southern yellow pine and liquid nails. Unfortunately none of the glue adhered at all and I’ts down to just a nail lam. Would a guy be better off sistering a couple 2×6 boards on each side of the current posts or trying to change columns out to an actual laminated column for strength? I think I found some of the problem being that there were no wind ties or truss bracing going from gable end to gable end, from post to post. Another mistake I made was doing 2’ o.c. Truss spacing. By following the truss drawings for bracing required had no mention of wind ties. I am assuming they thought it was going to be a stick-built style framing. The building is partially enclosed it has a 14’x14’ door that’s open on the opposite gable end. Will that have an effect on wind resistance and flex? I’m unfortunately not an engineer or a very good carpenter but I’m wondering if a few years down the road when the savings will agree to maybe do a mono truss porch every 8’ to see if that will help stiffen up this wall. It’s definitely taking the prevailing wind and I don’t have any plans for an interior wall to still it up. It will eventually be finished on the inside to have living quarters in it. I appreciate your advice. Thank you.”

To be blunt – your problem is you built a very large structure, without having site specific engineer sealed plans. You will now spend more to fix what you have, than what you would have paid an engineer. Your site is what is known as an Exposure C for wind – nothing to stop direct wind exposure in one or more quadrants. This requires roughly 20% stronger of a wind resistant design, than same design wind speed on a protected site.

For extended reading on wind exposure please see:

https://www.hansenpolebuildings.com/2022/06/wind-exposure-and-confusion/
https://www.hansenpolebuildings.com/2022/06/wind-exposure-and-confusion-part-ii/
https://www.hansenpolebuildings.com/2022/06/wind-exposure-and-confusion-part-iii/

Significant grief (and likely expense) could have been avoided had you ordered a Hansen Pole Building to start with.
Moving forward – first a disclaimer, please keep in mind, I went to school to be an architect, not an engineer, so any suggestions I may make, must be reviewed by a Registered Professional Engineer and are not to be construed as me practicing engineering.

Our engineers would typically have specified true glulaminated columns, fabricated from three 2400f (Machine Stress Rated lumber with a fiberstress in bending of 2400) for your endwall columns. 2×6 #2 Southern Pine has an Fb rating of 1000, or 41.67% as strong. A “fix” might be to add two (2) more 2×6 to each set of four currently existing – ideally one on each side. This entire assembly could be connected with Simpson SDWS22800DB timber screws, probably every six inches, from each side, staggered to avoid splitting and alternated so screws from each side are not running into each other.

But wait – there is more (feel like you just entered into an infomercial?)…..

At each endwall column, you will probably need to run a T brace (two 2×4 connected with SDWS16300 screws every 12 inches to form a T), These will need to attach to each set of columns at ceiling height and run through your trusses up tight to top chord of truss at eight feet from each end. Brace should be secured to column – expect four to six SDWS16300 screws, as well high end to truss top chord with Simpson LSTA12 (half on brace other half to top chord) – this will likely take some twisting of LSTA bracket.

This needs to be done to columns on BOTH ends of building, not just one.

This or similar, should greatly reduce your endwall deflection issues.

Posts and Collars, Girts, and Non-Vented Soffits

This week’s edition of Pole Barn Guru visits the topics of post and footing sizes, bookshelf girts for drywall, and non-vented soffits for building with spray foam insulation.

treated postDEAR POLE BARN GURU: I am currently 68 but I built pole barns as a younger man the biggest being a hay barn 24′ eaves X 80 clearspan trusses that we built X 160′ long. I am going to build a 30×60 and will use 6X6 posts 12′ to eaves, engineered trusses with 2X6 purlins 12′ span.

What diameter hole do I need?

I was thinking of using a 16 or 18 sonotube top of an 8″ footing below pour.

Does that sound reasonable?

I am in Grant county Wa.

Thanks for your time 🙂 JOSEPH in SOAP LAKE

DEAR JOSEPH: We have had clients much older than you, with no prior experience, successfully erect their own beautiful post frame buildings. Your 80 foot clearspan x 160 foot long and 24 foot eave must have been quite impressive structure!

Most of your area’s building sites are Exposure C for wind (open to the wind in one or more directions – https://www.hansenpolebuildings.com/2012/03/wind-exposure-confusion/), which is default value for Grant County. If this is indeed your case, neither 6×6 posts or 18 inch diameter holes would be adequate. One of our Building Designers will reach out to you to further discuss your building needs.

 

DEAR POLE BARN GURU: After reading all of the advantages of bookshelf girts I still find the idea of installing drywall sheets vertically over them a bit perplexing. Is vertical “strapping” of some sort required in addition to the girts or is there enough rigidity between the girts to keep the seam together? I’m assuming this would require the use of 5/8 thick sheets. We are planning on doing as much of the work as possible so our plan would be to have all of the ceilings hung by a pro and do the vertical wall hanging ourselves. All of the details for top of wall to truss connections and the prep make perfect sense to me, why does this detail escape me.
Always thankful for all of the useful info we have learned from your site. We are getting closer by the day to being ready to have our plans prepared for building. RUSS in PIPERSVILLE

DEAR RUSS: Thank you for all of your kind words, they are appreciated. The horizontal bookshelf girts will be stiff enough being attached to both the exterior siding (whether wood or steel) as well as the interior drywall to keep your seams together, without need for blocking at seam edges. You will find your sheetrock joints will be much smoother with vertical installation across these girts (https://www.hansenpolebuildings.com/2019/09/11-reasons-post-frame-commercial-girted-walls-are-best-for-drywall/). I used 5/8″ Type X drywall in my own shouse (shop/house) – because it is much more durable, absorbs sound better and provides fire resistance, however 1/2″ would have worked equally as well for standard performance.

 

DEAR POLE BARN GURU: I am looking at purchasing / installing a 30’X50′ pole barn style building with 16′ ceilings, including two 12’X50′ lean-to on each side and 12′ ceilings
I want to enclose about 12’X25′ of the left side lean-to for a canning kitchen area.

I am going to have a non-vented insulated roof assembly since we are using a closed cell foam spray, My question is would using 12″ closed soffit overhang be acceptable for the entire building.

Thank You in advance for the support, SAMUEL in CORINTH

DEAR SAMUEL: In my humble opinion most buildings without overhangs look overly industrial. Overhangs help to keep your building sidewalls cleaner and push rain runoff away from your structure. We can provide non-vented soffit panels and they would work perfectly for your application.