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You Have Questions

You Have Questions, We Have Answers

Long time readers are aware I will answer any questions – even when they become highly technical.

Loyal reader CORY in NEBRASKA will be a fantastic client, because he wants to know how everything works, in advance – leaving nothing to chance.

About Hansen Buildings He writes (in italics):

“I would really like to have clear space of 12’ 6” from top of concrete to bottom of bottom truss chord. According to Zach’s calculations (and mine) with the way I had planned only there is only 12’ 3”. With the 18 foot columns , if the frost line is 39” and I now set posts 42” down in concrete (instead of 48 “), pour 5” concrete floor and truss has a heel height of 16”+/- that would yield a clear distance of 12’ 7”. Check my work: 18’ x 12 = 216 “, 216 – 16″ heel = 200 – 5″ concrete = 195 – 42″ sitting depth = 153” of 12’ 7” clear distance. Do you or your engineers think the 42” depth will be a detriment re loading? If 48” buried is preferred, what is actual length of 18’ 3 ply post from bottom to notch? If that measurement is less than 18’ ( meaning a post of 18’ is measured from bottom to top of outside plies, can one safely add a 4″ or 6” block into notch with adhesive and secure with either screws or nails through all 3 plies and then remove outside ply to set double truss? (Mike the Pole Barn Guru says: Good try but would not get engineer’s seal probably! )”

Mike the Pole Barn Guru answers:

Typically with a 39″ frost line, holes would be dug to 40″ and you would hold posts up 8″ from bottom of hole – to create a mono-poured bottom collar. This puts 32″ of column at below grade. Top of slab (regardless of thickness) will be 3-1/2″ above grade. 12’6″ from top of slab to bottom of truss means we have used up only 15′ 5-1/2″ of columns. Throw in a 16″ heel and you have used 16′ 9-1/2″ of an 18′ column.

“With a double truss on a 3 ply column, cutting away 2 plies to set truss into notch would increase bending moment to notch side, would it not? Also only one ply to hold truss vertical under side stress. I realize that purloins add stability once in place. On 10’ purloins isn’t blocking (or doubling …..expensive) a good idea to eliminate flex out of purloin and keep all straight for steel installation?”

Our engineers check every column for eccentricity (truss loaded to notch in from one side) and only with a tremendously huge snow load and say a 3 ply truss notched into a four ply column, would this even begin to become an area of possible structural concern. Your roof acts as a long deep beam, prohibiting lateral movement of truss heels away from columns. Easiest method to keep purlins straight is to pre-drill roof panels and then adjust purlins towards or away from ridge so purlins fall in line with holes. It is quite simple to do and avoids having to add other members or blocking.

“I sent two plans to Zach , same building but roof peak at 90 degrees to each other. Zach has sent a sketch of the one ( east / west roof peak ) with the gable end facing the West , ( prevailing westerly wind as well as storms ) I believe that 40 foot width frontal height would be just under 21 feet with 14’ sidewalls and 4:12 pitch roof with 12” overhang. I thought that the North / South roof peak with longer 50 foot eave side with 24” overhangs and 14 ‘ sidewall and might have less wind load. Am I wrong? Is the 24” overhang a greater uplift hazard?”

Assuming eave heights, roof slopes and footprints are the same, 50′ span roof does add 20″ of overall roof height, however you only have 40′ of overall length to deal with. Endwall shear on the 40′ truss version is 3287.36#, 50′ truss version is 2962.8#. Overhang lengths are factored into the truss/column connections and frankly are such a small proportion of your total roof area so as to be near inconsequential.

“I used to work in the power line industry and to overcome forces from tensioning lines or angles, etc., the glulam poles we set had 4″ angle iron “ears” bolted vertically the bottom 6 or 8 feet to maintain plumb. Would adding 2” x 2” x 8” pieces of angle iron horizontally about halfway down the buried portion void your warranty? I feel it would counter uplift better than the pieces you sell.”

Our uplift plates are approved and have published validated numbers for uplift resistance. Should you desire to add angle irons ears, it would not void any warranty provided appropriate measures are taken to seal any column penetrations, although there is really no structural need for them.

This entry was posted in Cabin, Pole Barn Questions, Pole Barn Design, Building Overhangs, Pole Building How To Guides, Pole Barn Planning, Concrete, Footings and tagged double truss system, Uplift Plates, concrete bottom collar, eccentricity on March 9, 2023 by admin.

Blown-In Insulation, Uplift Plates, and Truss Spacing

This week the Pole Barn Guru answers reader questions about better blown-in insulation on 3/12 pitch ceiling, a reader with uplift issues and how to prevent them, and some concerns about truss spacing at 8′ oc.

DEAR POLE BARN GURU: Hello, I have a 30×48 pole barn with scissor trusses 6/12 outer pitch 3/12 inside pitch. It has metal roof with dripstop. Trusses are 4’ on center and I was going to place metal on inside ceiling 3/12 pitch then place blown in insulation on top of that. Would it be best to use fiberglass blown in insulation instead of cellulose? I will be sure to place baffles on eaves for proper ventilation. Do I need any vapor barrier between the metal and insulation seeing as I have dripstop on roof metal? Thank You! DON

DEAR DON: Yes, use blown fiberglass rather than cellulose. Cellulose has fire retardant chemicals in it, when combined with excess moisture, it will prematurely decay steel liner panels (and cellulose is much heavier than fiberglass). Unless you are located where there are over 8000 annual heating degree days, you should not have a ceiling vapor barrier.

DEAR POLE BARN GURU: The wind lifted my pole barn up about a foot on one end last spring and hasn’t settled back down. Wondering how to get it back down to earth? STEVE

DEAR STEVE: Your building has sadly become an experiment to show what happens when adequate uplift provisions have not been made during construction. Hopefully your building has been insured for replacement costs – so you can have this work hired out.

In order to successfully get a ‘return to earth’ your building should be disassembled back to at least a point where no column uplift is detectable – including removing uplifted columns from ground.

Re-dig all offending post holes.

Add an uplift plate on on side of each column at bottom. https://www.hansenpolebuildings.com/2018/12/uplift-plate/
Stand columns in holes, so bottom of column “floats” roughly 8″ from bottom of hole. https://www.hansenpolebuildings.com/2015/04/floating-poles/
Pour bottom 18″ or more of each hole with readi-mix concrete.

Re-frame building, replacing any damaged lumber or trusses.

Before putting steel panels back on building, confirm no slots have been created in panels due to tearing around screw shanks when building lifted. Replace any damaged panels.

DEAR POLE BARN GURU: We are having a 30 x 50 barn built, and our builder just put up the trusses. It is a stick frame barn on a slab and the trusses are spaced 8′ apart. The concern is that there are not enough trusses. It looks like a “pole barn” but is on a traditional slab identical to our house and the “poles” are not buried. Trying to find information on truss spacing has been difficult. Both dad and uncle think it is not enough and have traditional construction backgrounds. Please help. ASHLEY in ANDERSON

DEAR ASHLEY: Provided your building’s trusses have been engineered to adequately support loads when spaced every eight feet, there is nothing wrong with them. https://www.hansenpolebuildings.com/2011/06/pole-barn-truss-spacing/
What is wrong is it appears this building is being constructed without site specific engineer sealed structural plans. Chances are better than most you will have some future challenges due to this. Roof purlins should be attached to trusses using Simpson or USP brand joist hangers. Truss bottom chord bracing is missing and truss heels should be attached to walls with an uplift connector adequate to resist your roof flying away during a high wind event.

This entry was posted in Building Styles and Designs, Roofing Materials, Pole Barn Planning, Pole Barn Structure, Trusses, Ventilation, Footings, Insulation, Rebuilding Structures, Pole Barn Questions and tagged Uplift, pole barn truss spacing, Uplift Plates, truss spacing, insulation, blown in fiberglass insulation on November 23, 2022 by admin.

Pole Building Columns Without Ups or Downs

Post Frame Columns Without Ups or Downs

Once post frame building columns are placed into those holes in ground, there needs to be (or sure should be) a solid plan to keep them from being sucked out of ground, or sinking down into it.

FEATURE: Pre-mix concrete bottom collars attached to columns with pounded in Uplift Plates™..

BENEFIT: Uplift Plates™ supply superior resistance to uplift in attaching a mono-poured concrete collar to column bottoms and are quickly installed. Thickness and area of bottom collars keep building from settling.

EXTENDED READING ABOUT THIS SUBJECT:

Keeping columns from uplifting: https://www.hansenpolebuildings.com/2012/02/concrete-collars/

WHAT OTHERS DO: Here resides another realm with a plethora of possibilities. Simplest of these happens to be doing nothing. Columns are placed to hole bottoms and backfilled with earth. This provides no resistance to settling and very little to prevent uplift.

To prevent settling, throwing a pre-mix concrete sack in bottom of hole is popular with builders, due to being quick and easy. Best this effort results in inadequate thickness and area. Worst – concrete in area closest to bag outside hardens leaving a powdery core.

Sometime a sack or even two of concrete will be mixed with water, either in a wheelbarrow, or, more often, in hole bottom. Again resultant will be a poor design solution due to lack of thickness and diameter.

Precast concrete cookies are popular in some areas. Read about their challenges here: https://www.hansenpolebuildings.com/2012/08/hurl-yourconcrete-cookies/.

Poured in place concrete footings could carry downward loads, however in most cases small volume of pre-mix needed causes a “short load” charge from by concrete companies.

Some are even using a composite FootingPad® to replace concrete footings. Caution, FootingPad® website table covers fairly firm soil and utilizes columns every eight feet. Many areas have soil ½ to 1/3 as strong resulting in required bearing areas two to three times as large.

Uplift becomes an entirely different area. Simple version requires filling holes entirely with pre-mix concrete. Back in the day I did it this way as a post frame builder. Quick and easy to build, however not most cost effective solution for building owners who write checks for concrete!

Concrete collar article previously referenced, does address other uplift solutions.

WHAT WE DID IN 1980: Regardless of building dimensions or loads being applied Lucas Plywood and Lumber didn’t give a thought to either uplift or sinking. Since we didn’t provide plans or instructions, it was left to erection crew imagination.

This entry was posted in Concrete, Concrete Cookie, Footings, Columns, Pole Barn holes, Pole Barn Design, Pole Building Comparisons, Pole Barn Planning and tagged concrete cookies, Uplift Plates, FootingPad, premix concrete on December 14, 2018 by admin.

Properly Treated Poles, Ceiling Loads, and Uplift Plates

Properly Treated Poles, Ceiling Loads, and Uplift Plates

DEAR POLE BARN GURU: My pole barn is approximately 25 years old. My question is, does the foundation need to be treated for maintenance to prevent rotting? The wood that is underground was originally treated wood but how long does that last? The floor inside is concrete but there is no concrete around the framing which meets dirt on the outside. NORMA in CASSOPOLIS

DEAR NORMA: Despite what might be voiced by naysayers – properly pressure preservative treated lumber should, under most circumstances, last longer than you and I (or our grandchildren) will be around to see. If you are curious, excavate the top eight to 12 inches of soil around one or more of the columns and check on the condition of them. We are currently adding onto our warehouse – a 40 year old post frame building. Some of the existing columns were dug alongside and it was determined there had been no noticeable decay at all. I would suspect yours will be the same.

DEAR POLE BARN GURU: Can you strap a ceiling for drywall ceiling in a pole barn if the joists are 8 ft apart? TOM in BLAIR

DEAR TOM: I will do what I feel is some interpreting….where “joists” are the prefabricated metal connector plated wood roof trusses, and “strap” would refer to framing placed across (or more probably between) the bottom chords of the trusses.

If your trusses have been designed to support the weight of a ceiling load, then yes. Hansen Pole Buildings uses a 10 psf (pounds per square foot) design ceiling load for instances where gypsum wallboard will be applied. A five psf load might possibly be adequate with bare minimal framing and nothing ancillary hanging from the bottoms of the trusses. You would be well advised to consult with the engineer who designed your building, or the truss fabricator to insure your roof system is indeed adequate to support these loads.

Once truss adequacy is confirmed your engineer can specify the size, species and grade of the material to be used as ceiling joists as well as what he or she requires as a connection between the ceiling joists and the trusses.

DEAR POLE BARN GURU: What is used to hold the post in the concrete? galv nails pounded into the 6×6 treated post post? Rebar drilled through the post as a big nail? Galv-steel anti-lift brackets of some sort? GLENN in PORTLAND

\DEAR GLENN: Hansen Pole Buildings now supplies (as a standard feature) one or more UP-Lift plates per each structural column (the required number will depend upon analysis by the Engineer of Record). It would require a significant number of large diameter nails to equal the holding power of a single UP-Lift plate. Rebar through the column might prove to be adequate, however it does involve a significant amount of effort to drill the holes through the column, cut rebar to short lengths and seal the rebar at the edges of the column to prevent water infiltration. In any case, the ultimate responsibility for design of adequate uplift resistance should be left up to the engineer who designs your building.