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.

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.

Scissor Trusses Economy

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: Hi,

I recently built myself a pole-barn home in NY that used the traditional flat girt style with columns 8′ OC and a double 2×10 truss header and trusses 4’OC.

The overall result has been great as we have achieved net-zero energy with our all electric utilities and solar PV array.

I’m thinking of getting into the home building business and want to use the post-frame technology to deliver the most affordable and highly-engineered product.

After reading your site, I’m totally sold on the double truss system and 12′ OC truss spacing. However, using flat girts on either side of the posts gives us an extra 3″ of insulation and also reduces thermal bridging in the assembly for the spaces between the posts (essential for getting the heat loss down for the building).

Is there any way to combine the two methods? For example, i was thinking of using intermittent single studs between the columns that are anchored to the floor to support the flat girts in between the posts.

Or are there any creative solutions that you have used in the past or can think of? Here are a few photos of my project for reference. If you have any questions feel free to contact me.

Thanks, KNOWING IN NEW YORK

DEAR KNOWING: Thank you for visiting our website, we hope you will continue to avail yourself of the free information available within it.

Post frame (pole building) construction will certainly be more affordable than any other permanent type of construction, and it does afford the ability to create some deep insulation cavities.

The challenge of flat girts on the outside of the columns is they (in most cases) will deflect more than what is allowed by the Codes. Read more about flat wall girt deflection here: https://www.hansenpolebuildings.com/blog/2012/03/girts/

Here is an idea which might meet with all of your needs…..between the wall columns, install either bookshelf style girts (https://www.hansenpolebuildings.com/blog/2011/09/commercial-girts-what-are-they/) or construct a vertical stud wall with the thickness of the wall matched to the size of the wall columns. With bookshelf style girts, make the girts the next size larger than the columns, and leave 1-1/2″ sticking outside of the column faces. In the stud wall scenario, place 2×4 “flat” girts on the face of the studs, across the columns, at 24 inches on center. Regardless of the route, use a high quality building wrap to cover the girts prior to application of either sheathing or siding.

I’d recommend the use of BIBs insulation: https://www.hansenpolebuildings.com/blog/2011/11/bibs/

On the inside – Use reflective insulation with adhesive pull strips as your vapor barrier, then apply drywall.

Good Luck and let me know how you come out – I appreciate the photos!

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Greetings, are the “typical” roofs -as in your monitor style project 04-0328, considered “walkable” for once in a while fixes? Not planning on making it a habit –just good to know ADVENTURING IN ARIZONA

DEAR ADVENTURING: I’ve been asked this question more than a few times over the years, and have always wondered why it is anyone would actually want or need to be walking around on their roof. With steel roofing, unless it is installed improperly in the beginning, there should never be a “fix” to be made.

Shingled roofs are an entirely different story – as shingles are very susceptible to damage, especially from hail. For more reading on hail damage:

https://www.hansenpolebuildings.com/blog/2013/05/steel-roofing-5/

The answer to your posed question is – yes, the roofs can be walked on. Because steel roofing can be slippery, if you feel the desire to walk on the roof, please use care to step only where there is a screw – the head of the screw will give a traction point to help you stay on the roof. And be sure to use shoes with good soles on them.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Scissor trusses, or raised lower cord and false economy?

Some claim that the increased cost of the truss is offset by the reduction in side wall height. CHAFING IN CHAFFEE

DEAR CHAFING: For just a moment let’s assume the scissor trusses add no extra cost. A tall door is placed in the center of an endwall (after all – the concept of scissor trusses is most often to be able to get a taller door, into an eave height the door should not fit in). The door is opened and the VTT (very tall thing) is driven into the building. The then driver decides the VTT would be ideally parked off to one side, rather than right in the center of the building, where it cannot be easily gotten around.

A loud WHAP is heard, right before the roof caves in on top of the VTT, because the VTT has run into the bottom chord of the scissor trusses – which are lower closer to the sidewalls of the building.

In nearly every case I can imagine, it will be less expensive to have a taller sidewall and complete unobstructed use of the inside of the building, than to go with scissor trusses.

There are some cases where scissor trusses make sense – and none of them have anything to do with economy.

Planning upon finishing the ceiling and like the look of a vaulted ceiling? Scissor trusses make sense.

Your Planning Department has a restriction upon eave height (but not overall height) – scissor trusses again make sense.

The verdict – false economy.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Per square foot cost of steel pole with 6″ concrete floor and pitch roof with 14′ door. BONKERS IN BAY CITY

DEAR BONKERS: As the boss used to say, \$3 a square foot, but you need to cover at least an acre. Have an 8’ eave with no walls, lots of interior columns and an uninsulated galvanized roof.

Pole buildings, just like any other form of construction, become more cost effective as the “footprint” of the building increases. Want to lower the cost per square foot? Enclose more square feet. Or reduce the eave height. Or go narrower and longer rather than wide but shorter. Or don’t put on any doors. Or take off the overhangs, wainscot or other features. Or….get the picture?

The quickest and best way to get an exact price on any pole building is to put in a request for a quote at: https://www.hansenpolebuildings.com/freequote.htm

And if you get a quote, don’t compare a 40’ wide by 24’ deep to someone else’s 60 x 80 by only using “per square feet” as your measure. Get a comparison of “apples to apples” – that’s the only way you will know exactly what you are paying for.

Mike the Pole Barn Guru