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Perma-Columns, Posts, Trusses and Purlins, and Mono Truss Roof Venting

This week the Pole Barn Guru answers reader questions about the value of Perma-Columns, setting of posts, trusses and purlins, and the proper way to vent a mono-truss lean-to roof.

DEAR POLE BARN GURU: Are perma columns worth it? JOHN in TRUMANSBURG

DEAR JOHN: When I built my own 8000 square foot finished post-frame barndominium, I could have used any option for columns – mine are directly embedded UC-4B treated glulams. Although this article is over seven years old, it is still relevant to your question: https://www.hansenpolebuildings.com/2018/04/perma-column-price-advantage/

 

DEAR POLE BARN GURU: I’m planning a pole barn pavilion, and would like to have posts set at 10′ on center, and trusses at 5′ on center. Are 2×4 purlins laid flat sufficient (24″ spacing)? Or should they be on edge or upped to 2×6? Standard gable truss, 4/12 slope and 29 gauge metal. Thank you in advance for insight. BRETT in JOHNSON CITY

DEAR BRETT: In my humble opinion, you are looking at doing it in a much more difficult fashion than needed. Set glulaminated columns every 10′ (you could easily do wider spacing to reduce number of holes to dig, columns to set, etc). Align prefabricated wood trusses to match columns – single on each end, two-ply on interiors, with trusses notched into columns. This will eliminate need for truss carriers and greatly minimizes amount of truss bracing required (and usually reduces truss costs). Truss carriers are often under designed and rarely adequately connected to properly resist gravitational and wind uplift loads. Use 2×6 2400f MSR (Machine Stress Rated) purlins, joist hung on edge between trusses.

 

DEAR POLE BARN GURU: Hello, thank you for educating us on best practices. What is the proper way to vent a mono truss lean-on roof? Overhangs will have vented soffit and the rake is currently planned for unvented soffit. I am thinking of installing vented soffit in upper part of rake where the mono truss meets the side wall of the higher structure wall. I have enclosed a picture for reference. TIA NIKO

DEAR NIKO: Thank you for your kind words. Here is a sketch for you (rafter/truss being interchangeable):

Roof steel needs to be long enough to make it to high side of vented closures. You do not want to place vented soffit in rakes.

This entry was posted in Pole Barn Design, Workshop Buildings, Building Overhangs, Pole Barn Heating, Pole Barn Planning, Post Frame Home, Trusses, Barndominium, Ventilation, Building Interior, Columns, Lumber, Sheds, Pole Barn Questions and tagged , , , , , , , on by .

Tongue and Groove Pine, Eight Foot Post Spacing, and Truss Drawings

This week the Pole Barn Guru answers reader questions about the best method of adding tongue and groove pine to a vaulted ceiling, use of eight foot post spacing in quote, and truss drawings for metal trusses in Minnesota.

DEAR POLE BARN GURU: I would like to have a vaulted ceiling in my 34’x30’ hobby room. I would like the ceiling to be tongue and groove pine. These boards will be running parallel to the joist connecting the trusses. I will be limited to a crossmember every 12 feet. Is there a solution or do I need to add cross members to the joists? MICHAEL in OCKLOCKNEE

DEAR MICHAEL: If you do not have some sort of solid sheathing above your tongue & groove, you will have dust sifting through forever (I personally made this mistake not once, but twice – I was a slow learner). In your 34′ x 30′ area you will have double trusses every 10′, with ceiling joists every 2’ between scissor truss bottom chords. I would recommend you first apply sheetrock to ceiling joists. Then glue on your tongue and groove pine, concealed nailing where T & G crosses trusses, just for added measure.

 

DEAR POLE BARN GURU: I was recently quoted a build price for a 24X 24 building from your company, But the spacing of the posts was 12 feet apart. I am wondering if you have kits that have 8 feet spacing for the same building? ELIZABETH in PORT ORCHARD

DEAR ELIZABETH: Although it will be a tremendous structural overkill, we can certainly change column spacing to every eight feet, should you desire.

 

DEAR POLE BARN GURU: Good afternoon, I recently built a garage using Buffalo River trusses. I see your company is a dealer. When I bought my trusses I did not request for detail drawings with a MN stamp and now I’m realizing that I need one for the building inspector to review. Have you built any projects using these trusses? I’m looking for any info or drawings you could pass along. Attached is the drawing of the trusses I used. LOGAN in MINNESOTA

DEAR LOGAN: I am probably going to be the bearer of bad news. These trusses are designed for a ground snow load of 15 psf, spaced 12 foot on center. Moving them to 8′ on center, would equate to 15 x 12/8 = 22.5 psf. The LEAST ground snow load anywhere in Minnesota is 50 psf (https://www.revisor.mn.gov/rules/1303.1700/). This means the trusses you have used are not only woefully inadequate, but are also doomed to fail. You could try reaching out to the engineer who sealed these drawings directly, to request an engineered repair, however be prepared to have to weld a significant amount of steel in order to appropriately upgrade.

This entry was posted in Lumber, Pole Barn Homes, Pole Barn Questions, Pole Barn Design, Building Department, Barndominium, Roofing Materials, Pole Barn Structure, Trusses, Budget, Columns and tagged , , , , , , , on by .

Skylight Width, Gable Fans, and Post Spacing

This Wednesday the Pole Barn Guru answers reader questions about the standard width of a skylight, gable fans for ventilation, and post spacing for a roof only building.

DEAR POLE BARN GURU: What is the standard width of a skylight on a pole building?

ROBERTA in DAKOTA

DEAR ROBERTA: In most instances pole building skylights are fiberglass or polycarbonate panels with same configuration as 3′ width net coverage steel roofing. For some extended reading on skylights please visit: https://www.hansenpolebuildings.com/2012/01/skylights/

 

DEAR POLE BARN GURU: Just completed a 36×84 x 14′ high pole building. Self designed. I sheeted the roof, both gable walls, and the front wall for shear and strength using 1/2″ cdx. I used ice and water shield under the roof and house wrap on the walls. Concrete slab with 6mil vapor barrier underneath. No insulation. Also, no ventilation. Noticing I need ventilation, before things get moldy etc. I’m considering putting a 24″x24″ 5000cfm powered gable fan on the east side, and a 24″x24″ intake vent on the west side. Would this be adequate to keep condensation and moisture at bay? TODD in PORT ORCHARD

DEAR TODD: Lack of ventilation is a harbinger of future condensation problems with well-sealed buildings. Your building has roughly 51,000 cubic feet of interior air volume, meaning a 5000 cfm powered fan will turn your air roughly every six minutes (or 10 times per hour). This should be adequate, however a greater capacity might be worth considering. You will also want to look at actual NFVA (net free ventilation area) of your intake, as lack of intake area can restrict performance of your exhaust fan.

 

DEAR POLE BARN GURU: Hi, My name is Joe. I’m trying to build a pole barn with in an area of Washington that has a snow load of 15 PSF.  The building is 24′ wide by 38′ deep with 14 feet clear height. no side walls. Seems like spacing varies quite a bit from 8 ft to 12ft. Thought I would see what u would suggest for this?  I was thinking about doing 12 ft or maybe even 10 ft.  Any thoughts would be much appreciated? JOE in WASHINGTON

DEAR JOE: I would look at doing bays of 12′ – 14′ – 12′ first, however you should discuss options with whoever is going to engineer your building plans. Depending upon what you will be using this building for, it may be less expensive to cover one or both 24′ endwalls from roof to ground, than to have a roof only. A Hansen Pole Buildings’ Designer will be reaching out to you to discuss your needs, as we have provided roughly 1000 fully engineered post frame buildings to our clients in Washington State.

This entry was posted in Ventilation, Columns, Skylights, Pole Barn Questions, Pole Barn Design, Building Styles and Designs, Pole Barn Planning and tagged , , , , , , , on by .

Price Per Square, Scissor Truss Spacing, and Column Spacing.

This week the Pole Barn Guru answers reader questions about our “best guess at price per square…” for a Hansen Building Kit, spacing for scissor trusses, and if there is a national code for post spacing in a barndominium.

DEAR POLE BARN GURU: What is your best guess at price per square foot range materials and labor to build a Hanson Pole Building these days? STEVE in MAPLE PLAIN

DEAR STEVE: All Hansen Pole Buildings kits are 100% custom designed to best meet wants and needs of our clients, as such – we do not price per square foot, but rather by actual dimensions and features, taking into account climactic conditions at each individual building site (snow load, design wind speed and wind exposure). While most of our clients are doing DIY, largely due to a lack of quality building erectors, fair market value for labor is typically roughly 50% of what your building kit investment is (not including any concrete).

 

DEAR POLE BARN GURU: I’m hoping you can give me some advice. A pole building 30 wide with scissor trusses pitched at 10/12 out 5/12 inside closed cell insulation finished on the inside with 1″x8″ pine run horizontal ….will spacing the trusses on 4′ centers be alright? The building is in central Iowa zip code 51537.

Thank You so much!! JOHN in HARLAN

DEAR JOHN: These trusses may or may not be adequate for your needs, depending upon loads and spacing they were designed for.

The engineer who sealed your building plans is responsible (by Code) to review your truss drawings to ensure they comply with his or her design specifications as outlined on their plans. They also are to create a permanent bracing plan to satisfy all needed truss and building needs. This bracing plan must be shown on these same plans.

A caution, steeply sloped trusses impart a large horizontal wind load and building sidewall columns must be appropriately analyzed to insure structural adequacy. Columns specific to a 4/12 roof slope, may not be strong enough to carry these added loads. Again, your engineer can (and should) confirm.

 

DEAR POLE BAR NGURU: Hi, Barndominiums, is there a national code about how far apart the poles should be? 10 ‘ or 8′? Here in Kentucky, I’m under the impression that the poles have to be 8’ apart. Am I correct? Regards DAN in MURRAY

DEAR DAN: You would be incorrect. Poles (actually columns) are inanimate objects and can be spaced at whatever distance their size and grade is capable of supporting using sound engineering practice. Our engineers recently designed a building for one of our clients with columns every 18′ and many years ago, I did one with columns spaced 24 feet on center. In most instances (depending upon climactic loads and door/window locations) columns every 12 feet are most economical.

 

This entry was posted in Columns, Pole Barn Questions, Pole Barn Design, Barndominium, Constructing a Pole Building, Pole Barn Planning, Building Colors, Trusses, Professional Engineer and tagged , , , , , , on by .

Residential Building, I-Joist Purlins, and Post Proximity

This week the Pole Barn Guru answers reader questions about whether or not Hansen can provide a residential building kit in their area, if Mike advises the use of I-Joists as purlins, and post proximity– how close can two posts be to each other?

DEAR POLE BARN GURU: Do you build residential buildings in the greater Fort Wayne, IN area? BRIAN in FORT WAYNE

Click here to download our free brochure!DEAR BRIAN: Hansen Pole Buildings provides fully engineered, custom designed post frame buildings, with multiple buildings in all 50 states (including roughly a hundred of them in Indiana). We ship from over 4000 locations – so chances are we are ‘close’ to you! Your new building will be designed for an average physically capable person who can and will read instructions to successfully construct your own beautiful buildings (and many of our clients do DIY). Your building will come with full 24” x 36” structural blueprints detailing the location and attachment of every piece (suitable for obtaining Building Permits), a 500 page fully illustrated step-by-step installation manual, as well as unlimited technical support from people who have actually built buildings. For those without the time or inclination, we have an extensive independent Builder Network covering the contiguous 48 states. We can assist you in getting erection labor pricing as well as introducing you to potential builders. We would appreciate the opportunity to participate in your new home. Please email your building plans, site address and best contact number to our Design Studio Manager caleb@hansenpolebuildings.com or dial (866)200-9657 for immediate assistance.

 

DEAR POLE BARN GURU: I’ve read your reasonings and seen your snippets of engineering drawings that spec 2x purlins hanging between trusses. I’m wondering if now that I-joists are becoming so popular for residential use, if you’ve ever tried to use them as purlins. A 9.5″ I-joist would allow for 8″ of mixed closed and open cell spray foam, and a bottom flange of 1.5″ for light fixtures, wiring, etc. And I think I-joists would be lighter than 2x10s (and in this economy maybe even cost less!).
Thank you,
Thinking About A Hansen Handsome Barndominium, Or more accurately, GUY in JOHNSON CITY

DEAR GUY: I’ve used engineered floor trusses for roof purlins, but never I-joists. While I do not personally like them for floors (I find them bouncy), they do work as a replacement for dimensional lumber joists and rafters. I-joists are fairly strong when loads are applied directly perpendicular, however they are not strong in weak axis bending (e.g. loads applied when they are rotated from vertical). While they might work as roof purlins, it would take a significant amount of blocking and/or bracing plus some healthy engineering analysis in order to design a system to restrain them from buckling.

 

DEAR POLE BARN GURU: How close can the posts actually be to each other? Are there physical limitations to drilling two holes 12 inches apart? The reason I ask is I want to build a garage that mirrors the garage on my house, and the first 9 foot wide door is 25 inches from a corner and the spacing between the two doors is only 15 inches, rough opening to rough opening. Does one just dig a hole large enough for both posts? Or should two holes be drilled that overlap? SCOTT in BROOKSTON


DEAR SCOTT: Two posts can actually be in direct contact with each other, if necessary to support things like door openings. When two columns are close together, it is usually easiest to end up digging what resembles a trench, rather than a larger diameter hole (effectively drilling two overlapping holes).

 

 

This entry was posted in Building Interior, Columns, Pole Barn Homes, Pole Barn Questions, Barndominium, Pole Barn Design, Constructing a Pole Building, Pole Barn Planning and tagged , , , , , , , on by .

Uneven Ground, Greatest Strength, and Post Spacing

This Monday the Pole Barn Guru answers reader questions about building a pole barn on uneven ground, if spray foam adds the greatest strength, and post spacing for a roof only porch.

DEAR POLE BARN GURU: We were potentially looking to build. We were investigating our options and I came across pole barns. My potential issue is the land I would be potentially building on. Its on a hillside and not exactly flat. Is this an issue with pole barns? As most of the photos of homes are on flat ground. LESLEY in HAZARD

DEAR LESLEY: Fully engineered post frame (pole barn) buildings can be adapted to fit most any ground surface – from pancake flat to steeply sloped. Many design solutions are possible: cutting into hillside (will require a retaining wall outside of building perimeter or a foundation of concrete, block, ICFs, or pressure preservative treated wood); a combination of cutting and filling; filling to bring site up to highest grade (this is most common and minimize possible affects of exterior surface water infiltration) or as a stilt house.

Here is how I personally solved 12 feet of grade change for my own shop/house: https://www.hansenpolebuildings.com/2012/02/grade-change/

 

DEAR POLE BARN GURU: What would give pole barn the greatest strength- closed cell exterior walls or under roof?

Due to cost would closed cell under metal roof and open cell on all walls provide much additional structural support?

Would close cell all but price prohibitive so looking at next best option.

CAM in DANVILLE

DEAR CAM: In order to insure your post frame (pole barn) building has its greatest structural integrity, it should be fully engineered (not just trusses) to meet or exceed Code mandated design wind speeds and Exposure for your site. While closed cell spray foam insulation will make any surface it is directly applied to more rigid, I would not rely upon it as a structural solution.

Your site is located in Climate zone 5A. 2018 IECC (International Energy Conservation Code) requirements for residential energy efficiency specific R-49 for ceilings, R-20 for walls. For cost effectiveness you could do a Weather Resistant Barrier in your walls between framing and steel siding, then fill balance of wall cavity with kraft faced fiberglass R-21 batts. For your roof, order trusses with 18 inch energy heels designed to support a ceiling and blow in 16 inches of fiberglass on top of your ceiling. Control condensation with a well-sealed Reflective Radiant Barrier (least expensive for materials but more work) or an Integral Condensation Control applied directly to roof steel when roll formed (slightly more for materials, but easily installed). Provide adequate ventilation with intakes through vented sidewall soffits and exhaust at ridge.

 

DEAR POLE BARN GURU: Can I build a 24×24 gabled roof over my deck using only four posts? RON in TRUMANN

DEAR RON: It might be possible, but may not be practical as you are going to need to have 24′ long lumber for either purlins, or truss carriers. Chances of being able to acquire either, without purchasing full unit quantities, will be slim. We would typically recommend using 6 columns, spaced every 12′ along eave sides.

 

 

This entry was posted in Porches, Columns, Sheds, Pole Barn Questions, Pole Barn Design, Constructing a Pole Building, Pole Barn Planning, Ventilation, Footings and tagged , , , , , on by .

Continuous Foundations, Column Spacing, and Inside Closures

Let’s finish off the week with one more day of Ask the Pole Barn Guru. Today Mike takes on reader questions about connection with a continuous foundation, benefits of 10′ or 12′ column spacing, and replacing inside foam closures.

DEAR POLE BARN GURU: Hello. We are located in Ohio. We would like to build a 24×40 pole building. Zoning says it needs to be attached per their rules so we plan to attach with a simple fabric awning to meet zoning. The county says we need a continuous foundation if it is considered attached. Stupid right? The only thing touching both building will be a fabric awning. I have been told we can have an engineered foundation, or a 6″ by 38″ deep concrete wall poured, wood foundation or a traditional block foundation. Where would I begin to find details for an engineered foundation? I am struggling finding the info and where to start. RALPH in POLAND

DEAR RALPH: In a typical fully engineered post frame (pole) building isolated columns embedded into your ground would be complying and meet Building Code requirements. We would like to see your jurisdiction’s written requirement for mandating a continuous foundation, as often times these ‘requirements’ are just one person’s own feelings of how things should be done, rather than having an actual basis.

Should this indeed be an approved statute, we can have your new building engineered with your continuous foundation of choice. One of our Building Designers will be reaching out to you to discuss further, or dial 1.866.200.9657 for immediate service.

 

DEAR POLE BARN GURU: Are there any benefits going with 10′ centers over 12′ centers? I was thinking about going with 10′ centers because in my mind it seems like that would be a stronger building and would have less purlin sag over the years but rather go with 12′ centers to gain more parking space for a leanto? Any recommendations? Thanks BRIAN in PARRISH

DEAR BRIAN: Regardless of spacing of columns or trusses, a fully engineered post frame building will be designed to meet or exceed a specified set of wind design criteria – speed and exposure. You are better served to increase design wind sped, so your entire buildings is capable of supporting higher loads, than to merely move columns closer together. Provided Code required deflection limitations have been properly engineered for, any purlin sag, over time, should be relatively imperceptible.

 

DEAR POLE BARN GURU: Greetings, My metal roof is 15 years old and the inside foam closures have deteriorated.  1.  Are they necessary, and 2. if so, how does one replace them?

I hate to remove the screws along the eaves (or maybe even more screws farther up each panel), but see no other way to get replacement closures under the metal panels.

I’d appreciate any advice

Thanks SHERRY in RIO RANCHO

DEAR SHERRY: Properly manufactured inside closure strips are UV resistant and should outlive your building’s steel roofing. Personally, I find them essential, as without them small flying critters have a clear path to enter your building. In order to replace them, you will have to remove screws along your eave line. Once remains of old closures are removed, new ones can be put in place. Old screws should be replaced by both larger diameter and longer screws, to maintain integrity of connections and prevent leaks.

For extended reading on Inside Closures https://www.hansenpolebuildings.com/2015/12/the-lowly-inside-closure/

 

 

This entry was posted in Concrete, Footings, Rebuilding Structures, Professional Engineer, Pole Barn Questions, Columns, Roofing Materials, Pole Building How To Guides, Pole Barn Structure and tagged , , , , , , , on by .

Rebuilding, Post Spacing, as well as a Frost Wall

I this weeks blog, the Pole Barn Guru talks about, rebuilding a pole barn, ideal post spacing and a frost wall.

DEAR POLE BARN GURU: Hello, I recently disassembled a 36 x 100 pole barn and am rebuilding it at my house. It was covered with 2″ reinforced paper faced roll pole barn insulation with a 1″ foam board between the insulation and the metal. While removing the roll insulation it received many tears in the paper face. I would like to install a 6mil vapor barrier over my lumber then reinstall the roll insulation followed by the foam then the metal. Is this a good idea? The building will be heated and air conditioned but will not receive any kind of wall covering inside of the vapor barrier. Thanks DEAN in CORYDON

wind damageDEAR DEAN: I can’t say I am a huge fan of rebuilds for several reasons – damaged materials end up being used and it is pretty well impossible to keep from having holes in the roof steel which are going to cause leaks.

You should seriously consider the involvement of a RDP (Registered Design Professional – architect or engineer) to insure what you are rebuilding will meet Code requirements.

One problem right away – the foam board between the framing and the steel. Throw it away or resell it on Craigslist. The foam board pretty much negates the strength of the steel cladding due to the lack of rigidity of the insulation. It will also contribute to the possibility of slots forming around the screw shanks, due to movement of the building framework.

You should use a well sealed building wrap between the wall framing and the steel siding, then the insulation. If you are unable to repair the tears in the paper facing, you can use visqueen on the inside for a vapor barrier, however it (or paper facing) should be covered with an inflammable material to prevent possible fire issues.

DEAR POLE BARN GURU: Hello, I’m in Oklahoma which has high winds and severe weather. I am leaning towards having a garage built that is 20x24x10. How far apart should the columns be spaced? We have no HOA in our neighborhood and I haven’t reviewed the neighborhood covenants.  I’m really wanting to be smart on this because it’s a lot of money that I want to be solid investment. My goal is to save money, but be so cheap that building falls apart.  Thank you for your time. SHANE in OKLAHOMA

DEAR SHANE: The real answer does not come from column spacing, it comes from investing in a fully engineered post frame building which is specific to your building upon your site. Given your concern is for wind design, unless you have a site which is well protected from the wind in all four directions (buildings, hills or evergreen trees 30 feet or greater in height) you need an Exposure C for wind. You can get pricing on a variety of Vult wind speeds and determine what wind design you are willing to invest in.

 

DEAR POLE BARN GURU: I purchased a pole barn kit a couple years ago and I am just now getting around to building it. My county approved everything but they added an exception. They say that I need to add some frost protection. Either a frost wall or some sort of shallow frost protection. There are no plans for such in the blueprints and it is required by code here. So my question is what do I need to Do? Doing a concrete frost wall almost makes buying the pole barn kit unnecessary. I should of just did a stick built if I’m basically building a foundation.  I live in Bonneville county Idaho. Just wondering if you have come across this situation here and what the buyer needed to do? CAMERON in IDAHO FALLS

slab edge insulationDEAR CAMERON: You can do a Shallow Frost-Protected Foundation without having to thicken the slab edge – you can backfill on the inside of the vertical insulation board with sand. In the event your Building Official requires this to be added to your plans and sealed by the engineer, there would be an added investment for redrafting and sealing two new sets. For more reading: https://www.hansenpolebuildings.com/2016/11/frost-protected-shallow-foundations/.

 

 

 

 

This entry was posted in Building Department, Constructing a Pole Building, Footings, Insulation and tagged , , , on by .

To Remove, To Replace, and To Design!

DEAR POLE BARN GURU: Hey Guru! I’m getting ready to build a pole barn and I will have to remove a tree. The tree is basically right in the middle of what the floor will be. I will be putting a concrete floor in and was wondering do I have to completely remove the stump or can I just cut it down below grade and cover it with dirt and gravel? MARK in BROKEN ARROW
DEAR MARK: Completely remove it. You do not want any sort of organic material to remain under a building site. Eventually it will decay, sink and if you have poured a concrete slab over it, the slab could fail any you could find yourself parked in the bottom of a hole in the middle of your barn. Stump removal is relatively inexpensive – and it is something you could probably do yourself along with a properly sized piece of excavation equipment.

 

DEAR POLE BARN GURU: We have a pole building that had a 12’ X 12’ slider door that was recently damaged and needs replaced. Can you point me in the direction I need to go to get a replacement. We wanted to replace it with an overhead door but do not have sufficient clearance for our motorhome. JOYCE in FRANKLIN

DEAR JOYCE: Replacing a sliding door with an overhead door can end up being a near epic challenge as the opening sizes will not be the same. At the very least it will necessitate a custom width overhead door. Before you get too deep into the process, contact three local overhead door companies and ask each to come out to give you a quote on the door. They will be able to tell you what the maximum height is you will be able to get into your building (keeping in mind this may necessitate increasing the height of the door opening). Once this step is done, if you are not already over budget, run an ad on Craigslist under “gigs” best describing the work to be performed – which should include replacement of all of the steel siding on this wall of the building (otherwise it is never going to look right). I have no idea how large your building is, but could easily see this as being a three to five thousand dollar price tag before all is said and done.

Which leads back to – the solution might be to bite the bullet and just replace the sliding door with a new sliding door. You can probably get all of the needed components by a visit to the Pro Desk at your local The Home Depot®.

DEAR POLE BARN GURU: Storage for trailer 35 ft what is a pole distance set with 10 – 12 ft opening? TRACY in NAMPA

DEAR TRACY: I will have to read between the lines here and hope I am able to provide an answer which fits with what your question truly is.

For starters, if I had a 35 foot long trailer to get through a door, I want the opening to be about 12 feet wide. Going 10 feet wide appears to me to be risking some damage.

If the door is to be a sliding door, the space from center of column to center of column on each side of the door should be 12 feet. This will allow the sliding door itself (which should be about 12’2” in width to cover the opening and provide an overlap on each side.

For overhead doors, if getting a residential overhead door, the space BETWEEN the columns should be 12’1”, so as when the 2x jambs are placed on each side of the opening, the finished opening will be 11’10” in width. This will allow the overhead door panels to overlap by an inch on each side. For a commercial overhead door, increase the width between columns by two inches.

 

This entry was posted in Pole Barn Design, Pole Barn Structure, Pole Building Siding, Columns, Sectional Doors, Pole Barn Questions and tagged , , , , on by .

Pole Barn Post Spacing Revisited

Pole Barn Post Spacing Revisited

By far, my most read blog has been on, “Pole Barn Truss Spacing”. With nearly 50% more reads than any other blog I have written, it clearly is a fan favorite. I’ve had it referenced by clients, building contractors and code officials.

So when one of our clients wrote: “After talking with the building inspector he does not like the idea of post spacing 12ft apart with double rafters. Can you quote a standard setup so I can compare apple to apples, post 8ft on center with double 2×12 header and trusses every 4ft, no joist hangers needed for perlins?”, I felt obligated to answer.

(For clarification of the above, “double rafters” are “double trusses”.)

My response: While the building inspector may not “like the idea” of using post spacing 12 feet on center, it is not only a tried and true method, but it is also one which our engineers recognize as being structurally superior and will engineer seal. We have thousands of buildings in all 50 states, done with the exact same design. It affords the benefits of fewer holes to dig, fewer pieces to handle and install, engineered connections and the reliability of doubled trusses.

Given the correct loading criteria and an engineered building, we will guarantee the ability to obtain a structural permit from our plans. The post spacing every 8′, single trusses every 4′ resting upon headers is a system our engineers are not interested in risking their careers on. In the event of a single truss failure, this system will result in a domino effect and the collapse of the entire roof system.

After the winter ice storm of ’96-’97, I spent quite a bit of time studying roofs that collapsed -some of which were on my own buildings!  At that time, we were using two trusses on a pole, so we had this part “right”.   But instead of putting the two trusses together to act as a single unit, we put one on each side of the column with blocking in between.  The trusses were notched in, so this was another part we were doing well – transferring loads into the ground.  But the one part we missed, was putting the two trusses together.  Lumber is after all, a tree…with inherent knots and defects.  With the huge loading of ice that year…the truss “weak spots” gave way – and if one truss fails, it pulls the rest of the roof down.  This is when I asked an engineer to evaluate the truss system I was using as well, and he concluded the “probability of a second truss adjacent to the first one having the same exact ‘weak spot’ – just could not be calculated.”

pole spacingFrom then on, I started using double trusses, nailed together according to a specific nailing pattern (supplied on all our plans).  Since then we’ve had other winters with similar ice/snow loadings, and…no more failed roofs!  I had the engineer’s word, but even better – I had real proof from thousands of buildings which survived nature’s “test”.  We’ve been using the double interior trusses ever since.  Only one roof I’ve seen fail since then…and it was determined to have been due to the two trusses were not nailed together adequately – they had few nails holding them together.   Again – the trusses acted as “singles” and pulled part of a roof down.

We get the requests for abnormal (for us) truss spacings or post spacing every once in awhile. Instead, I prefer to turn it around and stress our advantages –

(1) Fewer holes to dig, digging is always the worst part, and the one which is outside of anyone’s control. If they hit a Smart Car sized rock on the next to last hole, are they going to move the whole building?

(2) Fewer posts to set, trusses to raise, purlins and girts to handle. The real advantage of pole building construction is having the least number of pieces, in order to do the job structurally. By using slightly larger pieces (generally 2×6 instead of 2×4, where it takes only 50% more wood, to be 246% stronger) we are being material efficient.

(3) Wider sidewall door openings without the need for structural headers. In the event someone wants to add a door or window at a later date, they have far more flexibility to do so.

(4) Does anyone REALLY want to stand on a 2×4 roof purlin 16, 20 or more feet up in the air? When the 2×4 purlin snaps, it is a long drop to the ground.

(5) Most building collapses come from connection failures. In our case the purlins connect to the trusses with engineered steel hangers (not just nails); the double trusses bear directly on the posts (not on the sides of the posts, or nailed onto a header). The load is transferred down into the ground and is not dependent upon nails to hold the entire weight of the roof.

(6) If you think about it, if you have a 48’ long building, with single trusses every 8’, you have a total of 5 interior trusses.  If you have double trusses every 12’, you have a total of six interior trusses, but only have to dig 3 holes instead of 5. Which would you rather do?

By the way – our client DID get his building permit issued, using our plans, by the very same inspector who originally “did not like the idea”.

This entry was posted in Pole Building Comparisons, Pole Barn Structure and tagged , , , on by .
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