How to Square a Post Frame Building Roof

Many builders believe if they have a building correct in width and length at ground, diagonals at ground are equal (footprint is square) and columns are plumb, then when they get ready to run roof steel everything will be perfectly ready to go.

This might be close to true for a small footprint building with a low eave height, however in most cases making this assumption will lead to a world of grief.

Today we will steal from Hansen Pole Buildings’ Construction Manual to achieve a perfectly square roof.

Note – ease in squaring a roof is one reason I frame my roof and install roofing prior to framing any walls. Everything moves far easier.

Figure 13-1: Squaring Roof

1. Check both endwall trusses for straightness (against a string line) from side to side.

1. Make certain endwall truss is plumb at each column. Properly set columns are either plumb or lean out slightly. To pull in, attach a cable from this column top to column base at the opposite endwall. Using a “come-along” move column top inward until plumb.

1. Using a stringline align all eave struts (purlins) to straight. Any nonaligned column tops can be pulled into place using a “come-along” also, using the same procedure as outlined in the last paragraph. This is critical as this building line will be a noticeable one.

1. Make certain the roof is square by checking diagonals from peak at one end to eave at the opposite corner. Refer to Figure 13-1 where diagonals AD and BC, AF and BE are equal.

Be certain to measure from the same “point” going each direction. Serious errors have been caused by lack of consistency. If uncertain, double check.

If any roof diagonals are “long”, run a cable and come-along from truss peak to opposite corner column (along purlin underside). Pull slowly until dimensions are equal. For best results, the difference in diagonals should be no greater than 1/8”. A very small “tug” can change a diagonal drastically.

NOTE: One side only may be squared up at a time. Place roofing on squared side, then repeat the process for the opposite side.

Dear Guru: Should I Add Trusses?

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: I had a 40×90 pole barn built by Pekul Buildings in 2007 with the intention of being cold storage only. The 40′ trusses are 4/12 pitch and on 9′ centers. I think the trusses were made by Midwest Manufacturing, and I can see a stamp on them stating 30/4/1 rating for 9′ spacing. I found their truss drawings on the Menards website and see a note stating essentially no additional bottom chord loading is allowed.

Now I would like to convert one end section of it into a 40×36 workshop with steel liner paneling and insulate it with polystyrene sheet insulation… I know I should have anticipated this before it was constructed, but my situation changed and long story short now I need a workshop of my own…

Your input is greatly appreciated, as you clearly are the pole barn guru!

Thank you, MINDFUL IN MUKWONAGO

DEAR MINDFUL: Thank you for your kind words!

Re-purposing pole buildings happens a lot, you will not be the first, nor the last to deal with issues of wanting to finish a ceiling in a building which was not designed to support one.

The first place I would start would be to contact Midwest Manufacturing and inquire about a repair which would allow for an increase in the bottom chord dead load to 5 pounds per square foot, from 1. More often than not, this is the least expensive solution.

While trying to add another truss to the opposite side of the columns, or in between the existing columns might be a solution, it is going to come with expense, lots of work to get them in place inside your building, and a fair amount of mental frustration.

Interior columns are not going to be a viable solution – your existing trusses are designed to clearspan, placing a column beneath them is going to entirely changing the load paths within the trusses and could cause a failure.

As a loyal reader, you know I am not a huge fan of steel liner panels for ceilings. https://www.hansenpolebuildings.com/blog/2013/08/steel-liner-panels/

If it works for you and meets your needs, wonderful.

For ease of installation, lowest cost and overall best performance, I would encourage you to look at blown in insulation.

No matter which path you ultimately follow, if you create a dead attic space, be sure to adequately ventilate.

https://www.hansenpolebuildings.com/blog/2014/02/pole-building-ventilation/

Mike the Pole Barn Guru

and a followup from Mindful…

DEAR POLE BARN GURU: Thank you for taking the time to reply, and so soon!

I sent an inquiry to Midwest Manufacturing and we will see how/when they reply.

I do have the ability and equipment to install additional trusses inside this building,  as I do some pretty complicated and technical construction work.  I also have a mechanical engineering background.  Just not sure if it is the best option for supporting a ceiling.

I am not against the echo effect of steel liner panels, and do admire their lighter weight and easier cleaning.  I plan on using the workshop for my automotive hobby work and occasional welding/fabricating.  I also plan on heating it intermittently to prevent condensation.

I am leaning towards using polystyrene sheets for insulation as I have a good source for free surplus material up to 8″ thick.  Free is good if it will work!

The building already has eave and ridge ventilation.

Condensation on the bottom of the roof tin is another issue.  I was misled by the builder as they said the eave and ridge vents would prevent this.  I am unsure of what can be done besides spraying insulation against that surface.  I have seen roof panels rust completely through (from the bottom side up) on a metal frame building with foil faced fiberglass insulation and heat, and do not want that problem with mine.

Thank you again for the fast response.  Your problem solving contributions make this world a better place.  I do the same automotive-wise for others. MINDFUL IN MUKWONAGO

DEAR MINDFUL: Thank you very much again – it really is about paying it forward.

Hopefully a truss repair will be the easiest solution.

If you do decide to add trusses, they should be directly attached to the existing ones – not on the opposite side of the column. None of the existing trusses is designed to be able to support a ceiling load, so the new ones would need to do all of the ceiling load carrying work.

If you do not have a good vapor barrier under your concrete floor, heating will actually ADD to the condensation problems, as it will cause moisture to rise through your slab. If you do not have a vapor barrier under the floor, then a good sealant should be added to the top of the slab and you may need to add ventilation.

There do exist some builders who either are lazy, or just do not have the knowledge to understand what the cause of condensation is. Eave and ridge vents alone do not normally prevent condensation problems. Pretty much your choices now are going to be spray foam, or to remove the roof steel, apply reflective insulation, and reinstall the steel.
Mike the Pole Barn Guru

DEAR POLE BARN GURU: I added a pole structure 30 x 32 (ready for trusses) to an existing 40 x 30 pole barn. It is square to the back of the building but it is out of square by two and three-quarter inches from the front of the structure. (hindsight is 20/20) I should’ve run a string from the front of the building, looking for solutions other than excavating around the posts and re squaring. OH NO IN ORCHARD PARK

DEAR OH NO: Whether you do or do not have a serious challenge depends upon where the “out of square” is occurring. Pole buildings can be very forgiving and can hide a plethora of oops!

What is important is the ability to have the roof planes square, and the columns on each wall in a straight line. If those two things can occur, then the rest can be worked around.

This is where it really helps to be able to work from a building kit which has explicit written assembly instructions, including diagrams and photos. You should make sure to refer to the ones you received with your building often as you continue on your installation.

As you do not yet have the trusses placed, there is plenty of time to be able to adjust things at the eave line so the width and length measures are 30 and 32 feet from outside of column to outside of column (assuming you set your columns to approximately these measures – some people hold their columns in 1-1/2” resulting in added work and cutting).

With the width and length measures adjusted to “right on” (is necessary), square up the diagonals of the corner columns and brace them so they stay securely in place while trusses and purlins are installed. Take caution to insure the roof does not grow or shrink while placing purlins.

Prior to installing reflective roof insulation and steel over the purlins, square up each roof plane – if you have followed my advice, this should be fairly easy. With the roof now square and the columns basically in a straight line at the ground, install the balance of the wall framing.

With the “unsquareness” you originally reported, there is a good chance one of your corner columns is not going to be plumb. This will not be the end of life as you know it – just run the steel panels on the wall to plumb and the differences can be hidden behind corner trims. The worst thing is – someone who is really looking will be able to tell the corner trim does not exactly parallel the steel ribs.

Mike the Pole Barn Guru

Are the Poles Close Enough?

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU:How close is close enough for pole placement? After setting and leveling poles to the string, the poles on one side of the barn are 1/2″ off (lengthwise) from the other side. Is this close enough? KARMIC IN KANSAS CITY

DEAR KARMIC: There actually exists a document entitled, “Accepted Practices for Post-Frame Building Construction: Framing Tolerances”. In the document, in Section 6.4: “Wall length. In rectangular buildings, the overall length of opposing walls should not differ by more than 2.0 inches.”

In my humble opinion “only” two inches would be a HUGE difference. Variations such as this need to be hidden somewhere and two inches would be huge.

In your particular case, if the poles are merely placed in the holes and braced, I would recommend adjusting a corner column to get equal overall lengths.

If the columns have been set in concrete, it is best to then make the overall dimensions at the roofline correct. This will make squaring up the roof to install roofing far easier. In the event this circumstance is the choice, when it comes time to do the siding, plumb the corner(s) which are most likely to be noticed.

On the out-of-plumb corners, the edge of the corner trim will not align with the steel ribs (there will be a ½ inch variation from top to bottom). Most people will never see it – but putting it on the least viewed corner reduces the probability.

DEAR POLE BARN GURU: Hi: How do I install fiberglass batts of R 19 in my walls of pole barn without touching the metal walls? Thanks. ART IN ALBION

DEAR ART: The easiest way would be to install a quality housewrap over the outside of the wall girts and under the wall steel before siding it.

In the event your pole building has been sided, there really is not a negative effect in the event the fiberglass happens to be in contact with the wall steel. It IS essential to have a vapor barrier on the inside of the insulation which provides a total seal. If the vapor barrier is not completely sealed moisture will escape into the wall cavity, and be trapped by the steel siding. When the siding is cold enough, condensation will form, saturating the fiberglass and reducing its efficiency.

You may want to read more on climate controlled pole buildings at:

https://www.hansenpolebuildings.com/blog/2012/04/climate-controlled/

DEAR POLE BARN GURU:What about putting the concrete up to the slab level?

CONCRETING IN CANTON

DEAR CONCRETING: I will assume your question is in regards to backfilling the columns. If so, there is no documented negative reason (lots of old wives’ tales) to not fill the holes entirely with concrete – other than cost (concrete can become expensive backfill). It will make your building very resistant to uplift forces.