Tag Archives: scissor trusses

Pole Building Rooftop Decks

Post Frame Roof Top Decks

Question: Can decks be constructed upon a post frame roof top?

Answer: Yes, and it may prove far simpler than one might expect.

Our typical request from clients generally revolves around having a very slightly sloping roof and to use EPDM (ethylene propylene diene monomer) rubber as roofing over plywood. This solution might work, however very slight slopes tend to be problematic.

One of my own post frame buildings, located lakeside at Newman Lake, Washington, happens to have a rooftop deck. This particular building’s location happens to be perched upon the rear (farthest distance from our lake front) of our steeply sloping lot. The 30’x36’ building with a 10 foot wide enclosed shed off left sidewall has a total footprint of 40’x36’.

This building happens to be tall. Very tall – as in 40’6” from grade to roof peak. Besides garage level, it has two floors above. Upper floor clearspans a 30 foot width with floor trusses. This level also has a vaulted ceiling, provided by scissor trusses (I’ve written about this particular building’s roof trusses previously: https://www.hansenpolebuildings.com/2018/08/post-frame-scissor-trusses/).

Smoky MountainsKnowing this building would be very tall, and there would be a 180 degree panoramic lake view, it was planned all along to have a rooftop deck.  Adding to design challenges, we wanted this deck to be capable of supporting weight of a hot tub and its occupants!

This deck would cover an area between pairs of roof trusses/sidewall columns, a space of 12 feet along the building length. Sidewall columns were extended through the roof steel, to support glu-lam beams. These glu-lam beams had their opposite ends supported by a roof truss system designed to carry concentrated deck loads (along with snow and ceiling loads).

Where columns and glu-lams penetrated roof steel, a thick, high quality rubber and acrylic elastomeric roof coating formulated especially for steel roofing was used. After over 20 years of service, no leaks have been experienced. Other solutions may have been to use EPDM rubber boots and flashing to seal penetrations.

Interested in roof top entertaining upon your future pole building? It can be done, just ask your Hansen Pole Buildings’ Designer.

 

Pole Barn Insulation, Oh So Confusing

Pole Barn Insulation, Oh So Confusing

How to best insulate any building can be confusing – with pole barns being right there with any other structural system. “Best” also has to include a balance between the upfront investment and the long term savings, throwing in the wild guess as to what future costs of heating and/or cooling might be. Energy costs are probably not going to get any less expensive, so using today’s costs in determination of the outcome should yield a conservative answer.

To me – a practical return is if I can have my investment returned within a seven year period or not. There are also some intangibles to be factored in, such as a well-insulated building being much quieter for the occupants.

Regular readers will recognize the volume of questions I receive from those who did not plan ahead for the eventuality of climate control and are now looking for solutions. This is an issue which can and should be economically planned for at time of construction.

Reader MATT in ROCKFORD got the ball rolling on this subject when he wrote:

“I am ready to build my dream garage but somehow I managed once again to stumble upon an area where people just can’t agree on a single solution. Insulation!!! There should be a single answer for each barn use. 1: Storage only use this… 2: Equine only use this… 3: Workshop/Garage with occasional winter heat use this… 4: Garage/Mancave/House with full time HVAC use this… Plus the difference is argued about whether to use a radiant barrier? Or vapor barrier and where to put them. Vapor barrier like Tyvek etc. outside, plastic vapor barrier inside between wall material and the studs. Up north, snow on steel. Down south sun blazing on the steel. To vent or not to vent is also important.

 I would like to have a person with proper insulation experience in the north and the south who can explain why and in which order ( pic or graphics would be fantastic ) of what is correct. And give definitive answers boasting absolute confidence instead of having an answer that seems wishy-washy. Many kit distributors like to sell things easy to ship (dbl bubble radiant barrier). Many builders like speed, convenience, and mark-up (radiant barrier). Seems like spray foam has issues too.

Ultimately I live in Alabama where humidity, mold, and insects are a definite issue. I am building my final dream garage/home and I am disabled with a limited income so I can’t afford to make a mistake.

 Ugh Please Help!

 I also forgot to mention or ask about insulation that follows the roof line like in a clearspan structure. Or using steel trusses or scissor trusses where the insulation may be next to the roof and there is no attic.   Thanks, Matt”

Matt ~

I feel your pain. Insulation and ventilation are areas where there are a nearly innumerable number of possible solutions, many of which both work and can be Code conforming. Over my nearly 40 years in the post frame building industry, my own feelings about how to properly insulate have changed – most due to the advent of new products, better research and the gaining focus on energy efficiencies.

Tune in tomorrow for the rest of the story!

 

 

Concerns of a Post Frame Building Kit Shopper

Hopefully most, if not all, of my loyal readers are those who have concerns when it comes to investing in a new post frame building (I do know some of you just enjoy my slightly skewed sense of humor, or find my writings otherwise entertaining). For those of you who are avid kit shoppers, I try to give honest advice to any question posed to me.

Reader TRAVIS writes:

“Hello, I’m shopping around potential kit purchases and have a few questions. 

First off I’m planning to finish the interior, are the long spans between trusses you design able to handle the dead weight of drywall ceilings? 

One of my main concerns is column rot as my area is fairly wet. What type of treatment is used on the columns, where do you source them from, and do you ever recommend concrete permacolumns? 

Is it possible to use half scissor trusses and half regular to gain extra height in only certain areas? 

Thank you any help is appreciated.”

Mike the Pole Barn Guru gives advice:

Yes, we are able to design roof systems to support virtually any dead weight – including gypsum wallboard (drywall). Whether a Hansen Pole Building, or not, it is just a matter of the proper loads being applied in the engineering design phase of the truss process, then (if the trusses are spaced over two feet on center) using appropriate framing between the bottom chords of the trusses to support the loads without undue deflection.

If you intend to insulate above the ceiling, make sure to ask for the trusses to be designed with a raised heel at least two inches higher than the depth of the ceiling insulation, to allow for full thickness of the insulation above the sidewalls. Normally this has little effect upon the price of the trusses, however the building must be made taller to provide the same interior clear height.

All Hansen Pole Buildings’ structural columns (supporting roof loads) are pressure preservative treated to a minimum UC-4B specification, which is the requirement per the IBC (International Building Code). Even under extreme conditions, these columns should more than adequately support your building not only for your lifespan, but also your grandchildren’s. The longevity of properly pressure preservative treated lumber has been well documented in scientific testing.

We’ve had clients use concrete permacolumns – if your concern is properly pressure preservative treated wood not being adequate for your situation, a less expensive (and easier to build) alternative would be to pour the column holes full of concrete and utilize wet set brackets.

It is possible to mix any combination of scissored and flat bottom chord trusses throughout your new post frame building to gain extra height or for aesthetic purposes.

 

 

Insulating a Barndominium

Residential post frame buildings are becoming more and more prevalent as consumers are beginning to realize they can save thousands of dollars in foundation costs and actually build their own beautiful and well insulated barndominium homes.

Steve from Northglenn posed this question:

DEAR POLE BARN GURU: Now that the “Barndominium” style home is more popular than ever, have standards and practices been developed for creating a well insulated/air sealed pole structure?

Particularly, how would you recommend designing well insulated/air sealed pole barn home with cathedral ceiling/exposed joists in climate zone 5b?
I would like at least r49 in the ceiling and r28 in the walls, but the more the better. I would like to avoid spray foam due to the costs, and the steel replacement factor; replacing damaged exterior steel which has been sprayed with foam insulation sounds like a nightmare.

Mike the Pole Barn Guru:

My thought is bookshelf girts with BIBS(blow in blanket insulation), plus 1.5″ of XPS sheathing (fully sealed/taped) outside of the posts, then either attach the steel to the girts through the XPS, or place 2x4s on the XPS and attach the steel to that to maintain an air gap.

 

The ceiling I am less sure of. How is the ceiling finished if exposed trusses are desired? Is drywall screwed directly to the underside of the girts? If so, what supports the edges of the drywall on the 2′ span between girts? What is the largest girt size that is reasonable? In order to get a r49+, the roof would need 2×12 girts with BIBS plus 1″ of XPS, then steel, or 2×10 girts with BIBS then 2.5″ of XPS.

Have you ever used roof SIPS to get higher R-values? If so, how are they attached to the girts?

What is the best way you recommend to accomplish this?

Thanks! Steve

Dear Steve: Might as well start at the end and work forward.
SIPS – (Structural Insulated Panel System) No, I have never used them. They would provide high R values, however they appear to be extremely expensive. As far as I can surmise, the savings in energy costs will never offset the added cost of the SIPS. I had done some preliminary research on the use of SIPS for post frame. However the people “in the know” never shared the information I needed to be able to write further about them:

SIPS


I would think to use SIPS would require the use of very long screws to attach them to the underlying roof system adequately enough to maintain structural integrity of the building.
For the roof, you are not going to want to place XPS (Extruded Polystyrene rigid foam board such as Owens Corning FOAMULAR®) between the roof purlins and the roof steel, as this will compromise the shear values of the roof steel.
SIP PanelWithout going to the expense of deep I joists or prefabricated parallel chord trusses for roof purlins, the largest readily available dimensional lumber would be 2×12, which even with BIBs is only going to net you about R-45. Plus the upper foot of the roof trusses would then be “buried” by the thickness of the purlins.
If your goal is to have an exposed truss, you might want to look at doing parallel chord scissor trusses to create an attic space in which you could blow in even R-60 insulation, then use a non-structural truss below to create the look you are after. Our friends at Timber Technologies are just one possible source of this type of truss:

(https://www.timber-technologies.com/titan_trusses.phtml)
On the walls, you have the same potential challenge with attempting to place XPS between the girts and the siding, as on the roof. The best results are going to be obtained when as much of a thermal break as possible can be created. Bookshelf girts can provide for a deep insulation cavity, then the XPS panels can be placed on the inside of the girts, and GYB (Gypsum Wall Board) can be installed on the inside of the XPS panels. You will want to have a quality Weather Resistant Barrier between the wall framing and the steel siding. Read more here: https://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/
The XPS panels will serve as a vapor barrier on the inside of the walls, so you will not want to have another vapor barrier (such as Visqueen) on the inside of the wall insulation.
Looking for a super insulated new home? Post frame construction is most likely the answer!

 

Overhead Doors and Eave Height

Putting a 14 Foot Tall Overhead Door in a Short Eave Height…

I’ve been doing post frame buildings now for a couple of years. Okay, maybe a couple of couple of years, as in 37 (ouch, am I seriously this old?). I’ve learned a certain amount of clients (and builders) are seemingly dimensionally challenged when it comes to fitting overhead doors into buildings. Quote request, after quote request has come across my desk, for the overhead door height and the building eave height to be the same!

Newer readers might want to review how eave height is measured on post frame buildings: https://www.hansenpolebuildings.com/2015/02/eave-height-2/.

Hansen Pole Buildings’ Designer Doug posed this question of me earlier today, which came from a client of his:

“Do you offer a vaulted bottom chord that would allow us to lower the sidewall height and keep 15’6” at the 14’ overhead door?”

And Doug added…..

“My instinct and experience says we need minimum 2’ especially with a 14’ high door but it never hurts to ask.” (This would be needing two feet of eave height greater than the overhead door height)

The building in question has a 40 foot wide endwall. With placement of the overhead door at the center of the endwall, here is my answer to Doug:

The bottom side of the top jamb will be at 14’2.5″ above grade, 15″ to clear = 15’5.5″. Door is 12′ wide, so allow an extra 6″ of width for the tracks. This means at 13’6″ from the sidewall, you need to have 15’5.5″ above grade. With a standard gabled roof and 2×6 top chord on the trusses, the door just fits.

If the scissor truss bottom chord was a 1/12 slope, the eave height could be lowered to 14’10.5″; 2/12 13’9″; 3/12 12’7.5″.

 

 

Now the kicker – with scissor trusses, your client had better drive straight into the building and not want to park close to one of the sidewalls, because those trusses make a nasty slapping sound when they get hit, right before the roof caves in.

Because the scissor trusses are going to require adding to the exterior slope of the building, the overall building height is going to be the same or more, and scissor trusses are more expensive than standard trusses – probably making the entire project more expensive, with less net interior clear space throughout the building.

Can he do it? Sure. Is it practical or safe? Probably not.

Pole Building Trusses

Pole Building Roof System – Dressed Up!!

For years I sat in church on Sunday mornings with my children and admired the magnificent trusses which supported the roof. Built from glulams with the joints connected with bolted steel brackets – they were nothing short of fabulous. To me (coming from a background of construction and prefabricated roof truss manufacturing), I believe I had a special attraction to them more than just the average parishioner.

Truss-FramingAs pole buildings have gravitated from the farms of the 1950’s into the mainstream of popular construction, their owners have been looking for more appeal than what was offered by the average tractor shed.

The aesthetics of massive exposed trusses somehow is appealing to many of us. By using glulaminated timbers to fabricate them, the members have very few flaws and can be readily finished to highlight the natural beauty of the wood.

By using prefabricated metal plate connected wood scissors trusses, the structure of the roof surface can be readily supported. These trusses may have conventional “heels” (the point where the top and bottom chords meet) and an exterior slope which is greater than the interior slope. By use of a raised heel, the bottom chord slope can be increased to give a more dramatic look, as well as creating a deeper insulation cavity.

Ceiling finishes are then often tongue and groove two or three inch thick material. Depending upon the spacing of the trusses, often no other bottom chord framing is required for their support.

Non-load carrying glulam trusses can be placed directly below the decking to give the impressive look, without sacrificing any of the “pretty” parts of the truss – as this work is being done by the hidden trusses above the decking.

Whether office space, a church, great room or man cave – if you want to “knock the socks” off your guests or clients, this one offers some distinct possibilities

Changing Bottom Chord Height

At least in my generation we were raised to believe the experts – whether it be doctors, attorneys, or building contractors really knew what they were doing. I know I have the expectation and I believe our clients expect the same from us – as they should.

Truss Drawing - Bottom ChordI recently wrote about an article my Uncle Neil had written for the Journal of Light Construction (JLC). Just out of being curious I did a search under “pole barns” and was amazed when I found the thread below (keep in mind these are JLC-Online Expert Forums).

Here is the question posed:

I would like to raise the bottom chord on two trusses in my pole barn. 
I have set many a floor truss and roof truss and know that this kind of modification is based on approval from an engineer, I was just wondering if any of you have done this in the past. The trusses are 42′ long with a 2X10 bottom chord, 3/12 pitch. I would like to raise it 12 to 16″ inches from the bearing point out 12 feet.

And the responses from the “experts”, and my take on each one:

Should be possible. We have done similar things using LVL and plywood gussets. Contact your engineer and have him draw you a repair.

At least this one recommends having an engineer involved. What the Original Poster (OP) is asking for is a major repair, and is very likely economically impossible (I always tell clients we can design nearly anything, as long as they have enough money to pay for it).

In the few cases where I’ve needed a truss repair I’ve always gotten them from the truss manufacturer… lo and behold they’ve been asked before and have a filing cabinet full of ready-to-go solutions.

I owned two prefabricated metal plated wood truss manufacturing plants over 17 years. There is no such thing as a filing cabinet full of ready-to-go solutions.

If you are only modifying two trusses you could sister the top cords with 2/12 rafters, (I get 21’ 7 ¾”, full rafter length, 3/12 pitch at 21’ run, btw, I also get a lateral change distance of 5’ 4” for a 16” rise, not 12’, so perhaps I’m not understanding you completely, the maximum new bottom cord length would be approximately 30’ 9”, if the seat cut of the new rafters are full bearing @3 ½”, not likely.) Nail them solid from both sides, pop your new ceiling line on the trusses to cut, cut on the line and cut out of the 2/10 bottom cord that is being raised to fit directly under the new rafters, nail well to the cut webbing from both sides. Add substantial gusset scabs over both sides of the new connections at the 2/10 to 2/12 rafters. Finish cutting the bottom cord as needed. Modify each bottom cord one at a time.

Without seeing it, this sounds like the modification I would entertain. Proceed at your own risk. Also, call the Truss Co and speak to their engineer.

I am guessing this expert is NOT a registered design professional (RDP – architect or engineer), but they are passing out dangerous advice as if they knew what they were talking about. No RDP in their right mind would give instructions like these (or any others) without, at the very least, a copy of the original sealed truss drawings.

And in the end, from the OP:

Thanks for the replies. I am going to call Cleary the builder and see if they have any stock
drawings for this application.

I would like to have been the fly on the wall at Cleary Buildings when this call came in, especially after the expert advice given by the experts. Pole building trusses are typically engineered so the design loads are very close to capacity (to do otherwise would be bad business on the part of the builder/supplier/fabricator).

My best guess as to a solution – would be to order scissor trusses strong enough to carry the loads and place them alongside the existing trusses, then remove the portions of the old trusses which fell below the scissors truss bottom chord. In any case – a truss should never be cut or modified in any way, without involving a RDP. Keeping your roof up, could be a lifesaver. Maybe yours!