Home >> roof systems

Tag Archives: roof systems

Dear Pole Barn Guru: Where Can I get Hand Lift Jacks?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays. With many questions to answer, please be patient to watch for yours to come up on a future Monday segment. If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: I am building a 32×56 x10 tall pole barn. I would like to install a garage door (18foot) in the eave side corner. How can this be accomplished? I am worried about the weight that would need to be supported from the 2 trusses that will be in this 18 span. MAROONED IN MATTOON

DEAR MAROONED: You should absolutely be worried about the load from the trusses across an 18 foot wide door opening.

We see people buy “off the rack” standard pole barn kits, or putting together their own buildings from the guess and go theory – neither one of which is going to adequately address the issues of how to span openings for doors such as yours.

Many lumber yards or prefabricated roof truss manufacturers will try to size a glulaminated or LVL beam, based upon trusses which are evenly spaced across the header, rather than having considered the concentrated loads which occur with post frame construction.

Not only must the dead weight of the trusses and their associated bracing be considered, but also the weight of all ceiling and roofing materials, as well as any snow loads. And this is just for the proper sizing of the beam. Connections to the columns at each end are crucial – both to resist gravity as well as uplift loads. Keep in mind, more buildings fail from improper or inadequate connections, than from any other cause. The columns at each side of the door opening also need to be checked for adequacy against a larger wind load than some, or all, of the other wall columns carry. It is not unusual to have larger dimension columns specified at each side of a wide opening, such as you propose.

If you have not yet ordered a building kit – make sure to look for a provider who can provide complete plans, specific to your building, with the engineering to back up their design.

If you are already out building, I would recommend contacting a registered design professional (RDP – engineer), who can adequately provide for you a proper design, given the plans you are working from and the design criteria.

DEAR POLE BARN GURU: I have a late 1970’s pole barn with fiberglass skylights. They are 94X32 with the center to center ridge peak 10 inches. The peak is flat and about one inch wide. These skylights need replaced. Do you have any product that would work for me. VEXED IN VANDALIA

DEAR VEXED: I’m never a fan of any skylight in any post frame building roof. Why? They are going to leak or fail, it is just a matter of when. Without seeing actual photos of your situation, my first recommendations are going to be to replace the skylight area in the plane of the roof with steel roofing. If you must have natural lighting through the roof, I’d recommend using a polycarbonate ridge cap.

DEAR POLE BARN GURU: Where do I find a set of the hand lift jacks that are like a boat trailer winch with a top pole cap that allows you to install your purlins on the ground and lift the 2 trusses at once, so I don’t have to rent a zoom boom or boom truck. I bought one of your kits and have poles set and didn’t think I would have the difficulty of finding these jacks. THANKS FROM TONASKET

DEAR TONASKET: Thought you could Google anything and get an answer, didn’t you? Me too, but what you are looking for appears to be a well kept secret.

Every set (either two to lift a pair of trusses, or four to lift two pairs along with all of the purlins between) of winch boxes I have ever seen were fabricated up by the person using them.

The most common version is a welded up steel box with 5-5/8” inside dimensions and no bottom. The open bottom will later allow the “box” to be slid over the top of a 6×6 column. Attached to the top of the box (usually welded), is a reduced drive hand crank winch designed for a boat trailer.

Most of the crank units seem to come from Harbor Freight – and the caution is to use the ones with steel gears, as opposed to nylon gears. I’m told the nylon gears just do not have the durability.

In most cases, steel cable is used for lifting, although straps could be an alternative. Regardless, the winches and cables or straps need to be adequately rated for the weight being picked up.

Have a column size other than 6×6? If 4×6, add a block of 2×6 to the side of the column. Larger than 6×6, chainsaw a notch into the top of the column to fit the box.

Another variant of hand lift jacks (requires the use of cables only and twice as long), places a pulley wheel on the top of the columns, and the winch is attached to a flat steel plate which is affixed to the outside of the column. This method does afford the ability to do the lifting from the ground, instead of having to crank off from ladders.

I’ve successfully lifted two sets of 80 foot span roof trusses, along with all of the roof purlins and truss bracing, using winch boxes.

Those who have built and used them, rave about the time spent building the hand lift jacks was well worth it. And these days, so easy to resell on eBay.

I’ve suggested to several people for them to manufacture lots of these, and rent them out. Even though there is a market – no one has taken me up on it as of yet

This entry was posted in Pole Barn Questions, Pole Barn Design, Trusses and tagged roof systems, fiberglass skylights, hand lift jacks, polycarbonate ridgte cap on September 16, 2013 by admin.

Bridge Bracing

Lauri is one of the newer members to the Building Design team at Hansen Pole Buildings. Pole buildings, while having the appearance of being fairly simple, are actually remarkably complex structures and involve the proper interaction of literally thousands of components.

Due to this, it is not surprising for a question to come up, which there is not an easy answer to. Today, Lauri came up with one for me….from one of her clients….

“Also I would like some bridge bracing between the trusses. I have seen instances where the roof sheeting was used to do this and it seems to me that this is a poor practice. I do want a ridge vent system, so I would like at least 2 lines of bridge bracing using 2X4s on either side of the ridge line between the trusses.”

Having grown up in construction (my paternal grandfather, father and his five brothers were all builders), been involved in the prefabricated roof truss industry as an owner or in a position of authority for over two decades, and been a general contractor myself….I had never heard of “bridge bracing”.

Off I dashed to the wonders of the Internet….Googling and Yahooing as if my life depended upon it.

It took some doing, but I was finally able to find “bridge bracing” as it would apply to wood frame construction. And it wasn’t at all what I (or probably the client) envisioned.

Here is how the term is properly applied…..Say one is framing up an exterior deck. All of the joists, including the rim joist are in place. 4×4 or similar sized posts are fastened to the inside of the rim joists, to support a railing. On the side of the 4×4 opposite the rim joist, are placed two framing members as blocks, equal in size to the joists, and parallel to the rim joist. By use of adequate fasteners, this double block (the bridge bracing), keeps the post from rotating once the final assembly is in place.

My supposition is this client is fairly unfamiliar with post frame construction and has made some assumptions. These could include the prefabricated roof trusses are spaced every two feet, and the roof is sheathed with either plywood or osb (oriented strand board). These assumptions would be true, in the case of typical stick frame construction. Even in stick framing, the stiffness of the roof sheathing is such as to preclude the need for even a single solid block of 2×4, between the top chords of the roof trusses at any point.

Yes, blocking could be added, or in the case of a pole barn, the ridge purlins could be doubled. However, there would be no added structural benefit and it would add to the cost of the building in both materials and labor. As all our buildings are designed to support the weight of the roof, including the framing and whatever roofing materials are chosen, “bridge bracing” becomes a non-issue.

This entry was posted in Constructing a Pole Building, Pole Barn Structure and tagged roof systems, ridge purlins, roof framing design, roof truss bracing on July 18, 2012 by admin.

Thermodynamics and Reflective Radiant Barriers Part I

A reflective radiant barrier inhibits heat transfer by thermal radiation. It does not necessarily protect against heat transfer by conduction or convection. Why do you need to know about reflective radiant barriers? It could mean thousands of dollars saved over the years for heating/cooling, in what you choose for not only roofing materials, but more importantly, what is placed between the roofing and building framing. Bear with me here.

In today’s science lesson…..

All materials emit (give off) energy by thermal radiation as a result of their temperature. The amount of energy radiated depends on the surface temperature and a property called the emissivity or the emittance. Emissivity is expressed as a number between zero and one at a given wavelength. The higher the emissivity, the greater the emitted radiation at a given wavelength. A related material property is the reflectivity or the reflectance. This is a measure of how much energy is reflected by a material at a given wavelength. The reflectivity is also expressed as a number between zero and one (or a percentage between 0 and 100%). At a given wavelength and angle of incidence the emissivity and reflectivity values add up to 1 by Kirchhoff’s law.

For those of us who never studied thermodynamics (most of us), Kirchoff did it for us over 150 years ago. While he appears to have been a pretty smart guy, most of his work will go over the heads of us average folks. The important thing to remember is – a good absorber is a good emitter (if something gains heat readily it also gives it off readily) and a good reflector is a poor absorber.

Reflective radiant barrier materials must have low emissivity (usually 0.1 or less) at the wavelengths at which they are expected to function. For typical building materials, the wavelengths are in the mid- and long- infrared spectrum.

Reflective radiant barriers may or may not exhibit high visual reflectivity. This is because while reflectivity and emissivity must add up to unity at a given wavelength, reflectivity at one set of wavelengths (visible) and emissivity at a different set of wavelengths (thermal) do not necessarily add up to unity. However, it is possible to create visibly dark colored surfaces with low thermal emissivity.

To perform properly, reflective radiant barriers need to face open space (like air or a vacuum) through which there would otherwise be radiation.

Moving forward in time from Kirchoff….

In the 1920’s patents were filed on reflective surfaces being used as building insulation. Recent improvements in technology had then allowed low emissivity aluminum foil to be commercially viable. Over the next 30 years, millions of square feet of reflective radiant barriers were installed in the US alone. Notable examples include projects at MIT, Princeton, and homes such as Frank Sinatra’s house.

So how does this work in a building?

Radiant solar energy strikes the roof, heating the roofing system (often shingles, felt paper and roof sheathing or steel) by conduction, and causing the underside of the sheathing and the roof framing to radiate heat downward through the attic toward the attic floor (or inside of the building shell when no enclosed attic space exists). When a reflective radiant barrier is placed between the roofing material and the building interior, much of the heat radiated from the hot roof is reflected back toward the roof and the low emissivity of the underside of the reflective radiant barrier means very little radiant heat is emitted downwards. This makes the top surface of the insulation cooler than it would have been without a reflective radiant barrier and thus reduces the amount of heat which moves into the building.

This is different from the “cool roof” strategy which reflects solar energy before it heats the roof, but both are means of reducing radiant heat. According to a study by Florida Solar Energy Center, a white tile or white metal cool roof can outperform traditional black shingle roof with a reflective radiant barrier in the attic, but the black shingle roof with a reflective radiant barrier outperformed the red tile cool roof. An option is to install both a reflective radiant barrier and a cool roof, for optimum performance. There are a wide variety of factors to consider in deciding whether or not to use a cool roof and/or a reflective radiant barrier.

For those of you sitting on the edge of your chairs, wondering where all this is going, I’m afraid you’ll have to wait one more day. Come back tomorrow and I’ll explain how Mike the Pole Barn Guru’s science lesson on reflective radiant barriers will help you to design the “perfect” roof for your new building.

This entry was posted in Roofing Materials, Pole Barn Planning and tagged roof systems, roof reflectivity, thermodynamics; thermal radiation on April 16, 2012 by admin.

More High Wind News – Pole Buildings Can Withstand Strong Winds

Pole buildings can be easily designed to withstand hurricane and tornado wind loads. The article below is from www.technewsdaily.com May 26,2011 and speaks to housing design under high winds.

Redesigned Roofs Withstand High Wind Events

The tornado that stormed through Joplin, Mo., on May 22 shredded an estimated 8,000 buildings and stranded desperate families that now must decide whether to rebuild or find a new home. For those choosing to rebuild, Rima Taher, an expert on wind-resistant structures, has a bit of advice: don’t do it the old way.

“You wonder why we keep doing the same things, making the same buildings,” Taher told Innovation News Daily.

By analyzing debris from hurricanes, Taher has come up with a set of guidelines for building new homes in areas prone to extreme weather.

“There are similar problems. So, what usually works for tornadoes would work for hurricanes,” Taher said.

When wind hits, the roof provides the most critical defense. But during a hurricane or a tornado, the roof is often the first to go. Taher found that increasing the number of slopes on a roof improves the aerodynamics of the structure and greatly reduces the amount of pressure exerted on it. She recommended building a roof with at least four slopes, rather than a traditional gable roof that has only two.

As wind swirls around a house, it can push on the roof from both the inside and outside. Taher suggested installing a moveable flap close to the seam of the roof. During hurricanes and tornadoes, the flap would open, stabilizing the air pressure. In hot weather, the flap would provide ventilation.

Taher also recommended spending a bit of extra money on hurricane clips that attach the roof more firmly to the walls than nails or staples alone.

Researchers at the Center for Building Science and Technology in France tested the recommendations by placing wooden models in a wind tunnel and used the results to design a “cyclonic home” that has twice the wind resistance a traditional home.

Moreover, most of the suggestions are simple to execute and well worth the investment.

“A lot of the things we suggest don’t really cost a lot of money. The expense is really minimal compared to the benefits,” Taher said.

Applying modern technology to pole building design, the roof trusses are directly connected to the columns, which are embedded in the ground. Rather than even depending upon light gauge “hurricane” clips for wind uplift resistance, seven gauge steel plates, attached with 5/8 inch diameter through bolts can create a positive anchorage between the roof and the walls. Low cost ventilated ridge caps help to equalize internal and external pressures, to relieve some of the uplift forces. Pole buildings can also be easily designed with roof systems having gables or hips in multiple directions to improve aerodynamics.

Hansen Buildings provides custom designs, including multiple gables, hips or other features to increase wind uplift resistance. Alternate designs, using T’s, L’s, gables and just about any design you can think of is possible. My feeling is, if a pole building can be structurally designed to meet code, we will find a way to produce the pole building kit!

This entry was posted in Pole Barn Planning, Pole Barn Structure and tagged pole building, custom designs, hurricane clips, roof systems, Pole Building Design on June 29, 2011 by admin.