Tag Archives: lean-to

What Kind of Trusses Are Pictured?

What Kind of Trusses Are Pictured?

This question was posed by Hansen Pole Buildings’ Designer Doug. Photo isn’t of a Hansen Pole Building, probably raising questions in Doug’s mind as it looks rather foreign.

Only actual trusses in photo are in raised center portion of this monitor style building. Interior trusses were probably sold to building owner as being “double trusses”. In actuality this system has only a single truss placed upon each side of columns. These trusses, even though only inches apart, do not load share. They are only as strong as weakest individual truss. Between trusses, sticking up beyond top of top chords are paddle blocks (read about paddle blocks here: https://www.hansenpolebuildings.com/2012/05/paddle-blocks/) to attach roof purlins.

Monitor wings (or side sheds/lean-tos) have rafters placed each side of columns with paddle blocks as well. Second floor (aka loft) extends out into wing areas, although quickly loses functionality as headroom decreases close to eaves.

More headroom could have been garnered throughout entire second floor had trusses and rafters been positioned to allow roof purlins to joist hang into their sides. When placed as “top running” purlins, interior clear height decreases by purlin thickness. Positioning of roof trusses as lowered, below purlins causes builder to have to frame outriggers (or tails) above truss in order to support sidewall overhangs. Each paddle block makes for a purlin stagger and eliminates one’s ability to predrill roof steel panels. This adds to possibilities of roof leaks being created by each stagger point.

Other concerns exist in this photo. Where roof purlins overhang single end truss, attachment has been made with yet another set of paddle blocks. With an assumption overhangs will be enclosed, this allows for outside air to enter in spaces created between purlins. This decreases efficiency of dead attic space airflow from eaves to ridge.

Solid blocking should be placed between end overhanging purlins to provide continuity of a load path from roof diaphragm to ground. As being built, load path has been divided.

Perimeter beams in this photo show to be inset between the columns. My curiosity wonders how they adequately attach? Your guess is as good as mine.

 

What Size Post Spacing?

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: Building a 32’x 50′ barn that’s 32′ high. Trying to determine the extension out from the ridge for the widow’s peak/ hay hood. Didn’t know if there’s a correct mathematical equation for this? PHILIP IN NEW KNOXVILLE

DEAR PHILIP: There is some mathematics involved, but it comes from a structural standpoint, rather than aesthetics.

A widow’s peak is an extended pointed overhang placed in the center end of a barn roof. Historically, they were used as a pulley support to raise hay bales into hay lofts. In modern post frame construction, very few widow’s peaks are actually used functionally, other than as shelter to protect a loft door. More often than not, they are strictly for aesthetics.

The width of the widow’s peak is usually 1/3rd to ¼ of the width of the gabled end of the building. The distance extended beyond the building endwall, or other endwall overhang is up to the eyes of the beholder, but is most typically three feet.

Now for the math…..the roof surface of the widow’s peak must be accounted for in the design of the endwall truss, as well as the supporting roof purlins. The truss manufacturer needs to be aware of the dimensions of any overhangs beyond the end of the building. The supporting roof purlins can be capably designed by the RDP (Registered Design Professional – architect or engineer) who has done the building design. The nicest looking widow’s peak at time of construction, can end up being far less than pretty if it sags over time.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: What is your typical post spacing and what is the maximum spacing the poles can be spread out? RICK IN WATERLOO

DEAR RICK: The most efficient post spacing is going to depend upon the wind and snow load conditions at any particular given pole building site. As a general rule, the best “bang for your buck” is most typically spaced every 12 feet, although 10 foot and 14 foot spacings are often a close second.

On fully enclosed buildings, the wall girts normally become the dictate on how far apart columns can be placed – they usually will fail at 16 foot pole spacing (again, depending upon wind loads).

For buildings where one or more sidewalls are partially enclosed, 24 foot spacings between columns can be fairly easily accomplished. On endwalls, with a clearspan truss, it is possible to have posts only at the building corners.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Does Macomb Township allow pole barn construction for a garage? Do you work in Macomb Township, MI? PETE IN MACOMB

DEAR PETE: Pole barn (more technically “post frame”) construction is a 100% code conforming construction system. I’ve found jurisdictions which have tried to prevent “pole barn” construction within their jurisdictions, and we have successfully won the battle every time. Jurisdictions can legislate what a building looks like, however it would be improper to attempt to limit a conforming structural system.

Should you (or any other reader) find a jurisdiction which has contrary ideas, please let me know – as I will have a friendly (and persuasive) discussion with the jurisdiction’s legal counsel.

Macomb Township does have an unusual requirement for any type of building – “rat walls”. You can read more about them here: https://www.hansenpolebuildings.com/2012/06/rat-wall/

As to where we do work, Hansen Pole Buildings provides complete custom designed pole building kit packages anywhere in the United States – including Macomb Township.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: I want to add a lean-to on my 42 x 48 pole building. Should I attach 2×10’s to the poles and put purlins on top of them as if continuation of the building, or should I put a ledger across the side and build accordingly. Thanks DION IN RUHKAMP

DEAR DION: Your cart may be slightly ahead of your horse. Before looking at the rafters and purlins, it might be a good idea to read: https://www.hansenpolebuildings.com/2015/07/shed/

Back to your original question – I personally prefer to attach the rafters directly to the columns with roof purlins on edge in between the rafters. As to 2×10’s – depending upon the width of the shed and your snow load, it is not likely they are adequate. With more information, I can give you a more definitive answer.

Mike the Pole Barn Guru