Tag Archives: single trusses

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.


Connecting Trusses Not Dots

Connecting Trusses Not Dots

This feature is probably not overly mentioned, however as most structural failures involve connections, it probably should be.

FEATURE: Double trusses notched into sidewall columns and connected with Strong-Drive® SDWS TIMBER Screws

BENEFIT: Trusses placed in a notch cannot slide down columns and Strong-Drive® SDWS TIMBER Screws resist uplift forces without a need for boring holes through columns.

WHAT OTHERS DO: A myriad of design solutions exist.

For trusses mounted every two or four feet upon truss carriers (headers between sidewall columns) attachment can be by toe-nail or engineered steel hangers to carriers. In some instances paddle blocks are inserted between carriers and trusses are nailed to these blocks.

With single trusses aligned with sidewall columns, trusses are most often placed into a notch cut into one side of columns. With nail or glu-laminated columns an interior column ply can be cut short to create an integral notch. Truss to column connections may include nails and/or bolts.

In designs with two single trusses, most often a truss is placed on each side of sidewall columns on top of bearing blocks. Bearing blocks may be nailed, lagged or bolted to column sides. Trusses are attached in same fashion as bearing blocks. Trusses are spaced apart along their length by paddle blocking installed between chords. Under extreme loading conditions trusses and their bearing blocks have been seen driven down sides of columns to rest upon building contents or even, the ground.

A variant on this places trusses closer together so they may be notched into sides of each column. This allows for elimination of bearing blocks and their associated challenges.

At Hansen Pole Buildings, we have trusses physically face-to-face nailed providing for a true load sharing between trusses. A notch is cut into one side of columns for trusses to bear. Attachment of trusses to columns is most often done by use of Strong-Drive SDWS Timber screws.

WHAT WE DID IN 1980: Lucas Plywood & Lumber placed a single truss upon each side of columns, on top of a nailed on bearing block. Trusses were attached to columns by means of a ¾” diameter, non-galvanized through bolt – entailing having to drill through nearly nine inches of wood and hoping to avoid steel connector plates at each truss heel.


Spot Problems with This Pole Barn Photo

Spot Problems With This Pole Barn Photo

One of my Facebook friends had posted this as a timeline photo as it brought back to her fond memories of a childhood spent frolicking in hay lofts. It was so bad, I just had to save it.

So, what’s wrong with this photo anyhow?

Obviously bird excrement over everything does not pose a structural problem, but one which I would have been trying to minimize, if not avoid. One thing which was leading birds into building – excellent nesting material provided by what was once a vinyl faced fiberglass condensation control blanket (aka Metal Building Insulation).

Long ago I had espoused about joys (or lack thereof) involved in installation of Metal Building Insulation (https://www.hansenpolebuildings.com/2011/11/metal-building-insulation-in-pole-buildings-part-i/). For those of you readers who did not click upon link and read it in full, suffice it to say birds love fiberglass.

Once condensation control blanket was torn apart – there was nothing left to prevent condensation from occurring below roof steel.

Moving forward, just glancing upon structure supporting hay loft, I would suspect a high degree of under design with only chance keeping it from meeting its demise.

All sorts of things are seen hanging from trusses. Amongst these are a block and tackle, which I suspect has been used to lift bales of hay into loft. Fortunately, individual small hay bales are relatively light, as I am pretty sure trusses were not designed to support added point load weights.

While not most effective structurally, trusses can be designed to be placed upon each side of a column – provided they are done correctly. Blocking should be placed between truss bottom chords, in order to prevent weak axis bending. A bare minimum would be every ten feet.

I see no web bracing, making this highly suspect. Older barns tend to have had bracing needs neglected. Single trusses (when placed not nailed directly face-to-face into a pair, they are single) require a great deal of bracing.

Knee braces are what I see as biggest structural issue. Not only are knee braces ineffective (https://www.hansenpolebuildings.com/2012/01/post-frame-construction-knee-braces/), but when installed improperly (as in photo) they are potentially throwing a load into roof truss bottom chords trusses were not designed to withstand.

Feel free to chip in with your observations.


Dear Pole Barn Guru: Can I Use Spray Foam Insulation in My Pole Barn?

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: In northern Idaho, just east of Coeur d’Alene, I had a pole barn put up without insulation figuring I would build 2×6 walls between the posts and insulate with batts and then plywood the walls later for a work shop. Can spray foam be used instead? Could I frame 2×4 walls instead of 2×6? Can it be sprayed onto the metal siding and roof without any negative effects showing up later? I will have a heater in there, but probably not on full time. QUIRYING IN COEUR d’ALENE

DEAR QUIRYING: Can you use spray foam? The answer is yes, however it is probably the most costly choice, and the Building Code requires any spray foam to be covered with non-combustible material (e.g. gypsum wallboard).

For the walls, you could frame a non-structural 2×4 studwall, holding it flush to the inside of the columns, and place batt insulation between the studs. The studs do not have to be the same depth as the insulation, and in doing so, you will eliminate a thermal bridge.

Beware, less costly (per inch of thickness, not R value) open cell foams are permeable to moisture – so condensation could become an issue. To obtain an R-19 rating from spray foam, be prepared to spend around $3 to $4 per square foot of insulated area.

While spray foam is relatively light weight, always check with the manufacturer of the roof trusses and the Registered Design Professional (RDP – engineer or architect) who designed your building to verify the weight of the insulation being added will not compromise the structural integrity of the building.

DEAR POLE BARN GURU: I sent in three pole barns that i am looking to get a quote for. my families barn just recently burned down a few days ago due to undetermined causes. We lost our animals in the fire which was devastating. Our pigs and chickens were our livestock and our food. We need to get a barn up and built soon to get our farm running again. I have a few questions about this, first off if i go ahead and purchase this kit how does it get delivered to my house. Second, if this is purchased is the supplies all in one kit that you ship out or is it a list a what we need and i have to get it? please get back asap thank you. NEEDY IN NEW YORK

DEAR NEEDY: I am deeply sorry for your losses. Fire is so devastating.

When you order from us, the materials are delivered to you via truck.

You are purchasing from us the design, the complete 24″ x 36″ blueprints which are specific to your building and show where every board is placed. Not only to we provide all of the materials for construction, but we give you detailed instructions as to how to assemble everything.

DEAR POLE BARN GURU:  What is your standard design practice to accommodate a wider O/C truss?  Double the truss? Or increase the truss member sizes?


DEAR VASCILATING:  Our most common practice design in general is a system using doubled trusses spaced most commonly every 12′ (although spacings 10′-16′ are also very common). The doubled (or more technically “ganged”) truss system affords some safety not found in single truss systems – as multiple trusses physically connected to each other all for true load sharing. The probability of two or more connected trusses having the exact same weak point is phenomenally low – reducing the risk of a catastrophic failure in an extreme loading situation. Ganged trusses also require less bracing than single trusses, adding to ease of installation, as well as lower costs and a “cleaner” finished appearance.  It also may mean no cumbersome (and expensive) truss carriers.  Lastly, if you put overheads in a sidewall, having the double trusses mean you could put as wide a door as 12’, and have plenty of room to put in a hoist system to lift a vehicle between the sets of trusses.

Vascilating then responded:

Thanks for the quick response. I assume, then, the practice is to utilize 12′ 2×6 purlins placed on edge on top of those trusses?

Is the spacing of 12′ the same for an attic truss? I recently got a quote from Hansen for a gambrel building with which I intend to have attic trusses. Is it common practice to finish a room using the knee walls of those trusses?

Dear Vacilating:

Every client gets my individual and undivided attention for as long as they need to get their questions answered.

The snow load will dictate purlin size, but they will be 2×6 or larger, joist hung between the trusses. Attic trusses will be the same, however may be more than just a 2 ply truss depending upon the span and load. Most typically people will finish those spaces with a knee wall.

Unless you are absolutely married to the gambrel look, the most efficient and cost effective design for multi-story space, is to just design a multi-story building. For about the same cost, you can get full room height from sidewall to sidewall