Tag Archives: gambrel trusses

Bracing Site-Built Trusses for Lateral Loads

Bracing Site-Built Trusses For Lateral Loads

Reader in SHINER writes:

I am building a gambrel style barn, 30×80, in two directions, in plan view, it looks like a cross. I am building the trusses based on an LSU publication, giving sizes of structural members, etc… I have built several structures before, not a gambrel style barn though. My Question, Guru, how do I brace the trusses for lateral/wind/racking/diagonal loads? I want to do an exposed ceiling of 2×10’s T&G, and am worried about how to brace the trusses so they don’t fold over like a deck of cards during and after construction. Surely the nails don’t provide all the lateral bracing? I’ve seen too many leaning barns over the years to know that nails alone don’t provide sufficient wind load protections. How are the trusses braced, one to the next, so they don’t fold/roll over? Your help is so appreciated, Thank you.”

Mike the Pole Barn Guru writes:
Even with my decades of truss industry experience, I wouldn’t begin to think of field constructing 30-foot span gambrel trusses. 

I did review LSU’s “truss” design (these are actually rafters not trusses), it is from 1988 and includes this disclaimer:

“This site makes available conceptual plans that can be helpful in developing building layouts and selecting equipment for various agricultural applications. These plans do not necessarily represent the most current technology or construction codes. They are not construction plans and do not replace the need for competent design assistance in developing safe, legal and well-functioning agricultural building system. The LSU Agriculture Center, the Mid-West Plan Service, the United States Department of Agriculture and none of the cooperating land-grant universities warranty these plans.”

Several problems – no design roof or wind loads are incorporated in their design and design values for Southern Pine lumber were down graded as much as 30% in 2012 https://www.hansenpolebuildings.com/2012/06/southern-pine/

Any permanent roof truss/rafter bracing system should be developed only by a Registered Professional Engineer. Given LSU’s information is highly out dated, should you wish to continue upon this path, I strongly urge you to reach out to a competent Registered Professional Engineer to design a structurally adequate system, including a permanent bracing system you can rely upon.

Maximizing Post Frame Gambrel Space

Maximizing Post Frame Gambrel Usable Space With Trusses

Hansen Pole Buildings’ Designer Rachel and I recently had some discussions in regards to maximizing post frame gambrel truss useable space.  Most often gambrel roofs are supported by one piece clearspan gambrel trusses. Largest downside to this type of truss system is lack of bonus room width. Usually you can expect a room from 1/3 to ½ building width with smaller span trusses (generally 24-30 foot spans). Sort of like this:

My bride and I happen to live in a gambrel style barndominium (for more reading on barndominiums https://www.hansenpolebuildings.com/2016/04/the-rise-of-the-barndominium/). It is actually probably more appropriately a shouse (shop/house). We wanted just a lot more living space than what could be afforded by a bonus room in a gambrel truss.

This is what we did…..

Center width of our home is 48 feet. We clearspanned this using 48 foot long prefabricated wood floor trusses, placed 24 inches on center. These parallel chord trusses are close to four feet in depth. With our 16 foot high finished ceiling downstairs (it is a half-court basketball court), this made our second floor level 20 feet above grade. Ends of these trusses are supported by LVL (https://www.hansenpolebuildings.com/2013/01/lvl/) beams notched into four ply 2×8 glu-laminated columns every 12 feet.

This got us across from column to column to support a floor, now we needed a roof system! We utilized trusses much like these, only much bigger:

Our trusses were so much larger, they had to be fabricated in two halves, split right down the center and field spliced to create a whole unit. We utilized the “Golden Ratio” (https://www.hansenpolebuildings.com/2012/06/gambrel/) to create slopes and pitch break points. Our steep slope is 24/12 and our upper slope is 6/12/ On the inside, our slope is 12/12 and our flat ceiling ends up at 16 feet above floor!

We also ended up with a very, very tall building. Roof peak happens to be 44 feet above grade! Living at 20 feet above ground does afford some spectacular views – we look due south down Lake Traverse and can see the tops of tall structures in Browns Valley, our closest town six miles away.

In my next article, I will clue you in on things I would have done differently, so stay tuned!

Brackets to Sonotubes, Housewrap, and Help with a Remodel

This week Mike the Pole Barn Guru gives some advice regarding the use of brackets with sonotubes, installation of housewrap, and the possibility of replacing a gable style roof with a gambrel.

DEAR POLE BARN GURU: Guru, I am looking at building a pole barn home. I like the idea of doing wetset brackets in concrete sonotubes, then after building is erected pouring the slab inside. My question is how will the grade board and slab be connected to the existing concrete and pole with wet set bracket. Thank you . STEVEN in COVINGTON

DEAR STEVEN: Your building’s grade board (aka splash plank or skirt board) will be oriented so upper 3-3/4 inches will be above top of slab. In this area, 10d common galvanized nails can be used. Below top of slab, fasten with two 3/16” x 3” Powers (www.powers.com) PC3DA-HDG galvanized steel split drive anchors (or equivalent).

Your building’s concrete slab can be connected to concrete in sonotubes by use of two five-foot lengths of ½” rebar bent to 90 degrees at center. Place one leg into tube leaving other leg out into future slab area at approximately 60 degrees from plane of splash plank (this will require cutting a short slot into top of sonotube.


DEAR POLE BARN GURU: Greetings, I’m at the point in construction where I need to read up on how to install house wrap prior to wall steel. I don’t have the Wall Steel chapter (Chapter 21) in my manual and I can’t find any mention of house wrap anywhere else. I’m assuming that I can’t put wall steel over cap staples unless they are under a rib. CARL in SPRUCE

Reflective InsulationDEAR CARL: Installation of housewrap will be a chapter in an upcoming version of our Construction Manual. Although it might be possible to install steel siding over cap staples, we are unaware of anyone who has tried it. To the best of our knowledge everyone has used just enough staples to hold housewrap in place and installed siding immediately. By running housewrap vertically you can place wrap right ahead of installing steel. Make sure to seal all seams with three inch wide tape.


DEAR POLE BARN GURU: I have a 24×47 detached garage and I wanted to remove the wood rafters and replace them with metal joist in a gambrel design with metal roof. Is that something your company would do? HARRY in SACRAMENTO

DEAR HARRY: We are not contractors, so could not assist with any form of construction. As post frame building kit suppliers, we do not use metal joists of any kind.

You might be able to find a contractor who would undertake this project, however my educated guess is it would be less expensive to demolish your existing garage and begin from scratch, than to do a remodel of this scope.