Replacing trusses in situ

[INTMD8]

Since I'm going to be tackling this project next weekend I thought I would seek the input of others here.

I have a 36x47 pole barn. The lower chord of the current trusses is 8ft from the floor.

This wasn't going to allow me to have a 2 post lift in the center of the building so I had Starwood build me some lam/ply trusses that will bring my center clearance to 11ft 3in (which happens to be exactly the height of my 2 post lift).

Anyway, the current trusses are at the center of the outer posts. The outer posts are not solid but 3 2x6's, center one being shorter to allow for the end of the truss.

My plan is to cut the outer 2x6 on one side so the new truss can sit flush up against the original.

Next I would run another 2x6 under the new truss to the ground and yet another one on the outside of the new truss and bolt them all together. (so the new truss is next to the old, bolted through/sandwiched between 2x6's).

Then I will bolt/screw the new truss to the original top chord. Opposite of that I will put "L" brackets from the new truss to the purlins.

After all this is done I will cut out any part of the old truss that exists below the new one.

Let me know what you think about this plan and if you have any other suggestions.

Also should mention these trusses are designed for 12ft on center and they will be 8ft on center so I'm told the building will be stronger when completed. (if you had any questions as to the strength).

Thanks!

-Jim

 

[Milton Shaw]

You have some 2x6 or so running as "strong backs" tying all the trusses together at the bottom. You are going to loose that tie with what you are suggesting. Have the new trusses been engineered to have that strength with out the ties. The trusses should handle the roof load ok, but I would worry about the strength of the structure without any lengthwise structure. My floor trusses and roof trusses required "Strong backs" to tie all the trusses together to make them react to the load together instead of as single truss. The engineers were very specific about what size lumber was used and how they were tied to each truss. Talk to the engineers about this before you start cutting things out.

 

[INTMD8]

Yes, I did plan to brace the lower chords of the new trusses as well but I will contact Starwood for details. The pics I've seen of these trusses in use don't seem to have any front/back bracing like that however.

 

[Chris705]

Jim - Your description of how to tackle this sounds well thought out. A couple questions.... Are the existing purlins above the truss top cord? Is there any diagonal truss bracing? Can't tell from photo. Can't you leave the existing two end trusses in place and not install new trusses on the ends? Linear bracing can be attached to bottom chords but any diagonal bracing may now need to attach to purlins. You might consider braces from bottom chord of both end trusses up to bottom chord of new adjacent truss. Would like to hear what new truss manufacturer says about req'd bracing. Good luck looks like a bit of work ahead!!

 

[Chris705]

Are there 6 new trusses or 3?

 

[INTMD8]

Thanks for the info. There are 3 new trusses to replace the last 3 in the building.

There is bracing at the last truss from the top chord to the wall but that will not be disturbed as the original top chords will remain.

I'll see what they say about bracing and update when I know

 

[joe_padavano]

I also think you've really done a good job of thinking this through. The lam trusses are waaaay cool. I've never seen those before, but it makes perfect sense. Nice find.

 

[PCO6]

I replaced all of the ceiling joists in my garage and had enough fun with that. This is a whole different matter. Good luck with your project. This will be interesting.

 

[INTMD8]

Thanks guys!

I emailed Starwood about the bracing and there response was

"I would recommend 2 rows at 1/3 points in your situation."


2 rows at 1/3 points? Not sure what that means honestly.

 

[Rock knocker]

How can you put those 8' OC, when the existing are 12' OC as are the point loaded columns?

 

[INTMD8]

How can you put those 8' OC, when the existing are 12' OC as are the point loaded columns?

I'm not. The existing are 8' OC.

What I was saying is the new trusses are designed for 12' OC but I'm installing them at the existing 8' spacing.

 

[LX-Markham]

2 rows at 1/3 points? Not sure what that means honestly.

Take the bottom arc of the new trusses, divide into 3 equal segments. Install the bridging (bracing) at those third points. You'll have 2 rows of equally spaced bridging.

Hope that made more sense.

Sounds like a good plan. Good luck! The hardest part will be getting those bad boys up there.

 

[INTMD8]

Take the bottom arc of the new trusses, divide into 3 equal segments. Install the bridging (bracing) at those third points. You'll have 2 rows of equally spaced bridging.

Hope that made more sense.

Sounds like a good plan. Good luck! The hardest part will be getting those bad boys up there.

Yes, just clicked, thanks.

Going to have a few guys, some type of lift and jacks. It will be interesting

 

[LX-Markham]

be safe.
those things look heavy and awkward.

maybe rent a small lift truck or something.

 

[davo727]

Those are pretty nifty. What did it cost for the 3?

 

[NUTTSGT]

I wonder if it would be easy to actually remove the roof and put them in from the top ?

 

[Chris705]

Renting or borrowing two of the manual duct lifts and some guys to brace as they go up seems like it may work fairly easily. The duct lifts are on wheels and could be rolled tight to your existing trusses once they clear the bottom chord. Just a thought....or scaffolding on both ends with your helpers to lift, pull one side at a time.

 

[little d]

Just thinking out loud here but, I gotta wonder how much effort it would take to unbolt and remove the old ones (one at a time) and replace instead of sistering and cutting out the old ones?

 

[warren57]

Your plan is structurally sound. All I would add is after sistering your truss to the existing columns, I would steel plate both sides and bolt through all those layers of 2x.
I too like your trusses. I just finished adding on to my shop and designed and built traditional style trusses. A lot of work with all the braces and gussets. Your style pretty much eliminates all that work. Very interesting. And very stout...

 

[NUTTSGT]

Just thinking out loud here but, I gotta wonder how much effort it would take to unbolt and remove the old ones (one at a time) and replace instead of sistering and cutting out the old ones?

That's what I thought was going to happen. I misunderstood that in reading the original post. That's why I suggested maybe removing the roof and installing them.

 

[cyamaha2007]

I helped a buddy install scissor trusses in a existing pole barn. We did it just like you, but the truss co said we should add 2x12 headers on the inside of the poles to help distribute the load on the poles, since the load will now be off center. Also, be sure the 2x6 that you,re planing to sister to the pole doesnt contact the floor. The floor will float and move independent of the posts; you dont want the floor to push on the sistered 2x6.

 

[INTMD8]

I appreciate the ideas. Plan is to use a manual lift and the help of a few friends. They are supposed to weigh about 400lbs each.

The trusses were about 2200.

I think removing the roof/purlins would be more difficult as the new trusses are 2 inches thicker than the originals and would not just slide into place. I would still have to cut/modify the posts.

 

[INTMD8]

Also, be sure the 2x6 that you,re planing to sister to the pole doesnt contact the floor. The floor will float and move independent of the posts; you dont want the floor to push on the sistered 2x6.

Good to know! I didn't realize there was any significant movement between the two.

 

[ms fowler]

Lack of lateral bracing ( strongbacks) is probably the number one cause for truss failures. The bottom chord must be braced. Follow what the truss manufacturer said--- 2 braces, each at 1/3 of the span.
You were wise to realize the need.

 

[INTMD8]

Update. All went as planned! 2 friends and I did most of it in about 8hrs yesterday.

I finished up the bracing and clean up today. 11ft 3in clearance at the center. Same height as the top of my 2 post lift

 

[Chris705]

Looks great!!

What were you thinking when you cut away the first bottom chord of the old trusses?

 

[starquestMM]

X2 looks great.

 

[INTMD8]

Thanks!

Honestly wasn't worried at all since the new trusses looked so beefy.

 

[Craptain]

Love the video.