Installing ceiling and insulation in pole barn-

[bobinyelm]

Update on my trusses-

Mine are rated for ZERO cord load with the rated snowload of 12" of snow.

If I de-rate them to less snow, I can use a ceiling, but I have seen MORE than 12" here, so that sounds like a poor trade-off.

I have a call into the truss maker if there is a way to modify them. The installer said he has seen it done with about 2 or 3 sheets of plywood applied to each truss-pair, but I'd need to rent a scissors lift and glue/screw LARGE gussets on them

I found for only $25 per truss more, I COULD have had trusses that would have supported enough weight for a fully insulated and sheet rocked ceiling, but no one mentioned such things when I bought the building kit. I would have gone for that in a heartbeat

Oh well, but evidently it CAN be done, so I will wait for a call back and hope it's a simple fix.

 

[galute]

I LIKE that price. I figured I'd be happy w/ $2000 or less.

My only reservation about cellulose would be that it would be tough to blow in after the ceiling was in, but I guess since I plan to leave one bay open to the purlins (so I can lift vans like my tall Sprinter full-height), I could crawl down the trusses on boards laid on the chords with the hose and work my way back as I blow. Unlike batts, where you apply as you go, with blow-in I'd only get enough blower "free-time" (Unless I rent one when each bay or two was done, since I'm guessing completing more than 2 12X32 bays/day on ladders would be pushing it.)

Also not sure if the upper vapor barrier would create a problem (the backside of the sandwiched insulation batting under the metal siding). If moisture made it up there and condensed and dripped (as it does now heating w/ an unvented NatGas heater) onto the cellulose it would be bad (insulation and weight wise). Right now my gable-ends are not vented, so maybe providing vents at the ends under the roof overhangs would reduce any chance of that. Did you install vents on your gable ends?

We put up a bay then blew in the insulation for that bay, put up another bay then blew it. Started at the back wall and worked our way toward the door. I bought the insulation from Lowes as they had the best price near me. They only required 20 bags for the free rent on the machine and let me have it for a couple extra days free since I bought so many bags. Doing it that way allowed us to blow it from a ladder or scaffold as we went. Much easier than trying to crawl all the way thru the attic.

I have a ridge vent full length of the building but no gable end vents. I use wood heat so I don't have the condensation problems that you would have using unvented gas. Maybe someone with more experience with that problem than me will chime in to help you with that.

 

[bobinyelm]

We put up a bay then blew in the insulation for that bay, put up another bay then blew it. Started at the back wall and worked our way toward the door. I bought the insulation from Lowes as they had the best price near me. They only required 20 bags for the free rent on the machine and let me have it for a couple extra days free since I bought so many bags. Doing it that way allowed us to blow it from a ladder or scaffold as we went. Much easier than trying to crawl all the way thru the attic.

I have a ridge vent full length of the building but no gable end vents. I use wood heat so I don't have the condensation problems that you would have using unvented gas. Maybe someone with more experience with that problem than me will chime in to help you with that.

Doing it one bay at a time makes perfect sense. It was the fact that it didn't seem possible to do the ceiling and insulation in one day that way, which obviously you chose not to do yourself, but Lowes gave you more time.

I haven't calculated how many bags I'd need, but I figure 6" is plenty in my mild climate. Side story-In a former house in Texas, we had less than 6" cellulose (I think they blew in 6" but it settles below the tops of the 2X6 truss chords). We added 3 1/2" FG batts installed crossways over the chords (we unrolled them and pulled the vapor barrier off). It made no difference in our energy bills, so we added a perforated reflective barrier over the FG that ALSO made no difference in our bills. The rest of the home was well insulated, so we really expected the extra insulation to make a real difference, but it didn't (except on paper). So given modest wall insulation, I think 6" will be a realistic compromise for insulation/cost/weight.

Since my building is fully insulated with the 2 1/2" roll batting, our roof has zero ventilation (as mentioned), and while continuous ridge would be ideal, I'll settle for ridge vents. I should also have soffit vents to work w/ the gable roof vents, which I won't have. But given the lack of temp extreems here, I think it will be OK.

Once I have my furnace operational, it will end the moisture problem I am fighting w/ the unvented heat I am using to make the interior livable now (working inside in 35 deg dampness of 90+% humidity w/o heat is miserable).

 

[galute]

Putting 12'' in the ceiling of my shop was way overkill for our climate too. This is going to sound stupid but I can't stand to be in my shop with the overhead door closed. I like to stoke up the wood stove and kick open the doors. I can putz around in my shop in a short sleeved shirt with the 10 x 12 overhead door wide open when the outside temp is in the 20's and the inside temp will stay around 70 as long as the wind isn't blowing directly in the door.

 

[bobinyelm]

I heard back from the truss manufacturer today and bad news- he said anything more than a sheet of moisture barrier stapled to the bottoms of the trusses would overload them to where they could collapse.

I asked if I could reinforce them, and he said no, but if I submitted the lb/sqft of what I wanted to add, he would consult their structural engineer and have him see if there was a way to do it.

I asked what the typical failure pattern is on the trusses if the chord has ceiling installed, and he said that the whole truss/roof just collapses. I would have thought the pressed-in nailer plates would pull loose, but he said he had no idea (despite working fror this company for 20 years).

Maybe it's a liability thing?

But I need to calculate the loading per sqft for a vapor barrier, a layer of barn liner, and 6" of cellulose and get back to him.

Maybe their engineer can come up with something.

 

[galute]

This boggels my mind. I have never been able to figure out how the top cord can have a specific load rating of say 30 pounds sq ft and the bottom cord of 0. They are attatched together by the risers between them. Any load applied to the top cord is going to transfer down to the bottom cord thru the risers as well as any load pulling down on the bottom cord is going to transfer to the top cord by pulling down on the risers. It just don't make sense to me. I guess that's why I'm not an engineer. LOL

 

[psu927]

It's definitely a liability thing.

 

[Ironhorse74]

For what it's worth here is the final product. I am happy with it.



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[galute]

For what it's worth here is the final product. I am happy with it.



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Very nice. I considered doing mine that way but in the end it just wasn't what I wanted.

 

[bobinyelm]

This boggels my mind. I have never been able to figure out how the top cord can have a specific load rating of say 30 pounds sq ft and the bottom cord of 0. They are attatched together by the risers between them. Any load applied to the top cord is going to transfer down to the bottom cord thru the risers as well as any load pulling down on the bottom cord is going to transfer to the top cord by pulling down on the risers. It just don't make sense to me. I guess that's why I'm not an engineer. LOL

I suspect what the truss company is saying is that if I load the bottom chord, I can't load the top one, and IF I want to be able to trust the top cord loading specs (snow load), I MUST leave the bottom chord loading at zero.

No free lunch in a minimalist design. I'll bet in Phoenix my exact trusses would be rated for less snow load (not requiredoing by code), but they would allow a ceiling since the truss would have excess strength not "used up" by code demanding a certain snow load.

Just my guess.

 

[bobinyelm]

Very nice. I considered doing mine that way but in the end it just wasn't what I wanted.

That look VERY nice. The heated area above the lower chords doesn't look excessive.

What pitch is your roof?

Did you ask how much you reduced you allowable roof loading (snow load) by adding your insulation and ceiling?

 

[galute]

That look VERY nice. The heated area above the lower chords doesn't look excessive.

What pitch is your roof?

Did you ask how much you reduced you allowable roof loading (snow load) by adding your insulation and ceiling?

I'm not real sure what the pitch is on my roof. If I were to venture a guess I would say 4/12. Whatever is standard.

I have a friend that is an engineer and owns a truss manufacturing company. Not where mine came from as they were part of the package when I bought the building. I asked him about what I did after it was done. Mind you this is just a conversation we had over a beer while shooting the breeze and not intended as advise on trusses. He said that the bottom cord on this type of trusses was designed to keep the side walls from pushing out when there is a load on the top cords. They're design is to be pulled on end to end and not carry weight. Not that they are not capable of some small load rating, just that one is not needed for this design so why stick your neck out for a rating thats not needed. Thats why they don't have a load rating. Most common reason for failure is they pull apart at the perforated plates that connect the boards when overloaded allowing the bottom cord to kick out and the whole thing comes crashing down. He also said that by screwing all the metal up there it would all but eliminate any of that happening as in they were not going to pull apart nor kick out to the side. I asked him if I should be worried and he said he wouldn't worry about it. If it comes down it was going to come down with or without the ceiling. Again, no calculations, no drawings, nothing. Just me bs'ing with an engineer I trust over a beer. Take it for what it's worth. <Zero.

 

[bobinyelm]

I'm not real sure what the pitch is on my roof. If I were to venture a guess I would say 4/12. Whatever is standard.

I have a friend that is an engineer and owns a truss manufacturing company. Not where mine came from as they were part of the package when I bought the building. I asked him about what I did after it was done. Mind you this is just a conversation we had over a beer while shooting the breeze and not intended as advise on trusses. He said that the bottom cord on this type of trusses was designed to keep the side walls from pushing out when there is a load on the top cords. They're design is to be pulled on end to end and not carry weight. Not that they are not capable of some small load rating, just that one is not needed for this design so why stick your neck out for a rating thats not needed. Thats why they don't have a load rating. Most common reason for failure is they pull apart at the perforated plates that connect the boards when overloaded allowing the bottom cord to kick out and the whole thing comes crashing down. He also said that by screwing all the metal up there it would all but eliminate any of that happening as in they were not going to pull apart nor kick out to the side.
Bingo-That fits 100% with my amateur engineering analysis! The major weak spot I see is that one metal nailer that splices the two portions of the 2X6 lower chord together. One could probably add a theoretical steel cable between the posts (my design uses two trusses next to each other, one either side of each post on opposite sides of the building) to prevent this spreading of the posts with truss load as would occur if the lower cord components were to separate. The upper chords are under compression loads, and the lower under tension loads.

I asked him if I should be worried and he said he wouldn't worry about it. If it comes down it was going to come down with or without the ceiling. Again, no calculations, no drawings, nothing. Just me bs'ing with an engineer I trust over a beer. Take it for what it's worth. <Zero.

No, I think you are right-on, in fact.

I am going to calculate a ceiling load in pounds divided by the sq ft covered by the ceiling, and present it to the truss guy as he asked and see what he comes up with, but I think reinforcing the nailer plates by screwing them to the wood, or by overlaying them with larger ones glued and screwed, or using a friend's suggestion of making plates from steel and bolting them through the wood would all be ways to strengthen the trusses.

Those nailer plates are just a quick and dirty way to construct the trusses (vs labor intensive screwing/gluing) and probably the weak points in the design. That's why I asked the truss guy what actually fails when there is a failure, but he side-stepped the question by just saying, "the entire truss fails," but that's as useful as looking at a crashed airplane on the ground in a million pieces and saying the "whole thing failed," just because everything is now broken, while ignoring that one small part likely failed FIRST and started the craft earthbound in the first place.

I COULD get lucky and have the truss company offer an informed suggestion on reinforcement, though I am sure that for liability reasons they will offer nothing.

I will ask him to send me a spec sheet for the stronger trusses they COULD have supplied (if only the building supplier had offered an alternative, or if I had asked) and compare it with mine (component dimension wise and joining method) and see how maybe I cam make mine more like it.

 

[galute]

Just an observation from Ironhorse74 pic. Has anyone else noticed that all these builders freak out when you ask about adding a ceiling saying not even one pound of load on the bottom cords then they hang several hundred pounds of overhead doors from the bottom cord?

 

[bobinyelm]

Just an observation from Ironhorse74 pic. Has anyone else noticed that all these builders freak out when you ask about adding a ceiling saying not even one pound of load on the bottom cords then they hang several hundred pounds of overhead doors from the bottom cord?

Yep, my overheads were installed exactly as in the photos here as well.

The more I look at the trusses, the more it strikes me that truss failures are probably rarely due to the wood members failing first, but rather the steel gusset plate fingers pulling free of the 2X structural members. Once that happens, maybe the wood breaks because the loads are no longer supported at their design points.

I have to think that either screwing the existing plate into the wood through the existing holes, or overlaying the plates with larger plywood plates that are glued and screwed or glued and air-nailed (nailing with a hammer often loosens things with the pounding would significantly straighten the trusses overall.

I am sure truss calculations take the pressed-in plate-strength into account, and I wonder if there is a coefficient for that which would be different of those plates were made and fastened more securely?

If so, overlaying larger, better fastened plates MAY significantly strengthen the trusses to where they would carry a lower chord load.

Too bad we don't have a structural engineer familiar with truss design reading here. I just registered at http://www.eng-tips.com/ were actual P.E. structural engineers do answer questions about truss design, and I intend to post my question there after I finish my registration and will report back here if I get an answer.

http://www.eng-tips.com/threadminder.cfm?pid=1066&page=1

 

[galute]

I was just looking at the pics and I noticed there is a big difference in the size of the plates on my trusses versus the plates on Ironhorse74's trusses. Mine are a lot bigger. I wonder if it has something to do with mine being single trusses versus yall's being double trusses. I would think we all would have close to the same snow load rating. If the bigger plates give me with a single truss close to the same rating as yall with a double truss and the only difference being bigger plates then there is your answer.

Here is a pic of mine. Compare to his pic above.

 

[Ironhorse74]

I think these regional engineering companies design it once and just make a formula for the variables. I would bet a fancy dinner at a drive through window that my pole barn and Bob's were designed by the same company.

 

[bobinyelm]

Well, I got my furnace is installed yesterday (the top is at the 11ft 6" level), and I will temporarily have it hooked up to electrical and gas in a day or so to see if the shop will dry out. I'll set the temp to 80 deg during the dry-out phase.

While installing the furnace, I ran the unvented nat gas heater to keep the shop at 50deg, and the builder swears the 3ft puddle at the far end of the shop is not from a leak and recent rains, but is condensation, so now we'll see for sure.

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[Firebrick43]

look up Midwest plan service truss design. https://mdc.itap.purdue.edu/item.asp?itemID=11874#.WGgLSsl9bnc


Has the standard disclaimer that they might not meet code but the code specs have changed. The plans have multiple loadings and as long as you use correct materials and the current(or exceed) loading for your local you will be fine. This is for site built trusses with ply shear webs.

http://www.public.iastate.edu/~mwps_dis/mwps_web/tr_plans.htmlThis page has the actual plans but is missing the
MWPS-9 which calls out the construction methods and such

You could also use this program
Purdue Plane Structures Analyzer

Think its under 200 dollars for a single license. Its what truss designers use to evaluate their trusses designs

 

[bobinyelm]

Thanks-

They say their designs probably don't meet modern codes (especially here where all trusses must be engineer certified), but I just want to be sure they won't fall down, and code is just one way of ensuring that. If they are rated for the load is all I care about.

If my present trusses will carry more if plywood gusseted, that's all I care about.

Now that my building has passed inspection, what goes above the planned ceiling to make it stronger is pretty much moot, unless the insurance company were to start probing after a claim.

Note: While looking your source up I found some free design software (like: https://skyciv.com/free-truss-calculator/) but I haven't yet tried it to see if it's applicable.

 

[bobinyelm]

I was comparing my trusses with some shown here, and I was struck by how SMALL the connection plates on trusses are.

Some plates are as small as 2 1/2"X 3 1/4" and the largest are only about 4 1/2" X 7" up at the peak, so small that they were all had to be installed at about a 30 deg angle (shown) so they could have some contact area on each piece of wood they are supposed to be joining.

Hard to believe that such small plates can provide the maximum strength built into the truss. In other words, if the strength of the joints were made "failure-proof" to where the wood would splinter and break before the joints pulled apart, I would think the failure point would be higher regardless of the load.

Then again, maybe I am underestimating the need for joint strength where the pieces come together?


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