Engineer needed for decorating trusses? 3

[rjpope42]

Hi all, engineer from another realm stopping in. I have a BSEE and Masters of Engineering in Materials Science, but neither of those qualify me to do structural engineering so I'm seeking some quick advice.


I'm looking to decorate the exposed 40' trusses in my shop, the thought being:
-attach dimensional lumber to the sides of the trusses to just make them appear to be the same thickness as the 6x6 poles.
-cut the slop off the 2x4 lateral braces, and maybe thicken them for visual balance
-add extra knee braces for symmetry
-stain all the wood dark brown

I've read that decorating trusses "usually doesn't require engineer involvement", and I'm removing nothing, only adding. But better safe than sorry, so I'm here to see if this gets a reaction of "nah you're just adding decoration that, if anything, is extra bracing so nailgun away" or if it's more like "hire a structural engineer or your trusses will collapse under their own weight"

Thanks for helping me get sorted!

(Working on uploading pics)

 

[rjpope42]

A couple photos of what I'm working with.

 

[KootK]

1) Correct answer = "hire a structural engineer or your trusses will collapse under their own weight".

2) If this was my shop, I'd do this without batting an eye.

3) Braces look like they could use a little beefing anyhow. Let us know if you'd like to do that strategically. It's not unheard of for the columns to be cantilevers such that the braces aren't required though so I wouldn't panic.

Is there such a thing as snow where you live? The greater the snow, the less the impact of your plan.

Hi all, engineer from another realm stopping in.

In exercising good judgment as you have, you've represented middle earth well.

 

[oldestguy]

I'd not do it. The reason is you are then hiding important parts of the trusses that carry loading. Then, down the road there is some accident or fire, etc. Your claim for damages likely would be of no value since you modified he trusses somehow. I'd also check with the insurance company now. They may invalidate any coverage right now.

 

[BridgeSmith]

As far as attaching extra 2x's to the side of the trusses, it will add a small amount of extra weight. Your profile says you're in NY, so I'll assume the snow load is fairly substantial. If that's the case, the extra weight should be negligible. If you offset the joints in your added pieces on each side of the truss (start with a full 12' piece on one side and a 6' piece on the opposite side of the truss, and continue with 12' pieces), it will make the trusses a little stronger.

As far as the lateral braces, not all extra is 'slop'. There needs to be enough extending past the attachment point so that the end doesn't split and release the nails or screws. It's been a long time since timber design class for me, so I'm not sure how much you may need to leave.

Adding the extra knee braces may stiffen the connection in ways that could cause some prying. I don't know if that's likely, or if there's a way to mitigate the effects. Hopefully, someone with more experience in this area will weigh in.

I don't know of any detrimental effects from staining it.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[r13]

Leave the wood work alone, don't do anything, but stain all wood to dark brown. It will be looks great then.

 

[rjpope42]

Thanks all!
Snow load region of 20lb/sqft, wind load region of 80mph, building 5 years old

Kootk, thanks for the honest input!
I don't know exactly what the story with my knee braces is, every other barn of nearly identical construction in my area doesn't have them, I had one old house builder tell me if it was him he'd just remove them so they aren't in the way (I added that to the scary bad advice pile)

In any case, I was planning on just thickening the trusses and copying the braces on the other side, what would be a more strategic way?


Oldestguy, thank you for bringing insurance into the picture for me! Hadn't thought of that.


BridgeSmith, good point on the overhang! Now my concern is that a lot of the joints have zero overhang, so the memo may have not gotten to the original builder :/[pre][/pre]

 

[KootK]

In any case, I was planning on just thickening the trusses and copying the braces on the other side, what would be a more strategic way?

Nothing, that's what I had in mind. Show off.

 

[Craig_H]

Part of me wonders whether it may be possible to buy new trusses, with center-span field splices, and throw them up there for cheaper than hanging around on a rolling scaffold, scabbing 2x's on the trusses? Heck, then you get some added skookum factor as well. Just a thought...

I'd be careful about adding knee braces. These can impose funny loads into the truss. If you do, add them so that they join the truss at a "node" (layman's terminology: where the sticks hit the shiny bits).

 

[BridgeSmith]

I don't think the edge distance needs to be much (probably just a few inches), especially if it's just nails connecting it. I am hoping maybe somebody that's more familiar with this aspect will weigh in with something more definitive.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[XR250]

If it was my shop, I would spend the time and money to insulate and sheetrock it so it is super comfortable to work in.
(i assume there is no insulation on the exterior)

 

[dauwerda]

rjpope42,
Any chance that this building had to be permitted when it was built? If so the city/county may have the truss drawings on file with the permit. Many jurisdictions that don't require full blown engineering for structures still require stamped truss drawings to be submitted with the permit application. If so, you should be able to look at the drawings to find the design criteria, many post frame trusses (not all) are designed for a 3-5psf bottom chord load to allow for ceilings, lights, etc. If the original design included this, then there really should be no issue with adding the architectural features you describe.

That said, I agree with KootK, if it were my shop I would do it without batting eye.


By looking at the construction of the building, I am fairly confident that it was built using "standard" techniques and there was no engineering done originally (other than the trusses). That said, the trusses were probably not designed to accommodate the knee braces, some builders put them in and some don't. In my experience, most engineered post frame buildings utilize the steel roof as a flexible diaphragm and the steel sidewalls as shear walls (sometimes the walls will need to have plywood/osb installed on the inside if the wall is comprised mostly of openings) and don't require any braces. Both knee braces and wall bracing in post frame construction tend to suffer at their connections, most of them are installed without adequate fastening. You can read up more on knee braces here,

https://www.hansenpolebuildings.com/2012/01/post-frame-construction-knee-braces/

(I have no connection with Hansen but they are very knowledgeable in engineered post frame buildings)

Based on the testing cited in the link above, if it were my building, I would remove the knee braces unless I knew the original building was actually engineered to include them.


Is the "lateral bracing" you are referring to, the truss bottom chord and web bracing that is shown in the bottom picture? If so, yes, you should be able to cut the excess ends off. I don't believe the NDS actually specifies a minimum edge or end distance for nails with a diameter less than 1/4", however maintaining a 1" distance between the nails and the end of the board should be adequate.

 

[Brad805]

You planning on holding dance parties or something? If not, I don't follow why you would a dime on adding wood to the existing trusses. This is what all pole buildings look like, and a bit of wood here and there is unlikely to change things much. Slap some paint on like suggested, and then spend money on some materials to improve the building envelope.

 

[KootK]

I was curious about the application too. My guess: attractive but thermally uncomfortable in-law suite.

 

[rjpope42]

Craig_H, that's an interesting idea, I'll be sure to consider it, thanks!

Dauwerda, thank you!! That's a lot of great information!!!


I wasn't planning on making this a barn build thread, but since y'all'r curious, I plan to do 3" closed cell foam on the walls, and have the finished interior wall set back a couple inches so the vertical poles are still visible. I was initially planning on doing a flat cieling under the trusses and faux wood beams to match the poles, but the wife really wants it vaulted and open. (Your next assumption that she's invading my man cave is incorrect, she spends just as much time in it as me).

So the outer cieling will be insulated with probably foam boards plus TBD then finished with the same material as the walls, leaving the majority of the trusswork exposed. The desire to thicken things and give a more "timber frame" type of look is for aesthetics. If I'm gonna stare at them all the time they might as well be prettier.

And while I'm not planning on renting out my dream shop build for random weddings and dance parties, it's on a beautiful 8 acre hay field, and the thought has crossed my mind.



tl;dr, I just want a really nice barn

 

[dhengr]

Rjpope42:
That type bldg. is a real nasty volume to heat, so I would reconsider the flat clg. under the truss bot. chord, and insul. on its upper surface, a good vapor barrier and blown insul. Then vent the attic space. I certainly wouldn’t paint or stain the trusses (framing up there) a dark color, since that just reduces reflected light to the living/working area at fl. level. There just isn’t much you can do to make those trusses and bracing in the roof system pretty. Those structures are what they are, and you shouldn’t pee your money away trying to change that much, it just won’t work very well. Paint everything above the truss bearing elev. white, and enjoy the lighter space, as is. Don’t mess around with any of the truss bracing or the knee braces, unless you really understand the roof system design, and really know what you are doing. That bracing is usually an integral part of the roof system stability, and maybe the bldg. stability too. Any of your changes could mean you have assumed the responsibility for the roof system, if anything goes wrong. Also, regarding interior insul., the interior surface of the roof and siding metal tend to become condensing surfaces if the insul. and vapor barrier details are not handled very carefully. And, that can lead to a real mess. With the flat clg. you could install a fake (3 sided, 1x4 sides and 1x6 bot.) beam below each truss to match the 6x6 post, and flesh out the knee braces without changing them structurally. A vaulted clg. is nice, but doesn’t work very well on this roof system.

 

[BridgeSmith]

If you want exposed wood 'beams' and you're going to put a ceiling in, you should consider screwing stained 1x6 or 2x6 boards flat along the bottom of the trusses and use them as ledges to support the ceiling panels, similar to a suspended ceiling, minus the ugly metal rails.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[phamENG]

I'd be cautious about adding a ceiling to those trusses. They are optimized like crazy with connector plates that hardly make theoretical sense but are proven with testing. If it was designed with no ceiling in mind, there may not be enough capacity in the truss to do it. They're spaced out pretty far, so you'll have secondary ceiling framing to add as well as gyp or whatever might be used. That weight will add up quickly if it wasn't meant to be there...

 

[rjpope42]

So regarding the insulation and vapor barrier of the exterior vaulted ceiling walls, I've a friend that co-owns an insulation business, I'll just be copying what he did on his own 60'*140' vaulted shop roof. Hopefully I'll also be borrowing his lift.

Climate control- yea it's more volume to pay for, but people climate control open spaces with vaulted ceilings all the time, that's not really insurmountable.

I acknowledge flat ceiling would be more straightforward... but for the purposes of this discussion, we are assuming I'm gonna vault it anyway.

There is a cost consideration, but that's also outside the scope of this thread.



I'm starting to feel bad letting this spiral into a DIY/HGTV conversation, so let's bring it home with the topic at hand!

It sounds like most importantly, I need to check to see if it was permitted and if the plans are on file anywhere. (It should have been permitted) See if the plans have anything to say about knee braces and psf load of the trusses. (After phamENGs comment, it sounds like this is required even if I go with a contractor installed flat ceiling.)

 

[KootK]

They are optimized like crazy with connector plates that hardly make theoretical sense but are proven with testing.

I designed these thing before and during college. And I worked for their trade association for a year after college. So, as a fairly knowledgeable prefab truss guy, I'm going to challenge you on some of this stuff.

1) What makes you say that the connector plates hardly make theoretical sense? I see them as being not that much different than old school steel gusset pltes with a bunch of nails in them. They are really quite elegant in the sense that they do a much better job of distributing connection loads relatively uniformly about the connected members relative to other wood connections. The toothed plate system is a product of evolution which is usually a good thing.
Corrosive environments can be a problem but won't be with this one. And don't kid yourself, all wood connections are validated through testing.

2) I don't agree that prefab wood trusses are optimized like crazy. The reason for that is that the economic incentive for the kind detailed optimization that you see with PEMB buildings just isn't there. Consider:

a) The plates are conservatively over-sized because you have to account for a rather large potential for misplacement.

b) Very often, the shop does not have exact plate sizes and will substitute much larger plates. Case in point: some of the plates on these trusses appear to be generously sized.

c) The plates are designed assuming that they are already pulled out of the member by 1/8" which is usually not the case with the final product.

d) Wood members used in trusses undergo a sort of unofficial, second grading process simply for the fact that curves, warps, large knots, and many other defects will render an ugly stick unusable in precise fabrication. As a result, the wood used in these trusses will typically outperform it's grade stress ratings.

e) Trusses have been tested for 3D system effects that are unaccounted for in design and, as turns out, enhance performance substantially.

f) The truss guys use about the same levels of load that your average, wood friendly EOR would use in the same situation. And they'll use whatever is specified if an EOR is involved in the project. This, because it doesn't make economic sense for fabricators to hyper-optimize given all of the stuff mentioned above.

Your main threat with pre-fabricated wood trusses is really winding up with a hack supplier having his trusses designed by hack designer who was a checkout cashier this time last year. Even given that, however, if your truss designs bear an engineer's seal, you're probably good to go. The software is pretty dummy proof the important output is very easy for an experienced truss engineer to review.