Old TJI joists 1

[DoubleStud]

I am doing a pretty extensive remodel (addition and pop top). The existing structural shows 18" TJI 25/35 24 F @ 16" o.c. I went to TJI website to look at their old series, I couldn't find anything with 18". I assume 25/35 mean series 25 OR 35. Not sure what 24F is. The existing framing has some crazy span with mid wall not declared as a load bearing wall. It would be nice if I can figure out the performance of these old joists before I decide what to do.

https://www.techsupport.weyerhaeuse...I-15-25-35-35X-55-DF-SP-Literature-1985-1997-

We will eventually have a permit to demo the drywall so we can verify the depth.

 

[XR250]

What is the span?

 

[DoubleStud]

XR250, this is the part I am trying to figure out. Some areas it has 25.5 ft span. I will eventually figure out whether these joists stop and start or go full 25.5 ft. There is an existing wall that breaks the span, but this wall does not line up with a beam or wall below it. So I feel like this wall does take load from these joists and maybe share the load to joists down below. The architect wants to remove this wall. So I want to see the performance of these joists.

 

[DoubleStud]

Crazy to me how people were able to build anything from these old structural plan. Barely any details. You have no idea whether the beams are flush or below the joists. Walls are not called out if load bearing or not. Ledgers were not called out.

 

[ChorasDen]

Email techsupport@wy.com. They can give you a code report from the production era of the building, if you have the build year.

 

[jerseyshore]

24F seems like a glulam designation so it's probably an Architect who used a lot of glulams at the time and just wanted to specify the Fb of the TJI's in that way.

 

[jerseyshore]

Crazy to me how people were able to build anything from these old structural plan. Barely any details. You have no idea whether the beams are flush or below the joists. Walls are not called out if load bearing or not. Ledgers were not called out.

It's because for a single family house you don't even need plans. Any half-ass contractor can build a house and there's a good chance they'll have no issues. It's why it's hard to convince clients that an additional jack post is needed here or a 3 ply beam needed there because they have been building houses off of napkins for hundreds of years and they're mostly just fine. Until they're not.

 

[XR250]

The wall is likely adding support - whether intentional or not. Removal of it will likely cause increased deflection of the joists which may lead to sheetrock cracks. Might want to warn the owner.

 

[DoubleStud]

Update, I contacted Weyerhaeuser and they were as confused as I was with the call outs. Going to rip drywalls and figure out what's going on. Maybe look at the stamps on the product.

 

[dold]

25/35 = LL/TL? I.e., 25psf live, 10psf dead. Similar to a bar joist designation? Was 25psf ever a LL requirement for such a structure in your jurisdiction?

 

[DoubleStud]

No. This is on the roof an it is in the snow country. This particular county uses 100 psf for flat roof.

 

[RontheRedneck]

What was written on the plan may have nothing to do with what was actually used. We often get plans in that have something called out that we can't easily get, so we substitute something else. No telling what might be up there.

If they are 18" deep and a 25' span, that's within the 18/1 span/depth ratio that I use. So I wouldn't have any problem with it.

 

[XR250]

No. This is on the roof an it is in the snow country. This particular county uses 100 psf for flat roof.

That would have been useful information

100 psf seems like a stretch for an 18" i-joist spanning 25 ft.

 

[phamENG]

100psf may be what is used now, but what about when the house was designed and built?

 

[jerseyshore]

25/35 were old TJI designations so it seems like the architect put both options on there for the joist designer to use.

I'm guessing this is just like a regular arch dwg where everything is made up and the points structure doesn't matter.

 

[Eng16080]

As noted above by XR250, I think it's unlikely that the 18" joists spanning 25' will work per (current) code with a 100 psf snow load. Most currently manufactured I-joists at 18" deep would not support that load.