STRONG framing!

[MushCreek]

I've always kinda wondered just how strong TJI floor joists are. After all, they don't look like much. The drywall company delivered the drywall, and stacked 44 sheets of 4 X12 drywall in one spot. It runs parallel to the joists, so the majority of the weight is being carried by just two 12" TJI's. That's 3600 lbs.! It scared the heck out of me, but I tried to measure the deflection, and found- none. There was basically a car parked in my living room, with no ill effects. I also worried about the flimsy metal connectors on each end, with the little stubby nails bearing all of that weight, but evidently they're up to the task, too. I know that there is support from the ledger nearby, and through the sheathing to the other joists, but still....

[VannL]

Looks like it's time for a 200 gallon aquarium!

[flyingvan]

My fear is the long term (100 year) stability of the adhesives.  If it suddenly turns to powder my offspring will be standing in a pile of wood chips

[Don_P]

Equally true of plywood or many engineered products, fire is another concern. They are a good use of otherwise low grade timber so take some of the pressure off of the forest, always plusses and minuses. Short term wood can handle significant overload, there are adjustment factors in many engineering calcs for short term loads like construction, wind and snow versus long term loads which cause something called "creep deflection" or "creep set". Under long term overload wood deflects but becomes more plastic than elastic and takes on a permanent deflection, I imagine most of us have seen that in old structures with undersized joists or rafters that have a permanent belly in them. Generally the kids stocking drywall haven't got a clue about the loads they are imposing. A townhouse in VA collapsed a few years ago when it was improperly stocked.  But then often the supers don't know either. There was a large skyscraper going up years ago and an engineer was called in because parts that he had specified were not fitting. On his site visit he noticed they had stocked one floor with most of the marble flooring for the entire building  Luckily, for most residential projects we just don't get to that level of overload... although I've not missed by much a time or two. It's amazing how fast you can throw a big pile of lumber into midspan on a floor deck with a Lull 

[flyingvan]

     My last Fire Ground Survival (FGS) training had a segment on the dangers of roof collapse from the lightweight trusses everyone's using.  It opened a discussion about floor collapse through TJI's.  There's been some good research on the subject; just sounding the floor doesn't help, it'll sound and feel solid until it collapses, and they collapse quickly with fire below.  (The recommendation was advance into the room with a thermal imaging camera; more important be very aware of the building construction where you work)
     Twice now I've seen the hacking plumbers do to framing, with no respect or regard for structural integrity, where they hogged a hole through tji's to run the waste pipe from toilets and took out a bit of the bottom chord.  Add to that the weight of bathroom fixtures, and the likelyhood of water damage from partially closed shower curtains or overflowing toilets, and you get my vote for the location of the first TJI to fail.
     Yet another advantage of doing it all ourselves.  We can plan out the TJI placement so things like toilet drains will end up between floor joists, not through part of them not designed to be cut.   Also why I used one piece vinyl flooring in the bathrooms and generous caulk all around---I can't get my family to close the shower curtains all the way and my wife insists on shower curtains instead of doors, as they are an important part of decorating.

[MushCreek]

The only holes I put in the TJI's are small, for PEX and wires. I'm very careful with engineered products. The rules for LVL's are very stringent as far as drilling goes. I plan a double-1/2" drywall for the basement ceiling. This is supposed to give a 1 hour fire stop. There's no doubt that properly used, they are strong, and they are much lighter and straighter than regular lumber. I was going to use 2X12's originally, but the quality is terrible.

[cbc58]

engineered joists will disintegrate when exposed to wetness/moisture at a much faster rate than framing lumber.   learned this the hard way when we had a leak and the joist ends soaked up the water and crumbled.