TJI's or standard floor joists?

[Thoughts-from-Jules]

Anyone want to weigh in on the advantages of TGI's vs standard floor joists?  We originally liked the idea of TJI's but we are curious of costs differences and advantages and disadvantages to each.  I think in our house plan they will be 15' long spans but we can put in runners in crawlspace to lesson the span etc.

I have to admit I kinda like the idea of standard nominal lumber.....I am not sure why but it might have to do with the fact that there will already be so much plywood materials (sheeting on exterior walls, subfloor etc) anyone have concerns over outgassing of the man-made materials?  I have some mild chemical sensitivities (mostly strong household cleaners, laundry soaps) and I wonder if there are any places to eliminate plywood products without it costing us a fortune for alternatives?  I know our house has diagonally run 1x10 subfloor under hardwood flooring.....is that not done anymore?  This house was built in the 50's.

Any feedback on this?  Is this an uncommon concern and not worth thinking about?

[Alan Gage]

No real experience either way but I like I-joists from the standpoint of lighter weight, arrow straight, consistent, and less wood used overall.

I think when I priced some out they were about $2/foot for 14" 

Remember when looking at span ratings of I-joists that it may assume 3/4" flooring glued and nailed/screwed.

Alan

[rick91351]

Fire chiefs and firemen from what I understand and read would like to see TJI just go away.  From their line of business they are not good.  When you talk to the draftsman and engineer tell them your concerns.  They will spec your drawing or plans out to whatever you want.  (If code).  They work out your foundation for you.  That is part of the engineering.  They will tell you where you need to put what.  They might call for piers or stem walls or ??  That is why they get the big bucks.  And have a whole lot of letters behind their names and we here don't.

You could ask to spec out a 1X10 sub floor but I have a feeling it is going to be more than you want to spend. Unless you are not willing to take a chance with more man made materials.            

I understand your concerns over man made materials.  This coupled with those found in nature.  Running the gambit from mercury and lead to radon gases it is a wonder any of us live to the tender age of sixty.  Radon especially us living in granite rich areas.  Mercury, lead and other metals can find their way into our water supplies without the help from man.

[Squirl]

TJI's are straight and level.  You don't have to worry about finding the crown.  They use less trees because they are made from wood particles that would normally be wasted.  That being said they use lots of petroleum in the glue. 

The downsides are they can be harder to transport.  They cost more.  IIRC, they are also pickier about nailing into them sideways and running utilities.  They also don't hold up to exposed weather very well.

You don't really see diagonal running subfloors as much. It is not as strong as perpendicular.

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_5_sec003.htm

[davidj]

I used TJIs and was happy with them.  The only real pain was that I didn't make any effort to line up the punch-out holes, which I could have done to some extent if I had thought about it in advance.  Dropping 20' TJIs in single-handedly was easy, definitely a plus.

That being said, if I did it again I'd have probably gone with 2x10s, really just for minor reasons:
- slightly cheaper
- fire issues (not a huge deal in our case as it's only over a crawl space)
- slightly less fussy with the details

This was in a 20x30 with center girder, so 2x10s would have been fine strenth-wise.  The TJIs, with 1 1/8" sheathing, result in a floor that feels almost like concrete (which is good, as we're putting down slate).

One thing to look out for with TJIs - the specs are fussy about holes near the bearing points - any under-floor wiring needs to be pulled in a foot or two from the wall if running perpendicular to the TJIs.

[Don_P]

Actually if you run board sheathings they should be run diagionally. It requires thicker wood at certain spans but it triangularizes the structure giving much better bracing to each plane. Board sheathing from local mills can probably compare favorably with ply costwise, labor is much higher. The building will breathe better, solid wood acts as a hygric buffer where engineered woods are pretty effective vapor barriers IMO. I do know one firefighter who got out on the carpet as the TJI's collapsed early. I've put them all in but prefer solid sawn when reasonable. Having run a panel press until I sensitized to formaldehyde I can say I've never reacted in a new house. Now the little blue porta john in the yard... they can load them with formaldehyde.

[Squirl]

Interesting don_p.  I never thought of the bracing aspect.  I simply saw that it required more (thicker) lumber so I thought it wasn't as strong.  I forgot that technically the diagonal sheathing is forming a right triangle with the joist and therefore spanning a 41% greater distance.  Which of course would require a thicker board.  I still have not seen it done that much.  Then again I haven't ever noticed any board sheathing on new construction except on the loft projects posted on this forum.  I can't imagine the time consuming labor that goes into diagonal cutting of all those boards.  Rough sawn 1 x pine is around 50 cents a board foot and 3/4 in plywood is $20.  So the pine is around .12 cents cheaper per board foot. When you factor in the labor though, it becomes more costly.  I wonder how the strength compares?

[Thoughts-from-Jules]

Great thoughts.  I never even thought about the fire aspect of things and how fast they'd deteriorate compared to solid lumber.  We do have a local rough cut mill....I am not sure prices but I could check. I imagine 4x8 sheets would be nice to handle faster, more uniform, and easier to haul.  We might do a little research either way.

[MountainDon]

Rough cut may or may not be graded. If not graded it won't meet code and may be difficult for you to know/guess at what they sell you. It also may not be dried down to KD specs; 19% moisture content.