*
“I” joist have some benefits, but they are misleading people about tradional framing materials ( demension lumber) with their ” I joist” advertising.They put the blame soley on the lumber.
Plywood or O.S.B. sheathing that has not been glued down with PL 400 construction adhesive to the joists will eventually squeak ,regardless of joist type ( I-joist or 2×12 ).I’ve had problems with both. Floor screws carefully installed are an alternative to glue and nails, but screws some times strip their threads and some even break when over driven, both produce squeaks.
Floor fasteners that miss the the joist and not pulled will squeak as the fastener and joist will rub against each other.
Cross bridging installed tight together will squeak where they intersect
Solid block bridging ,unless perfectly cut and fitted between the joist will squeak (nails work loose).
Sub floor for vinyl, squeak if not properly installed.
Over spanning a joist ,using poor grade lumber or using a joist with high moisture content may contribute to squeaking.
Glueing and nailing each sheet as it is laid will insure a quality floor over the life of the home. I don’t believe that the their Floor System is any better than traditional methods. Quality lies in the design and installation .
I have installed I-joists with strandboard supplied for boxer joist. The strandboard was very heavy and the edges soak up water like a sponge. It rained heavily during this project and our floor’s over all dimensions grew 3/8 of an inch as the 1 1/4 strandboard swelled
Replies
*
I'm new home improvement so please forgive me for this but what the heck is up with engineered joists.I'm designing a garage with a second floor spanning 20ft.I figured I would use TJI.I had it sized and the manufacturer quoted me for 14" TGI/pro 250.Price is $4.96/ft(CAN).Just for curiosity, I calculated the strength of both 14" TJI and standard 2"x12" dimensional.Turns out that the 2"x12" is 98% the strength of the 14" TJI.Price is $2.12/ft.What's going on here? TJI is 2.5 times the price but only 2% stronger.Even if I double the 2"x12" I still come out ahead.I agree that TJI is lighter and uses less material, but this doesn't seem cost effective to me.Am I completely wrong on this or what?
Here are the calculations if anyone is interested in double checking(I could be wrong.)Thanks
Gaby
*Framing with engineered lumber, such as I-joists, provides other benefits that are difficult to put a price tag on. Specifically, the framing members will not warp, twist, have defects such as knots, and are virtually perfectly straight (unless you order them with a camber.) None of these features make for a quantifiable stronger product, but can pay back in terms of quality, saving time for subsequent phases of a project, and for culling bad pieces of lumber (ie - you shouldn't have to order an "excess" quantity of material with engineered lumber.) Engineered lumber also provides that "feel good" attitude that you've used a more environmentally-friendly product, which can be used as a selling point. How does the extra cost add up for the whole project? An extra thousand dollars (plus or minus)? Seems worth it to me for all the intangible benefits.
*I must applogize for my hastiness(I'm a little stressed these days).Turns out there was a misunderstanding about the price of TJI between me and the supplier.It's a little higher than 2x12but not 2.5 times.Everything is OK.I will be using TGI for my project.Sorry for freakin' out.Gaby
*"I" joist have some benefits, but they are misleading people about tradional framing materials ( demension lumber) with their " I joist" advertising.They put the blame soley on the lumber.Plywood or O.S.B. sheathing that has not been glued down with PL 400 construction adhesive to the joists will eventually squeak ,regardless of joist type ( I-joist or 2x12 ).I've had problems with both. Floor screws carefully installed are an alternative to glue and nails, but screws some times strip their threads and some even break when over driven, both produce squeaks.Floor fasteners that miss the the joist and not pulled will squeak as the fastener and joist will rub against each other.Cross bridging installed tight together will squeak where they intersectSolid block bridging ,unless perfectly cut and fitted between the joist will squeak (nails work loose).Sub floor for vinyl, squeak if not properly installed.Over spanning a joist ,using poor grade lumber or using a joist with high moisture content may contribute to squeaking.Glueing and nailing each sheet as it is laid will insure a quality floor over the life of the home. I don't believe that the their Floor System is any better than traditional methods. Quality lies in the design and installation .I have installed I-joists with strandboard supplied for boxer joist. The strandboard was very heavy and the edges soak up water like a sponge. It rained heavily during this project and our floor's over all dimensions grew 3/8 of an inch as the 1 1/4 strandboard swelled
*One of the best features of I joists is true diminsions every piece is the same width. this is great for second floor applications. Around here once you get above 16 foot the I joists are priced in line with 2x lumber.Rick Tuk
*Gaby: I personally don't like working with I-joists. I've never done it since I've been on my own. I agree they have benefits but I prefer traditional materials. About your calculations:You are correct that the maximum stress in the two types of joists are nearly the same. however the deflections of the beams are not. Deflection of any simply supported beam is inversely proportional to the moment of inertia of the cross sectional area. (say that three times fast). >ymax = -(5 * w * l^4)/(384 * E * I)In your situation I for the I-joist is 247in^4 and I for the 2x12 is 190.1in^4 (you calculated this as truly 12" high, not 11.5)The deflection of the 2x will be 30% more than the I joist.We're also assuming that the I joist materials have the same modulus of elasticity as lumber. I don't know that this is actually true. If the glued up laminated I joist flange is less prone to stretching, there cold be a huge difference in deflection.