I am going to be building a new house so I am sure I will be asking many questions in the future. My first is concerning the use of I-joists. I am building a house with a walkout basement and plan on using the I-joists instead of traditional 2x lumber. I will have several different spans, the longest total span being 34' and the longest free span being 18'. What size of i-joist would you recommend and would you use 16" or 24" centers? The loads would be those typical to a single floor house with a basement.

I am also wondering if the I-joists are harder/easier to work with vs. 2 xs. I realize the longer lengths would be difficult but I mean as far as cutting lengths for different things such as a cantilevered floor or a stairway opening.

Gill Tape

If it were me, I'd use something like a TJI 11.875" x 210 series at 16 oc for the 18 foot spans. If you have considerably shorter spans in some areas, and you want to save money you could then go 24 oc or 110 series at 16 or 24 oc, depending on the circumstances.

Personally, I used 3/4" t&g OSB sub floor at 16 oc, and I'm very, very happy at the performance. Stretching it to 24" could potentially make it a bit soft, depending upon your tastes and floor coverings.

I think they are very easy to work with. First of all, they are all straight. Secondly, routing any plumbing and electrical through the floors is a lot easier. You also have the advantage of not having to splice floor joists. They are also pretty darn light, compared to 2x12's. When I built my house, I installed 32' 11.975x110 series by myself, for the main and second floors.