We are just about to start constuction on our new home. The contractor that I have chosen is pushing toward using 2"x12" floor joists instead of TGI's. I have read about the advantages of TGI, but this contractor is from the old school and is in favor of solid wood, and also does awesome work. We are planning on using as much ceramic tile for flooring as possible in this same area. We will use the cement underlayment under the ceramic tile. The contractor suggests that he can save me about $1,000 using the 2"x12" lumber. Are 2"x12"'s ok across an 18'3'' opening?