Fasten plywood to the joists,get a Roofer to put down a torch down modified roof with all the needed flashing,lay 2x4 pt stringer in the direction of the flow,screw the ipe to the stringers, do not screw past the stringers into the roof. That 1 1/2''will allow plenty of air movement, use counstruction adhesive on the stringers. 10' is way overspan for a 2x8. John

John, if I am already over span for the 2x8 joist, I probably shouldn't add more weight with plywood and additional stringers, should I? I was going off of the specifications at the lumber yard when I chose the 2x8 joist. Is it just that the IPE is too heavy for them? The beams are all double 2x10's mounted to 6x6 posts. Thanks for your info.

The Beams sound fine,just the 2x8 span,thats too much for balsa wood decking much less ipe X 20 for an upstairs project x100 if you add a few Folks up there having a beer. If the frame is already up you could add a couple of rows of blocking cut in real close, that would help a bunch,if you do add the roof the 1/2'' plywood fastened with counstrucion adhesive that would stiffen it up a little as well.Those specks were for just a smigen over faliure for a celing system inside a house, framing a deck is a whole nother smoke. J

I agree with John.. always overbuild. Span tables are always a little generous.
2x8 will give you the span, but not for free. The deflection will be L/480, around 1/4 inch++This doesn't take into account prolonged winter drifting or the ipe as an unusually higher dead weight.
If you bump that up to 2x10, your deflection with be L/857. You will have no sag, bellying with time, creaking, bounce, etc. You're talking a few extra dollars for the upgrade from 2x8 to 2x10 for decades of service.

I guess I really screwed up. Can't use IPE because of the weight. Got any suggestions on a good composite decking? I originally was going to use composite, but then I started reading horror stories about it growing mold/mildew spots all over it. Then I started researching alternatives to the composites and found out about IPE. I thought I have found my solution, but now my structure won't support it. I don't want to create the possibility of danger when my friends are all over "having a beer". Why do companies put out specs on treated lumber and recommend joist sizes when they are just under a failure point? Do they expect no one to have parties on their decks. Anyway, if anyone can recommend a good composite or plastic decking, I would appreciate it. Thanks for all the advice John and Gorillabuilder.

ipenovice, i feel bad for ya. I didn't know you already had it done. Maybe you can add more joists and blocking to stiffen it up.
The 2x8s can span 10 ft, but you'll just have a heavier dead load than normal with the ipe decking. Like John said you can stiffen it up and still pull it off and be fine.

Most composites are just as heavey if not more then 1x6 ipe. J

Thanks guys. Am I going to have any issues using 1x6 instead of 5/4 IPE? I read some issues with cupping on the 1x6. I was going to use the clips, but your other forum repsponses have convinced me to face screw it. I am going to cut out all of the 2x8 joist and replace with 2x10 joist. I may get a discount at the lumber yard when I go back to buy the 2x10's since the sales associate recommended I use the 2x8's.

Novice Guy,,hold up a sec,,,before you do all that cutten,,, 2x8s with a 10' span,with two runs of blocking,,are going to be about the same as 2x10s spaning 10'with no blocking far as bounse goes, something to think about.Side Note>>> I dont know how far the joists are apart 16-24''

John, my joist are 16" on center. I only cut out the first floor of joist. Only about 16 and replaced with 2x10 joist. I had not installed the second floor joist yet, so I went ahead and put 2x10 joist up there. Feels a lot stronger than the 2x8 joist did. I still think I should block them down the center of the 10 span if that will help stabilize the deck. With the 16" on center joist, do you think I will notice much bounce using the 1x6 IPE as opposed to using the 5/4 IPE? Thanks for all your help. This WEB site is great.

Blocking that span with the 2x10s is a good idea.Then you should be fine with 5/4 or 1x6. J

FYI most 5/4x6 composites weigh 2.7 lbs. per linear ft., 1x6 ipe weighs 2 lbs per ft. & 5/4x6 ipe weighs 2.5 lbs. per ft. The only composites that are light in weight are Eon & Timbertech 2x6 T&G.

Al

Thanks for the weights Al. I never did get any answers to my question about how much "bounce" to expect if I use 1x6 IPE with 16" on center joists. I have beafed up the joist to 2x10's, so I don't think I have a structural integrity issue any more. My main concerns now are the "bounce" and also cupping with the thinner 1x6 IPE. John H. replied that I shouldn't have any issues with cupping if I glue the stuff down when I face screw it. Still, I will be 875lbs lighter if I use 1x6, which is a lot of weight. Thanks again for your info.

You will be fine with 1x6 ipe screwed down over counstruction adhesive fastened to joists 16'' on center with a 10' span enhansed with one row of 2x10 blocking thru the center I do it all the time with no bounse issues, you can put 5/4 down with the same results using the same fastening system. J