How do ash or elm compare to S/P/F so far as structural requirements?

[Erin]

OK.
So I know S/P/F 2x6 T&G will span my 3'4" OC floor beams and give me a firm floor.  

But I recently found a "local" sawmill about 200 miles away who is happy to do custom stuff and says he can do T&G.  My options (or at least, his recommendations for a resilient floor) are ash, elm or white oak.  
I'm having a devil of a time finding out how these compare to standard S/P/F dimensional lumber though.  

Will any of the above span my beams?  

[MountainDon]

Stiffness of materials is defined by the modulus of elasticity. Simply put the higher the modulus, the stiffer the material.

Using the chart available here... 

Strength Properties of Commercially Important Woods  you can check the average rating for many common woods. A quick look indicates that those hardwoods should be fine replacements, all other factors being equal. There can be some variation in stiffness in the way wood is sawn.

[Erin]

Thanks Don.
That's exactly what I was looking for. 

[Don_P]

Any of them will far exceed SPF as far as deflection is concerned. Do make sure you are talking about dried material or shrinkage will be a major problem.
Given the choice I'd avoid the elm, it tends to turn into propellors and rocking chairs, it generally has spiral interlocked grain. Ash is a beautiful wood as is white oak. Ash is a high starch content wood so can be candy to powderpost beetles if that is a problem there, which I kinda doubt. White oak is also decay resistant. I imagine you all know ash is used for sports equipment and takes impact well as opposed to say maple baseball bats (who's idea was that  ) I worked in a whitewater canoe livery for awhile and my job during the week was to repair the damaged boats from the previous weekend. I ran out of ash rails at one point and had some red oak at home so I fixed one boat with red oak rails, they lasted one trip  . Quartersawn white oak is some beautiful wood, it has very wide rays that catch the light and really look fine, think Craftsman style furniture. Course red heart elm is mighty fine looking too, and then curly ash is something as mesmerizing as a fire, wood is good stuff 

this is a link to the FPL's tech sheets;
http://www2.fpl.fs.fed.us/TechSheets/HardwoodNA/hardcommon.html

[PEG688]

I worked in a whitewater canoe livery for awhile and my job during the week was to repair the damaged boats from the previous weekend. I ran out of ash rails at one point and had some red oak at home so I fixed one boat with red oak rails, they lasted one trip  .

What they do rot    

[NELSELGNE]

from http://www.boatdesign.net/forum/showthread.php?t=17726


The white oaks are denser, stronger and more rot resistant, than the red oaks. The physical structure of the reds cause them to be very porous, which isn't good on a boat, nor helpful at resisting rot. A 1/4" square by 12' long section of red oak, if placed in a container of water, will produce bubbles if you blow on the end like a soda straw. This is a function of it's fiber orientation and causes it to "wick" moisture throughout the piece.

[Don_P]

The red oak broke on light impact, it is more brittle than the ash. Ash is not decay resistant either and in the few rare cases where a set of rails lasted into a second season we had to watch for decay. for a personal boat, keeping it well finished is the key there. These were well overworked boats that usually did not last more than 2 years before being sent out to a small calm pond somewhere to live out their final days.

Red oak is porous, the bubble blowing lesson is a good one for kids. Try it with a red oak and then with any white oak with the exception of chestnut oak. The whites develop tyloses that block the cells and make them impermeable. That's why white oaks are used for tight cooperage like whiskey barrels and reds were used for slack cooperage like nail kegs. Sure didn't want that precious refined corn leaking out onto the floor  . Its also why white oak takes a whole lot longer to dry. I've got some nice thick 4x12's I cut out of a big dead one that I'll let season for some years before thinking about using for a set of stairs.

The midwest has a higher ratio of white oaks as compared to reds, I'm the opposite up in the Blue Ridge, we grow very fine northern red oaks so my flooring cabinets and trim are all red oak, some from as far away as the end of the driveway where a huge old bacterially infected one died and tipped over. It had the infamous acrid smell when green, often called cat pith oak. It was a result of the previous farmers turning livestock into the woods. Their hooves scar the roots and soil borne bacteria slowly move up into the tree causing shake and the smell. Alot of that wood went into the woodstove but it still yielded almost the entire set of cabinets. My nephew was about 6 at the time and came over to visit just after we had stickered the lumber in the living room to dry (I married well). He leaned over to my sister and whispered "somebody peed in here". It took a couple of weeks for the smell to dissipate. In badly infected trees the wood can smell every time the humidity rises. Sears had to recall an entire run of dressers one time on account of that wood being used as drawer sides.

[Don_P]

The FPL has recently gotten around to updating their titles and this gem popped out, hot off the presses;

http://www.fpl.fs.fed.us/documnts/fpltn/fpltn-147.pdf