A long while back I posted a question about repairing a treadmill deck.
Most of the responses were helpful pointing me in the direction of oak as
the decking material of choice.

In the time since then I replaced it with more MDF, out of expediency more
than anything. Well now that I have some proper time on my hands I priced
out some rough 5/4 oak planks. But before getting into it, I was curious
about how to do the replacement.

I'm wracking my brain trying to determine HOW to create the replacement
deck. See, the deck is 17"x28"x13/16" and the dimensions are very
unforgiving as it is supported in 6 places only - 4 corners plus 2 on the
midspan edges. So I look at what I have available, for argument's sake 9"
wide 5/4 planks of 6', 10', etc.. lengths. That would give me either 2
planks running lengthwise or ~3+ planks running widthwise. I could get
4/4ths just as easily too.

What would be best here, run the planks widthwise or lengthwise? I have to
tie the planks together in a way that is very durable and strong - I will be
running on these things and so it has to take approximately 300 lbs of
impact for long periods of time. So I was thinking, okay, widthwise planks
and tie them together on the bottom with thin plywood. But how to secure
them to the plywood, would glue be enough or would screws be mandatory for
bond strength? I can't see doing the planks lengthwise, as there is nothing
supporting them in the middle and the middle is exactly where my feet will
be landing.

See that's my problem, I can't get past the feeling that no matter how I tie
the planks together, they'll never be strong because what ties them together
won't be strong. And the chances of me finding an oak plank 18" wide is
nill.

I can just as easily throw out the whole replacement scheme altogether. I
sufficient MDF to last a lifetime if need be, I just wanted to go with
something better.

I can post a photo of the original broken deck if you want to see where it's
supported.