I'm doing a stairway out of red oak, i have a fairly nice shop, planner, joiner, routers...

I'm making my own planks for the stairs, custom fitting them.

Why do the T&G planks I buy have grooves on the bottom? Can't i just buy 3/4 inch red oak and use biscuits to join them on the treads?
I'm going to use screws on the overhanging treads, countersink them and peg the holes, and then use construction glue, they'll never move..

The rest of the tread is just nailed so expansion isn't an issue..

And I've got all the time in the world, so I can do a tread a day...

But what's with the grooves on the bottom?

Thanks,

P.S. I'm not a carpenter, just a lowly gynecologist who likes to do his own stuff...

PS. It's also possible that the grooves remove wood that is not needed but adds weight, whic always effects cost. If you are paying to ship it across the country, removing unneeded stock makes sense. Thinner wood also dries more quickly.

From what Ive been told , the grooves are to equalize pressure in the board to prepare the surface of the flooring to be sanded.Ive been told that if you take a solid piece of wood and sand it aggresively that the sanding process makes unequal tension in the board. So if the flooring comes pre relieved my grooves on the bottom them is stabilized.

Now this may all be a rumor and the grooves may qjust be to give the bottom of the boards a little breathing room. Now Ive worked with a few stair installers and the solid treads they install dont have any grooves in them, but of course those treads dont receive the same intense sanding that the hardwood floor does. So take you pick but I dont think it will matter for your stair treads.

If you're making your own treads, no need to groove the bottoms. Just select some boards with nicely milled edges and bisquit them together. For the nose, you'll want to add 5/16" material to the front to 1/2 round over as a typical tread is 5/4 stock (1&1/16" thick). So you can glue up 3/4" stock and add the 5/16" x 1&1/4" piece at the front then 1/2 round it over. Now it will appear to be a full tread.