Carpentry and Woodworking - Plywood for Riser & Skirt board??

Is it ok to use plywood for my risers and skirt boards? They will all be painted white. I heard and read that you need to use a finger joint board 1x10 or 1x12 for the skirt board. I have found some finger joint 1x12x6' but it cost around $30. I have found some risers at HD but they are oak(48") and $15/piece. They are also not long enough (I need 4 to be 54" long). I cant find any pine or poplar risers which I'm sure will be cheaper. I'm guessing the reason for just not using a regular (non finger joint) board is because it might bow over time. I have noticed this on my temp treads that are 2x12. Thanks for any help.

P.S. I need a sliding miter saw and I don't have much of a budget. Has anyone have an opinion about Ryobi. HD has a 10" sliding miter saw for $200. Thanks again.

yes, it is ok to use plywood as risers, painted or not. 3/4" ply or even 1/2" if supported and nailed properly will suffice. The key is making sure they are properly installed and with support behind them. You could also cut a shallow groove in the underside of the tread to give more stability and easier alignment of the riser.
Same goes for the skirt board....use ply if you wish. Cut you will need to put a cap on top of the skirt but that is not unusual. A 1/2x3/4 strip will hide the edge. Join the 12" strips and the joints in the skirt should be glued with an overlapping joint and it will work great. Good luck. Joe.

Thanks for the reply. I went to my local building supply and they had some plywood but I was not that impressed. I looked at what they called BC Plywood which is smooth on both sides. It was still a little rough (which could be sanded) but it also had some splits in it. I went to HD and they had some that was perfect, really smooth w/o cracks, but the largest size I could find was 2'x4'. The book I have says to use 1x10 or 1x12 finger joint board but I could not find any. What have you guys used for skirt boards and risers? Should I use a Poplar 1x10? Will a poplar 1x10 bow? I would probably go ahead and use the BC plywood but one of my skirt boards is on an outside wall and will be fully exposed. Thanks for any help.

I'm a painter not a carpenter but I've painted a lot of risers and skirts that were cut out of plywood. Oak plywood is usually used if they stain and I think birch is probably the most common for paint...... but you can hide a lot with paint. I've taken sub standard plywood [pine too] and filled and sanded to get a nice looking job.

Do you know if those splits in the plywood will get larger?

Probably not - plywood is a lot more stable than normal solid wood.