We are remodeling our house, and I’ve ran into a couple problems that I’m sure somebody here can help me out with.  

Problem #1 - What is the best way to get rid of painting mistakes such as paint runs, or rough paint (the kind you get when your dog sits against a wall with wet paint).  Is there some type of sandpaper that you can use to make the paint consistent?

Problem #2 – We currently have carpeted stairs with metal railings and are going to be replacing these with oak stairs and railings.  I tore up the carpet and confirmed that we have regular wood for the existing stairs.  I have bought a “How to build stairways” book, but it mostly deals with building a new staircase.  What is the best way to approach putting in the new stairs?  

Just tear everything out and wing it?  I don’t think it should be very tough if I am reusing the existing frame (or whatever you call the planks that the treads rest on ).  Is there anything special that I should know about getting the treads and risers down?  I’ll worry about the railings later.

And one last question, how important is it to put polyurethane on oak baseboard trim, or other pieces of trim that are not constantly being walked on, etc?  If it is very important to seal it, what is the best type of product to use if I do not want to change the appearance of the wood?

Thanks for the info

I guess I will hit up the paint runs since we are doing some painting now. Once it is dry no magical sand paper makes it look even, unless you went with flat paint. If it is gloss or semi gloss, the best you can do is sand that part down a bit so it is flat again and paint over it one more time. Many thin layers. At least that is what we are doing for furniture. If it is a wall and you are only doing two coats, then I would still sand it down and just do that area again.

You don't "have to" put polyurethane or other coating on the base board, but it's not a bad idea.  One you've got something on the wood, it is much easier to clean, it will last a little longer, and look better (though this is my opinion).  Make sure you put on at least two coats (three is better) on those base boards since they will take a lot of abuse (follow manufacturer's instructions).  They're going to get kicked, hit with the vacuum, scraped with furniture, etc.  Just remember, NOW is the time to do all this stuff because once you're done with the work, you won't want to go back and do it again.  We're finishing up the remodel of out house, and believe me there are a lot of things I wish I did when we still weren't living here, it was messy, and I had the will.  Now that everything has calmed down, we're all too tired of the dust, noise, and aggravation that comes with those things.  Good luck.

Poly isn't necessary but it's a good idea.  It protects the wood from moisture, dirt, and UV rays.  Gloss Poly cleans up the easiest but is pretty shiny and may stand out quite a bit.  You'd probably be better off with satin or semi-gloss.

Poly won't change the color of the wood very much.  That's the job of stain.  The poly will give it a little more depth and highlight the grain.  The contrast between the light and dark portions of the wood will be more accented, but the color will be pretty much the same.  The contrast appears greater with glossier finishes.  Try some on a small portion and decide if you like how it looks.

You pretty much have to put some sort of finish on your stairs, so you'll probably want to just use the same thing on your trim to match.

Do finishing before you install trim and treads/risers.  Make sure you finish both sides, don't get lazy and just do the front.  If you do then it can absorb and release moisture at different rates and cause warping and splitting.  Less likely on the trim than the stairs because it is thinner, but its not a hard step.

Use an oil-based poly.  Using water based finishes "raises the grain" and requires some sanding after the first application to knock it down smooth again.  Some water based finishes claim not to raise the grain.  Don't believe them.  Oil based take a little more time to clean up but it is a good tradeoff.  If you use disposable foam brushes then you can even skip the cleanup.

Good Luck!

What's a housing joint?  I've never heard that term before?

Is that when you router out a groove on the bottom of the tread, and when everything is put together the riser sits in the groove helping to lock it in place?