hey guys so i have hardwood stairs that were stained and then varnished with polyurethane. I was told i would have to revarnish after about three years and it has been three years so how should i go about doing this?
What grit sandpaper will i need and whats the best varnish to use? (i live in Canada)
btw im hoping to do this without having to stain the wood again

Thanks in advance!

First, I'm not sure why you were told that you need to refinish after 3 yrs. Was it a water base? Usually, you only need to refinish every 7-10 yrs.

Also, yes, if you want to change the stain color, you will need to sand down to the raw wood, otherwise the stain won't stick and everything will peel.

I'm not an expert on grits, but it does depend on the species of wood.

If however, you need to screen & recoat, that's a different story. Then, you would be buffing and adding a coat of poly and not changing the color.

Debbie Gartner aka The Flooring Girl
http://TheFlooringGirl.com
Westchester NY

If you are just trying to add a coat sand lightly with 220 grit, vacuum than wipe down with mineral spirits. Varnish and Polyurethane are different finishes so you need to find out what you have .

thanks for the help and yes its polyurethane that was added as a finish.
Also the last thing i want to do is remove the stain, i just want to remove the old coat of polyurethane and add a new one.

You can't just remove the poly. Your just scuffing it with the 220 to give the new coat something to grab to.

oh okay makes sense, any specific type of polyurethane you recommend i use?

ah, now I understand. You want to do a screen and recoat (or a buffing). Basically, as mentioned above you buff it/scuff it up and then add another coat of poly so it sticks in better.

First, I would try to go back to see what type you already have - oil or water. It's often ideal to use same type as it will adhere better.

Lenmar is a good oil based one, and there is another we use, but the name is escaping me. If it's water based, bona is a good one, esp bona traffic.

Debbie Gartner aka The Flooring Girl
http://TheFlooringGirl.com
Westchester County, NY

Hartco is another great oil based poly.

Debbie Gartner aka The Flooring Girl
http://TheFlooringGirl.com
Westchester County, NY

I only use Bona Woodline for oil