Renewing old wooden stairs to their former glory is a lot of work, but former glory is definitely worth aiming for if you like the look and patina of old wood. Here's how to do it.
Begin by vacuuming your stairs clean, then remove the bulk of the old varnish with a liquid stripper. If your stairs are painted, you've almost certainly got lead to deal with, and that's another story. Lead paint requires special safety precautions. For stripping varnish, things are simpler. I find citrus-based formulations work well. Next, you'll need to do sanding and it's going to take time and the right kind of tools.
Start work with a 5" random orbit sander spinning a 120-grit disc on open areas of the stairs. You'll need to switch to a detail sander to get into the corners. These tools are made by a number of different manufacturers, and they all include a triangular head designed to reach into tight spots. With all the close-quarters sanding you'll need to do, it makes sense to buy one of these tools rather than renting. After sanding all areas with a 120-grit abrasive, do it again with finer, 180-grit, then vacuum everything and prepare for refinishing.
The type of finishing product you choose is critical, and I definitely do not recommend the approach typically used to finish floors. This is a combination of stain and film-forming urethane, and although it looks great when new, it looks quite bad when the surface starts to wear from foot traffic. And the only way to restore it completely is with another horrendous sanding job -- something you'll never want to do again.
This is why you should consider finishing your stairs with oil. I've recommended it to many homeowners and used it personally. Initial application involves brushing on and wiping off four or five coats of oil. This seals the wood and offers a moderate amount of protection. As foot traffic inevitably begins to create visible wear, wipe on another coat or two of oil. The stairs will look as good as new. Renewing a stained and urethaned finish flawlessly is nearly impossible, and ease of renewal is why I like oil so much.
If you simply want to protect the wood without additional color, use polymerized tung oil or wipe-on polyurethane. If you'd like to darken the wood, choose a dark oil. The more coats you apply, the darker the colour gets.
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Contributing Editor Steve Maxwell has been helping people renovate, build and maintain their homes for more than two decades. “Canada’s Handiest Man” is an award-winning home improvement authority and woodworking expert. Contact him by visiting his website and the blog, Maxwell’s House. You also can follow him on Twitter, like him on Facebook and find him on Google+.