Floor finishing

A new adventure here. We just stripped the carpet off one of the downstairs rooms. There is quite old unfinished fir flooring. The adjoining living room had more vertical grain. This seems to have more flat sawn. It does have a sub floor under it. The room is about 12x24. I've put down plenty of wood flooring but have not done the finish and most of that work was many years ago. The condition of the floor is quite good as it had linoleum over it which had not been glued down. There are some water marks on one corner, but the floor is good there. I will rent a RO floor sander and edger. What grit should these be finished to? What finishing process would you suggest and what materials?

There was a thread not too long ago, where I recommended renting a Varathane RO floor sander. See if you can find that thread. He ended up following my recommendation, and I think it worked out pretty good. I believe his was a Fir floor too.

Lowes rents those machines around here. You don't need an edger with one of those, and it's hard to screw up a floor.

Go through all the grits. Don't skip one. They come in packages of a few, and tell how many you need per size of floor. If Lowes has this setup where you are, buy plenty of sanding disks, and simply return any leftovers.

I would buy floor finish from a dedicated floor finishing supplier. I'd use the Bona of your choice. You just flood it on, and push it around with a squeegee type applicator. The floor finish supplier will sell those too. I use those applicators right up to the edge, but haven't seen a youtube video of anyone else doing so. There are plenty of videos available. Just search Bona Floor finishing youtube.

Here's what the machine looks like, and packages of disks: https://www.amazon.com/Rust-Oleum-20.../dp/B0078IUXO0

Good advice

Thanks for the info. I did spend an hour on the Bona site and look forward to getting this done. I've checked out the local rental places and will get down to the Depot/Lowe's stores as well. First I have to empty the room and get all the furniture someplace to do this. Onward through the fog!

Which Bona product did you use?

I've been very happy with the Bona Traffic, in my shop I used the Traffic HD and found it to be nearly bulletproof. It's the only application where I use a water based poly.

Since I prefer the amber look of an oil finish to the blue/white of water based urethanes I did a first coat with Bona AmberSeal.

Having the correct application tool and practicing your application pattern a few times is important with these products, the catalyzed finish starts to harden while you look at it. You need to work quickly and efficiently, there is no going back, and you certainly don't want to be caught with a puddle of finish in a corner. It's not hard, but I found that rehearsing the motions took a lot of stress out of the actual process. It was still a lot like those glue-ups that are a little too complex where one of your glue blocks goes missing in the middle.

Sanding to 150-180 grit was plenty-- up to 120 with the drum sander then 150 or 180 with the disk/polisher machine. I've tried the RO machines but didn't have enough patience to use them for the whole process. it was fine when I did floors that just needed the old finish knocked down, but for new maple floors that needed leveling out the ones I could rent were just too slow. They are a lot less dangerous in unskilled hands, it's not hard to make a divot with the drum sander and 36 grit paper if you don't keep it moving.

Actually going to put a coat down on previously finished oak floors. What type of prep do I need to do?

a lot of testing. Some floor finishes can't be recoated without sanding down to bare wood.
edited to add: and especially if it's ever had wax, or any kind of floor polish put on it.

Tip on applying flooded on finishes. I don't use the jug that the finish comes in to pour from, as seen in videos, but buy a plastic watering can, with a long, thin spout. I have a helper lay the bead, while I do the squeegeeing. We do it really fast. I keep the squeegee at an angle, so it pushes out the excess to the side of the next pass.

Size of next bead of finish laid out depends on how much excess I'm pushing out to the side on the last pass. It makes sense once you get into it, but having a helper makes it go a lot smoother, and less work. Having a helper is especially important if you have two rooms meeting across a hallway.

I've never had any luck cleaning the brush type squeegees, so they just get tossed. The tools for them come in metal, and plastic. I bought the metal one first, thinking it was better. It wasn't. Both tools have the rod that the applicator slides over longer than the applicator. That leaves some sticking out on at least one end.

That's the reason I bought the plastic tool. I cut it to a length so I can slide the applicator on, and it leaves some of the applicator sticking out both ends. Like this, I can push the finish right up to the edge of the floor, with no cutting in needed on the edges, or even corners.

To finish up how I did this. I sanded to 120 grit. The local wood vendor sold Dura-seal products and that is what I used. I also had removed the old thrashed baseboard so I could sand and finish with no edge marks. The Dura-seal filler went ok. Another sanding, two coats of sealer and two of poly. I used the lambs wool applicator on the sealer and poly. That went really well. Very careful taping of the poly sheeting and good cross ventilation kept the dust contained. Net/net, she likes the room now and I’m going to skip floor work in the future. To much hands and knees at this point.