I will seriously look into unfinished floors.
However, I have read that pre-finished floors are much better finished (in clean rooms etc.) and on-site staining and varnishing can be adversely affected by dust.
Who would you suggest I use for doing on-site finishing in the Montreal area?
In your case the unfinished is the answer, and any responsible supplier would confirm this, in a case of an uneven subfloor. Some suppliers may have a warehouse full of prefinished flooring that they need to move. That’s why they mention these floors are adversely affected by dust. A lot of airborne dust is created during the floor sanding process, but I just applied the final coat on one of my own floors a few days ago, and it is as smooth as glass.
How do we do it? Simply hire a professional for the floor sanding at least. Then simply vacuum up all the dust, from the floor and any ledges. Apply one thinned coat of polyurethane. Wait 1-2 days for it to dry at 21 C. Scuff sand the floor smooth, vacuum and tack rag with varsol. Allow solvent to dry. Apply a heavy coat. And repeat the same thing for the last coat. Always brush the finish on with a good quality 4″ bristle brush. It’s not rocket science but you may have to ask quite a few contractors before you find one willing to do such a thorough job. That’s why I suggested you apply the finish yourself. If you want about the same durability, you can try the water based finishes instead, so be sure to read my article about Dura Seal 1000 finish available in the search box at the top of this web page.
Oh, and if you were considering stain the floor, I would instead find a pro to do the whole job, sanding, staining and finishing. This is far too tricky a job for the amateur to tackle on a weekend job. Whereas the pro will recognize the sanding marks that have to be removed so that the stain will take evenly. And it is very easy t pull the stain off when coating the wood. Be sure to have 3 coats of poly applied over the stain. Read my article in the available in the search box at the top of this web page about how to hire a contractor. Be sure to see the prospective floormans stained jobs before you choose a company. Expect to pay quite a bit for this rather specialized service. Also be aware that only oak and a few other woods take a pigmented stain well, maple will turn blotchy.