I'd put as much varnish on that floor as I had the money or patience to put on. I would do a small section at a time.
Linda C

Excuse my ignorance in these factors but wouldn't putting varnish seal in the filth already there or cause problems in the crawl space??? How do I clean it prior to any varnish? Doesn't varnish have to be applied to a clean surface? Can varnished surfaces be mopped?

Thanks in advance.

Go ahead and mop it with a damp, not soaking wet, mop. I'd use Murphy's Oil Soap and rinse it with vinegar and water and dry it with towels in small sections so the water doesn't stand on the surface. After that I'd paint it with floor paint which will cover any remaining staining. Floor paint can be very creative if you like and is very durable. It also comes in a water base for easy clean up.

Here is a link that might be useful: Wood Cleaner

It seems to me that using Murphy's Oil Soap could be a real problem. If Compost_hugger_nancy wants to paint or varnish the floor later, it might be reluctant to stick.

I would rather seal in the dirt than try to mop it and soak the wood.....and you will put a real floor down eventually, won't you?
You are not varnishing for a beautiful finish but to "isolate" the dirt.
Varnish also works very well as a way of removing musty smells in an old chest of drawers....you seal the bad stuff in.
Linda C

Wouldn't denatured alcohol work on an unfinished wood surfaces? Once cleaned with that, it should seal or paint well.

How about exterior grade porch paint? You can mop that as needed until to get to the next stage.

Sweep as best you can. Use a damp rag/sponge in the corners where dust accumulated and wasn't swept up. Don't worry about trying to remove stains or other past problems. Then paint the whole thing with floor paint. Big Lots sells floor paint - not much of a color selection, but it's cheap. Depending on the condition of the wood, you may need to use some paint primer first. It will save you money in the long run, since you wont be wasting money on paint that never will properly adhere to the wood in the first place

If you feel creative, and have time, you can paint patterns. Simple squares and rectangles are nice for the non artisitc. You can keep the subflooring for years without installing anything else - but make sure all exposed surfaces are always covered with paint. It ever starts to chip/flake repaint immediately! And preferably before that ever happens.

Defintely do NOT use Murphy's Oil soap. It is not recommended for wood floors. Nothing can be put over it like poly,paint or even stain. It would have to sanded off
and you get uneven coverage.

If the floors are that stained I vote to paint them. If the stains are mostly in the center you could stain and varnish them and do faux wood planks. In either case I would paint some area rugs to add interest and warmth. Place your furniture first so you know how big.

Wood planks are easy. Draw your "planks" with a ruler and a magic marker. Make two dots/nail heads in the end of each "plank". Then stain and varnish.

I think a painted rug would add a lot of charm and still fit your budget. Do a search on painted floor cloths for some examples. Even if youre not artistic you could do something geometric with circles and squares if you use painters tape.

Or you could do a braided rug. A braided rug looks hard but its really just time consuming. THe "braid" is made with small foam brushes. You need one for each color. Hold your brush upright and dab it on the floor to make a line \ then /. THis makes your "braid". Start in the center of your "rug" and work your way out making a spiral of different color \ / dabs. Its only paint. If you screw up just wipe it off and start over.

Dont forget to seal your creation with a couple coats of varnish.

I'm a lurker here. So, Hello everyone!
I've seen some beautifully stencilled floors which is great for people like me who aren't artistic.

Nancy, I would vac the floors very well then clean with a bleach solution. This will remove the dirt, stains and also kill any mold that might be growing. Then if you chose to and money is not an issue then I would paint the floor with and oil based paint. This should get you through until you can finish the floor properly.