Homasote under the paneling

That was common in the early 1950s before drywall dominated the construction industry for buildings that couldn't afford real plaster.

snipped-for-privacy@rochester.rr.com wrote the following:

It is common as interior walls which will be covered with a more durable surface. Its value is that it is more soundproof and has more R value than sheetrock. What do you intend to have as a finished surface?

I usually just take the cover off a light switch to see what the backing material is. Our 1958 Chicago suburb house has 1/2" sheetrock covered with 1/2" plaster for all walls, the extra plaster makes a huge difference/improvement/loss in sound transference. Outer walls are the same on the inside side, plywood with tarpaper under cedar shingles for the outside walls. Only problem is the occasional woodpecker.

Actually, the standard for the 50s was 3/8" gypsum lath, (replacing the problematic wood lath) which came in boards 48" long X 16" wide, over which was about a 1/4" rough brown plaster base covered with about a 1/8" coating of hard white plaster. Homosote and other products were produced and sold as a cheaper solution the the cost of a full plaster surface, drywall became the standard and the other products died out.

Painted drywall is what I planned on.

I was hoping there was drywall under the paneling that I could clean up and paint... The Homasote means I need to get a couple of friends in and hang some sheetrock.

Yep, you can hang it over the homasote, or rip the homasote off and hang the drywall directly to the studs. You may have to consider how each would affect corners to other walls with homasote backing.