I am replacing badly damaged 3/4 oak in a hallway in a house built in 1913 - about 120 sq. ft. Have ripped out all the hardwood. Subfloor is 1" x 12" rough planks nailed diagonally to joists. I planned to secure plans with deck screws but have encountered two problems. In reading your forum it seems pretty clear that subfloor needs to be very level and solid before nailing down the hardwood. Need the advice of you experts.

1.) The planks are quite rough - there are cracked pieces, knots missing and a gap of about 1/2" between boards. Seems to be some spongy spots due to this. Do I replace any damaged planks? That is must the surface be perfect or can I reply just on securing with screws into the joists?

2.) The house has settled (you would too after almost 100 years!). There is a dip over an 8' span of at least 1" in one section. I plan to lift the planks and add shim material to joists to raise the level. Should I replace with plank material - I doubt I can get 1" x 12" or can I put down 3/4" plywood in this section as long as I get the levels to match to existing?

3.) Sorry one more - If I do keep some of the planks, should nail holes and other voids in the planks be filled? If so what filler material?

Thanks - this is new project for me as you can probably tell. Found your forum to have the best info that I can rely on.

Newbie

Minor voids, nail holes, etc. do not need to be filled. Gaps between the subfloor planks are also of no real concern.
Having said that, and since it is only 120 sq. ft.; have you considered removing the subfloor in this area entirely? and replacing it with 3/4 plus 1/4 ply after leveling the joists. Remember that where the subfloor runs under other existing floors, briging will be required between the joists to support then and prevent movement.

1) This is normal for old subfloors. The gaps are not a problem. You should cover the subfloor planks with 15 lb. asphalt saturated roofing felt paper. If the old section did not have it, you still should put it in the area you are replacing. Be VERY careful driving screws into those old dry planks. Odds are, they will crack and split. If you must use screws, pre-drill pilot holes first.

2) If you can carefully remove the subfloor planking, fur up the joist a little, then re-install the planking without damaging it, then I say no reason why you cannot re-use it.

3) Do not bother trying to fill holes or gaps. Those are normal with these types of subfloors. You may experience some noise or squeaks with that subfloor. If you can get the noises out, great. If not, then live with it. It is an old home just doing what old homes do.

Thanks for both of your replies.

I will try to carefully lift old boards - but I suspect Dennis is correct. I will end up having to toss away a certain amount as it is very dry and brittle. I will end up replacing with plywood. Plus as noted, as the subfloor boards move towards inside of the house they go right underneath the wall. They will need to be cut so they can be lifted out to shim the joists. Once cut on replacing I will have to install supports between the joists close to the wall to support either the old boards or the plywood.

One thing I have learned living in an old home - very few renovation projects take less time than I planned, instead they alway take more. Like Gary says - that's just the way old home are.

Ya, my house was built in 1902 and has been under renovation and re-renovation for the 24 years I have owned it. So boldly going where no man should ever go, I recently purchased another house as an investment. (1917). Well it is certainly going to be an investment, lol.
But, during all of the reworking in both of these houses, I made no attempt to make the floors flat other than what I considered reasonable, replace the trim, or otherwise make it look like a new house.
I think we should carve Gary's statement in stone.