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canflyboy 11-08-2012 04:52 PM

Does my old T&G plank subfloor need sanding before I proceed?
I just finished tearing off a couple of layers of underlayment off the main floor of my house - over 100 years old. The remaining subfloor is 3 1/4" T&G planks (about 13/16" thick). The planks are loose and I plan on screwing them down to the joists (as reccomended by Jazman)

In the kitchen area, I plan on covering the subfloor with 3/4" plywood and installing a luxury vinyl tile (probably Alterna). In the family room and dining room, I was thinking of covering the floor with 1/2" plywood and installing 3/8" or 1/2" engineered hardwood flooring.

The planks on the old T&G subfloor are cupped (both ways). Should I take a sander and level these down before installing the plywood?

Also, the planks seem to be made out of a softer wood, possibly pine. In heavy traffic areas, the planks around the wood knots are worn. The knots protrude - some up to 1/8". Should the knots be sanded down to level before installing the plywood?

My thinking here is that the airspace between the plywood and planks left by the cupping and knots might give me soft spots or squeeks.



joecaption 11-08-2012 05:15 PM

Want to do this one time and do it right?
Remove everything down to the floor joist.
Almost always old houses ran under sized joist for the spans, there rough cut, there notched on the ends so there weakened, very common to also have instect and fungus damage.
It would give you the access needed to add piers and beams, checked to see if there level and flat, remove or at least sister new ones.

Yes I know there run unnder the walls, not a big deal to just use a tow kick saw and cut them right up to the wall.

JazMan 11-08-2012 08:36 PM


Please, next time do not start a new thread when asking about the same project. We now do not know what was already said so far.

Concerning this question, it sounds like the planks are too far gone and need repairing. But, are you saying the planks are cupped both ways in the same room? How is that possible? Cupping indicates too much moisture from below, you need to fix that with better drainage, more ventilation, a vapor barrier if the crawl space is dirt and probably a few other things. How to fix depends on where you are and the conditions.

Sometimes fastening near the edge makes the cupping go away if slight, but may not work for you. If it is slight and the overall floor is flat, you need thicker underlayment to stiffen things up. In such a case 1/2" will not do.


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