Hardwood floors sound like Rice Krispies, need helpful ideas

[Perry Holbrook]

We bought a small house built in 1966 last year to live in while the new house is being built. We will either flip it or use as a rental. There is about 700 sq ft of oak hardwood flooring nailed down with cut nails. The sub floor is 1x6 slats with 1/2" space between them. For the most part the floor is firm and level. After we removed the old and dirty carpet and pad that had been installed over the hardwood we discovered the problem. The floor literally sounds like snap, crackle and pop, pretty much all over. It's so loud that a night time trip to the bath room wakes the wife. I refuse to rent/sell it the way it is.

I think the noise is from the tongue and groove sliding against each other because when you step on a noisy spot bar footed you can feel movement. The builder of the new house suggested going in the crawl space and screwing through the slats into the oak, but I think that means screws in a 6x6 pattern. A flooring guy said they could not be fixed in a manner so they could be refinished and said if we cover with carpet or something else he would screw through the oak into the floor joist. He thought that would stop it, I'm not convinced.

I'll probably have to do one of those ideas. However, being a thinker like the rest of ya'll, I wonder if there is another option. What if we sanded the oak to bare wood, then thin down some slow cure low viscosity epoxy resin and flood the bare wood with that. The theory is that the resin will soak in, swell the oak, and then laminate it to each other and the sub floor. Then we could apply a top coat finish. It's probably a crazy idea and I can think of some possible problems, but do you think it is even worthwhile to do a small scale test of the idea?

Thanks

[Kev Williams]

instead of resin, what about linseed oil?

[Tom M King]

I ran a thousand screws up from underneath in one. I screwed right through the subfloor boards, into the flooring to tie it together better. It had a full basement, with no ceiling in the basement, so wasn't that bad to get to. It got almost all of the noise, but I decided I didn't want to flip any more houses for multiple reasons other than easy money.

[Greg Funk]

I'd pull all the oak, screw the shiplap down or replace with plywood and put the oak back with staples and then refinish. I had an uncle that would make a bunch of thin long wedges that he would hammer at 90 degrees to the flooring. He was able to pull flooring quickly using this method. Probably not worth it if you're just selling the house but it's what I would do if I was going to live there.

[Mitch schiffer]

I have dealt with this issue many times as a contractor. it is typically not the entire floor though. It is usually the higher traffic areas. Screwing from the bottom is the best if you are trying to save the floors. If you screw from the bottom and still have squeaks you can run a bead of construction adhesive on each side of the joists and that should help. It can be screw from the top in a 6 to 8 inch grid with subfloor or laminating screws if you are going over it. There are specific screws meant to be driven in for the top and they leave a hole that gets plugged, however this is really intended for a localized area. I have had one oak floor with very narrow planks that would split with about every other screw and I had to remove it and install new subfloor. There are some old hardwood floors that are only about 3/8" thick and none of these methods work on that. I have only seen a couple of the old thin hardwoods so I don't think they are very common.

[Kris Cook]

Sounds like you have access from below. I would consider driving shims between the joists and the subfloor, augmented with construction adhesive as a place to start.

I just removed a floor in our house built in 1910. The old floor was squeaky, bouncy, and chock full of screws. Pulled up the old flooring and saved what I could. Replaced some of the rough-cut sub-flooring planks, where necessary. I put down 5'8" T&G underlayment plywood. Then installed new White Oak flooring. A lot of work but the floor is solid and no bouncing, sags or squeaks.

Pulling up the original flooring and re-using would be ideal but I am not confident you would be able to save the boards without destroying either the tongues or grooves. Maybe try Greg's method if you wanted to go that route.

[Bill Dufour]

Sounds like the sub floor is only half there. It should be two layers at 90 degrees. One layer with 1/2 gaps is going to flex under load. Epoxy will just flow through the cracks and all drain away. I suggest plywood over it all.
Bill D

[Jack Frederick]

Spending 700 sq ft of time working under the house in a crawl space is, to me, a pretty heavy lift, especially is insulated. Unless this oak is pretty spectacular I’d pull it and install some of the new engineered flooring. Once the oak is up you can rescrew the sub flooring. I’m looking at doing the same in the upstairs of my place.

[Perry Holbrook]

Sounds like the sub floor is only half there. It should be two layers at 90 degrees. One layer with 1/2 gaps is going to flex under load. Epoxy will just flow through the cracks and all drain away. I suggest plywood over it all.
Bill D

Thanks to everyone for your thoughts and especially to Bill. With the subfloor flexing due to the lack of a second layer the oak is moving as well. Screwing thru the oak into the joist as the flooring guy suggested doesn't fix that.

[Perry Holbrook]

Spending 700 sq ft of time working under the house in a crawl space is, to me, a pretty heavy lift, especially is insulated. Unless this oak is pretty spectacular I’d pull it and install some of the new engineered flooring. Once the oak is up you can rescrew the sub flooring. I’m looking at doing the same in the upstairs of my place.

Crawl space is low, maybe 18" but it is not insulated.

[Bill Dufour]

Before plywood a subfloor was 1x boards run at 45 degrees to the outside walls. Then a layer of paper to seal drafts. I suppose it also stops squeaks. Then another layer of 1x wood at 90 degrees to the first run. Kind of like two plys plywood.
Seismic testing has shown that old growth wood run at 45 degreees as siding under stucco is good enough as a shear wall and does not need to be covered with 1/2" plywood. This assumes a reasonable amount of nails were used.
For modern construction the plywood has to be nailed 3-4" apart on the edges and 12" in the field. So diagonal wood can be strong and solid.
Bill D

[Mitch schiffer]

1 layer of 1x6 on a diagonal with gaps and hardwood on top is common for old houses. There is not usually a second layer.

[Bill Dufour]

1949 california house use two layers.
Bill D

[andy bessette]

I'd pull all the oak... replace with plywood...

This is the only fix that makes any sense.

[Rick Potter]

Agree. You say you will sell it or rent it. Pull the oak, put down plywood or OSB over the space sheeting and cover it with carpet or Luxury Vinyl planks.

PS: Use adhesive as well as nails when putting down the plywood.