How to prevent wide pine floors from cupping?

[John]

I'm soon going to be installing wide red pine flooring in widths from 6 to

12 inches and want to take any and all precautions to stop any cupping from occuring later on. Right now, the boards are acclimitising stacked and stickered. They are prefectly flat.

House and boards are very dry (forced hot air & new england winter). I plan on face nailing every board, as well as porta-nail the side tongues.

I've researched and found some suggest sealing the back of each board, and using a snake of construction adhesive (no felt paper) to also glue the boards down!

Has anyone glued wide plank flooring? I'm afraid the boards will just pop free once the glue hardens up.

Any suggestions would be appreciated.

-Johny B

[George]

Old birds building board/batten barns used to put the heartwood out and single nail close to center - what would theoretically be the top of the crown. Of course, they floated under the battens, rather than edge glued, but the use of nails versus adhesive - unless extremely flexible - will allow a bit more to happen with the wood short of splitting.

[John]

Yes, I can see that nailing the heck out of each board, or using screws even would help. I just can't bring myself to trust construction adhesive. The floor needs to move some I expect.

-john

[habbi]

What about ripping a few shallow cuts up the underside of the boards. All the wood flooring I have ever installed (lot of oak and some juniper) has them from the factory and I assume it is to prevent cupping.

[Duane Bozarth]

...

No, the back relief is to primarily allow for setting on two edges only to alleviate rocking over slight sub-floor imperfections similar to casing around a door or window frame...

12" wide flat flooring is going to move (a bunch) unless it is pre-finished on all sides w/ a totally moisture impervious coating (which ain't a gonna' happen). Trying to nail it down more is simply going to exacerbate checks and splits. No more than one nail per board near center and the hidden edge is best bet I think altho I've never tried flooring that wide...is it T&G, shiplap, ...??? What's the thickness? Is it flat- or riff-sawn?

[John]

It's T&G. If I understand the terms, it's flat sawn. Tree sliced from top to bottom.

I've got 200 year old floors now that have wide boards, and are face nailed

2 or 3 nails depending on with. They are quite flat.

-john

[Mike Marlow]

This is a common misconception. I have pine floors in my house and they are about 23 years old now. They run from 10 inches wide to 16 inches wide. When they were installed, they were simply face nailed with cut nails. The boards are run perpendicular to my floor joists and are nailed into every joist with nail spacing approximately 3-4 inches across the face of the board. There is no construction adhesive under the boards, they are simply nailed down. My floors were professionally installed and finished and they have not checked or cracked in 23 years. They do move - the gaps between the boards can run between 1/8" and 1/4" in the driest parts of the winter, and they close to half that in the summer. The boards were fit tight when they were installed but the lumber was still somewhat green and after it shrank we were left with permanent gaps.

My floors were laid unfinished and are not T&G. Once the floors were laid, they were sanded and finished with a stain and 3 coats of poly. They need re-finishing now in areas, but all in all they have held up much better than I first expected pine floors to hold up. So - mine are not finished on all sides. Yes, that does make them move somewhat, but like I said, they are face nailed across the boards and no splits. No warps. Just a slightly varying gap between them depending on the season of the year.

If I had to do it again, I would except that I'd find well dried wood.

[Pat Barber]

They might cup after this fastner but I don't think so...

I'm soon going to be installing wide red pine flooring in widths from 6 to

[fredfighter]

As noted, finishing the wood front and back and to a lesser extent all around the edges can be done to minimize cupping. That is not to say that HAS to be done on any particular floor, only that it will help prevent a problem.

Proper installation will help, including the proper sort of moisture barrier underneath if the floor is over a crawlspace or unheated basement.

The other thing that can be done is to control the humidity in the house using humidifiers/dehumidifiers as the necessary. Typically cupping occurs because of a moisture gradient in the wood as moisture diffuses in or out one face faster than the other face., though wood that is flat at one value of relative humidity may be cupped at a different value even after it has time to stabilize. Depends on the wood, not necessarily on jsut the species but also how the tree grew (reaction wood) how fast it grew, how big the trunk was when it was cut, how it was cut (quartersawn is most stable) etc etc.

If you keep the relative humidity constant, the wood should be stable.

[John]

I actually had a few boards of 10 inch SYP floor crown heavily about a month after install. These boards were edge and face nailed with Porta Nails. Not saying it's the fault of the nail at all, but it would seem that if 3/4 thick by 10 inch board really wants to move it will.

I'm just looking for ways to prevent any moisture problems that may exacerbate the problem.

Moisture barrier on dirt in the crawl space sounds like a good idea.

-Jeff

[tweaked]

Duane Bozarth wrote in

Nope. The only reason for the two backcuts is to save weight in shipping.

Poster needs to visit NWFA website and try to find the industry standards. I am not familiar with pine, but for example on 5/16" oak, we use one nail every inch across the board with a nail within 1/2" of the board edges- every 7 inches. A lot of nails! On 3/4" T&G, anything over 4" requires screws and plugs at all board ends.

Like others have said, moisture barrier and wood aclimation are important. I would let the wood sit in the heated room, for 4 weeks minimum. More depending on its history. Has it been stored in a heated wharehouse? What is the moisture content? Standard practice.

A vapor barrier under the house is easy, cheap insurance as well as the standard felt paper or kraft paper under the flooring.