I have an older 1955 home (in N. Texas) that was completely remodeled by the previous owner (a home inspector) back in 2001-2002. The majority of this 1600 sq ft home is done in 3/4" solid red oak flooring, some of it (about 25%) is the original oak flooring. Over the last 2 years the floor has started buckling. However, it appears at first glance that it is actually the OSB subfloor that is pulling loose from the joists. Pulling off one of the crawl space vents and peering under the dining room, I can see that the OSB has pulled away from the joists about 1 1/2 to 2 inches. As of right now, I have 3 rooms that showing this buckling problem and in most cases there is a rise in the floor of about 1 1/2 to 2 1/2 inches all within 3-4 feet of the surrounding floor. It also appears as though in the case of the dining room, that the exterior hardy board siding is pushing outwards and inch or two. There is also noticable cracks occurring in the corners of these same rooms.

I had a foundation guy out about a year or two ago and he suggested that it may be due to moisture in the crawl space and he recommended installing (their very expensive) french drains around the exterior. He also said the piers and beams looked fine but that he thought there was NOT enough venting installed. There is no sitting water under the house but I suppose it does remain relatively moist.

What do you guys recommend doing in my case? Should I contact another foundation guy, a structural engineer, flooring guys??? I'm just really confused on what I should do and what you think the underlying problem is here. I obviously don't want to have to put $20K or more into this house, and don't mind doing some of the work myself to save some money where possible, I'm just at a loss as to what is happening and how to resolve. I'm thinking I at a minimum I need to install a ground covering to reduce the moisture coming into the crawl space from the ground...but from there, what?

Install the black 6mil plastic first. Check out the grade of your yard to see where the water is draining from. Make sure your gutters and downspouts are in good shape with no clogs and rain diverters are still there. Its odd for such an old floor to just start moving like that, normally by that age the floor is pretty stable. Have you changed anything to the house in the past two years. Sounds like you could also have a leak somewhere as well. If your subfloor is 2" off the floorjoist then you definatly have a serious problem.

Thanks Kevin. Is there a special kind of plastic to use? Does this just get laid down on top of the ground and get held in place with bricks/rocks or are there any kind of special considerations that need to be made?

The yard is almost entirely flat. We have high quality gutters in the front of the house that divert water through pipes out to the ditch. However we don't have any gutters in the rear and haven't installed any as because of our flat yard, there is no good place to divert the water to...unless of course I route the water all the way around the house and back out to the ditch through more pipes. Also, two newer homes have been built around us over the last 2-3 years. With both homes, they raised the grade for the foundations. One home is about 50 yards from the rear of our house and the second is 10 yards away. With the closest one, a shallow diversion ditch was created to help route runoff to the ditch.

As far as the old floor moving that much, the real problems seem to be in the rooms where the new h/w flooring (and OSB subfloor) was installed. I'm not sure if they pulled up the original h/w floors and put new OSB down before reinstalling the h/w, but I would guess not.

Leaks - we have none that we are aware of, and have had both a plumber and an insurance adjuster look and neither could find a leak.

So what type of person/company would you advise that I reach out to? Flooring expert, a foundation person, etc? Just not really sure who would be the best to seek advice from.

The plastic is nothing special just get the right thickness and get the black. lap it up the walls 6-8 inches and use brick or rock to hold iin place. IN the back yard your prob going to have to do some digging and install oneof thoseblack drain pipes leading to a box that collects the water. Ive seen them at the big box stores just dontknow the tecnical name for the things but if you look in the dept where the irrigation stuff is you should see em. Its just a plastic box with holes in it to le the water drain.

Well I looked last night and I just don't see how it is possible for someone (not myself) to be able to lay and secure ground cover underneath. There is very minimal clearance under the joists and beams...maybe only 8-10 inches at most in some areas. Are there alternatives that would be sufficient? Circulation fans installed in the vents? FYI, the ground under the access panel in the center of the house seemed a little on the moist side...not wet, definitely not dry, just moist.

I'm sorry to hear your dealing with this.
IMO there's a few issues that can be causing the excessive ground moisture in the crawl space after all these years. Lately I have heard of abnormally high water tables, due to excessive rainfall. Also even though you mention the terrain is flat, and you dont visually see water in the crawl space...I have run into situations where water has run within an impervious layer within the soil. Both these issues resulting in capillary rise of ground moisture. The soil does not have to look or feel wet, but as you mentioned "moist", or damp.
Now a day the 6 mil black plastic is required, ( actually some areas calling for 8 mil), but I understand plastic was not required years ago. Also, these days, crawl spaces are usually a minimum of 24" under the floor joist, or 18" under the girder. I would still consider having a contractor checking it out to see if there's a way to roll out the plastic,( what may look near impossible to you or me, may be "all in a day" to someone that's dealt with it before). I would also seriously consider diverting the run off on the back of the home. From the way it sounds, it's possible that's the root of the problem, or one of them.
Venting....Buliding codes in most areas require cross ventilation in a crawl space equal to a least 1.5 percent of the sq. ft. area within the crawl space. This is very important in itself. And to answer your question about fans....IMO you need to have the cross ventilation, or your just moving the moisture around, and capillary action takes it up through the floor.

Moist crawl spaces usually appear as cupping. The bottom of the board is wetter than the top.
The bottom is swelling and the top is not.

Buckling, is an extreme moisture gain. Humidity gains causing the entire board to swell, are more commonly the cause. Very very severe crawl space moisture can do it, but the signs will be visible.

Do you go on vacations and close the home up and turn the HVAC off or to a level it does not run as much?

Is that crawl space built to code? Eight to ten inches seems a little on the low side.

I'd listen to the foundation guy. Flat exterior grading is bad, water just sits instead of running off.

there is a local company here that is called "the crawlspace cleaner" and all they do is get rid of the junk under your house and roll out plastic like its suppose to be under the house. Check in your area there is probally someone who will do it for a small fee. craigslist maybee idk.

I am missing something here. OSB did not exist in 1955, so where did it come from? I am guessing that there has been historical problems of this nature with the house, that led to the necessity of subfloor replacement at some point.
Lack of MB over the soil in the crawl space, compounded by poor ventilation and drainage around the house, and perhaps even other moisture related issues.
I would think that you could go to the previous owner (home-inspector?) with at least a few questions. He may be able to give you some long term background on the remodeling that could help resolve this situation.
Here is my "best guess" and why I conclude this:
It would take a mighty amount of moisture penetration to cause the OSB to lift 2 inches off the joist system, unless; for instance, the structural integrity of the joists themselves were compromised by excessive moisture and repeated subfloor repairs and refastening due to the same problem historically. This could lead to the screws or other fasteners not having enough bite into the weakened joists to even help hold the subfloor down. Although, in all fairness to the fasteners, nothing will stop a wood product from expanding when subjected to increased moisture content.
I believe you need a structural engineer to get under there and check for deterioration of the joists, moisture content, etc.
This could also explain the failure of the "Hardy Board" on the exterior walls if the studs have been adversely affected as well.