my guess and not sure if you have access but probably a foundation issue.

Did the rippling occur anytime before?

65+ yr old foundation wouldnt surprise me to have some kind of crack thats lettting moisture in.

Possible to rent a moisture meter and check out the area?

Hi. Thanks for the reply. Never noticed anything (of the like) before a few weeks ago. It just seems weird as (although on a slab) we are a good 3 feet (or so) above street level. I was wondering if plumbing pipes (embedded in the slab) might be an issue but the cupping wood does not seem to be near any pipes (or where they might be routed). Also..where can one rent a moisture meter? Cheers.

You could try a big box home improvement store, you could always buy one online, but it might be wasted money for your needs.

remember my guess is only speculation based off the info you gave, so theres still quite the possibility im wrong. and if it is a foundation issue i hope i am, because thats not fun to fix.

the rippling does sound like a moisture issue, and if you are sure theres no piping embedded in the slab near the affected area, then that leads one to believe its coming from the concrete.

Now if you are able to get a hold of a moisture meter and the area is not showing a higher level of moisture then its back to the drawing board.

Looking at your drawing again, do you have forced air, air conditioning? are there ducts going along that line where the rippling is occuring?

Hi. No...there is no air along that line. I will attach a pic of the AC line/ducts. The rippling is right in line with that one wall...yet..no wood tiles "along the wall" seem affected...only the ones at the "door openings" on each end. Cheers.

Does your HVAC system have a drain pan? It's possible that it is over flowing, if, it is not draining properly.

If there is a concrete joint, check where it meets the exterior wall outside and see if there's anything that might cause water to pool.
Did you check the back edge of each bedroom closet?

Also make sure it couldn't have come in at the front door. I had a situation once where an irrigation line shot at a front door, water flowed in, got under the base of a wall and soaked into the wood floor. By the time the owner got up the standing water was gone so it was quite a mystery.

Hi. Thanks for all the replies. I climbed on the roof this morning. I didn't see anything obvious (roof was replaced 8 years ago). I checked the AC drain pan (and pump)..dry as toast in that area. The area near the front door does not appear to have gotten worse (yet). The area in the middle of the house seems to be spreading a bit. I am in a bit of a panic now. Not sure what to do. Should I call a plumber or a home inspector? I'm pretty good a fixing things but this is (I think) getting beyond my element. Again...no noticeable loss in water pressure. No signs of water pooling anywhere outside. No noticeable roof problems (and poked around all nearby walls and closets and don't see anything problematic). Any advice appreciated. Cheers.

Sounds like drainage from exterior issues. You've had plenty of rain and that's when it started. Rain on the ground = water under the slab. Slabs are NOT dry. They can act like a sponge. When the ground is dry, the sponge is dry. Once the ground is SATURATED then the water's "path of least resistance" is up through the slab. Cracks in the foundation = a big leaky spot. And foundation cracks LOVE to go in (relatively) straight lines.

I would bring in someone who deals with "foundation issues" or someone who deals with exterior drainage.

Thanks for the reply. It's raining lightly (currently)...BUT.. it hadn't rained for several days...yet the wood tile swelling has continued to expand little by little in the center of the house. Would a foundation continue to "wick" moisture like that (despite a lack of heavy rain)? Also..what might I be looking at (in terms of a fix)? Would it be an "exterior seal" or do think I might have to rip out my vintage wood flooring? Also....how can I rule out that this is not a plumbing issue (old pipe deterioration)? I know where all the water outlets are..but I don't know the routing of the pipes beneath the house (only speculation). Been poking around the local government/city websites and don't know how I could ever even find that out (given that house was built in the mid 50's). Sorry for the scatterbrained reply..just trying to sort this out. Cheers.

Thanks for the reply, Cancork. I will make the appropriate calls asap. Cheers.

UPDATE. Had numerous plumbing and leak specialists out to inspect the house. No issues found in the water or drain pipes. The last person I had out pulled up a piece of parquet tile and we found the problem: subterranean termites. Never would have guessed. As the termites infested the wood (with their chewing and mud tubes) it left moisture in the weak flooring causing it to swell and buckle. After several termite "evaluations" I decided to take on the work on myself. I trenched around the house slab and treated with Taurus SC (Termidor equivelent). I also drilled into the porches and carport (where the walls aren't exposed to ground) and treated those as well. It was alot of work. Time will tell, I guess. I have 15-20 parquet floor tiles in pretty bad shape. I plan to pull those up and drill through the slab (inside the house) and inject some of the termiticide at those areas. I DO HAVE A QUESTION (for those who have experience/knowledge in this area) regarding further "spot treatment". I have a box of parquet wood tiles in my utility room (that I saved when expanding the floor of my kitchen). I plan to use those to "patch" the termite damage in the house. I was thinking that I might take a few of those tiles and spray the UNDERSIDE of them with the Taurus/Termidor. I'd let them dry thoroughly (outside) and then place them (termiticide DOWN) in the house (in the vacated tile areas). My intention would be to "bait" the existing termites (curently in the flooring) and expose them to the termiticide. Would this be safe? I have pets and don't want to risk them. If the termiticide is dry and on the OPPOSITE side of the wood flooring it would seem so. Just want to be sure. It would only be a small amount that I would use. Any advice appreciated. Cheers.

I would not have guessed termites, but you do live in Florida.

Another update (and flabbergasted)..........

I treated the perimeter of the house (and interior..including spot treatment) as described above (with a DOUBLE dose of Taurus SC). Last month I replaced many of the parquet tiles (with the leftovers that I had). Pulling each of the old/eaten ones up I saw dead termites by the thousands. I patched and filled in with the old tiles and thought it was all over. Months had passed (at this point) since the original infestation and I had seen NO sign of termite activity at all. TODAY...I noticed a slightly shoddy wood floor tile (only one...and in an area of the original infestation). I thought I might have missed it when I replaced the damaged floor areas last month. I pried it up and found live termites AGAIN. What went wrong? Is it possible a few bugs survived the Taurus SC treatment? I honestly don't know what I missed (as I was very thorough when I treated the perimeter of my house. Any advice appreciated. Cheers.

Termites are funny beasts. They will stay away from areas where they find their "dead" buddies...and then go to another spot to see if they can find another route to the food source. They are not like ants (ants share information and then take poison bait back to the nest where everyone feasts and then dies). Termites can work independently of one another. If one finds poison....it will die. The others will find a "work around" solution....and the problem/infestation continues.

This is why termites are super difficult to control/eradicate. So long as they have a food source, they will continue to find ways to get to it. One dead termite = one dead termite. This is how they differ from ants.

Now that you have tried the DIY eradication, you will need to bring in the big boys. Local specialists who have worked with your soil type, build type, infestation type and the exact species of termite will have the most amount of knowledge (there are more than 40 versions of this funny critter in the USA...and that doesn't count Africa and Asia).

A design website with people from all over the world may not have a great deal of knowledge of your particular set up.

Keep us posted.

Just thought I'd post another update. After the last (but isolated) termite "return" I racked my brains over what I might have missed. Knowing that my house was built in 1955 I had developed a suspicion about the house drains (I did a bit of research on old house construction, slabs, etc) and decided to investigate another area. There is a bathroom very close to the affected areas...and the bath drain is behind an interior wall (only 6 feet from the worst of the chewed up flooring). I took a hole saw (the kind you use to install a doorknob) and opened up the wall behind the bath drain area (about 18" above the floor). I shined a flashlight in there and (sure enough) there was a large slot cut in the concrete slab to allow for the bath drain to exit the house....like a 15" by 36" (or more) hole in the slab...I could see dirt plain as day. Well...I took my mixture of Taurus SC and soaked the entire exposed dirt area very thoroughly. I also used Fuse Foam termiticide and sprayed a healthy dose inside the area (behind the tub) before sealing it up. So far no new sightings of the pesky little buggers. Fingers are crossed. I know that subterranean termites need a moisture source...maybe I have just enough of a drain drip/leak to provide that (and keep them UNDER the house). Anyway...there is another bathroom that I will apply the same treatment to this week (although I have no signs of wood damage in that area). Better to be sure, I guess. Old houses have old plumbing and old drains.....just a little moisture might be all it takes to keep the termites alive. I hope I never have to post bad news to this topic again. Cheers.

AND.....the hits keep coming............

I have not seen any further activity in the house. I keep checking...but nothing. Holding my breath but hopeful.

HOWEVER...today I decided to clean out my shed. It is an all wood 8x12 structure that I built myself in the corner of my backyard. It is built upon four 6x6 posts (embedded in concrete) and is four (to six) inches above the ground (suspended). I had a large hardwood tabletop and a big piece of butcher block countertop stored in there. As I was removing items I noticed a large blemish on the tabletop. I thought I might have scarred it with a bicycle that I'd had hanging next to it. Nope....termites. I pulled the tabletop (and butcher block) away from the wall and they were prettly well chewed up. I soaked them with bug killer (because I didn't want to unleash live insects into the wild) and hauled them to the curb. Then I noticed that tremites had chewed up the plywood inner wall of the shed. Mud tubes (might as well be..mud WALLS) were erected in the corner of the shed. One single mud tube went all the way to the ceiling. It had all been hidden by that giant tabletop. There was damage in one other area as well....and I could HEAR the termites munching away. The damage is pretty harsh but IS salvageable (and does not appear to be structural). I doused all the affected areas with Termiticide. The termites also munched on other pieces of scrap project wood I'd been storing in there. I trenched around the back and side of the shed and (in the back) found a LIVE cluster of termites and mud tubes centered around some decorative stones I'd placed around the base of the shed. This area is CONSTANTLY moist (due to rain and shade). I soaked the trench in termiticide (including the backfill) and will complete the treatment for the front and other side tomorrow. I am exhausted. If anyone else has gone through this...I feel your pain. The destruction of these little buggers is unreal. I am confident I can patch my shed up...but man....what a frustrating pest to deal with. Cheers.

Update...I think I got them (or at least I hope). I trenched the shed (even drilled through the floor of it it) and doused all areas with termiticide. These little dudes prefer wood that it is not treated. They went for the plywood sheathing, the exposed tabletop and butcher block...but DID NOT eat any siding (and did not penetrate the Tyvek wrap on the structure). I saw a couple of munches on some left over treated scrap (I'd saved) but they definitely went for the "easy lunch" first. This is a PSA...if you live in the south in a "damp" area...please inspect your house (and your wooden shed..if you have one) to look for any "odd" deterioration in anything that is made of wood...and do it repeatedly. You might want to consider preventative treatment also...just in case. Cheers.