Greetings all! I am new, and registered at it appears that there are a lot of really good tradespeople on this site, and I may find some help here. I am a Journeyman Carpenter, so have shared many jobsites with Flooring Specialists. Now I have a problem!! I live in So. California. up in the foothills, near Pasadena. I moved into a concrete slab house 12 years ago, and had 5" x 3/4" solid Hickory plank installed, over 3/4 inch Ext. Plywood, bedded in mastic, over a slab with 2 coats of epoxy concrete sealer. We have forced air heating, and hunidities are changing a lot--The floor is slightly cuppedan ,d the gaps are about 1/16" on an average. My problem started 2 years ago.--An irrigation waterpipe , outside my sliding door, under the exterior slab started leaking (Old galv.), but it was not apparent--THe moisture apparently wicked sideways, under the sill of the doors, and into, or under, the plywood, on edge to approx about 5 feet inside the room. This was not noticed until I saw water appear OUTSIDE the door, took my concrete saw, cut the area open, and saw the problem. I have since cut off and re-routed the irrigation lines. I have waited about 2 years, and as everything has dried out, I have a area of flooring that is lifting near the middle of the room. If you walk on it , you can see the movement, up and down, with pressure, approx 1/8 ". I am guessing that I either have separation between the hardwood, and plywood, or it is deeper, between the plywood and slab. Any ideas or ways to handle without tearing it all out? Anyway to inject some liquid structural epoxy through some drilled holes, and weight the area down? OR does the suspect area need to be torn open, inspected and replaced? There would be a lot of lacing involves, on both ends of the damage--The floor above is not damaged--No discoloration, or splitting.. Any help from the Flooring gurus on this site would be appreciated. Thanks much for your time and ears! Best, Macc

Hard to tell without looking at it. I would first try to figure out if the plywood is loose, or the hardwood. Maybe drill a pilot hole and sink a finish nail, that should tell you. If it's the plywood....the only thing I can think of, off the top of my head, is maybe drill a hole and countersink a few Tapcons into the slab. Large hole, but maybe you can plug it. Hickory does have some nice variation to possibly hide plugs.
DriTac does manufacturer a solid wood repair kit, for solution to voids and hollow spots over concrete. This is meant for thinner solids and Bamboo glued direct over concrete. I'm not sure if it would suck down plywood underlayment, with 3/4 hardwood on top. It may fill the void, and work well.

OOH this would be a challenging situation I'd like to try and fix. Sounds like the ply was not fastened to the slab but just "embedded" into the mastic? What is the mastic?

If thats the case I'd bet it has released itself from the slab. If it were me I would drill out a few spots and try and tapcon the area in a few spots and see if that helps. Then fill the holes with plugs. Hiding those plugs might be the most difficult problem though depending wether or not it is a site finished floor or prefinished.

Thanks guys! The floor was put down over 3'4 ply, that was layed into mastic (I believe Henry's roofing ), and shot down with Hilti fasteners every so often. They then ground down the heads , prior to laying the floor. I assume they just wanted to compress the plywood flat until the mastic had set . Also, the floor was site- finished, natural, with the old oil based 3-coat, Polyurethane (nasty stuff--smell and all)--Floor needs to be refinished, at some point, to trowel fill the gaps, and to sand out the cups. I am afraid to sand the flood in this condition as the weight of the sanded will just make the floor go up and down, and leave patterns.. I am familiar with tapcons, but still need to know if the whole floor (subfloor/hardwood) is floating or not. THe plugs necessary to hadnle the countersink for tapcons, and the OD size of the driver would be pretty big (1/2" or more). I have not heard of the fill product mentioned(Dri-Tac) Who makes it , and is there a spec site to review. Thanks again, all, so much. I really appreciate your time--Any help I can give regarding framing, subfloors, finishing, baseboards, doors etc, just give a holler--Doors always open. Best, Macc

Tapcon sells a kit with bits and all in it. I gots one round here somewhere.