No the vapor barrier will add even more issues. Most likely the issue is the solid wood. Florida should always be engineered and not solid for this exact reason, at least from all I know. I'll admit I am not the most knowledgeable with flooring but have always been told only engineered, never solid in the deep south.

I agree on a slab engineered is what is usually advised and not sure why a vapour barrier on a second floor . I never use wood in FLA the humidity levesla re all ove rthe map and tile , even thought I don't love it, is usually the best choice .

I think you need to control the humidity in your crawlspace better. I’m in savannah ga (similarly damp) and on a crawl. We put in 6mil plastic throughout the crawlspace and it dropped the humidity immediately. We paid our pest control company to do it- I feel like it was something like $.25/ sq ft. You can also encapsulate the crawlspace which is much more money. We also looked at putting fans in our vents but the plastic was sufficient. Obviously make sure your gutters and grading are working correctly/ we had one home that would have a pond under it after a rain.

too damp, installed too tight

Thanks all for your feedback! I appreciate it!

We do have a 6mil plastic barrier over the dirt floor of the crawl space. That is something we have done. I looked into fully encapsulating, but that is more $$ than replacing the floor :)

What’s the crawlspace ventilation like? Ie are you on piers or a continuous cmu foundation with vents.

We also have solid bamboo, except we live on the Oregon coast, literally backed up to a National rain forest. Our builder (who builds on the coast) told us we wouldn’t need dehumidifiers. Flooring was well acclimated and we finished building and moved in at the end of last summer. A month later the rainy season started again and BAM! the floor started buckling. We were able to get it to settle down, but now we have dehumidifiers on each floor and we don’t ever expect that to change. If we ever have to re-do the flooring, it will be engineered, but we will still need the dehumidifiers. (We don’t have an HVAC system because it’s not needed for comfort here.) We are saving up for the wall mounted kind now instead of relying on the portable kind. We should’ve given more heed to our next door neighbor who also always runs dehumidifiers, but her house is really old and our builder said ours wouldn’t need it. He was wrong. We do have a vapor barrier over the section of our basement that is over a crawl space. The entire house is the solid bamboo except for a couple of bathrooms, and the section of the basement that isn’t over a crawl space and is unfinished and just the bare concrete.

skmom - how does the flooring in section over the crawl space with the vapor barrier look?

Honestly, we do have a section of the bamboo in our bathroom closet, over the crawl space, that was installed with a vapor barrier (same time as the upstairs) and it lays much better than the rest over the crawl space.

We have a humidistat on our AC unit. It keeps the humidity inside under 50%. It reads 46% now, and it has been raining some today.

Hallett & Co. - the crawl space ventilation could be better, in my opinion. We are on a continuous cmu foundation with vents. I thought about putting some fans down there - maybe that will help.

Thanks all!

We recently put in engineering hardwood in our 1956 ranch which is over a crawl space. 8 months before doing so we had the crawl space encapsulated including adding dehumidifiers which noticeably reduced the humidity in the home. There is also some type of sensor which monitors the humidity in the crawl space. Our floor installer advised not to get bamboo under any circumstances. We are in Georgia. When they removed the old flooring which was a laminate with underlay, there was moisture which he said was caused by the underlay.

Avoid the large companies that advertise on tv and you may find a company that can encapsulate for a more reasonable cost.

FYI to commenters, buckling is when your whole floor swells and areas peak like a pup tent. Cupping is when each board takes a curvature due to differences in moisture between the top and bottom.

@Timothy Winzell, thank you for explaining the differences between cupping and buckling. Our floor was cupping then. We have had a floor buckle before, but it was in our last home and that was solid red oak flooring and it was after water damage in the kitchen from leaking appliances.it happened twice by the fridge and once by the dishwasher. Each time we were able to dry it out enough so that we didn’t have to replace sections of the floor, though the spot by the dishwasher always kept a little squeak. So in our current home the floor was cupping... all over the house! Some areas were worse though, and our bedroom closet (walk in) took the longest to be flat again.
@ T. Jones, the basement flooring over the crawl space looks just like the flooring in the rest of our house, perfect again. Once we got the humidity thing figured out I’m super happy with the bamboo we chose, even though we would probably choose engineered if we had to do it again.

@Timothy Winzell, we definitely have buckling. The flooring is peaking/rising (like a tent) at the seams between each board. The boards themselves look fine, no visible curvature to them.

@skmom - good to know. Thanks!

Thanks for all of your comments! After reading them, my thought is that we need to control/reduce the moisture in the crawl space... One of the biggest signs that this might be the case was when the new AC was installed and it started pulling down the humidity, the floor went flat. Now, after time that I think is the flooring absorbing moisture from the crawl space below, it is buckling again.

It sounds like our best best may be encapsulation or at least some fans...

I would start with some fans- you can get them on Amazon, the biggest hassle is adding an outlet.

@Hallett & Co. - Sounds good. That should be easily doable. I can run an outlet under there pretty easily. I have even mentioned this to a friend of mine and he recommended that multiple fans be blowing the same direction, as in an inlet side and an outlet side...

You did not need a moisture barrier installed under the flooring but, you do need a moisture retarder. The MR would have slowed down the permeating of the moisture from below and prevent your flooring issue.

Not sure how the cork was installed. But, you could have installed a layer of Aquabar or use a paintable product like Bona R541 or Wakol Pu 280.

You need to air seal subfloors to prevent moisture (air) transfer just like you would air seal a wall to prevent drafts (carries moist air). You just cannot seal it off completely, otherwise it will rot.

When installing ove crawl space, garage floors, or slabs. We always recommend installing some type of moisture retarders to assist with the prevention of moisture issues.

@T.Jones wrote: " we definitely have buckling. The flooring is peaking/rising (like a tent) at the seams between each board. The boards themselves look fine, no visible curvature to them."

You have it analyzed incorrectly. A buckle is like a pup tent in the floor, usually caused by excessive wood growth or by normal growth that isn't allowed to expand. That is why I wrote "buckling is when your whole floor swells and areas peak like a pup tent"

You have CUPPING. If you put a straight edge perpendicular to the plank direction you'll clearly see that the edges of each piece are higher than the center. This is caused by the bottom of each piece being wetter that the top such that it grows more and takes on a concave appearance.

There are some exceptions where the floor looks like it's cupping, caused by boards expanding due to moisture, where the floor is so well adhered that the expansion compresses the edge of each board. This generally doesn't happen over an entire floor and it has the same root cause, excessive moisture.

Cupping can also be convex, but that's usually a result of a floor that cupped concave, was sanded, and has since dried out.

Why does this matter? Because each type of issue can have separate causes, leading to varying solutions. Buckling without cupping or with little cupping could be a sign of atmospheric issues or installation mistakes. Cupping is usually a sign of excess moisture, either from the site or from a leak.

Your CUPPING is most likely from the humidity in the air condensing on the subfloor and migrating into the flooring material, causing the bottom of each board to grow more than the top. This will also cause the entire floor to expand. If it's high enough, it could eventually rot.

I'm going to disagree about putting a moisture barrier over a wet subfloor. I have see instances where there was no choice but to lay a BARRIER under a floor.

Prefinished planks are very tricky. When installing an unfinished floor, we let it sit for a minimum of two weeks to acclimate. That is generally sufficient for an unfinished wood to soak moisture in from above and below. With prefinished plank you can only acclimate from one side and some Bamboo is even coated on the bottom. Many installers don't remove the material from the cartons and when they do they don't stack it properly or leave it long enough.

Your issue seems to have a clear cause, since the flooring upstairs is unaffected. It's from moisture underneath.

Without removing your floor, there are two solutions I can propose. The first would be to sand your floor and apply a more permeable finish like a hardwax oil, or stain and paste wax. This would allow moisture in the floor to pass through and be removed by HVAC. I've seen where the opposite was done, an old floor with moisture passing through gets refinished with an impermeable finish, resulting in cupping.

The second would be to block the vents under the hose temporarily, install dehumidifiers in the crawl space, wait until the entire structure dries out, then install insulation from underneath. Sprayed icynene would work well for this and you may already have local contractors doing this in attics, where workers are used to working in confined spaces.

" I never use wood in FLA the humidity levesla re all ove rthe map (sic)"

This is not accurate. Florida humidity isn't all over the map. It's actually rather consistent, especially when compared to other climes. Outdoor humidity generally ranges between 50% and 80% where I am. INDOOR humidity ranges between 40% and 60%, whether you're in a condo on the water or in a house in Belle Glade. When it's hotter and more humid, HVAC works harder and indoor humidity is often LOWER than it is when it's cooler outside. AC works harder when it's hot out, dehumidifying the space as airborne moisture condenses on the cooling coils, and doors are kept shut to keep the heat out.

Compare this to other areas where it really is all over the map. Picture what happens in northern states where humidity can drop to near zero when it's cold, and even when the air is just cool, it can't hold as much moisture. Every year I see posts here about how someone's new floor is shrinking in the winter or expanding in the summer, due to huge swings in humidity. These people have to purchase, install and maintain extra equipment to add moisture to their indoor air.

My family business has been installing wood floors in south Florida for almost 100 years. Even wood floors in an unconditioned houses don't move much. It's only when you have a humidity imbalance that there's an issue. People often seal up houses, install more efficient windows and HVAC systems, but they ignore the underneath of a frame house. Picture an 80 year old wood framed cottage in Palm Beach (that's now worth million$$), that had drafty windows and marginal cooling, or no cooling. Now, put in new windows, doors and a fancy AC, so the occupants can chill it to 68 degrees. What is the result of hot humid air meeting a chilled subfloor? Fortunately most new construction is on slab (which has its own challenges), but this means that many contractors haven't been exposed to this issue before.

Thanks All! I very much appreciate your thoughts. I agree that it seems that moisture is coming up from the crawl space - that's the best explanation.

Our crawl space is about 3.5 feet tall. I am 6'2" and can easily sit with my back straight in the space and not really have my head hit the subfloor above. I say this to say that there is a lot of cubic feet of air that accumulates down there. The venting is OK but could probably be much better.

The floor is floating, so I don't think we could refinish. Even if we could/should, I doubt we would want to. My goal is to deal with this problem from underneath (if possible), since the floor is already down and it took us about a year and a half to get it all installed. So, it sat out of the boxes around our house for 12-18 months (and was well acclimated) while we did other construction, mainly the kitchen. I like the idea of "block the vents under the hose temporarily, install dehumidifiers in the crawl space, wait until the entire structure dries out, then install insulation from underneath." This or just sealing off the crawl space sounds like the best option. Second best seems to be fans, which would not deal as well with the humidity underneath, but may be a step in the right direction.