House too humid causing floor cupping? DIYers or pros, any ideas

[firelyve]

My flooring (strand woven bamboo, engineered/floating) cups and gets waves a few times a year.  I spent some time a few weeks ago in South Carolina with a friend who had flooring doing the same, only even worse than ours.  She was convinced that the joists/subfloor was expanding/contracting with humidity, and I helped them encapsulate their crawl space.  Not sure it's going to help, but definitely can't hurt.  It was very warm, and super humid in her crawlspace. 

Here in Virginia, my crawl space isn't crazy damp and never gets too hot, even in summer.  It's got some insulation stapled to the subfloor from the underside.  I bought a hygrometer, and even when the AC is running almost all day at 72F, humidity inside house is 41-77%.  I like to open the windows and turn the AC off as much as possible.  It's a small house (1008 SF total).  With the AC constantly running for the last several months, floor is flat and stable.

Any ideas on what I can do to lower the house humidity and help prevent the floor from cupping and warping?  Would encapsulating the crawl space help?  Is a whole house humidifier necessary, or does anyone think I can get just one or two smaller units and place in opposite sides of the house?

I've read pros and cons on humidifiers, especially the inside units.  They create heat, use quite a bit of energy on the downside, but can reduce the humidity, making it more cool at a relative temperature and help your AC cool more efficiently on the upside.

If anyone has any ideas, recommendations or experience with this, I'm all ears.

Thanks!

[TimCFJ40]

We had Bamboo flooring in a past home and I wouldn't do it again.

Ours would swell in the summer and shrink in the winter fairly significantly in the width direction across the planks.  Our longest span in this direction was across several rooms and totaled probably 50'.  We would have 1" gaps at the ends in the winter, and it would start to push up in the middle in the summer.

Fortunately for us, we had three room transitions across this distance.  I cut a 1" slot in the flooring in each of the room transitions, and put in a matched bamboo T threshold screwed to the subfloor so the three rooms could expand and contract separately.  It still had some trouble spots, but helped a lot.

I've since used LVP instead, and been much happier.  Thermally stable, completely waterproof, and seems to be just as durable.

Sorry for your experience.  I'd only recommend bamboo for rooms less than 10x10, and even then I'd take great care to have SIGNIFICANT room for thermal expansion all the way around the floor. 

[firelyve]

Our house is small, but of course the bamboo is in the main living space/entry (10' x 17') and then extends down the all for another 13', for a total run of 30' without any transitions.  My wife bought this stuff 10 years ago, and I had very similar stuff at my townhouse before we married.  I was sold on it's durability (I had a big dog at the time), they said it was super hard.  Unfortunately, doing some research now it seems the stuff is terrible with moisture. 

I can't put in any transitions, but I can probably look to get some more space on the ends of the 30' run.  That will probably help and be the easiest solution if there's no better way to control the change in humidity with ease.  I just checked and they didn't raise the base boards up above the floor, they just added some quarter round.  The additional 1/2"+ on each side might make a difference. 

I'm trying NOT to spend money on new flooring, because otherwise it's still in decent condition if I can get it to stop it to swelling and cupping occasionally. 

Appreciate your response, it helps point me in a direction.

[uniwelder]

I don’t have anything helpful to add for OPs problem, but want to point out a distinction. I also have bamboo floors and absolutely love  them. However, it’s not a floating floor, which seems to be the real issue. Mine are stranded, tongue and groove, that are nailed to the subfloor. I don’t notice any difference in shrinkage between winter and summer.

[TimCFJ40]

I think if you raise the baseboards and have clear expansion room under the base and the quarter round, you'll be OK.  Probably measure now to see how big the floor is at full expansion, then have it minimally fill this winter.    No matter what you do, if it doesn't buckle in the summer you'll have a gap somewhere in the winter.  And they weren't lying, it is very hard and durable, but that's about it for positives. 

[Just Joe]

We had a high humidity crawlspace at a previous house. There was a plastic ground cover and insulation stapled to the bottom of the floors but what helped was a fan with a humidistat that pulled air out through the crawl space vents. The fans x2 were larger version of a desktop computer fan.

We did not have problems with our DIY installed solid oak floor at that house. We did have one bedroom door whose fit changed with the seasons.

On PBS "This Old House" we have seen crawlspaces and attics which were insulated with spray foam and then included in the heated/cooled envelope of the house. Not sure if that is ideal in our part of the country.

In our current house with a basement we run a dehumidifier that has a humidistat. It cycles. It definitely makes a difference generating a significant amount of collected water but alone can not drive down the humidity in the basement unless it runs alot at some expense.

No wet floors even after multiple days of rain. However I've paired that with a heat pump water heater in the garage portion that does assist the dehumidification in it's normal cycles providing hot water. The dehumidifer in the finished portion runs less.

I have also added a Honeywell thermostat that circulates the HVAC air each hour in addition to whatever HVAC cycling is required to maintain temps. And I added an air return to the ductwork trunk down there. I will eventually partially or wholly block the return on the floor above causing 100% of the circulated air to move through the basement. That has helped too.

I'm aiming for incremental changes to judge the value of the changes as I go along.

Lastly - what is the status of the OP's house gutter system? Our house previous owner's thought rain chains were so aesthetically pleasing that they were preferable over properly draining the water away from the foundation. That part of the ground does not drain - so alot of moisture stays in that ground. And I noticed a bit of mold on the concrete wall in that part of the basement. So, I'm reworking that gutter so it properly drains through a downspout and then the water is moved 50-75 ft away from the house to a part of the yard that drains properly away from the house.

I think all these things together will help us reach our goal.

[sonofsven]

Our house is small, but of course the bamboo is in the main living space/entry (10' x 17') and then extends down the all for another 13', for a total run of 30' without any transitions.  My wife bought this stuff 10 years ago, and I had very similar stuff at my townhouse before we married.  I was sold on it's durability (I had a big dog at the time), they said it was super hard.  Unfortunately, doing some research now it seems the stuff is terrible with moisture. 

I can't put in any transitions, but I can probably look to get some more space on the ends of the 30' run.  That will probably help and be the easiest solution if there's no better way to control the change in humidity with ease.  I just checked and they didn't raise the base boards up above the floor, they just added some quarter round.  The additional 1/2"+ on each side might make a difference. 

I'm trying NOT to spend money on new flooring, because otherwise it's still in decent condition if I can get it to stop it to swelling and cupping occasionally. 

Appreciate your response, it helps point me in a direction.

Did they nail the 1/4 round to the floor or the base?
If it's nailed to the floor, it's no longer floating, so I would start there.

[firelyve]

The quarter round was nailed to the base board.  I think raising the base boards will give a little extra expansion, so that's a good idea.

I've got gutters, so that's taken care of.  I'm not sure what the humidity is under the house.  Inside, it seems high at least in the summer, never dropping below 40%, and running up to 77%, with AC running a lot at 72F.  I'll take my hygrometer into the crawl space and see what it says down there.  It's hard for me to believe that the humidity can be caused by moisture seeping up from the exposed ground and columns below into the joists/subfloor.  But I could be totally wrong, so it's another good thing to check.

Encapsulating the crawlspace would be pretty inexpensive and I seeing as just helped do it for my friends house, definitely not beyond by skills. 

No one has any experience running small, portable indoor humidifiers to help control the environment inside?

[Paper Chaser]

You don't have to raise the baseboards/ quarter round. If you've got an oscillating multi tool with a wood blade, you can use it to trim the bottom of the baseboard without removing anything.
I'd put some painters tape down first to avoid tool marks on the floor.

As for your larger problem, any air in the crawl space will end up in your living space. It easily enters through penetrations for ductwork, plumbing, wiring, etc thanks to the stack effect. Encapsulating the crawl can only help, but you'll need some way to condition that space afterwards. You can either use existing ductwork, or have a commercial DE-humidifier that's kept in the crawl.

[bacchi]

If the crawl space insulation is right under the subflooring with no air gap, it will hold condensation. Do not do this.

https://buildingscience.com/documents/building-science-insights-newsletters/bsi-115-crawlspaces-either-or-out

We are continuing to see buckled wood floors over crawlspaces and moldy vinyl floor coverings (Photograph 1).  You can’t solve the problem building vented crawlspaces with “fluffy” stuff smushed into floor joists (Photograph 2).

[bolded]

[sonofsven]

The quarter round was nailed to the base board.  I think raising the base boards will give a little extra expansion, so that's a good idea.

I've got gutters, so that's taken care of.  I'm not sure what the humidity is under the house.  Inside, it seems high at least in the summer, never dropping below 40%, and running up to 77%, with AC running a lot at 72F.  I'll take my hygrometer into the crawl space and see what it says down there.  It's hard for me to believe that the humidity can be caused by moisture seeping up from the exposed ground and columns below into the joists/subfloor.  But I could be totally wrong, so it's another good thing to check.

Encapsulating the crawlspace would be pretty inexpensive and I seeing as just helped do it for my friends house, definitely not beyond by skills. 

No one has any experience running small, portable indoor humidifiers to help control the environment inside?

Humidity is worse in the summer because warm air holds more moisture than cold air.
The moisture can enter the crawl space in a number of ways, including directly through the concrete walls of the foundation.
You said "moisture seeping up from the exposed ground into the joists/subfloor" -- any ground should be covered by a vapor barrier, black plastic 6 mil thick at the least. Spread it evenly and cut it to fit. That could be the bulk of your problem right there.
How old is your house? These days we make quite an effort to coat the exterior of the foundation below grade with products like tar to slow or stop the water infiltration into the crawlspace. In the "old days", not so much.
How is the grade outside? are there areas that slope towards the building? This could hold moisture next to the foundation.
As per de-humidifiers, yes, they can work very well to control the humidity in the crawl space by removing the humidity, but at a cost. They are fairly expensive to run (electricity), and you would have to plumb in a drain somehow. The ones I use for drying out a house I just empty the gallon or two out of daily, which would be impractical in a crawl space.

[Sibley]

If the crawl space insulation is right under the subflooring with no air gap, it will hold condensation. Do not do this.

https://buildingscience.com/documents/building-science-insights-newsletters/bsi-115-crawlspaces-either-or-out

We are continuing to see buckled wood floors over crawlspaces and moldy vinyl floor coverings (Photograph 1).  You can’t solve the problem building vented crawlspaces with “fluffy” stuff smushed into floor joists (Photograph 2).

[bolded]

Just so you know, you're going to cost me probably $10k.

[big_owl]

The quarter round was nailed to the base board.  I think raising the base boards will give a little extra expansion, so that's a good idea.

I've got gutters, so that's taken care of.  I'm not sure what the humidity is under the house.  Inside, it seems high at least in the summer, never dropping below 40%, and running up to 77%, with AC running a lot at 72F.  I'll take my hygrometer into the crawl space and see what it says down there.  It's hard for me to believe that the humidity can be caused by moisture seeping up from the exposed ground and columns below into the joists/subfloor.  But I could be totally wrong, so it's another good thing to check.

Encapsulating the crawlspace would be pretty inexpensive and I seeing as just helped do it for my friends house, definitely not beyond by skills. 

No one has any experience running small, portable indoor humidifiers to help control the environment inside?

Before we finished our basement it was just concrete though it was in the conditioned envelope of the house.  It was always musty in the summer for obvious reasons so we eventually got a portable dehumidifier for it. It worked great and took care of all our problems.  It used to pull a ton of water out of the air so I'd always have to empty it but eventually I just hard piped it into the condensate drain lines from our house HVAC and that took care of it ..eventually when we finished the basement we did proper.vapor.barrier and insulating and never had any problems with moisture again so I eventually donated it. 

[Miss Piggy]

No one has any experience running small, portable indoor humidifiers to help control the environment inside?

In our last house, we had a small mold problem on the first floor joists (in the basement/basement ceiling). We remediated the mold, solved the water infiltration problem with an awning outside, and from that point forward, we ran a dehumidifier in the basement 24/7. It felt like a constant "battle" - kind of like years ago, "experts" would talk about how a person's body has a "set point" it wants to weigh, our basement had a "set point" moisture level it wanted to be. But I do feel like the dehumidifier helped. Just get one that has a hose you can put into a drain. If we didn't have that hose/drain setup, there's no way in hell we could have kept up with dumping the bucket as often as it would have required.

[Just Joe]

If the crawl space insulation is right under the subflooring with no air gap, it will hold condensation. Do not do this.

https://buildingscience.com/documents/building-science-insights-newsletters/bsi-115-crawlspaces-either-or-out

We are continuing to see buckled wood floors over crawlspaces and moldy vinyl floor coverings (Photograph 1).  You can’t solve the problem building vented crawlspaces with “fluffy” stuff smushed into floor joists (Photograph 2).

[bolded]

Great link. I think that article identified why our previous house was humid underneath.

[surpasspro]

I have a 3 season cabin with issues with the floor boards warping.  There is a crawl space with fiberglass insulation that is falling down.  It probably is holding moisture and rodents are also making nests in them.  I'm looking to get the insulation removed and have spray foam added.  The spray foam will act as a vapor barrier which I hope will prevent my flooring from wraping due to moisture.  Depending on that works I may add lvp flooring over my floors and also help with leveling.

[Sibley]

I have a 3 season cabin with issues with the floor boards warping.  There is a crawl space with fiberglass insulation that is falling down.  It probably is holding moisture and rodents are also making nests in them.  I'm looking to get the insulation removed and have spray foam added.  The spray foam will act as a vapor barrier which I hope will prevent my flooring from wraping due to moisture.  Depending on that works I may add lvp flooring over my floors and also help with leveling.

There are 2 types of foam, open and closed cell. One will act as a vapor barrier, the other will not. Make sure you get the right one.

[sonofsven]

I have a 3 season cabin with issues with the floor boards warping.  There is a crawl space with fiberglass insulation that is falling down.  It probably is holding moisture and rodents are also making nests in them.  I'm looking to get the insulation removed and have spray foam added.  The spray foam will act as a vapor barrier which I hope will prevent my flooring from wraping due to moisture.  Depending on that works I may add lvp flooring over my floors and also help with leveling.

I think a better option is to deal with the moist crawl space by putting thick plastic sheeting on the ground, all the way to the foundation, and making sure there is plenty of ventilation; deal with it before it gets into the crawl space, in other words.

Also, make sure you're not getting any roof runoff that drains toward the crawlspace.

If you don't have a foundation because your cabin is post and pier, I would pull the floor insulation and leave it out. If you can't seal off the crawlspace then you will get critters in eventually, and they love to nest in the insulation.

I've worked on a few old beach cabins that have no floor insulation and no skirting because of the possibility of flooding. Those joists are in good shape and there are no moisture issues since there's a lot of ventilation.

I'm not a fan of spray foam because it's a nasty chemical.