Need help figuring out floorboard cupping

[Foursquare]

Happy New Year everyone!

I wanted to start getting advise from ya'll before talking to any contractors about my flooring problem--I dread talking to contractors unfamiliar with old house issues, as we all know how that tends to go

Our house was partially renovated and updated after Hurricane Katrina 10 years ago. The house had gotten 6 feet of water inside (its raised off the ground 3 feet, and then had 6 more feet of water inside), and the interior walls were ripped out and sheetrock installed. The then owner/flipper also retrofitted central heat and air into the house and sanded and varnished the floors. The floors on the second floor are doing just fine, however the floors on the first floor are progressively starting to cup and slightly float or separate from the subfloor. Reading typical websites about hardwood floor cupping issues, the cause is always identified as moisture from the crawlspace below. And while this is possible (and I expect likely), there aren't any moisture sources nearby or under the house in the ground-- we are on a sand "ridge" from a geologically former beach line, and the water table is likely around 20 feet down through this fairly sandy soil (makes garden centers and the water company real happy!). But of course the outside ambient air holds enough water (humidity) to drown a person!

So while I don't have wet soil issues to deal with, I guess I still have moist/humid ambient air under the house since we are in the Deep South and fairly close to the Gulf of Mexico. So I'm thinking dry inside air/moist outside air causing the floors to differentially swell along the bottom of the floorboards along the interface between the floor and subfloor. There are signs of my floorboards swelling into each other cause the tongue and groove joints between each board to compress and start to rise up along those edges.

That's it in a nutshell, and I'm open to questions, pointers, requests for photos, etc.

Regards,
Foursquare in Mississippi

[Sashguy]

http://www.joelstiburek.com

[wletson]

Two quick questions... hopefully it will get you an answer quicker.
Is the space beneath the floor open, ventilated or totally framed in?
Can I assume from you post that you are running the air conditioning a lot?
Oh, and are the floors original, or did they replace 10 years ago as well. If they were installed too tight to the walls, there is no place to expand, so they buckle.

[phil]

I don't know if it is useful or immediately obvious but when i was laying my stairs I spoke to one of the instructors and he gave me a pointer "lay all the treads heart side up"

looking at the end of most any board will reveal the rings. the heart side is the side towards the center of the tree. laying this side upward causes the boards to cup in such way that they don't rock. If you lay them the other way, then the boards will cup like a U and the board will tend to rock, thus pulling it's own nails.

now if you were to arrange a tabletop to be glued up , one would then alternate, one board heart side up, the next, heart side down and so on , this is to average out the natural warpage.

y

it is the changes in the humidity that warp lumber, not necessarily just that it is humid, but humid on one side and not the other will cause warping.of course the wood wants to expand on the wetter side.

You may have some choice with certain kinds of flooring and not with others. if it is vertical grain it will be more dimensionally stable than flat sawn lumber. It won't cup as much but it will still grow and shrink with changes in humidity.

the lumber will shrink across the grain as it dries, expand across the grain when it absorbs. the length won't change very much, but yes , some.

I would think that these factors need to be taken into consideration in an environment with such wild changes in humidity. it might amount to the floor needing to be laid with larger gaps than you might get away with in a more gentle environment. if the wood expands beyond the point that it's nails allow , it has tremendous force so yea it will pull the nails or shift the flooring over from where it was nailed, or buckle the whole floor.

Anything that might help control the difference in humidity from one side of the floor to the other, or overall changes in humidity might be of help. perhaps paint/varnish/sealing the wood would help it stop from changing so rapidly. I don't think any paint or coating can really keep the wood from absorbing moisture, but perhaps it helps with abrupt changes.

[Foursquare]

http://www.joelstiburek.com

I believe I read an article at Building Science Corporation about spray foam insulation, particularly for the underside of raised floors in the humid south-- I'll need to find that again. It was a case study that shed great light on reasons to do the sprayed foam after all, if I recall.

[Foursquare]

Two quick questions... hopefully it will get you an answer quicker.
Is the space beneath the floor open, ventilated or totally framed in?
Can I assume from you post that you are running the air conditioning a lot?
Oh, and are the floors original, or did they replace 10 years ago as well. If they were installed too tight to the walls, there is no place to expand, so they buckle.

--It is on brick piers with probably 75% or greater closed off by brick.
--Yes, we run the a/c regularly, but tend to keep it moderate compared to others in the South-- set at around 74-76 degrees.
--Floors are the original 3.5" wide hard pine tongue and groove. Perhaps they were installed too tight for the expansion and contraction that comes in the modern era with thermal variation as a/c cycles?
-- It appears that after the storm they were only refinished. Unsure how they were finished before.
--The house did not have central air before, only some window units and then gas heat. Now it is heated and cooled by the all electric a/c-heat pump unit, one up and one down.

[Foursquare]

Hi Phil,

I don't know if it is useful or immediately obvious but when i was laying my stairs I spoke to one of the instructors and he gave me a pointer "lay all the treads heart side up"

-- since the floors survived all these years without signs of any buckling and loosening from the subfloor boards, I'd guess they were installed properly a hundred years ago. The first 5-6 years in the home the floors did not exhibit any problems, but have started to loosen and cup (very slightly) in the last 12-18 months. I'd actually describe it as compression and slight rising along the joints, as opposed to true board cupping.

looking at the end of most any board will reveal the rings. the heart side is the side towards the center of the tree. laying this side upward causes the boards to cup in such way that they don't rock. If you lay them the other way, then the boards will cup like a U and the board will tend to rock, thus pulling it's own nails.

now if you were to arrange a tabletop to be glued up , one would then alternate, one board heart side up, the next, heart side down and so on , this is to average out the natural warpage.

y

it is the changes in the humidity that warp lumber, not necessarily just that it is humid, but humid on one side and not the other will cause warping.of course the wood wants to expand on the wetter side.

You may have some choice with certain kinds of flooring and not with others. if it is vertical grain it will be more dimensionally stable than flat sawn lumber. It won't cup as much but it will still grow and shrink with changes in humidity.

the lumber will shrink across the grain as it dries, expand across the grain when it absorbs. the length won't change very much, but yes , some.

I would think that these factors need to be taken into consideration in an environment with such wild changes in humidity. it might amount to the floor needing to be laid with larger gaps than you might get away with in a more gentle environment. if the wood expands beyond the point that it's nails allow , it has tremendous force so yea it will pull the nails or shift the flooring over from where it was nailed, or buckle the whole floor.

Anything that might help control the difference in humidity from one side of the floor to the other, or overall changes in humidity might be of help. perhaps paint/varnish/sealing the wood would help it stop from changing so rapidly. I don't think any paint or coating can really keep the wood from absorbing moisture, but perhaps it helps with abrupt changes.

--My gut is telling me that you are onto something here. I think I need to come up with strategies to mitigate the difference in temperature and humidity across the height of the floorboards (top side/bottom side speaking). So far I'm thinking of opening up the crawlspace to provide more ventilation down there, however I need to consider if that will only bring more moisture in that will then cool and condense out the moisture from the air. Other options would be to climate control the subspace (hmm, that doesn't sound reasonable), or blowing closed foam insulation along the bottom of the subfloor boards.

Any word on what other people in the south have concluded from spraying the closed cell foam insulation under their raised flooring?

By the way, this is the stuff I'm talking about...

insulation-image-008-300x225.jpg (21.9 KiB) Viewed 1501 times

[Foursquare]

Heres a link to that article that Building Science Corporation (joelstiburek.com):

http://buildingscience.com/documents/in ... rawlspaces

And a specific link to the same ideas applied in Louisiana:

http://www.lsuagcenter.com/nr/rdonlyres ... lowres.pdf

I'v got a lot of reading to do...

[phil]

I had some rubber flooring which I had laid over my kitchen floors to protect them after refinishing to keep them nice while I went about work on the rest of the house. I lifted and cleaned under them periodically and found some grit was getting between the rubber and floor and scratching. I laid craft paper thinking it might help the scratching.

then I noticed one day a few months back that the paper was wet. to my horror the paper was all soaked and the floor. The dishwasher drain hose had hardened up and cracked. it was probably a week before I noticed something wrong. the paper had helped to wick the water everywhere.

in my case the flooring had swollen. I had used some water based putty to help fill cracks and it was getting pushed out and the boards as you describe were cupping, the cracks were tight as a drum, it needed more room for expansion. the problem sounds similar, but not the cause.

my problems were fixed quickly, the drain hose fixed, flooring shrank back to it's normal size. damage was minimal.

The linked articles describe your issues with moisture well. I'm wondering if a suspended ceiling, but instead of acoustic tiles, a barrier made of closed cell foam might help? maybe you could let a little heat under there then, or create air movement with a fan? just thinking out loud... humidity controlled switch, or timer operated fan maybe?

I saw someone in a cold climate that was laying a basement floor. the house was on a slab. He made a subfloor first by laying 2x4's on edge. he left an opening at the end of each end, alternating so the air had to go back and forth through the maze of "baffles" then he put a heat run into this subfloor area. it was to keep the floors warm in very cold weather. (Prince George BC)


Phil

[matchbookhouse]

Conditioning (climate controlling) the crawlspace is a proven technique for reducing the humidity to an acceptable level for your flooring as well as the house substructure. I had my crawlspace done in 2004 and have added more improvements since then, such as the interior French drain and 2 sump pumps. However, the pretty much continuous use of a commercial dehumidifier couple with the sealed, lined crawlspace envelope has worked exceptionally well, as the typical reading even in really wet weather is about 43% humidity. And I live 3 blocks from a river in humid eastern Virginia.