Floorguy,
THere must be air between the felt and the bottom of the wood for there to be water vapor....
The same as your previous example,,, how much vapor containing air can there be between felt and the bottom of the wood and the top of vinyl and the bottom of cushion?? How did the air get to the top of the vinyl flooring? How did the air get to the top of the felt?
No AIR....... NO VAPOR !!

By the way Floorguy, I'm not trying to pick on you.. I'm trying to understand how Dew point has any bearing on water BETWEEN layers of flooring when there is no air or air movement.

Ray, I thought pourous materials could in fact harbor and transmit water vapor. In other words, vapor drive happens through materials, not just through air, right? So couldn't the vapor move top-down from the room, through the wood flooring, and hit the felt, which retards its passage to the (at times) less humid crawl space?

Floorguy raises a good question, though: Does vapor blocked by a vapor retarder accumulate into water puddles on the felt? Only when dew point is reached, I guess, which is not going to happen 3/4" from the interior of a home in San Diego. My assumptions.

Right now, 9AM in July, the house is open (doors, a window that we keep open all night), 66 deg, 87 rh, 61 dew point. The car and grass are dry.

If interested, Here's a good graphic showing temp, rh, and dew point throughout the day today.
http://www.wunderground.com/cgi-bin/findweather/getForecast?query=92104&hourly=1&yday=195&weekday=Sunday

-brad

I have a hard time accepting that moisture vapor penetrated a floor finish, then 3/4 of an inch of solid oak but then, was stopped by a thin layer of 15 lb. asphalt felt. The floor finish is way more "moisture resistant" or impermeable than the felt is. Perhaps the neighbor's floors have large gaps between the boards and he has skylights condensing moisture vapor. Or maybe moisture condensation does take place on top of the floors and penetrates through gaps and cracks in the floor. But one would see that progress throughout the day. Also, IMO, the swings in temperature and relative humidity are way too wide to expect good performance from a solid strip or plank floor. If I were the one making recommendations of wood flooring products, I would recommend a stable species, perhaps quarter sawn or an engineered floor. Also, Mexico is only about an hour away. Ever been there? Ever notice that in all the hotels, the floors are tile. No carpet or wood. Think about why. It's not only durability, it's suitability. IMO, in the environment bhammerstrom is describing, neither wood nor carpet are a suitable floor covering if the occupant does not control the environment within normal and accepted parameters.

Ray, Ray, Ray. As an inspector qualfied to inspect wood flooring, have you ever seen the bottom of a ¾ solid NOFMA spec, milled board of flooring?? Let me ask you, Is it flat? LOL!!

Floorguy,
Is there enough Cubic Feet of Air to hold enough vapor to condense on top of the felt under the wood? I don't think so

Unless there is air movement...

However;; we are talking about San Diego...

Wood floors were fine prior to the time of Air Conditioning... This described home never had air conditioning and is now experiencing a problem.. What is the difference between now and 10 years ago in this home? BUILT in the 1930's?
What is different? What changes were there in the home?

OK, didn't mean to start such a disputed topic. . . all in the name of learning, right?

First, let me say that, in my 25 years of experience here, San Diego has probably tens of thousand of structures with oak strip flooring nailed directly onto wood floor joists (no paper) that have not cupped after many decades--the majority of which, I would bargain, have no air conditioning. Gary--Not alot of wood in Northern Mexico to build raised-wood floors, that's why so much tile? 17 minutes to Tijauna. No skylights. No gaps. No hothouse orchids growing inside. No wet T-shirt parties in the living room. No daily rice steamer in the kitchen, although that is common in some areas of SD.

The new 3/4 walnut at my neighbor's house (no A/C) is a freak thing. I interviewed him today:

It's been 4 months (unusualy dry months) since his latest attempt to remedy the cupping and water found on the double layer (I found out) of felt that the installer put down. No cupping as of today. My neighbor never did, as it turns-out, complete the plastic sheeting install over the crawl space dirt (he always thought that theory was bogus anyway, since his dirt was bone dry), but he did notice a fan of fungus roots sprouting from the dirt up to his floor.

What he thinks (and what his hired fungus remediator thinks), is that the poria (correct spelling this time) invaded his floor by way of some planters at the fireplace. This stuff makes long white root-like structures that can pipe water up to the otherwise dry wood for the fungus to eat. It got to the floor by climbing the relatively damp interior side of the fireplace foundation, up to the elevated 3-inch mortar bed for the hearth, traveling along the bottom of the mortar bed and to the floor joists, and finally through the 2-layer paper (at laps?) and to the yummy walnut flooring.

He said that when he demo'ed the 5ft x 12ft living room area affected by the fungus, acutal droplets of water were flying on his arms from these McDonald straw-sized "roots" of this fungus that were growing between the felt and the flooring. This is the where the water came from. Not high rh in the home, or A/C, or showers. . .but fungus.

He ended-up replacing joists and flooring (for a 3rd time), and placing concrete in the planter area around the fireplace exterior in an effort to deprive the poria of a water source. The crawl space remains dry--and plastic-free (he still doesn't buy that idea). Maybe next winter we'll get some acutal rain, and I'll let you all know how it's performing.

So aside from all of that, why should I put felt down under my 3/4 solid on wood joists, again? Noise? Air infiltration?

--Brad

Gary was right !! The Fungus did it !!

Felt is for sound/noise/sqeaks and a vapor retarder. Mostly noise.

Now, now fellas, do I have to put you two(Floorguy & Ray) in the corner?

Interesting discussion.

Brad,
Follow the installation instructions for NOFMA certified flooring, even if your flooring isn't NOFMA certified. It calls for installing 15 lb. asphalt saturated felt paper over a wood subfloor when nailing the flooring down. It also calls for a 6 to 8 mil polyethylene vapor retarder installed on the earth in a crawl a space. And yeah, I forgot Tijuana was so close to SD.

There has to be moisture for a fungus, or as we call it wood rot, to manifest.





Poria is one of many wood decay fungi that feeds on dead wood. It sounds like science fiction and looks like it too, but poria, like all decay fungi, is an organism that needs moisture to break down and utilize wood as a food source, according to forest product experts at UC Berkeley. But unlike other wood-decaying fungi, which tend to destroy only a six inch area around a plumbing leak or wet window sill, poria has the capacity to begin in wet soil as opposed to just damp soil.


Experts say this water-conducting fungi differs from most other wood decay fungi in several respects: Large, semi-tough water-conducting roots called rhizomorphs are formed which transport water by capillary action from a constant source (usually damp or wet soil) to dry wood in a building, wetting it sufficiently to support decay. As decay proceeds, water is conducted to dry wood adjacent to that already colonized fungi. In this manner, as long as the supply of water is available, water-conducting fungi can colonize and decay the wood to the entire structure. "In other words, because fungus does not have teeth to help it eat, it has to spit on the wood. And the enzyme it secretes turns the wood to mush. Any piece of wood exposed to this fungus is destroyed" says poria expert Glenn Sigmon.


When poria attacks a building, spectacular damage often results once well established it can destroy large areas of floors and walls every year or so. Fortunately, control is relatively simple, i.e. the permanent elimination of the water source. Although poria is relatively rare, the rapid and extensive damage it can cause makes it desirable to understand the conditions leading to the attract, the signs indicating an attack is in progress, and methods of prevention and control of an attack.







That is some rare, but bad arse fungi!!!!!!! I have seen it in the woods, on dead trees.

I, too have seen it, but in a building. . .

Anaheim, California. Investigating an 8-year-old condo with a stairway where a lady stepped through her rotten mid-landing one day. Turns-out the dryer duct became disconnected as it passed through the space under the landing on it's way to an exterior wall. The dryer pumped hot, moist air into the hidden space under her mid-landing for a few months. The spot where the exhaust duct was located was adjacent to a planter area and was always warm and damp from what little dryer air made it out.

Enter the fungus.

As described to me, poria starts usually in landscaped areas then enters a building. The roots pump water up to the otherwise dry framing.

When we removed the stucco from the exterior wall at the stair well, we found the plywood totally involved with the fan-like structure of fungus--very wet. The plywood was crumbly, some of the studs were, too.

And this was in the middle of the Los Angeles basin, not some primevel forest! Science fiction-esque stuff, poria. The Fungus That Ate L.A!

So Blammer::::::::::

Your neighbor has no such problem? You made a post knowing the problem?

Not sure what you mean, Ray. Maybe re-read the first post. He had a problem I want to avoid. . . I got an update from him July 16 and relayed that info in a post. . . He presently has no problem, but only 4 months into it. He's a bit anxious about next winter. . .

-Brad

Before you put wood flooring in your house you ought to be checking The MC of the 1x6 subfloor boards ... top and bottom sides. You definitely need to completely cover and overlap all the soil in the crawl space. Run the (minimum) 6mil plastic moisture barrier up the stem walls about a foot alway around the perimeter.

The felt should be used over the subfloor and overlap it about 4"-6" in your situation. The wood flooring has to be within 4% MC of the 1x6 subfloor if using 2 1/4" strip... 3" and above the MC should be within 2%.

If this were my house i would put down a layer of BC plywood underlayment and either go with a solid or engineered wood floor.