Moisture Moisture Moisture...

fixitpete

Application:
1st Floor over crawl. about 30"-36" from grade to joist in crawl. High humidity area (coastal).

Subfloor: T&G Board (hardwood)

Finished Floor (to install): Brazilian Cherry 3-1/8" 3/4"

Moisture @ Subfloor: 15%

Moisture @ Flooring Material: 6% (Lowest Ligno will read).

Difference between Subfloor and Materials: Approximately 9% (Maybe more since 6% is the lowest the meter will read for the material).

Issue: No plastic barrier on grade in crawl.

Point to this post: Do you think that by adding the plastic barrier to the crawl this should solve the problem of moisture in the floor? Or does the high (coastal) moisture area lend to the issue more than the barrier will help? What else would you be looking at? I plan on using Aquabar - B for the moisture barrier as well.

Thanks and... Seasons Greetings!

Burby

Money is the 1st question, how much they have to spend and or how well they want it to work.
Alot depends on water table level, added condensation from hvac lines, & present ventelation.

6 mil poly works well here in southeast SC on the coast with added crawl space rated fans, especially if you can create good cross ventilation

Ideally is the crawl space encapsulation with a dehumidifier

Thank you & happy holidays to you as well.

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Poor Floorman

Applied industry standard, NWFA Installation Guidelines Section 1, Chapter 1, Part 1
#7 states:
"Crawl space should be a minimum of 18" from ground to underside of joists".
#8 states:
"Crawl space earth should be covered 100% by a vapor retarder of black polyethylene (min. 6 mil) Meeting ASTM D-1745".

Start here.
If you can't meet these, you're trying to fix a leaky faucet with a balloon.
Sooner or later the balloon will give way and you'll have a bigger mess to clean up.
Next, in the crawl space, check the M/C of the under side of the subfloor and joists. Also a R/H and temp inside the crawl space.
After the 1st 2 standards are met and you attain 3 readings from the crawl space (R/H, Temp and M/C) you are ready for recommendations on product and installation.

Hope this helps.
Following Applied Industry Standards can give your installation the best chance for success, not following these guidelines and your installation is destine for failure.
It is not if it will fail IT IS WHEN.

A little math
9 x .00300 = .027" x 3.125" = .084", across 10' you could expand over 3.25". That's more than the width of the plank you started with.

fixitpete

I will take the readings as indicated in the replies above... and report back here when I have them.

I've been considering have a concrete slab poured in the craw for three reasons and I'm wondering if this is just the reason I need...

A) The crawl DOES get water in it often (remember, coastal area) so there are times when you can have several inches of standing water in the crawl -- if I do a slab down there, I'm wondering how that would effect things in the moisture department.

B) The slab would make it VERY much nicer to work under there... I could get a creeper and just slide around and do what I need to do under there.

C) It would be MUCH MUCH MUCH cleaner...

What are your thoughts?

P.S. How can I say "Thanks" for all the help?

jamestrd

sounds like a slab will just be a sponge..i think what you need to do is create proper drainage so water dont accumulate.. french drains of some sort to redirect water.. my opinion, a slab will probably fail in current conditions...ground water must be high for it to sit like that..that much pressure will blow apart a slab in no time.drainage,
insulation with 6mil over the dirt, then put any floor you want with proper barrier underneath..

fixitpete

"Proper drainage" -- Not when you are at exactly sea level. The slab is very common in the area, but I can understand the "sponge" idea that you're talking about, and it makes sense.

My only question is that during the flooding season, How do you keep the 6+mil plastic in "place"? Or would gravel OVER the plastic be an idea?

My concern is that the plastic will be "pushed up" as the water rises below it.

rayh78

Dont understand the crawl space rated fans.
I thought it was high humidity in SC.
So the fans would bring more humid air in the crawl space espically when its raining. Agree with the dehumidifier

Floordude

Interesting situation. It is 3 feet up and the subfloor is 15%.

Is it pressure treated subfloor?

It is possible on the coast, for the underside of the subfloor to be exposed to a consistent 75%rH and above. Enclosing and dehumidification may be the only option to get'r done.

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fixitpete

Subfloor is T&G Maple (no pressure treated).

I'm really on the fence with what to do. If I put down 6 Mil. Poly, then two questions come to mind:

1) Where does the water go during floods? (Can't think I would want it to sit on top of the plastic... like a pond)
2) How do you keep the high water table (during high tides, etc.) from "pushing" the plastic up and/or moving it around?

What about a barrier that allows water to go DOWN but not up? Sort of like that weed barrier that you put down? Would that work?

fixitpete

I'm reading the "Insight - New Light in Crawlspaces" (ASHRAE Journal) - one way or another I'm going to solve this problem the *right* way for my application... I'll drop by the "Insulation" forum on here...

Thanks, for the help -- I'm sure I'll be back soon.

Floordude

You don't want water channeling into the crawl space in the first place. You need to keep all moisture from getting under the home. Gutters, vented retaining walls, french drains. Or close it all up and dehumidify.

With a 15% subfloor and an interior capable of drying out to 8-10%, you got problems.

If the Maple substrate is OK, you may have to acclimate the wood to 13-15%, before installing it.

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fixitpete

I wish there was a way to keep the crawl space from not having water in it to begin with, however, when the floor of the crawl is below sea-level -- and often below high-tide... that makes it hard.

Go here for more detailed information on what I'm dealing with: http://www.contractortalk.com/f80/cr...ng-post-50252/

jamestrd

Problem 1) water pools in crawl space...Never good for anything, so solution

direct water from home, even if not 100%, still better than not... so make french drains aqnd direct the water as much as possible away from the home... re grade if necessary

2) moisutre barrier,

as long as you have wtaer pooling with no air cuirculation, it will alwasy be high unidity and mositure effecting your subfloor.

so my thoughts..

put moisture barrier over your exisitng subfloor. maybe 30lb felt, aquqbar, or whatever you like..even 6 mil will be fine.

screw down 3/8 underlayment.

install engineered flooring with Bostiks Best..

no moisutre will go to that floor.
and if it does, it can withstand Moisutre content of 15% no problem...thats what engineered floors do.. you will expand, but will not cup..

acclimate your subfloor for a few days(new underlayment and install)...


DO NOT open your materials until you install.do NOT try and acclimate them.they are kiln dired and sealed in box to 8% MC.
Follow instruction for proper trowl type and size..will depend on thickness of material..

Usually 3/16x3/16x3/16 V notch, or for 1/2" thick materials, 1/4x1/4x1/8


problem solved.

fixitpete

a) material is hardwood (3/4" t&g cherry) -- not engineered.
b) water is already as directed away from home as possible. problem is not with rain water re-direction, but rather with water table. this is coastal so tidal flow is the issue. Water comes in (and up) based on tide since floor of crawl is below sea-level. French drains, etc, wouldn't apply here since drain would be below sealevel and hence always full.

thanks for any help you can send my way.

jamestrd

exchange materials and see above post, typos and all.

fixitpete

Thanks for the advice. I appreciate your time.

Floordude

That is why along coastal regions like that, you see a lot of ceramic tiles. Wood is not the right flooring for you, even though you want it so badly.

I see your expectations not being met, once it all goes south, after it is installed.

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fixitpete

I really appreciate your input on this. I've consulted with several concrete and moisture abatement people that I've dealt with over the years and it seems that as long as we conform (somewhat) to ASTM 1993 and add a surface pump we will significantly reduce the moisture in the crawl space, allowing for installation of the material that we're after.

Basically, the plan is as follows:

Grade soil toward the lowest point, in this example, toward one corner. The thinnest section of slab shall be 3" --

Next a vapor barrier that conforms to ASTM1993 (WR Meadows or Bituthene (I *THINK* "System 4000" conforms)(?)

at the low point we're going to J-Bolt a starboard (heavy plastic) material that will receive a surface mounted submersible pump. This pump will only run when water accumulates from flowing off slab, or during a flood (during a flood, it won't stop until water recedes or water is vacated.)

Pour slab.

Done.

This -- In combination with Aquabar-B (just because) -- should provide an exceptionally good substrate and environment for our materials.

Floordude

Go for it, and let us know how it all works out. I don't mean the day after the install. I mean how it is next year.

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fixitpete

Thanks... (let me know if you have any information on various ASTM related data for crawlspace moisture reduction when it comes to correcting moisture issues to property acclimate hardwood flooring.)

This is a pretty technical application -- so specifics are key. Saying to just use a different material because their may be challenges to the material decided isn't a solution.