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My crawl space in our new condo has a significant moisture problem. Situation is as follows:
2 to 4 inch ratslab with plastic over the dirt. Ventilation systems in. Location adjoins a wetlands area.
The builder has been in several times and claims nothing more can be done. My 1 year warranty expires soon. Any suggestions?
Thanks
Replies
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Ira,
Excessive moisture can be dangerous to the wood underpinning of your house. I once did a repair job where the A/C condensate drain had been draining under the house for who knows how long. The fir 2x8 joist had become so spongy that you could stick a pocket knife through them although they had not been in direct contact with the water. Major repair.
If the ventilation system is working properly, that's a good start. If the plastic is over the dirt, that to me is a bad thing. No amount of air flow is going to get under the plastic and dry out the dirt.
Just a thought.
What's a ratslab?
It seems to me that if this is a current problem, it should be covered until it is fixed regardles of the warrenty period. Better see a lawyer.
Ed. Williams
*Ira, great advise.
*Fred - are you saying that the air entering the crawlspace is bringing in moisture that condenses in the crawlspace?If that is the case, why does the local building code in Western WA require continuous 6 mil vapor barrier and foundation vents based on percentage of cubic ft in crawlspace? Is it possible this is another one of those regional issues? We've been building this way for the 20 years I've been working in this area and the only moisture problems I've seen, or heard of, were in buildings without vapor barrier, or venting, or both. And I remodel, so I get under a lot of old buildings.confused, as usual - Jim
*So, would the ideal crawlspace have no vents and no vapor barrier? Or no vents and a vapor barrier? Or what?
*FredL,"Building scientists"?Get real.Ed. Williams
*The ideal crawl space would be a short basement complete with proper damproofing, vapor barrier under a concrete slab, insulated walls and conditioned air. But who can afford to do this without going ahead with a full height basement?
*Ed,Building Science CorpDan
*Hi Ed,Building Science is a for hire consultant group that anyone can hire to provide "expert" testimony. They will work for either side and present evidence to support pro/con positions for their clients.Not to be taken seriously, anymore. The founder used to have credibility but now sends flunkies to do the audits.Gabe
*Gabe, Do you know if any of their books are worth owning? Specifically, Humid mixed climates and their moisture control books. Understand the Expert Witness thing, been there done that.JonC
*I'm sorry, but we've been building in Texas for years without the help of these guys.Sound to me like they made themselves up a job.Ira,Looks like your thread started some shit.Thanks,Ed. Williams
*JonC man, do you guys in the lush, gentle, fertile, mild, sunny, Willamette Valley do your crawlspaces the same way we do up here in the cold, damp, miserable, dreary, desolate, Puget Sound region? - jb
*Think so Jimbo.Did you see the picture I scanned in on the air tight ceiling thread? Mom"s so proud. Hope to have you crawling around under that sucker soon. I think all our under house and siesmic stuff is the same but I'm not sure about our insulation stuff above. We may require more than you but you require mechaninical ventilation. Does that make sense?JonC
*Ed,
Joseph FuscoView Image
*Morning JonI read everything I can get my hands on, so my answer is yes. However, remember, you are reading an opinion.Gabe
*In hot, arid areas, I'd think the passive ventilation of the crawlspace would work, at least if there was a significant amount of moisture coming out of the ground. Once you take care of the moisture sources as you ought to (the ground, water leaks) I can't see why you'd want the vents ... except perhaps for radon.
*OK, here's a question, what if the vents are to allow air flow to take moisture out from inside the crawlspace? Here on the glacial till, we have a tremendous amount on ground water in the rainy months. If you dig a hole 3 or 4 feet deep pretty much anywhere, you hit water. Ground water. I assume this ground water is underneath our homes. So, because condensation happens on the warm side (bottom in winter) the vapor barrier helps keep moisture out of that cavity in cold months. But in warmer months, condensation occurs on top of same vapor barrier. The vents then allow enough air flow for the air to absorb this moisture and carry it out of the crawlspace. Instead of letting it build up under there and create problems. What about it? - jb
*Youngbobjb,It could be that a poly vapor barrier just ain't right for your area. Maybe something like Tyvek that breathes may be a better choice for under house vapor barriers.Is the "lack of" or the "improper use of" a vapor barrier causing big trouble with homes in your area?It could be that a vent fan might be an option as far as moving the air around under homes in your area. It is very humid here, and we install a lot of foundation fans. But we don't have any real problem with rot under houses. However, you could dig to China and "maybe" hit water around here although we are on top of the Edwards Auqifer.Would like to hear more,Ed. Williams
*Ed - here's the problem. I don't doubt what FredL says. And yet, it is contradictory to what we do here. Read my earlier posts in this thread and you'll see what I mean. So. I went to bed thinkin' about this, woke up thinkin' about it, got an e mail from somebody I don't even know askin' me about it, and I've been ponderin' it most of the day. The questions I just posed are the best explanation I can come up with. So, at the risk of having my (virtual) head bit off, I posed the question. 'Cause, like I said to that e mailin' stanger this morning, there is nothin' I hate more than doin' somethin' I don't understand, or really believe in. I want to gain an understanding of why I do what I do, and I think I need other people's help. - jb
*It helps to keep in mind the term "relative humidity." That is, whether a given amount of water in volume of air makes it "wet" depends on the ambient temperature.The vent problem is during the summer the vents will bring in lots of warm humid air onto that cool crawlspace floor. The cool crawlspace will be perpetually damp like a cave; and any moisture from the ground will only make things worse. The plastic stops the moisture from the ground; closing the vents stops the moisture from the outside air. If the space were hermetically sealed, the most moisture you could have would be that contained in the air volume, not much. It is the constant introduction of additional water vapor that makes for soaked framing.During the winter, cold air that carries little moisture will only become drier when it encounters your warm framing. However, some of that air may be sucked into the house, accumulating moisture in the house air and bringing in more moist air behind it. So again having an unsealed crawlspace will cause problems, when the warm moist hoise air escapes across and condenses into relatively cold framing. (If you are sucking in air from the crawlspace, then you must be pumping it out elsewhere...)Or at least that's my understanding!
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So, unless I'm confused, we still haven't answered Jim's question yet--1.) ideal under house situation 2.) to plastic or not to plastic. This is very timely, actually, I have a client I'm doing carpentry odds'n'ends for as well as coordinating trades, etc. and the HVAC man came and duct'ed the crawlspace before the insulation man did his plastic thing (the insullation chief is acting contractor for the HVAC trades, they've formed some kind of triad, like the mob) SO! The insulation man said you need the plastic so, DO I GO IN AND RAISE HELL TOMMORROW OR NOT? P.s- we're in ole virginny. FredL, Gabe?
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OK, andrew, I think I understand what you're sayin', and I gotta run, but there is some faulty reasoning in your post; "...summer...warm, humid air...winter, cold air that carries little moisture..." . What I'm sayin' is, what you describe is the exact opposite of our humidity situation here. (I think) In winter, we are in an axtremely humid climate, you can actually taste the water in the air, even when it's not raining. Summer air is MUCH drier here. (again, I think) I'll check back in about 3 hrs. - jb
*Jim,It seems to me that this is "much ado about nothin".Nobodys house is falling down.I can't tell you how many times I've seen some guy try to make more of something than what there is.They don't know what they're talking about, but they can sure baffle you with "scientific" bullshit.Just a thought from Texas.Trust your gut.Ed. Williams
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Ah, yes, Thank God we have a Texan in our midst. Sean, let me get that man a drink.
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Relative humidity -- the humidity % doesn't tell you how much water is in the air, you must know the temp. as well. Humid cool air and not-humid hot air might have the exact same amount of water in them. Up where you are -- lots of vegetation, right? -- there is usually a fair amount of water in the air year-round.
I'm just not Mr. Science Teacher! Sorry :)
I do know that a ratslab is a few inches of concrete sprayed on the dirt to keep the varmits at bay, out west where they don't need real foundations ... someone asked about this.
*Will there be problems down the line if the insulation has problems and the installer says, well i wasn't allowed to do my job? What's his motive anyway?
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Andrew, I guess you're responding to me,
I don't know, you see they're all in cahooots! It's one bid with three different contractors, the insulation man is acting GC, they've got the local power company in on it somehow and the city helps finance the client, supposedly because it helps conserve elec. I'm in the phone book under potatoessmall as well and it's all kinds confusing.
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clayB,
Have a beer on me, and don't sweat it.
Let the big heads fight it out for themselves.
Mr. Ed.
*Here in Oregon, and I think it's also true up where Jim is, the arguement while both interesting and confusing to me is academic in new construction. Our code requires a 6 mil poly barrier and loads of venting in the crawlspace, and the same poly under the basement floor. In crawl spaces they usually want it to come up the inner foundation walls 6". Most folks put it right over the piers before framing up the beams. Right or wrong, if it aint there, your underfloor wont pass period.From personal experience, the cleanest driest houses I've crawled around under here have been newer ones with poly and venting. The worst houses I have seen in the area were older houses without poly where people had closed off the vents to protect their pipes, keep the floor warmer or whatever. Major rot problems.While Jim lives on the wonderfully drained glacial till where you can put a post hole down 3 or 4'before having it fill up with water in the winter, here in the yucky, wet, muddy Willamette Valley you'll be lucky to make 6 to 12". Not to mention the cultural advantages up North.No Answers, JonC
*Most of the moisture problems I've personaly seen in crawlspaces I'm sure were due to plumbing leaks or incorrect drainage [slope ] on the outside of the foundation . Once it gets wet under there it takes quite awhile to dry out . Chuck
*Now JonC, man, tell 'em the rest. Tell 'em that your "winter" is a mere blip of 6-8 weeks, while ours lasts well over 6 months. Had to build a fire again tonight. Any better down there? - jb
*Been raining and cool here Jim. Dont know why they keep coming north.JonC
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My crawl space in our new condo has a significant moisture problem. Situation is as follows:
2 to 4 inch ratslab with plastic over the dirt. Ventilation systems in. Location adjoins a wetlands area.
The builder has been in several times and claims nothing more can be done. My 1 year warranty expires soon. Any suggestions?
Thanks