Crawspace vapor barrier question

[Tim H]

Originally posted by sirch

Here's my two cents (for what it's worth), I really don't think leaving a space at the outer edges makes any difference. I have inspected crawls (of all ages) that never had a vapor barrier and could not find any moisture issues. Most damage I find was caused by leaks from kitchens and baths. Heck, down here the humidity in the air is in the 80 and 90 % range most of the year.

On the other hand, I have inspected crawls of all ages that had no barriers/improper barriers installed, that have had siginficant moisture related issues.

I have found that the environments of crawlspaces that are not properly capped by barriers are extermely hard on ductwork, air handler cabinets and furnaces.

One thing I have yet to see is a non plumbing related moisture issue in a crawl with a properly installed barrier.

Tim

[Phillip]

Originally posted by Tim H

Originally posted by sirch

Here's my two cents (for what it's worth), I really don't think leaving a space at the outer edges makes any difference. I have inspected crawls (of all ages) that never had a vapor barrier and could not find any moisture issues. Most damage I find was caused by leaks from kitchens and baths. Heck, down here the humidity in the air is in the 80 and 90 % range most of the year.

On the other hand, I have inspected crawls of all ages that had no barriers/improper barriers installed, that have had siginficant moisture related issues.

I have found that the environments of crawlspaces that are not properly capped by barriers are extermely hard on ductwork, air handler cabinets and furnaces.

One thing I have yet to see is a non plumbing related moisture issue in a crawl with a properly installed barrier.

Tim

I have seen them dry with no barrier and have seen them have problems with barriers.

I have yet to see a barrier that completely installed right

[Tim the Termite Guy]

Originally posted by sirch

Here's my two cents (for what it's worth), I really don't think leaving a space at the outer edges makes any difference. I have inspected crawls (of all ages) that never had a vapor barrier and could not find any moisture issues. Most damage I find was caused by leaks from kitchens and baths. Heck, down here the humidity in the air is in the 80 and 90 % range most of the year.

[Tim the Termite Guy]

Hi again Fellas,

I've been in the termite biz for about 5 years mainly doing inspections. Granted, some of you have more field experience than I, and I am always willing to listen to reason, but reading through the posts it sounds like everyone has a different take on this. Maybe there is no "one size fits all" answer. When I see big gaps in vapor barriers What comes to mind is poor workmanship, and I've seen my share of sloppy vapor barriers. Sometimes they get wadded up and drug around too. I suppose as long as the water is recondensing on the underside of the plastic, then it benefits the substructure by helping to lower the moisture content of the wood thereby reducing it's palatability to wood destroying organisms. The guy that originally trained me was an old timer who knew alot and probably one of the first to start putting them in around here. His preference was to let the subarea soil "breathe" at least a little. Thats one reason why I like to leave a bit of dirt showing along the foundation. Another reason is in case some runoff does occur it can percolate away. And then there came the fateful day I popped the hatch on a old house to inspect the crawl and the soil was right there at the bottom of the joists. Evidentally the house had settled to the point where you couldn't get under it. That got me wondering: if the soil stays softer, the house sinks quicker? hmmm.

Tim

http://timthetermiteguy.com

[energy star]

I cover the entire floor and block all vents closed with insulation. Never open them.

[Tim H]

Originally posted by SonOfSwamp

Originally posted by Brandon Whitmore

Brian,

I was taught the same thing a few years back at a training seminar.

Well, that most likely means folklore. HI "trainers," taken as a breed, are folklore geysers.

The italicized "info" in the original post sounds like a guy trying to get himself hired for a Larry-Daryl-and-Daryl job.

FWIW, having crawled a few thousand crawl spaces in Middle Tennessee, I can say that many were 100% dirt, and quite a few were dusty dry. House ages ranged from 100+ years old to newish. Most had no problems. The ones with problems were the newish houses with "positive drains, " which of course routed water to the foundation walls.

Do these folklorists ever walk into a bookstore?

WJ

This info from the original post?

The vapor barrier in the crawlspace is inadequate, as it doesn't cover 100% of the soil under the home. I recommend that this be corrected immediately. This is important because the barrier limits the amount of moisture that can evaporate out of the soil into the crawlspace.

A proper vapor barrier consists of black, 6-mil polyethylene sheeting and must be applied from wall to wall of the foundation. It should cap the footer and lay tightly against the sidewalls, overlapping at least a foot at all adjoining sheets and be tightly sealed around the base of support piers. Ideally, the barrier is secured to the foundation walls, and overlaps at adjoining sheets are sealed with waterproof tape. Additionally, the barrier should be applied with some slack so that it can float free without separating and still inhibit evaporation if minor flooding occurs.

If so, I am not really sure what you mean by "sounds like a guy trying to get himself hired for a Larry-Daryl-and-Daryl job".

I was describing the proper way to install a barrier. There is obviously some legitimate debate regarding the necessity for barriers, but is there any doubt about the correct way to install one?

Tim

[Tim H]

Thanks for responding, Walter,

Well, sure. First, there's the decision regarding whether or not the crawl needs a plastic cover at all. A hundred-year-old house that was built before poly sheeting existed could be just fine without the cover. I've seen hundreds of such houses. They needed nothing.id="blue">

I have seen the same thing hundreds of times. I was reporting on a particular house that had recently had a barrier installed. I was trying to describe how to correct it. The decision to install a barrier had already been made.

As noted in other posts, there are many ways to skin the poly cat, so to speak. One need not specify a color for the poly, nor a given thickness.id="blue">

I agree that I should not have described a color (and do not any longer), but I still report that 6 mil is the minimum thickness that should be used. I can cite sources, but it is really common sense that anything thinner won't have the puncture resistence needed to withstand things like inspectors crawling around on the barrier.

Your description contains a glaring logic flaw: "The vapor barrier in the crawlspace is inadequate, as it doesn't cover 100% of the soil under the home." If you're going to use an absolute such as "inadequate," you should cite one or more reputable sources. Sooner or later, you'll run into somebody who'll challenge your recommendations.

Failure to cover the whole crawl doesn't mean the barrier is "inadequate;" nor does it mean that the crawl needs a poly barrier "immediately." That's hyperbole. Pardon my saying so, but that's where the text starts sounding like a sales job. "Crawl space plastic half-price if you buy today!"id="blue">

Failure to cover the entire crawl is inadequate per recommendations found at buildingscience.com (and others). It is also illogical to think that a barrier does not have to have complete coverage. Without complete coverage it can not be a barrier.

Per Webster a barrier is something material that blocks or is intended to block passage. Cant do that if you dont have complete coverage.

If I reported the same thing now, I would likely state something like "the barrier is not installed in accordance with recommedations made by xyz.....".

Immediately was another poor word choice, and I am not sure why I included it (It wasn't an attempt to take advantage of anyone, as you implied). I certainly don't agree that calling an improperly installed barrier inadequate is a "glaring flaw in logic" (if it is, a couple of thousand people read it and didn't notice. Not saying it wasn't a logical flaw, but 'glaring' is hyperbole). In my opinion it is not as glaring a flaw in logic as saying someone "sounds like a guy trying to get himself hired for a Larry-Daryl-and-Daryl job", based on the fact that the guy descibed a method for installing a vapor barrier differently than you would have described it .

Pardon my saying so, but that's where the text starts sounding like a sales job. "Crawl space plastic half-price if you buy today!"id="blue">

Quite an inference for someone so devoted to the rules of logic. Just so you know, I am not a thief, I am not a con artist and I am not some backwards assed Larry, Darly and Daryl looking to take advantage of people. I am also not someone who publicly implies such things about others based on such a paucity of information. Home training and stuff.

You use another absolute: the sheeting "must be applied from wall to wall," etc. There are lots of ways to seal up a crawl space. If you think the method you describe is the only way to seal a crawl space, you'd better be ready to cite reputable sources.id="blue">

Again, I am using recommendations that can be found at the web site you cited below. Building science.com (among others) recommends a continuous barrier mechanicaly attached to the walls and sealed at the penetrations. Are you recommending unreliable sources?

As an aside, how do you seal a crawlspace without going wall to wall? This MUST be done. The rest of the description illustrates what is ideal and what should be done. Not absolutes.

A proper vapor barrier consists of black, 6-mil polyethylene sheeting and must be applied from wall to wall of the foundation. It should cap the footer and lay tightly against the sidewalls, overlapping at least a foot at all adjoining sheets and be tightly sealed around the base of support piers. Ideally, the barrier is secured to the foundation walls, and overlaps at adjoining sheets are sealed with waterproof tape. Additionally, the barrier should be applied with some slack so that it can float free without separating and still inhibit evaporation if minor flooding occurs.

In short, you get in way over your head by dictating certain materials and methods, and telling your reader that there's only one way to seal up a crawl -- and it's your way. By citing no reputable sources, you take on all of the responsibility for the materials and methods, and how they'll perform in the future.

In short, I would agree. But why do you assume that I could not or did not cite reputable sources? I only posted a small section of the report.

No offense to bug men, but taken as a breed, they are as full of folklore as home inspectors. Where does this info come from? Is the guy who taught you this educated? What are his credentials? What are his sources?id="blue">

That is why I didn't believe the bug man and came hear to see if my doubts were well founded. I had no confidence in the bug mans info, so I didnt really look into his sources. My doubt as to the veracity of his information prompted my original question.

My humble suggestion: Verify your statements and be ready to cite sources. You might want to take a look at www.buildingscien

ce.comid="blue">

Again, I am not sure why you assume that I can't cite sources. I wasn't seeking advice on how to properly cover a crawl, or even whether or not this house needed a barrier. I was looking for feedback on the 'new barrier/old house/ wood shrinkage thingy.

I look at buildingscience.com frequently. Thanks.

Tim

[Jeremy]

I see buildingscience.com referred to quite often here on TIJ and I have to agree that it is great source of a wealth of information. But, what about the IRC? Would it not have more legs to stand on if this topic were to become a real dispute? After all it is what more jurisdictions adopt as the base for their codes. Wouldn't it be a better source to site?

Opinions?

[energy star]

May I say that a 100 year old house is anything but a tightly constructed home. Homes are much tighter now. We are puuting a cap over the ground sorta speak. Go flop a piece of plastic on the ground, say 10 x 10, go back the next day and its wet underneath. Some people pay 6 to 12k to encapsulate their crawl space in the mid atlantic region.

[randynavarro]

Originally posted by Jeremy

I see buildingscience.com referred to quite often here on TIJ and I have to agree that it is great source of a wealth of information. But, what about the IRC? Would it not have more legs to stand on if this topic were to become a real dispute? After all it is what more jurisdictions adopt as the base for their codes. Wouldn't it be a better source to site?

Opinions?

It's a conundrum. The IRC is the authority and law, yet the work that many others, especially Lstiburek are far ahead of the code cycles.

One of the first things that comes to mind is the attic ventilation methods that are widely adopted and accepted.

They were established right after WWII and haven't hardly changed.

Now Lstiburek and a host of other are pushing for condition, sealed, non-ventilated attics.

[hausdok]

Hi

Well, I wasn't going to say anything about it; but this has gotten to the point where I guess I should. In all fairness to Tim, I don't know where he got his comment, but it looks to be word-for-word the language that I've used time and again in reports and have posted here and on the JLC building science forum when the question of how to install a barrier properly comes up. If I had to, I could backtrack it and come up with very solid sources for all of it.

Generally though, they started with Dr. Joe and went from there. When I first got into this gig back in 1996 crawlspaces and vapor barriers were a curiosity to me; I'd only ever been in a very few in my days helping my father and those I didn't like, so I didn't know a whole lot about them. When I moved here to Washington State and realized that I was going to be in them about 95% of the inspections I did, I decided to learn as much as I could about them and how they should be properly detailed.

One of the very first sources I went to was the Oak Ridge National Laboratory Site where I found a Moisture Control Handbook free for the downloading. That book was authored by none other than Dr. Joe L. and it's been my bible for more than a decade. When I have a question in my mind about why something moisture-related is behaving the way that it does in a building I go straight to that book, do some reading and then follow the trail of references that Dr. Joe used to get my answers.

Dr. Joe's section of Vapor Diffusion Retarders has a pretty good list of references at the end. I went on to research as many of those other references as I could find. One of those was a paper by Home Energy Magazine which I still have but the link no longer works; another was a paper by Jeff Tooley on Pressure Differentials that helped me understand stack effect better, and that paper led me to JLC where I read some of Tooley's other articles on how to properly install and detail vapor barriers (Dr. Joe likes to call them Vapor Diffusion Retarders 'cuz he says there's no way to absolutely stop the moisture diffusion - you can only slow it down.). in crawlspace.

Tooley, and another Tooley (a brother, perhaps?) in turn, did a lot of work with Advanced Energy Corporation to figure out how to best seal crawlspaces under various conditions. It was those references - Dr. Joe's writings, Tooleys, the articles from Home Energy Magazine and a few more references, where I came up with that method and I'll stand by it. I don't care what climate you're in; if you install a barrier that way and detail it properly, diffusion of soil gases/moisture into the building are no longer going to be a problem.

Now, whether or not you'll need to control air movement into and out of the space above that barrier is another question entirely. Around here, as long as the floors and pipes beneath the floors are insulated, there's almost no situation where having too much ventilation to a crawlspace will hurt a home; regardless of the season. However, if I were in North Carolina with it's extreme summertime humidity, I'd do exactly the same thing with the vapor barrier but I'd have to take an entirely different approach to foundation vents, because that very warm/humid exterior air is going to naturally want to diffuse into a cooler/drier crawlspace where it's going to condense all over every cool surface under the home. In a situation like that, I think mechanical ventilation controlled by a humidistat, or no ventilation at all, work best.

Yeah, I know that there are hundreds of folks who've found uncovered soil under homes and those homes didn't have any problems; I've found a few of those myself. However, those are the exception, not the rule, and I think any home inspector who isn't recommending that 100% of the soil under a home be capped is looking for trouble that sooner-or-later, is going to find him or her. Bottom line, a proper barrier should cover 100% of the soil under the home. Dr. Joe says that a barrier that is covering 90% of the soil is going to be 90% effective, but that even that 10% can cause issues. That's good enough for me.

The floor issues that you're describing can just as easily be controlled by adjusting the amount of under-house ventilation and interior environment to achieve proper equilibrium. Keep the soil capped, and there are ways you can consistently control those issues, uncover the soil and the amount of moisture migrating upward into the home will constantly fluctuate, depending on season and the amount of moisture in the soil surrounding/beneath the home, and there'll be no way to consistently control that movement.

ONE TEAM - ONE FIGHT!!!

Mike

[energy star]

I have met, talked and listened to John Tooley. He loves this stuff.

Mike has a very good post, kinda brings it all together.

[Jeremy]

Originally posted by randynavarro

It's a conundrum. The IRC is the authority and law, yet the work that many others, especially Lstiburek are far ahead of the code cycles.

True, and it is fortunate we have guys like that. They will always be ahead of the code cycle with ideas that should be tested and proven before becoming law. Without them there would be no progress. Now we are starting to see provisions in the code for some of those ideas, such as conditioned, non-vented crawls. Having these options as a "legal" way to do things is great and prevents us from being trapped into only doing the minimum, but it's not always necessary that we exceed minimum requirements.

When advising someone to go with the latest and greatest, rather than what is laid out within industry standard, I think we need to be sure we are not advising them to join an experiment. If I am the one to "sell" them on someone's new idea, will I also be the one they come to for the guarantee? That would be my concern and makes me wonder why we wouldn't stick with the IRC as a rule for source cites.

Don't get me wrong, I like buildingscience.com and don't condemn it in anyway. I'm just thinking in terms of inspector liability.

[kurt]

The building codes are woefully inadequate on many of these (important) issues, and they also point the way to a better structure.

Joe L. falls into spells where he imagines houses to be some sort of fragile work of glass, where the slightest bump or inopportune move results in catastrophe, and often he's right but sometimes not.

Both are right and wrong. That's where we come in. Or, at least, that's how I think about it.

There's no one out there doing much field research, except us. How many folks bring themselves into the process, and offer opinions?

I do. It's very obvious that some properties on crawls don't need a vapor barrier. Plain, simple. Others can turn into mushroom farms.

Can folks tell the difference? I think that's the important part.

Of course, I recommend every crawl be sealed, but I also temper these recommendations with observations of conditions. If there's a house that's been hanging around just fine for 40 years without a vapor barrier, the attic is clean, no sign of moisture, and the occupants are happy and have good teeth, why would I get humped about vapor barriers?

What I try to impress on folks is the house is a functioning entity. If one element is changed, it alters the balance of everything else in the house.

Yeah, it's a little weird, and I'm sure the liability police will howl that I'm leaving myself open to evisceration by high powered attorneys, but I don't care.

There's usually too much of one thing and not enough of another. I try to figure out what those things are, and tell my folks about it.

[Tim H]

Originally posted by hausdok

Hi

Well, I wasn't going to say anything about it; but this has gotten to the point where I guess I should. In all fairness to Tim, I don't know where he got his comment, but it looks to be word-for-word the language that I've used time and again in reports and have posted here and on the JLC building science forum when the question of how to install a barrier properly comes up.

Mike,

The statement is reworked boiler plate from Inspect Express. I shortened it and verified it for accuracy, using multiple sources. I understand that you helped with this software, so it is more than likely your statement.

Tim

[BENCHMARK]

I had called as defective on a 48 yr old house.

In my state Indiana wood floor joists 48 year old are Douglas Fir which is much slower to gain moisture out of the air. I don't think that very many inspectors know that wood gains moisture based on several criteria: relative humidity as opposed to humidity, species and percent of sapwood as opposed to heartwood. Southern Yellow Pine has been the species predominately used here for the last 35 years. It is highly absorbant and is primnarily sapwood which absorbs more readily than heartwood; way more!

For these reasons Doug Fir, & older woods which often contain much higher percentages of heartwood can often handle humidity conditions that would rot yellow pine.

These woods also change dimension less so movements from humidity changes tend to affect structures & floorings of these woods much less.

Originally posted by Tim HThe vapor barrier in the crawlspace is inadequate, as it doesn't cover 100% of the soil under the home.

100% coverage is optimal not necessary in most situations. Several other people down the thread have affirmed this logical statement. I don't know where you got your specs on a vapor barrier but in some ways thery are understated & others over the top. Keep things in perspective & call it a ground moisture barrier.

The termite guy says that he left a 1' gap around the perimeter of the crawl on purpose. He said he had to do it that way or the sudden lack of moisture would dry the framing so quickly that the floors would buckle.

I inspected a house last spring which had just had a 'perfect' ground moisture barrier system installed a couple of weeks before I got there. The barrier was 10 mil & extended up the foundation walls to the top where it was fixed with a treated wood strip. By the end of the summer (an especially dry one) the walls in the house were cracking over the tops of interior doors & interior walls were 'wrinkling' the drywall tape where they met the exterior walls.

These clients thought the house was falling in and almost called their attorney before me. (I may not be out of the woods yet)

When I looked in the crawl, I found everything nice & dry, in fact the Yellow Pine floor joists were around 7% RH. They outer perimeter joists, covered on the inside of the crawl by fiberglass batts have a moisture content of 15%. I did not write down the moisture contents during my inspection, because they were inside the normal range & the moisture system looked 'perfect'!

It is my opinoon that the whole floor structure, beams included, underwent a straight line drying which dramatically changed their dimension; with the outer perimeter joists drying less & changing dimension less.

I installed crack monitors on most the the interior cracks & on two tight cracks in the foundation that were noted in the original report. Nothing has moved since October. I think the event is over but my clients are not so sure and they have a bunch of cosmetic repairs to make.

The bottom line here is when there are yellow pine or other sap wood species floor structures in a crawl which has been very wet for an extended period; drying this crawl down is very likely to result in differential downward movement as the wood structures dry & shrink. This is more at the beams!

This is the second time I have heard this (not completely covering on purpose).

Sounds like folklore to me. Anyone ever heard this? Is my statement accurate?

Thanks,

Tim

It's making a lot of sense to me!

[hausdok]

What you experienced doesn't surprise me; it's very common here in new homes.

Some builders here don't bother to put down a barrier until after they've dried the house in and completed it. You'd think that with our wet climate they'd know better. Anyway, because of this, the house continuously obsorbs moisture for months on end. Then, not long before delivery, they'll install the barrier and deliver the home. In almost every instance, builders will warn the clients to expect to see some cracking and movement throughout the home because they know that all of the framing is going to shrink; it even occurs in homes built with engineered lumber. The builders typically come back at the one year mark and repair the damage if the buyers request it. Sometimes the damage is minor, sometimes not so minor.

You tested 15% moisture in the rim joist after the place had dried in? Since 17% or better will support rot, and it probably was much higher at the time of the inspection, those homeowners probably don't realize how close their home had come to something far more serious than cracks and movement caused by lumber shrinkage.

This past Tuesday I inspected a brand new home where the builder had plenty of crawlspace ventilation under the code formula and had put the barrier down early but never bothered to install vents under one room that sort of juts out from the rest of the crawlspace with cold air on three sides. It's also the hardest part of the crawl to get to and the person that put the barrier down got lazy and left it about 10 inches shy of the far wall. Conditions in the crawl were perfect everywhere except under that room; under that room, water was literally dripping from the insulation and running down the foundation wall where evaporation from that 10-inch wide by 10ft. long strip of earth was condensing on the rim at all three sides. When I pushed the insulation aside to look behind it, moisture drained out of the insulation like a squeezed sponge and the floors and rim close to the perimeter on all three sides were covered with blue-green mold spots about the size of a dime.

Your story has just proven what I've been saying all along - uncovered soil gives off a lot of moisture that the house should not be exposed to in the first place. By not insisting that it be dried in, one takes a huge risk. By all means, warn folks that fixing it will cause things to dry and shrink but don't tell them it's OK because it is not.

ONE TEAM - ONE FIGHT!!!

Mike

[Tim H]

The bottom line here is when there are yellow pine or other sap wood species floor structures in a crawl which has been very wet for an extended period; drying this crawl down is very likely to result in differential downward movement as the wood structures dry & shrink. This is more at the beams! id="black">

The crawlpace I was concerned with had not been "very wet".id="blue">

This is the second time I have heard this (not completely covering on purpose). Sounds like folklore to me. Anyone ever heard this?id="blue">

It's making a lot of sense to me!id="black">

Still makes no sense to me to install a barrier incorrectly. If the decision has been made to install one (after considering the relevant factors), it needs to be done right. id="blue">

100% coverage is optimal not necessary in most situations. Several other people down the thread have affirmed this logical statement.Keep things in perspective & call it a ground moisture barrier.id="black">

I'm sorry, but I don't see it that way. To say that an optimal installation is not necessary in 'most' situations is not all that logical. If a detail were not necessary, it wouldn't be optimal; it would be extraneous.

What difference would it make to call it a ground moisture barrier rather than a crawlspace vapor barrier? What is the difference in perspective?id="blue">

Timid="blue">

[Scottpat]

Another good source for crawlspace sealing can be found at this site: http://www.advancedenergy.org/buildings ... wl_spaces/

They have a few different ideas than Dr Joe, but they tend to agree on many of the same ideas and concepts.

[energy star]

All kinds of info.

http://www.basementwaterproofingmassach ... m/blog.php

[robert1966]

I agree with your assessment. If you leave a opening or 1 inch void in the vapor barrier, it seems useless to have the vapor barrier to start with.

Robert Welch

www.atexinspects.com

Originally posted by Tim H

I got a call today from a termite inspector (more often than not, they are the guys that install vapor barriers around here), about a recently installed vapor barrier that I had called as defective on a 48 yr old house. I used this statement:

The vapor barrier in the crawlspace is inadequate, as it doesn't cover 100% of the soil under the home. I recommend that this be corrected immediately. This is important because the barrier limits the amount of moisture that can evaporate out of the soil into the crawlspace.

A proper vapor barrier consists of black, 6-mil polyethylene sheeting and must be applied from wall to wall of the foundation. It should cap the footer and lay tightly against the sidewalls, overlapping at least a foot at all adjoining sheets and be tightly sealed around the base of support piers. Ideally, the barrier is secured to the foundation walls, and overlaps at adjoining sheets are sealed with waterproof tape. Additionally, the barrier should be applied with some slack so that it can float free without separating and still inhibit evaporation if minor flooding occurs.

The termite guy says that he left a 1' gap around the perimeter of the crawl on purpose. He said he had to do it that way or the sudden lack of moisture would dry the framing so quickly that the floors would buckle.

This is the second time I have heard this (not completely covering on purpose). The first time was about a month ago when a termite guy from a very big national company said his company training literature instructed that vapors barriers should be installed leaving room for the ground to 'breathe'. No kidding (at least he didnt claim that the floors would buckle).

Sounds like folklore to me. Anyone ever heard this? Is my statement accurate?

Thanks,

Tim

[jeanknc]

HELP!!!!!!!!!!!!!!!! in North Carolina .. doing online 'research' ...

we have hardwood floors separating .. varpor barrier installed in crawl space 18 mos ago (when we closed on this house); house 10 yrs old and never had any barrier - inspector found some mold and very damp etc (july); SUDDENLY .. maybe I've noticed for 2 mos approx.. uneven flooring (hardwood) and some carpeted.. CREAKING all of a sudden.. alot;

and then noticed separations in flooring .. 1/4" almost.. all over the house; neighbor went in crawl space Sunday aftn and found immmediately that the supports w/ wood on tops .. was moveable.. and the wood has contracted ... HOW TO FIX? PUll back, or fold over some of the sheeting to allow about 70% coverage .. leaving some moisture to affect dry wood? Do I need a flooring guy? It's really a shocker. But I know this is the problem. WEIGH IN !!!??? help!!!

( thanks, glad I found your post - exchanges here )

Jean

What you experienced doesn't surprise me; it's very common here in new homes.

Some builders here don't bother to put down a barrier until after they've dried the house in and completed it. You'd think that with our wet climate they'd know better. Anyway, because of this, the house continuously obsorbs moisture for months on end. Then, not long before delivery, they'll install the barrier and deliver the home. In almost every instance, builders will warn the clients to expect to see some cracking and movement throughout the home because they know that all of the framing is going to shrink; it even occurs in homes built with engineered lumber. The builders typically come back at the one year mark and repair the damage if the buyers request it. Sometimes the damage is minor, sometimes not so minor.

You tested 15% moisture in the rim joist after the place had dried in? Since 17% or better will support rot, and it probably was much higher at the time of the inspection, those homeowners probably don't realize how close their home had come to something far more serious than cracks and movement caused by lumber shrinkage.

This past Tuesday I inspected a brand new home where the builder had plenty of crawlspace ventilation under the code formula and had put the barrier down early but never bothered to install vents under one room that sort of juts out from the rest of the crawlspace with cold air on three sides. It's also the hardest part of the crawl to get to and the person that put the barrier down got lazy and left it about 10 inches shy of the far wall. Conditions in the crawl were perfect everywhere except under that room; under that room, water was literally dripping from the insulation and running down the foundation wall where evaporation from that 10-inch wide by 10ft. long strip of earth was condensing on the rim at all three sides. When I pushed the insulation aside to look behind it, moisture drained out of the insulation like a squeezed sponge and the floors and rim close to the perimeter on all three sides were covered with blue-green mold spots about the size of a dime.

Your story has just proven what I've been saying all along - uncovered soil gives off a lot of moisture that the house should not be exposed to in the first place. By not insisting that it be dried in, one takes a huge risk. By all means, warn folks that fixing it will cause things to dry and shrink but don't tell them it's OK because it is not.

ONE TEAM - ONE FIGHT!!!

Mike

[hausdok]

Hi,

So, the house was 10 years old and for a decade the crawl was functioning like a huge humidifier, now things are shrinking as the wood is drying out. It's winter/spring. When the humidity comes back in a couple of months you'll probably see some changes then too as the wood starts to take on moisture.

Go to the Advanced Energy site. If anyone can point you to someone in the Southeast to figure that out, they can.

ONE TEAM - ONE FIGHT!!!

Mike

[Denray]

When using clear plastic sheeting and caulking that sticks to plastic and concrete you can see exactly wherer the bead has made full contact or not. Squash it down so it is about 1 inch wide and there will be no voids. Lots of wrinkles happen and with the clear plastic you can see the caulk inside and spread it as necessary. And it is a bitch to do in a house that is already up. Hire some kids or some yahoo's and they will probably hack it.

[randynavarro]

Interesting idea about the clear plastic and caulk.

I've had the privilege of laying plastic in two crawl spaces. It wasn't easy rolling the plastic from one end to the other and keeping the plastic in place where you wanted it. If you use caulk, wouldn't the plastic just pull right off the concrete as you worked across the space?

Also, I always recommend black plastic. Honestly I can't remember where I got that from because it isn't in any requirements of which I'm aware. I do know it eliminates the greenhouse effect if there's ambient light that makes it in to the crawl space via the vents.