Vapor barrier

I guess I could have brought this up in my other post, however, my photo didn’t show it. This same house had no vapor barrier in the crawl space. I noted in my report that it was a needed repair. However, is there ever a situation where the vapor barrier would not be needed? For example, any crawl space that might meet a certain height requirement. This one actually had a 7 block height down there.

Any dirt crawlspace, with or without ventilation should have a vapor barrier installed.

Thanks. Kind of thought this was the case.

There is a minimum 18" clearance but have not run into maximum. has to have vapor barrier

Thanks Phillip. One more question, would you recommend that a vapor barrier be added if the crawl space were below the minimum of 18"?



I personaly would recommend one if it needs it. Common sense can go a long way. My parents home has never had a vapor barrier, and its dry as dust. I was just under the home in april. It has always been dry.

The purpose of a barrier is to reduce the amount of moisture in a crawlspace. If you test the wood and its 5% why would you tell somepne they needed it.
If its new construction, then in many areas it is required, but use your best judgement.

Thanks Sean. Point taken. I did have one that only had 14 - 16 inches of clearance and the foundation did not go all the way around the house. It sat up on concrete block columns. It was really dry down there, however I did go ahead and recommend that a vapor barrier be installed.



Ditto. I let everyone know the amount of vapor barrier present, or if it’s absent. But if conditions are dry, I’m fine with it.

My house has a dirt crawl space. It’s been just fine for over 100 years. I’d be pretty pissed if some home inspector said it “needed repair”.

I believe I actually recommended a vapor barrier to be put under the one I was referring to that had less than the 18" clearance. There was some moisture on the surface and places where it looked like water had been sitting (see pic), but I couldn’t determine exactly where it was coming from. It’s been a year on this one, so my memory is a little foggy. I know the place was a dump and the guy ended up not buying it anyway do to much more serious problems with the roof structure. The roof’s surface had more waves in it than the Atlantic.



Where a barrier is needed, they’re pretty much useless unless it is covered with several inches minimum pea gravel. Or, you can get a thick, heavy duty vapor barrier encapsulation process for about $5000 in a 2,000 sq, ft crawl. The barrier goes up the interior foundation wall and is fastened near the sill.

I have 4" concrete encapsulation with spray foam cell over the interior foundation walls and sill. I could place a cup of water on crawl floor and it would take weeks or longer to evaporate, Dry is cool…:cool:

Around here you typically won’t find anything more than heavy poly over the dug out dirt surface. Nothing extra. Probably why we have so many issues in these parts with termites.

Not for a home built before that became a requirement and only in areas where it’s required. Getting into code here.

Vapor barriers are installed to help reduce the amount of moisture that finds its way into the crawlspace from where it can be pulled into the home by stack effect or the concentration or temperature gradients.

I call it if I see some evidence that there’s a problem, or if I know that it was required when and where the home was built.