Replies

1. 
   deadnuts | Sep 14, 2014 09:34am | #1

   Are you turning the crawl space into a conditioned space?

1. 
   jimmiem | Sep 14, 2014 10:29am | #2

   Crawl Space

   The house had 2 room additions.  One addition is on the side of the house and one addition is on the back of the house.  Full foundations were poured for the additions but the floors were left as dirt. Access to the additions from the original basement are through window size openings.  The full basement is unfinished and very damp and musty despite running a dehumidifier constantly.  The thought is that the dirt floors are contributing to this condition so adding a moisture barrier to them would be a good place to start.  The basement as well as these crawl spaces will be left unfinished for the forseeable future.  

1. 
   deadnuts | Sep 14, 2014 11:20am | #3

   I take that as a "no"...for now.

   If so, I can't think of one good reason not to install a HD vapor barrier over the dirt floors. Exposed earth release quite a bit of moisture and it will help alot. I would recommend using 10 mil fiber reinforced polyethelyne. This usually comes in a white color and either 10' or 20'  wide rolls. You can buy it online at specialty stores that focus on selling products that improve wet basements and crawl spaces. Overalp joints by a foot or so and use manufacturer recommended  seam tape at all joints. Of course you will have to protect the poly film with some sort of crushed stone (like pea gravel) if it is going to get any kind of regular traffic.

   The question after than becomes: What do you do about a vapor barrier on the walls. The vapor barrier will stop the ground moisture, but low level vapor drive will want to push moisture up from under the floor barrier into the concrete walls. They will slowly wick moisture and release it at the first opportunity to equilibrate. That usually means releasing a certain amount into your surrounding framing and/or your conditioned building envelope.

   If it were my basement/crawl space(s), I would run the continuous poly floor membrane half way up the wall for now. I would use 3M all purpose spray adhesive to stick it to the walls and seal thevery  top edge with butyl rubber or elastomeric type caulking. I would also consider adding aluminum termination bar to mechanically anchor the top edge as well. This will not constitute "encapsulation", but is a good starting point which you can build into that concept in the future. After abvove outlined installation is completed, I would monitor the RH and moisture content levels in these spaces for improvement. You can build on this installation as the need or function of the space changes over time (i.e.still damp, or you choose to transition to conditioned space).

1. 
   jimmiem | Sep 14, 2014 01:33pm | #4

   Crawl Space Vapor Barrier

   Thank You.  As you said there are a lot of online retailers.  I'll check some out.

   On another subject, I was having some subfloor squeaking issues when prepping for hardwood floor install and you had provided ongoing advice to deal with the squeaks.  I followed all your advice, including removing every nail that had been used to install the plywood subfloor.  The hardwood is installed and it's solid and quiet...Thank you again on that one. 

1. 
   deadnuts | Sep 14, 2014 02:19pm | #5

   Glad to hear it (or not, as the case may be:). Good work!

   BTW, you might want to get yourself one of those inexpensive pen type thermometer/hygrometers made by General.  They're only about $25. Stick that in your crawl spaces to document Temp. and RH before installing your vapor barriers; then after. That way you'll know exactly how successful your efforts are on that front.

2. 
   jimmiem | Sep 14, 2014 03:30pm | #7

   Good Idea

   Good idea on the temp/humidity device.  Will be good to know if working in the crawl spaces was worth it.

3. 
   jimmiem | Sep 14, 2014 03:31pm | #8

   Good Idea

   Good idea on the temp/humidity device.  Will be good to know if working in the crawl spaces was worth it.

2. 
   DanH | Sep 14, 2014 02:32pm | #6

   The reasoning behind selecting "conditioned space" or not is this:

   If you have a "conditioned space", that means it's exchanging air with the rest of the house.  Any moisture/odor/whatever that gets into the air in the crawl will eventually find its way into the house.

   If you have an "unconditioned" crawl then the crawl is (mostly) sealed from the rest of the house and (presumably) separately ventillated to the outside (with, eg, vents in the foundation walls).

   In both cases it's sensible to apply plastic to the floor to minimize the amount of moisture that enters the air in the crawl, since, even in the "unconditioned" case, a substantial amount of moisture is apt to migrate through the floor of the 1st floor, etc.  But in the case of a "conditioned" space it's even more important to reduce moisture migration into the crawl (and hence into the house) to an absolute minimum, and thus one may wish to vapor-proof the walls of the crawl as well as the floor.

   (There are other issues with regard to insulation, but that depends on where you're located.)

1. 
   jimmiem | Sep 14, 2014 03:37pm | #9

   Crawl

   The crawls are opened to the main basement.  The crawls are not sealed and not vented to the outside.  The musty smell is making its way into the rest of the house.