If you've never heard of crawlspace encapsulation a quick internet search will enlighten you... quickly. The basic principle is to completely cover the ground of the crawlspace with a heavy vapor barrier and even run it up the walls to block any moisture that might come in through the concrete blocks.
Step 1: Why?
I wanted to make sure there were no future problems and that's when I first read about encapsulation. I didn't know what it might cost though. To give you some idea why I chose to do it myself:
After a woman I work with heard about this she had someone come and do it for her and paid $8,000.
I paid about $300 to do this 30' x 25' space. That's a savings of nearly 97%. Boo. Ya.
I think I made the right choice.
Step 2: Needful Things
This stuff is tough. They are three ply 15 -17 mil vinyl, tear resistant, mildew resistant, waterproof. They are made to last years outdoors exposed to UV and winds, so just imagine how long it will last in the dark under your house. Hell, people use these for pond liners!
And they have cool stuff printed on one side of them. Check out the pictures.
I estimated that I'd use 2 of the 14' x 48' models. They come in many different sizes.
Step 3: More Needful Things (How Awful Would That Movie Have Been?)
Other than that you'll need the usual stuff.
- A Drill --- one capable of drilling into concrete with a concrete bit
- Silicone caulk
- Sharp utility knife
- Tap Con or any other brand of Masonry screws ---- usually they're blue and come with an appropriate sized drill bit
- Furring strips --- enough to go completely around the perimeter of your crawlspace; you can pre-drill these every 2 feet to save from doing it in the crawlspace
- Extention cords
- Knee pads
- Dutch courage
Step 4: Doing It
If you're up for doing a lot of cutting and going back and forth you can carefully measure your crawlspace, work out a little diagram, and cut it piece by piece.
* Use the drill to make holes in the concrete. Hold up the furring strips and use them as a template for your drilling.
* Apply a bead of silicone along the top of your concrete blocks, this will be a watertight gasket that will keep the humidity rising out of the Earth down under the barrier.
* Arrange the tarps so that once they are screwed in place behind the furring strips they will drape down the wall and onto the ground.
* Spread everything out evenly and cut away excess in as big of pieces as possible. These pieces we ended up using in patching holes where needed.
* You'll want to overlap any cuts by at least 1 foot. In many instances I ended up with 2 feet. You can use HH-66 to seal the joints, but I chose not to. I know that the water line running into the house has been in the ground since the early '60's and that the huge old cast iron drain will need to be replaced so I didn't want to have to cut and patch later. You can use housewrap tape if you wish, but my overlaps were so big that I didn't bother with either.
Step 5: Done
Was it worth it?
Oh heck yeah. I was amazed at how warm it kept it in the winter. I put a thermometer with a high and low memory down there during some of our coldest days that winter single digits and low teens) and the temperature never got below 54 degrees. As an experiment I didn't reopened the vents for a year and haven't noticed any new growth of mold. If that trend continues then after this summer I may seal the vents permanently. I've done other work in the crawlspace and it's completely no problem at all to go in there. So clean and bright. Many times I've gone in there in pajamas because I've remembered a tool or something I'd left behind on the last trip in.
If you have moisture issues, it's definitely worth it. If you think you might have to hide from a massive government plot to kidnap you and experiment on your DNA, it's definitely worth it. If you live in an apartment you probably don't have a crawlspace. So who's house are you in? You're weird.