I had the Orkin guys over to my rental for a termite problem and they tried to sell me crawlspace encapsulation. And the cost seemed excessive - $5000 for about 1000 ft.².

Is this really something I need to be concerned about? They said I had some fungus on the floor joists (showed me photos) and signs of mice.

I had my insulation company stop by and they said they just recommend replacing some damaged insulation and making sure all of it was installed properly for $250. Big difference.

In a word, no. It's funny they are trying to sell it because of mice. Mice will penetrate the plastic sheathing they put down in about 2 seconds so it won't help. The fungus on the floor joists could have been on the wood when the house was built or as a result of a one-time plumbing problem where the wood was saturated. Fungus needs moisture to thrive long-term, properly insulated and sealed from the outside, there should be no moisture for continued growth. The encapsulation would actually make matters worse in the case of a plumbing failure as it will hold the water in and not let it escape creating a perfect breeding ground.

My bug guy hates it when he sees a crawlspace encapsulated with foam.

Bugs will still eat the foam as most is cellulose based. Plus you can't see what is under the foam. You could have a major problem and someone covered it with foam.

Now if you just want to put a thick plastic sheet down in the crawl, taped at the overlapped seams and up the wall a little bit that can help with moisture issues. I have found that doing that after the gravel is in the crawl usually just means you will be poking holes in it when you have to get under there for maintenance.

Also in my area they don't like insulation in the floor joists as it can hold moisture and that attracts bugs.

In our humid va environment it’s better to remove all of the insulation from between the joists. When the moist outside air hits the crawl space, it condensates and the insulation holds the moisture.

TL;DR: reduced radon, increased storage.

We have crawl space under just one room of our own house. It has an opening into the basement, but not to outside spaces.

Years ago, when we had been in the house maybe a year, my husband increased the depth of the opening, and my kids and I spent a summer digging out bucket by bucket. We got the depth to where I can 'walk' on my knees in there. Husband then installed very heavy plastic over the floor and up the walls, secured with cleats into the walls. We laid a used living room rug in there to protect the plastic as we crawl upon it, and its nicer on the knees. Clean, dry storage galore, which is a big bonus in our smallish house. Husband also added insulation between the joists, making the floor of the room above much more comfortable.

Husband has tested our basement for radon; the crawl space reads nice and low. Over our two sump crocks, much higher. So, for reducing radon, and providing nice dry storage, for us it worked well.

A couple- few years ago, we had the stonework on the front of our house redone when we changed the front door to something more decorative. Mice found their way in that first winter. I had grandkids help haul everything out of crawlspace, then I pulled down insulation, threw out the parts with mouse nests, spray foamed all of the rim joists, washed joists where mouse pee got on there, and re- insulated. We'll see if micies find their way back. We had lots of critter activity when the rock facade on the house was first redone, not only mice, but snakey too, but not so much activity lately. I think snakey was a good mouser.

I would not encapsulate a crawl space unless it would be for a primary residence unless humidity or flooding are issues. Last year, a crawl-space contractor quoted me the following for encapsulation.

VaporBlock Plus 5.00 per sq foot

6 mm Black Plastic (NOT SEALED) 2.50 per square foot.

Drainage matting .90 per square foot

My place is in a flood-prone area. He ended up installing sump pumps like my other neighbors.

I hope that everything works out well for you and take care.

Fipronil (trade name Termidor) is the best termiticide you can buy. It was developed in Australia and has been on the US market for about 25 years. Many pest companies want to use Premise or some other chemical that will last for about 4 or years and then you'll be calling them out to do it again (and again, and again).

Ed, I use Termidor as well. Last house I had to use it on was my daughter's new place. I went ahead and hired my bug guy to do it so when she decides to sell in the future it will show she had it professionally treated.