Encapsulating Our Mountain Cottage Crawl Space

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Many of your homes sit on a crawl space. If you've ever been in the crawl space, you know how it smells. Mold may be growing on walls or beams and that moldy air ends up in your home.

Both the house we live in and our mountain house have a high crawl space. They both smelled awful and we weren't able to store anything in them because those items would smell, as well. 

The crawl space at our house is very large and is sloped from 2 feet at the front of the house to 6 feet at the back. For these reasons, we paid a company to to encapsulate the crawl space at our home to give us some much needed storage space to store all the things we kept in the 2,000 sq ft basement at our last house.

The crawl space at our mountain cottage isn't as complicated.

It is 6 feet high from one end to the other and is 900 square feet (30' x 30'). The humidity in the crawl was many times above 70% and it smelled awful down there. We were also concerned that this air was traveling into the house and affecting air quality and humidity.

Mr. DIY got an estimate for basic encapsulation of the crawl space  from a local company was $5,000, but the cost for the encapsulation of the crawl space at our house, which is 3 times larger, was only $6,700 
 Plus, the  estimate didn't include digging a trench all the way around the perimeter and installing a sump pump, which probably would have been another $2,500. Since the humidity was so high, Mr. DIY felt this was very important to keep the humidity level at  55%.

So, Mr DIY decided to do it himself (back in 2017)

It. Was. A. Big. Job.

Thankfully, the dirt floor was pretty flat, so no leveling was needed.

He started by sealing up the air vents with with 5 layers of foam board and attached it with spray foam. Just a heads up: he put black plastic facing the outside, so you wouldn't see white plastic on the air vents, when outside the house.
Next he put up the plastic on the top part of the walls and columns. The
back of the top edge of the wall plastic had a dry glue strip and used a caulking activator, which seals the two pieces together.  At our house, tape and  special attachment screws were used.

After the walls, he began the big job- digging a trench around the perimeter 18" deep x 18" wide and the hole for a sump reservoir.

The hole for the sump was dug and the sump reservoir set in the hole. He drilled holes in the sump sides and bottom, which prevents the sump from popping up when water seeps in and surrounds it.  He learned this the hard way after a big rain and the sump popped up out of the ground.

 The white pipe is a pipe from the bathroom above.

Here is the final set up with the sump. Since the sump is below grade at this point, it had to be pumped up and outside.

Digging the trench was a big job!

Here are the steps for the trench.

• dug trench 18" x 18" approximately a foot from the foundation.
• barrier fabric laid down(to prevent dirt from getting in the pipe)
• 2" gravel laid
• tube set on gravel (tube is a landscape drainage tube with holes in it and    covered in a fabric sock.)
• added  more gravel to fill up the trench
• folded fabric over gravel(Mr. DIY used bagged gravel because it was easier to handle than bulk)

The dirt was full of rocks of varying size and Mr. DIY didn't want them poking through the plastic on the floor, so he diyed a contraption called a tromel to sift the dirt from the rocks. This would have been too difficult to sift by hand.
Here's how it works:

After raking the dirt smooth, he installed the plastic on the the lower part of the walls and the installed the plastic on the floor.  Plastic on the floor is overlapped a foot and then taped to each other.

He would unroll out the plastic on the lawn, then bring it in partially folded.
This part would be so much easier with two persons.

Mr. DIY also replaced all the insulation too, since it smelled musty.
Here's how it looked all finished.

If you notice, there is no insulation on the left side, which is where the view porch is. A few months later, he replaced the porch floor with manufactured decking that is watertight and keeps water from dripping into the basement. This will be a later post.

Here's how the crawl space looked when we first looked at the mountain cottage before we purchased it.

Our 6 ft+ tall realtor couldn't stand up straight in the crawl. Thankfully for us, we are shorter, but still have to be careful walking under beams.

Top part of walls and columns covered.

Thick ml plastic can be found online. Fortunately, Mr. DIY found a company that sold the plastic, tape, caulk activator and other supplies in his travels and was able to pick them up.
He used 12 ml white plastic on the walls and  45 ml Plastic on floor (15 ml plastic with 30 ml felt for floor)

The total cost was around $1,800 and a whole lot of work.

We purchased this dehumidifier from Amazon. We've used this same dehumidifier in the basement of our last house (2,000 square feet) and it lasted several years. The $1,200 commercial dehumidifier at are house that came with the company installed encapsulation was replaced after a year under warranty and we just replaced it again - a year and a half later.

We chose a dehumidifier that was larger than needed because our crawl space was so damp. We would rather have it oversized than undersized and working too hard. We've had this one for a year and a half.  Amazon has other sizes - be sure to read the reviews before you buy one!


I think Mr. DIY did an outstanding job and it looks even nicer than the job done at the house we live in. If you would like to compare, you can find that post HERE.
Thanks so much for stopping by! Pam


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