Crawl Space Vapor Barrier Question

[victorjessie]

Hi everyone,

I'm considering installing a vapor barrier in my crawl space to address moisture issues. I've read that it can help prevent mold and improve overall air quality.

My crawl space has a dirt floor and some spots stay damp year-round. I'm thinking of using a 6-mil polyethylene barrier.

Has anyone here installed a vapor barrier before? If so, do you have any tips or recommendations on the best practices for installation?

Also, how much of a difference did it make in your home's moisture levels and air quality?

Any insights would be greatly appreciated!

 

[victorjessie]

Hi everyone,

I'm considering installing a vapor barrier in my crawl space to address moisture issues. I've read that it can help prevent mold and improve overall air quality.

My crawl space has a dirt floor and some spots stay damp year-round. I'm thinking of using a 6-mil polyethylene barrier.

Has anyone here installed a vapor barrier before? If so, do you have any tips or recommendations on the best practices for installation?

Also, how much of a difference did it make in your home's moisture levels and air quality?

Any insights would be greatly appreciated on crawl space vapor barrier!

thanks in advance for any help

 

[Mandy Onderwater]

In our childhood home we had a LOT of moisture issues, causing mould. Our crawlspace had a dirt floor too, and especially after rain it could actually have standing water in it.
We grew up poor, but eventually someone let us borrow (and later cheaply sold it to us) a dehumidifyer. We would empty bucketloads of water daily, but it helped us so much!

We never owned a vapor barrier, but I have seen them in videos. Some people actually combine it alongside with a small automatic dehumidifyer in their crawlspace. Technicians who have to enter the crawlspace (when done right) actually love the barriers as it keeps them a lot more clean, rather than crawling through mud (depending on the available space).

@daveb do you have any humidity issues as you do hydrophonics? And do you maybe know anything regarding this?

 

[daveb]

Actually, the south wing of the house is over a crawl space; this is where the kitchen and dining are and part of my hydroponics. Years ago, a company that came in laid a plastic sheet over the dirt floor of the crawl space. This was not adequate because it only sealed the floor and did not address the complete moisture infiltration through the sidewall of moisture vapor. I later sealed the walls with a membrane that continued down to the poly they laid, and then I placed another direct on that and sealed the new stuff on the wall to the new floor sheet with glue. A foamboard with a reflective surface was also installed on the outside walls over the membrain, which was pressed into place, and braces were strapped to the floor joist to hold it in place.

So if you have spots that are constantly wet and this is water infiltration from outside of the foundation where water drops because there is no eavestrough and it seeps back in, then this should also be addressed first. In a wet area, if you cover it, the water has no way to evaporate and can gradually saturate the soil and cause other issues. If the issue in crawl space is due to water runoff from outside seeping under the footing of the crawlspace walls, you should install a perforated pipe in a trench that has crush stone in a continuous run around the perimeter of the wall, either outside or in, and an outlet that diverts it away from outside to a sump drain if you do it inside.

If it is seeping in from outside, a French drain around the outside of the house can work wonders for damp cellars and crawlspaces. This needs to be addressed first, even if it's a low spot on the property where water pools underground. This should be looked at, and a drainage ditch with pipe should be put in to move the water away from the house, then place the vapor barrier.