Was just looking for some input on different techniques for ensuring a permanent seal between a block foundation wall, and a 6 mil. poly barrier resting on a dirt crawlspace floor?  If one could referrence specific products that would aide also.  Thanks in advance for your input.

Views: 6065

Reply to This

Replies to This Discussion

I use CCA treated furring strips and mastic in the caulking tubes. Wrap the plastic around the strips, apply mastic, and fasten to the block with a hilti gun. Time consuming but it seems to work.

Tim,

I have used a recommend a product from crawlspacerepair.com called "Foundation Seal Tape".

It is a very strong and tacky double sided tape that is also waterproof.  I apply it continuously around the crawlspace about 3" below the top.  I use 15 mil poly that goes down the wall and then across the floor.

The tape seals and temporally mechanically holds the barrier in place until I ADD mechanical fasteners every 2 feet for  permanent bond.  

I highly recommend this product.

Tripp

I use the same mastic I use for sealing ducts, in my case Air Seal polymer adhesive.  Brush on a thick layer, then attach to the foundation wall as James describes.  I also use it for the laps across the crawlspace floor.  I don't trust the tape that Tim mentions.

I'm of the opinion that mechanically fastening the furring strips is a necessary, time consuming, and therefor costly step merely to insure the vapor barrier stays in place till the mastic dries. Once it dries, your not pulling the VB off without some effort.  If I come up with an easier alternative to temporarily hold the material in place, I'll test that theory and get back to you.

Tim,

I imagine you're using foam on the walls in the crawl space? If so, I have recently switched to foaming over the vapor barrier. It has been a very effective approach, assuming someone doesn't crawl through the space like a bat out of Hell and rip the barrier off the wall.

I run the poly up the walls (about 6 inches) and spray over the poly, and spray especially thick at the interface of the walls and the floor of the crawl.

Just my take on this, given personal experience and a genuine concern for the cost of projects getting out of control for the average HOs.

Don't use poly, use EPDM roofing material. Then you can use sprayfoam to seal.

Pat, about what are you paying per square foot of the EPDM membrane? I assume you use a roughly 60-mil product?

Thanks in advance!

Patrick

The EPDM can be purchased at 40 mils and 60 mils. I use the 40, over the past couple years we have paid between $0.80 and $1/sf for it. We buy black material. The white is much higher cost. It is very unlikely that it will see any sunlight or wear, so i see no reason to go thicker.
We usually spray foam fom the subfloor down on th EPDM and at east 4 ft in long the bottom of the wall and seal all joints. I am in upstate NY, 7000 HDD, so frost penetration under the wall governs how much of the floor we spray. I usually spray the whole floor if the space is less than 16 ft across. That is an arbitrary choice.

I do know of one job where the owners decided to tear down the existing house and put a year round residence in place of it after we did this work. he is a friend of mine, and he called to tell me demolishing the house was easy with an excavator until they got to the crawl space. Apparently the EPDM stretched enough so the excavator could not pull far enough to pull it loose from the block. In the end it pulled the blocks out still attached to the EPDM.

Impressive story Pat.

Thanks for the info on the EPDM!

I think you may have made a convert out of me (from poly vapor barriers to EPMD).

The foam manufacturer's make an extra sticky single part foam - same chemicals as the air sealing foam, different proportions.  We use Convenience Products Foam and they make one called Panel Foam.  This sticks the plastic up quite well, then we use it stick 2" board on the wall overlapping the plastic by a foot or so

i haven't heard of this before.  as far as I know all urethanes are 1:1 ratio, so i would sooner believe the resin/iso mix is 1:1, but the chemical reaction time is slowed a lot. 

have you gone back to one of these a month or further after install to see how the adhesion is? 

generally we get worse results with single component and dual component 'portable' or 'unheated' kits than we do with plural component heated kits.  those electric wraps for the cylinders are well worth the cost and hassle. 

Pat

I have no doubt that the ratio is 1:1, but not all are the identical formula.  We have been doing this for about 10 years and have had occasion to get back in to see up to 3-4 years later - no problem.  The 2 inch board is not extruded styrene but iso board with faces on it.

Any problems w/ VOC in crawl space during application or migration to home through floor?

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Tom Mallard replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Right, that reinforces my understanding of how it works, I was after what to plug in for values in…"
1 hour ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Products like these dont have an R-rating. You still have to have the R-rated insulation to meet…"
2 hours ago
Graham Irwin replied to Tom Conlon's discussion Whole House Fans - Love 'Em or Not?
"Thanks for the input. The next question to ask is "how much cooling power is delivered in each…"
3 hours ago
Brandon Walton commented on Brandon Walton's blog post 12 Things Every Home Performance Contractor Should Have on Their Work Truck
"Totally off topic William, but yeah could use a bit more I suppose "
3 hours ago
William H Nickerson commented on Brandon Walton's blog post 12 Things Every Home Performance Contractor Should Have on Their Work Truck
"One more thing...you need a little more bend in that cap"
4 hours ago
Tom Mallard replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Sounds like the perfect, thin insulator adding enough thermal inertia to separate two masses and/or…"
4 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"OK Tom, I think I am on the last questionow,,,I think.  LOL Going under the building and…"
6 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Tom, sorry for having to break this up but my responses I guess are too long. You talking about the…"
6 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
" "
8 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"I guess I got too mlong winded ther, it cut me off. 1.  Spray the coating on the ducts, plenum…"
8 hours ago
Kurt Shafer replied to Tom Conlon's discussion Whole House Fans - Love 'Em or Not?
"Jan, Here are some facts. the 30 inch fan from Home Depot (not one I would recommend) is rated at…"
8 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Hi Tom. It looks like I will have to start off most of my answers to questions with this…"
8 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service