I was reading on buildingscienceconsulting.com the other day and saw where they suggest a poly barrier between the footing and foundation to keep moisture from migrating up through the footing into the foundation wall.   So, realizing poly is cheap I put in down and then set my forms on top of it.  Almost immediately I could see water droplets on the back side as it was a hot day and the footings were only 12 hours old.  Have I created a slip joint for my wall to slide on?

Here's the link promoting vapor barriers, check out Figure 1 and the Capillary Break over Footing http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements/

Any thoughts?  I was accused of believing everything I see, but I suppose someone could say that about using ICF's.

(there's still time for me to pull it out)

Ben

I would be careful with the way you have that setup. To me it seems that having the vapor barrier setup like that is going to promote water intrusion between your icf wall and footing. The plastic is also going to create an undesirable cold joint. I would remove it immediately. If you want to install a vapor barrier you should remove the plastic and install it on eigther side of the icf wall after it is poured.

I'm interested in the responses you've gotten to this question over in your other thread. I have been planning on doing the same thing when I build specifically because of the recommendations at buildingscience.com.

In my case I don't expect to have a problem of wall slippage for three reasons. I'm putting dowels every 18". I see you spaced them at 48". I expect the roughness of the footing surface and the sheer weight of the wall to generate plenty enough friction between the wall and footing to resist slippage. I will have only about 2' - 3' max backfill against the wall.

What I don't find at buildingscience.com is hard information about how much of a problem there really is with moisture migrating via capillary action through the footing and into the wall. What's the chances of there being enough moisture creeping up the wall and behind the foam to cause mold to form? Or will that moisture be of such a low level that it evaporates through the foam into the basement or crawl space fast enough the wall stays dry? One thing we do have as a guide is the universal practice of placing foam between the foundation and sill plate in stick built construction. Why? Undoubtedly to keep moisture from migrating from the foundation into the wood of the wall. That practice right there, in my mind, says it is a real issue. On the other hand, the IRC requires PT wood against concrete only within 8" of ground level, or if the concrete is in a wet location. That would indicate moisture does not migrate very far.

Here's a quote from there which you've probably seen: Therefore the basement wall should be damp-proofed and vapor-proofed on the exterior and a capillary break installed over the top of the footing to control “rising damp”.  Damp-proofing and vapor-proofing in these locations is often provided by a fluid applied coating of bitumen.  In the past, capillary breaks over footings were not common.  They were not needed when basement perimeter walls were uninsulated and unfinished on the interior, because these conditions permitted inward drying of the migrating moisture.  For finished basements they are an important control mechanism.  Without them, moisture constantly migrates through the foundation, and then into the interior insulation layer and interior gypsum board lining.

My vote in response to your question would be leave the poly sheeting there and maybe pull it up the wall on the outside and under whatever dampproofing and waterproofing layer you're putting there. That way water on the outside will be directed to the footing side of the poly and not the wall side of it. Or, you may cut the poly back tight against the wall/footing corner and seal that corner.

Whichever way you go, do it because you are convinced in your own mind it's the best way to go. I don't see that there is a clear definitive answer either way.

Guys, as long as your pouring the basement slab before back filling there will be no shear issue with the wall and footing connection. As Pete said you could be creating a water migrating path to the inside though. Dmaceld you still have time to use either Fast foot or visqueen under your footing if your concerned with this issue. You then can purchase any of the liquid membrane waterproofing to roll or slop brush the top of your footing down over the visqueen or Fab-Form which will seal the capillary issue.

Dave

I thought of the visqueen under the footing, but unfortunately after I'd poured. 

I've purchased roll on (Karnac) damproofing to apply to my ICF's exterior, and figured if water did  come in under the foundation wall at the joint it would be under my slab and enter in the gravel bed.  I don't know if having poly between the foundation  and footing makes that joint any less water tight  than simply the cold joint of 2 separate pours without poly. 

Ben

I was looking at the Fast Foot info again last night and thinking maybe that really is the way to go. How easy is it to install at steps in the footing? I'm going to have 4 steps in the wall footing, each being a 16" drop, and at least 8 in the floor support pony wall footings, mostly 16" drop.

It works great for steps, this is where it shines the most next to commercial grade beams. Also check out quick formz (rebar grabber) if you didn't see it in another post.

Dave

I agree..use Fastfoot! I always carry it in the trailer, and once you make a drop, the rest are easy.

As to the poly question, I have never interpreted or seen poly being advocated between the top of the footing and the bottom of wall??? The intent is to stop water migration, albeit very slight in my mind, from coming thru the footing and either into the wall or into the slab!

Note: as a licensed BO I would not accept the poly on top of the footing, and that's without even trying to find a pertinent code section!

Fastfoot is the best, step footings included.

Kevin