I am doing a slab on grade for a SIPS house oriented for passive solar gain. As I need to insulate the slab anyway I figured I would use ICF's for the footing. I live in the pacific NW any tips?

Do you mean, use ICFs for the frost wall? If so, yes use ICFs to keep the floor better insulated. You should also don't want non-decay resistant wood near dirt/grade. So if you are using wood sips continue ICFs above grade some. Have you considered doing an all ICF house?

I do plan to go up high enough to keep the wood off the ground, (I need to go up a little just for plumbing purposes ) but I am not a builder and I have learned about this stuff from books and the web. Most builders I talk to don't Know much about energy efficient building so my plan is to help educate my builders and I need as much Knowledge as I can get. I have seen slab designs using foam board on the outside( I assume that is the frost wall you are referring to) and under the slab . I figured ICF's would be a good substitute for the foam board.

Yes, use ICFs for your foundation, up to floor level. Use taper top forms for the top row. When pouring the forms, leave the top row filled only half way up. Remove the top 4" of the inside layer of foam, assemble your backfill, subfloor insulation, etc. so that it finishes level with the inside form. Then when you pour your 4" slab, the concrete will flow over and fill the unfilled portion of the forms, locking the slab and wall together. Now, assuming you are using OSB sips, install a treated 2x sill plate that is ripped to the overall width of the SIP (caulk, expanding foam, or some other form of air/moisture seal should be installed between this sill plate and the concrete). Next install your bottom plate for SIPS centered on the treated plate, and install SIPS per mfg specs.

Wes, Thats some good info. I was wondering about cutting that inside form back.... So please answer this, When I fill halfway up the last form how do I level the concrete and also when I pour the slab section will I have to reinforce the outside piece of foam to prevent blow-out? Also, Is that taper top form
a common piece?

vb,
Don't worry about getting the concrete too level in the form. A little bit rough will help the bonding with the slab pour. I would reinforce the outside piece before pouring. If the concrete doesn't cause a problem, the power trowel probably will. I think most companies make a taper top form. If not, order a regular form, use a saw to remove some of the foam by hand. Not as pretty, but will work just fine.

As to the question concerning the reinforcement of the outside foam, not all systems are alike.  If you cut the top web connector  out of the system certainly you will need to reinforce the foam.  Some systems can be done without external extra support.

Agree here.  I would also recommend either 1) have a few bent rebars back into the slab from the foundation wall to increase your bonding/reduce cracking or 2)  trowel off the top of the concrete in your foundation wall, then lay down a "slip" layer such as poly or thin fiber board to allow the slab to move independant of the wall which again will reduce/remove any potential for slab cracking.  Good luck!

 

sounds like Wes is saying I want a good bond between foundation and slab while Jake says Independant movement is best, Who's right?

Talk to foundation contractors who are familiar with the soil conditions and climate in your part of the world. Here in the mountains in Pa, for example, no one worries about cracking and shifting because bedrock is never far away. Radon is a big deal however. Termites potentially are another local issue. Some jurisdictions want bare concrete above grade so infestations can be spotted early. In a cold climate, you'd want thermal breaks between the slab and stem walls if soil conditions permit, particularly if you plan radiant heat in the slab.

I am in the Paciific N.W. -so its not too cold. the termite issue though.... anybody know?

You are going to have to ask, after ascertaining the design criteria required by your local government. (Google the government's name plus "termite protection" or "frost line" or "seismic condition". Or walk into city hall and ask for a building permit kit.) The good news is that building inspectors aren't overworked these days. The bad news is that you must know enough about the building code (2006 IRC in most cases) to ask a yes or no question that isn't readily apparent elsewhere. My experience in a small town in Pa is that the inspector is as eager as I am for me, as a novice, to avoid big mistakes, but it's not his job to spec my home for me. "Code Check Complete" is a searchable if occasionally vague reference for 2006 IRC. But that may or may not be what applies in your case.

If you are placing a slab and insulating it you should consider putting pex pipe in on a 12 inch pattern for future infloor heat. Even here in the pacific NW you will need back up heat.
We can help with that.
Dan

Got that part covered Dan but thanks for the input. Just in case though, where is Blueridge co located?

We have our home office on Vashon Island, just outside of Seattle WA, and a distribution site in Kentucky, and the Wisconsen area.
Dan

Sorry vb - my 2 cents worth wasn't ment to say one way was better than the other, just 2 different ways of attacking it from a buildability point of view.  If I was incorporating radiant floor heating, I would probably isolate the slab.  If no radiant heat, the bent bars installs/builds fairly quickly and is one less step.  Attempting to reduce cracking may assist in tile finishes, etc.  If you are installing a floating floor, minor cracks are irrelevant. 

Thanks for your responses everyone ...Now is there anybody who does ICF concrete work in Snohomish county WA, who will give me a price do do this work ?

vb,

We are Mount Vernon WA, I just read your thread and this is an application we have done quite often. If you would like, contact Karen at Icfcontractor@comcast.net

ICF Contractor