Guys,

What is your approach to a slab pour in an ICF basement.  Do you strip the bottom course of foam so the slabs butts up directly?  Do you embed ties in the wall prior to pour?  My plan is to pour the walls, strip the bottom most 6" of foam and pour the slab on top of the footers and let it abutt the concrete wall directly.  Expansion joints necessary?

Thanks,

Leonard

Only strip the foam if you did not use key-way footings or dowel pin the walls to the footing. It sounds like you have not done the walls so do the key-way footing and/or pin the walls to the footing, do not strip the foam. But if you don't take this advise strip only one space between ties 24" o.c.

What is you area and what is the 'accepted normal practice' in your area?

Is the slab structural or is it just a standard basement slab?

Where are you at in the construction process now?

Guys...thanks for the replies.

The wall will be tied to the footers with dowels (#5, ?18" OC, engineer to decide). The slab is not structural, just a basement slab. I plan on 6" of #57 clean stone, XPS foam (?1-2"), mil vapor barrier, 6" slab on top of that, reinforced with grid rebar either #3's or #4's (I don't like the rolled mesh, keeps rolling up).

Leonard

IN ALMOST ALL BASEMENTS WE NEVER STRIP THE FOAM OFF. MOST WALLS ARE DOWEL INTO THE FOOTINGS #5 16" C/C. ONCE THE WALLS ARE POURED WE PREP STONE FOR SALB,6MIL OR 10 MIL VAPOR BARRIER, AND INSTALL 8' X 20'FLAT WIRE MAT. FLAT MATS ARE ALOT EASIER TO WORK WITH, THEY COME IN SEVERAL LENGTHS, WIDTHS AND GAUGES( 5'X10', 5'X5' ,8'X12').WE ALSO SUPPORT THE WIRE WITH WIRE CHAIRS TO MAKE SURE ITS UP OF THE BOTTOM.

I rarely cut out the foam. We will sometimes cut out the foam on long walls. I typically dowel #5 every 16". With the first row of horizontal rebar tying into the vertical dowels, I believe you get a very strong wall at the base. I don't think removing the foam in an unheated (radiant floor) basement really matters, but as anal as it seems, I believe some heat is zapped away if foam is removed in a radiant floor basement (more or less depending on how much foam is removed.
I had a bunch of system platon I needed to use up, so I installed in the last basement I did instead of 6 mil and it worked very well.
I agree with TB MACS, the mats are much easier to work with than the roll mesh,......and much safer too!!


Bunt

Gentlemen...as always thank you for the replies...

IMO, 6" slab for a basement is way overkill. 3" to 4" is plenty enough. Consider using fiber reinforced concrete instead of rewire or rebar. Only a few $ per yard additional and a whole lot less hassle. My garage floor is only 4" at most, with fiber. The only cracks are in the control cuts and you have to look really close to see any fibers sticking out.

In my County 3.5" is code...most guys around here pour 4-5" slabs. Fiber is a neat idea...I just always liked steel.

Leonard

I just poured a 35x60 barn with helix a few weeks ago. We saw cut every 12' and there are no visible cracks yet. I think the steel fibers (not the typical fiber re-enforced concrete that most think of, but the steel fibers like helix) provide a slab or wall with a much more uniform strength. The fibers transfer the loads and stresses unifromly throughout since they are uniform throughout the concrete. Typical wire does not transfer loads uniformly since it is placed typically at the bottom of the slab (hopefully!!!). Nice to work with too, ya don't need to worry about tripping over and making sure the mesh is off the ground, etc. Much easier to achieve a quality job, ya just need to make sure the fibers are put in properly at the batch plant or on site.


Bunt

In my case (non-structural basement slab), no foam will be removed.  I had a thread on here a month or so ago asking essentially the same question since some ICF install manuals show a solid slab to wall connection, and some (most) do not.  The consensus was that the floor slab did not need to have solid contact with the concrete in the wall.  Plus, that 2.5" of foam on the inside of the wall helps to thermally isolate the slab.

In my case, I'm going to pour the basement slab before I stack the wall foam.  This may involve a little more work on my part installing the slab forms which will be materials left over from my footing pour - 2x4 on edge screwed to a 2x4 flat which will be anchored to the footing 4' oc by drilling 1/4" holes through the 2x4 and into the footing and driving two duplex head form nails to lock it down).  But it makes for an easier slab pour and less chance of damaging the foam with a power float.  This slab will then provide a solid 5" high inside support for the foam.  Then I will move the 2x4 slab forms to the outside edge and anchor down similarly to form a cleat.

Here is a previous discussion that we had on this subject:

http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/4/postid/45969/view/topic/Default.aspx

Arkie,

If I missed your point I apologize...why are you pouring the slab before the walls are up? One issue I can see is the anchoring of bracing for the walls would be more difficult if securing directly to concrete. In my plans we call for doing the footers, laying the clean stone for the slab, erecting the walls, doing the floor system (prior to the pour), then using a pump to pour the slab.

Leonard

Arkie6,
There is a lot less labor intensive way to accomplish what you are talkiing about. The advise I got from the Amvic dealer worked great(I never would have thought it would).
Try this. Pour you're footer and wet set the #5 dowels for the wall. Next, set your first two couses of blocks. With two courses the staggered interlocks will start to self level. Square and level the first two courses, the glue them to the footer with Foam-2-Foam adhesive. Now you have the forms for your floor and a good start on your wall. Surprisingly the glue will have no problem hoding the concrete.
Be sure to put a drain tile around the inside and outside of the footer so any water that gets under the floor has a place to go. By the way, the trowelling machine might scuff the foam a little but it won't hurt a thing.


Leonard,
I agree with Mac, 6" seem like a waste of concrete and money(about 50 to 60 cents a square foot of floor over 4 inch) and really won't gain you anything unless you plan to park a loaded semi in your basement.

Greg

Bunt.....just curious.....how much did the helix add cost per each trk of concrete?

Easier to screed the concrete off and get it level, and easier to finish the floor with a power float.  I discussed my reasons why in that other thread I mentioned.

I plan on installing my bracing on the exterior side of the wall.  But it could be done on the inside as well either by drilling a 1/4" hole in the slab to anchor the kicker or by running a 2x4 along the floor from the vertical brace back to the angled kicker.

Robinc, I've had the helix for a while and I don't remeber what I paid, but I believe at a dosage of about 10lb/yard, it came out to somewhere around $15/yard. The dosage varies obviously on the application. If I remember correctly, helix told me that whatever the rebar or mesh costs, the fibers will be about 10% less.

Bunt

Thanks!!