Lbear
Veteran Member
Posts:2740
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| 25 Dec 2013 11:23 AM |
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What is the best method if utilizing a slab-on-grade design and trying to insulate the stem wall? I was told that running ICF from the footing up to the height of the slab top works but how does one transition from the stem wall to the main exterior wall if both are ICF?
If the exterior finish will be stucco, how would one break/transition from the below grade ICF stem wall to the above grade exterior ICF stucco wall? I would also need to incorporate a termite shield because code requires it.
Would one have to still insulate the bottom of the slab-on-grade with EPS or since the ICF stem wall is 18" tall, the interior slab is well protected from migrating cold/heat?
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jonr
Senior Member
Posts:5341
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| 25 Dec 2013 01:39 PM |
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What is the best method if utilizing a slab-on-grade design and trying to insulate the stem wall? Use a FPSF and eliminate the stem wall :-). |
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Lbear
Veteran Member
Posts:2740
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| 25 Dec 2013 02:32 PM |
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Posted By jonr on 25 Dec 2013 01:39 PM
What is the best method if utilizing a slab-on-grade design and trying to insulate the stem wall?
Use a FPSF and eliminate the stem wall :-).
Local code frowns on FPSF. It's still relatively new to the USA, only got accepted into National Code back in 1998. If you ever lose the EPS (termites, rodents, etc), you are in serious trouble. |
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FBBP
Veteran Member
Posts:1215
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| 26 Dec 2013 11:51 PM |
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Bear - the wall should continue from the footing to the trusses. If you are concerned about supporting the floor, there are a number of options.
The first would be to get 98% compaction and then just float the floor.
Second would be to run the outside layer of ICF continuous and cut off the inside panel at bottom of slab. Pour your slab and then continue stacking the wall with the outside panels matched up and the inside flat cut on bottom and sitting on the floor slab.
The third and my preferred way is to install a brick ledge on the inside so that it winds up about 2" below bottom of slab. When you prep the sub base for the slab, you keep it at the height of the brick ledge and then lay down 2" of eps and pour your slab. If you have radiant heat in the slab you may want to drop the sub base another 2" to allow for 4" of eps. (even with the 18" insulated stem wall, your ground temp will be significantly below your room temperature so insulate it unless your ground is very dry and it acts as the insulation.)
All the acrylic stucco manufactures make a parging for below ground and in contact with ground situations. It has more cement in it then the stucco. If you are putting in the termite shield, consider parging to the shield and stucco above. |
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Lbear
Veteran Member
Posts:2740
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| 28 Dec 2013 10:16 AM |
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Posted By FBBP on 26 Dec 2013 11:51 PM
Bear - the wall should continue from the footing to the trusses. If you are concerned about supporting the floor, there are a number of options.
The first would be to get 98% compaction and then just float the floor.
Second would be to run the outside layer of ICF continuous and cut off the inside panel at bottom of slab. Pour your slab and then continue stacking the wall with the outside panels matched up and the inside flat cut on bottom and sitting on the floor slab.
The third and my preferred way is to install a brick ledge on the inside so that it winds up about 2" below bottom of slab. When you prep the sub base for the slab, you keep it at the height of the brick ledge and then lay down 2" of eps and pour your slab. If you have radiant heat in the slab you may want to drop the sub base another 2" to allow for 4" of eps. (even with the 18" insulated stem wall, your ground temp will be significantly below your room temperature so insulate it unless your ground is very dry and it acts as the insulation.)
All the acrylic stucco manufactures make a parging for below ground and in contact with ground situations. It has more cement in it then the stucco. If you are putting in the termite shield, consider parging to the shield and stucco above.
It's actually from the footing to the "SIPs"  Do you have any links to these details? So the ICF can run from the footing and then all the way up to the top of the wall where the SIPs would attach. If one used a peel&stick membrane on the ICF, I assume the stucco would NOT stick to that, correct? |
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arkie6
Veteran Member
Posts:1453
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| 28 Dec 2013 01:16 PM |
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Stucco won't reliably stick to waterproofing membrane. Why do you need peel & stick? Are you putting in a basement or is your floor slab below grade level? Or is it for termite / insect concerns with the foam? If just for insect concerns, another option that is probably more durable is to screw 1/2" Durock cement board to the exterior foam from the top of the footing to the point where your stucco starts and presumably where you would cut in a metal termite shield. Then parge coat this cement board with fiber reinforced surface bonding cement from the top of the footing to where the stucco starts.
After the ICF wall is poured and before installing the cement board, cut a thin slot in the foam using a circular saw and abrasive blade all the way to the concrete in the wall where the top of the cement board will stop. Screw a temporary horizontal 1x4 to the ICF ties below the intended cut line to provide a straight edge for the saw to make a straight cut. Install the cement board up to this cut line. Apply the cement parge coating at the top of the cement board including filling the termite shield slot in the foam. While the cement is still wet at the top, slip your metal termite shield into the slot all the way to the concrete in the wall. Then continue and finish the cement parge coating over the remainder of the cement board down to the concrete footing. Then install stucco above that. |
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joasis
New Member
Posts:44
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| 28 Dec 2013 05:02 PM |
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We always do a "wet set", meaning we set the first course of blocks on the footing, and bed them in 1/2 an inch or so, using batter boards and tight lines to hold height and dimension. I rarely run a floor to the footing any longer, and always float them with the living area finished floor level with the top of the blocks (bottom of the teeth). Depending on grade, and how the footing is set up, we have a fully insulated floor perimeter. |
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| Ladwig Construction<br>Hennessey, Oklahoma<br>405 853 1563<br>Residential and Commercial Contractor<br>ICF's and Steel |
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FBBP
Veteran Member
Posts:1215
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| 01 Jan 2014 09:16 PM |
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Bear - with your 18" I would just float the floor. If you put in 4" of concrete, 3" of foam and 8 inches of drainage you are almost there. Just add more drainage or foam.
I would not use peel and stick in your scenario. You don't have living space below ground level so it's not really needed. I would probably use cement parging from the footing to the termite barrier. It is such a small area and it will slow down the critters from entering the foam.
joasis - what do you see as advantages of wet setting the first layer? |
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Lbear
Veteran Member
Posts:2740
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| 01 Jan 2014 10:00 PM |
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Posted By FBBP on 01 Jan 2014 09:16 PM
Bear - with your 18" I would just float the floor. If you put in 4" of concrete, 3" of foam and 8 inches of drainage you are almost there. Just add more drainage or foam.
I would not use peel and stick in your scenario. You don't have living space below ground level so it's not really needed. I would probably use cement parging from the footing to the termite barrier. It is such a small area and it will slow down the critters from entering the foam.
By "floating" do you mean having the slab NOT connect to the stem wall/footing? Parging the stem wall up to the termite barrier with cement is better than doing the Durock? Is there any special brand of cement parging that you recommend for below grade? |
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Lbear
Veteran Member
Posts:2740
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| 01 Jan 2014 10:05 PM |
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Posted By FBBP on 01 Jan 2014 09:16 PM
Bear - with your 18" I would just float the floor. If you put in 4" of concrete, 3" of foam and 8 inches of drainage you are almost there. Just add more drainage or foam.
I would not use peel and stick in your scenario. You don't have living space below ground level so it's not really needed. I would probably use cement parging from the footing to the termite barrier. It is such a small area and it will slow down the critters from entering the foam.
By "floating" do you mean having the slab NOT connect to the stem wall/footing? Parging the stem wall up to the termite barrier with cement is better than doing the Durock? Is there any special brand of cement parging that you recommend for below grade? |
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FBBP
Veteran Member
Posts:1215
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| 01 Jan 2014 10:19 PM |
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Floating - yes. There is no real advantage to tie it to the walls at that point.
Parging is much simpler and is bonded tight to the foam so nothing gets in between. It is moisture proof.
Just ask your ICF supplier for a compatible underground parging. They all carry one and will recommend one that is available to you.
Which block are you going with?
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Lbear
Veteran Member
Posts:2740
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| 02 Jan 2014 12:12 PM |
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Posted By FBBP on 01 Jan 2014 10:19 PM
Floating - yes. There is no real advantage to tie it to the walls at that point.
Parging is much simpler and is bonded tight to the foam so nothing gets in between. It is moisture proof.
Just ask your ICF supplier for a compatible underground parging. They all carry one and will recommend one that is available to you.
Which block are you going with?
I am going with Nudura block. I assume one would parge both sides of the ICF stem wall? Any negatives to a floating slab? |
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Alton
Veteran Member
Posts:2164
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| 02 Jan 2014 12:43 PM |
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Allowing the ICF form to serve as an expansion joint should help reduce the chances of the floating slab cracking. Isolating joints around protrusions through the slab should also help to reduce cracking. Allowing the slab to expand and contract without restriction is the best way to go, especially if the floor will be radiant. A double vapor barrier under the slab will reduce friction. A slab restrained is more likely to crack. Of course, there are many more things to do to reduce slabs cracking. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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Lbear
Veteran Member
Posts:2740
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| 02 Jan 2014 10:23 PM |
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Posted By Alton on 02 Jan 2014 12:43 PM
Allowing the ICF form to serve as an expansion joint should help reduce the chances of the floating slab cracking. Isolating joints around protrusions through the slab should also help to reduce cracking. Allowing the slab to expand and contract without restriction is the best way to go, especially if the floor will be radiant. A double vapor barrier under the slab will reduce friction. A slab restrained is more likely to crack. Of course, there are many more things to do to reduce slabs cracking.
Alton, would doing a 4" reinforced slab (#4 rebar at 18" oc), then 2" of EPS foam, and finally 4" of compacted AB, be a good base for an interior floating slab-on-grade design? My other choice would be a mat or raft slab. From what it looks like, the beam portions of the concrete are not insulated. That would of course be a negative. |
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Alton
Veteran Member
Posts:2164
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| 03 Jan 2014 09:28 AM |
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Lbear,
In my area, I would recommend the following for an above grade, non-radiant slab:
3000 PSI 4" thick concrete slab without rebar
Waterproof membrane (two layers)
R-10 Expanded Polystyrene (EPS)
Compacted sand
Undisturbed earth
For below grade, radiant slab:
4200 PSI 4" thick concrete slab without rebar
Waterproof membrane (two layers)
R-16 EPS
6" (minimum) of clean, compacted gravel
Undisturbed earth
In an earthquake area, you may need to reinforce the slab with rebar. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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Lbear
Veteran Member
Posts:2740
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| 03 Jan 2014 09:45 PM |
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Would a waterproof membrane be necessary with EPS? Couldn't the concrete slab be poured directly onto the EPS foam?
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Alton
Veteran Member
Posts:2164
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| 03 Jan 2014 11:07 PM |
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Visqueen (Vinyl) is often used under the slab when the slab is raised. A better waterproofing membrane (and possibly radon barrier) should be used under a below-grade slab. One of the two membranes for below grade slabs could be inexpensive Visqueen since its role is to allow the slab to expand and contract without restriction that could create a crack.
Concrete could be placed directly onto the EPS if the slab is raised above the existing grade. However, installing Visqueen reduces the chances that the slab will wick moisture through the joints of the EPS. Another role for the Visqueen is to keep enough water in the concrete to maintain the water-to-cement ratio. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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joasis
New Member
Posts:44
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| 06 Jan 2014 08:43 AM |
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With compaction, floating is an option that may reduce cracking of slabs. You have to remember that it is all about math. Wet setting blocks allows us to have dead level starting for walls, when footings can and do vary in height. This technique is not for inexperienced builders. It requires a few experienced helpers, perfect batter lines, and not trying this with hot mud. |
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| Ladwig Construction<br>Hennessey, Oklahoma<br>405 853 1563<br>Residential and Commercial Contractor<br>ICF's and Steel |
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