Nudura Inserts
Last Post 14 May 2014 06:06 PM by eric monkman. 58 Replies.
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dmaceldUser is Offline
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11 May 2014 06:34 PM
Posted By eric monkman on 11 May 2014 05:23 PM

4 inch core does take intelligent mix designs and rebar detailing , advantage less concrete form pressure

Going with the premise that fresh wet concrete is a fluid, pressure is determined solely by height. The other two dimensions do not come into play. A 20' column of water exerts the same pressure laterally regardless if the column is 4" diameter or 10' diameter. The pressure on the foam is the same whether it is a 4" wall or a 12" wall.

Even a retired engineer can build a house successfully w/ GBT help!
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11 May 2014 09:03 PM
Technically Bernoulli and you are correct. However, when you consider friction of the walls and the fact that the rebar clutter slows down the flow quite a bit it does make a difference. For example, if you poured a two inch wall (if one existed) the friction of the aggregate alone would allow you to pour extremely high without incident. What happens with a Twelve inch wall is flow can strike the existing concrete below sometimes uninhibited by walls or rebar. Now kinetic energy can add to the hydrostatic pressure.

Interestingly, enough when you pour a wall that is much thicker than 12" -- let's say 36 inches, kinetic energy is largely absorbed by concrete below and has less of an effect -- plus with really wide walls you almost cant get enough trucks to the pump to impact the walls -- like on a slab.
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12 May 2014 09:41 AM
Quad - •••must be in a desert climate••• I suspect that in the next decade, we will look at mass much differently and find different ways to measure its impact. At that time we will put this urban legend to bed once and for all. My experience is in the Calgary area and when I do reverse heat loss calc's (i.e., I know the energy going into the building) I have to rate the ICF wall at greater the R 50 and no infiltration to come close to the energy my boiler is using. Since "everyone" agrees 5" of foam can only be in the low R20's, the rest must be mass effect.

btw - you are welcome to come and pull the strapping off my house and any of my other projects in the Calgary area. They are gun nailed with 3.25" spirals. Maybe you use a difference plastic then other blocks?

Eric - as above, we will have to disagree with regard to mass.
4' walls are challenging to consolidate due to the limited distance between the bar and the panel. With less volume to absorb the energy from the vibrator, the pressure on the form actually increases, especially it the head gets stuck between the bar and the foam. On the other hand, if you charge the customer more for the inserts and supply less concrete, it must be a sweet deal ;-)
eric monkmanUser is Offline
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12 May 2014 06:51 PM
Looks like we have 2 debates going here :-)


In the north we heat space, and when we come home at night, we want to bring the temperature up to speed fast.
Stands to reason that Mr Coleman built all his coolers with the insulation on the inside face.
The last thing we want to do is loose a bunch of BTU's warming up a thermal mass, rather than our toes :-)





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12 May 2014 07:20 PM
Eric - I agree that there should be foam on both sides as in a proper ICF wall. However the amount of concrete inside the ICF still makes a difference.
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13 May 2014 03:04 AM
My engineer said that consolidating a 4" concrete core is quite the challenge, especially with a moderate rebar schedule. He also stated that structural concrete is a minimum of 4" and therefore recommends and uses 6" concrete cores as the standard. The savings in concrete from a 4" vs 6" core is minimal at best and one loses the added mass/strength that a 6" core provides.

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13 May 2014 07:59 AM
Posted By Lbear on 13 May 2014 03:04 AM
My engineer said that consolidating a 4" concrete core is quite the challenge, especially with a moderate rebar schedule. He also stated that structural concrete is a minimum of 4" and therefore recommends and uses 6" concrete cores as the standard. The savings in concrete from a 4" vs 6" core is minimal at best and one loses the added mass/strength that a 6" core provides.



Your engineer is not an accountant 4" vs 6" is 33 1/3% difference in concrete. Yes it can be a challenge to get concrete into the wall depending on rebar grid and experience of the guys working on site. Weigh the options of everything before making the decision. On 2000 sq.ft. of ICF wall you just bought an extra 10 m3 of concrete or 13 cu.yds, That ranges from $ 900 - $ 2500 depending on your local concrete prices. As we all know selling ICF is a challenge enough based on perceived notion that it costs too much, 4" can make you more competitive.
Chris Johnson - Pro ICF<br>North of 49
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13 May 2014 09:32 AM
LaFarge Agilia wall mix should flow readily around congested rebar in a 4" ICF form but the mix will cost more than most other wall mixes.
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13 May 2014 09:57 AM
The biggest loss in my mind, when changing from a 6" ICF for above grade walls to a 4" is in the sound reduction capacity of the product. As you all know, one of the key advantages when building a full ICF structure is sound deadening properties of ICF, which is largely based on the thickness of the concrete core. A 6" wall is virtually sound proof, while a 4" wall does allow for some sound transmission.

That being said, if a customer wants a 4" - either for cost savings, or if a narrow lot size necessitates maximizing floor space, I always order concrete with a 1/4" pea gravel and have never had a problem. That being said, we pay about $20/m3 more for pea rock than regular aggregate in our area. So you are saving some volume of concrete but paying more per meter/yard. Also, there is normally more rebar spec'd to account for lost concrete, which makes costs even more comparable.

I always recommend above grade walls be built with 6" concrete (including my own home). The small material savings does not outweigh the added benefit of a 6" vs 4" ICF. Interestingly enough, one of the few regrets customers have after finishing a full-ICF home is "should have done 6" instead of 4" for main floor" (the other big one is "should have built main floor with ICF rather than just basement").
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13 May 2014 10:09 AM
If overall wall thickness and acoustics are bigger issues than thermal insulation, Polycrete Big Block comes in a 1.75" EPS option. The steel wire mesh inside the EPS panel allows it to withstand 1,200 lbs/sqft of lateral pressure and that's still stronger than nearly all other ICF products available in North America.
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13 May 2014 10:49 AM
Posted By Alton on 13 May 2014 09:32 AM
LaFarge Agilia wall mix should flow readily around congested rebar in a 4" ICF form but the mix will cost more than most other wall mixes.


Be very very careful with that…it's not for the light at heart using that product in the walls.
Chris Johnson - Pro ICF<br>North of 49
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13 May 2014 11:13 AM
Posted By Chris Johnson on 13 May 2014 07:59 AM

Your engineer is not an accountant 4" vs 6" is 33 1/3% difference in concrete. Yes it can be a challenge to get concrete into the wall depending on rebar grid and experience of the guys working on site. Weigh the options of everything before making the decision. On 2000 sq.ft. of ICF wall you just bought an extra 10 m3 of concrete or 13 cu.yds, That ranges from $ 900 - $ 2500 depending on your local concrete prices. As we all know selling ICF is a challenge enough based on perceived notion that it costs too much, 4" can make you more competitive.

Out here the pricing on 3,500 psi is $85 per yard. So the extra 13 yards of concrete for a 6" core would cost around $1,105 more than a 4" core. One would have to add additional rebar reinforcement on a 4" core vs a 6" core, so that adds rebar & labor costs. In the end it's a wash or it actually might end up costing more $ to do the 4" core due to the added reinforcement, labor, engineering and issues with consolidating into a 4" core.

Not trying to be divisive here but if $1k is a make it or break it deal then that person shouldn't be building a home in the first place. They should be renting as they are not in a financial position to be building because $1k on a job site is nothing.


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13 May 2014 11:33 AM
You missed the point…it's not the $ 1000.00 creating a problem not to build, it's the $ 1000.00 comparing to other products available, i.e. why would you use ICF if it is going to cost us $ 1000.00 more.

And again it's the area your in, not all areas require more bar.

You cannot blanket statement everything. Costs vary by area for various reasons, don't discount something to everyone because in your area it may not work satisfactorily.
Chris Johnson - Pro ICF<br>North of 49
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13 May 2014 07:35 PM
Chris, well done. Lbear have your engineer read up on a new innovation developed in 1998 at the University of Michigan. It's called Helix it makes the rebar issue a non starter along with Fritz Pak No.7 in the mix, pouring a 4"wall, easy. It's also the cost of the bucks and pump charges and for some customers the thickness of the wall can be a problem.
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14 May 2014 09:04 AM
WE TRIED THE LAFARGE AGILA...NOT FOR ICF !! IT IS SO SOUPY, IT ACTUALLY FLOATED THE FORMS OFF THE FOOTER, WE TIED OUR REBAR TOO, RUNS THROUGH THE MOST TINY OPENING, AND IT ACTUALLY DID NOT SET UP AS FAST AS THEY CLAIMED, SO WE ACTUALLY HAD TO CALL THE POUR OFF, BECAUSE WE COULD NOT GET PAST THE WINDOW SILLS.
DONT TRY IT, WE ARE A PROFESSIONAL ICF/CONCRETE CONTRACTOR, GOOD FOR SLABS BUT NOT FOR ICF WALLS, HUGE AMOUNT OF HYDRO-PRESSURE AS WELL....TRY FILLING YOUR WALLS UP WITH WATER FIRST BEFORE YOU TRY IT.
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14 May 2014 09:39 AM
Bill, what core width did you use?
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14 May 2014 10:01 AM
6" core, but core would not have made a difference
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14 May 2014 12:10 PM
Posted By billnaegeli on 14 May 2014 09:04 AM
WE TRIED THE LAFARGE AGILA...NOT FOR ICF !! IT IS SO SOUPY, IT ACTUALLY FLOATED THE FORMS OFF THE FOOTER, WE TIED OUR REBAR TOO, RUNS THROUGH THE MOST TINY OPENING, AND IT ACTUALLY DID NOT SET UP AS FAST AS THEY CLAIMED, SO WE ACTUALLY HAD TO CALL THE POUR OFF, BECAUSE WE COULD NOT GET PAST THE WINDOW SILLS.
DONT TRY IT, WE ARE A PROFESSIONAL ICF/CONCRETE CONTRACTOR, GOOD FOR SLABS BUT NOT FOR ICF WALLS, HUGE AMOUNT OF HYDRO-PRESSURE AS WELL....TRY FILLING YOUR WALLS UP WITH WATER FIRST BEFORE YOU TRY IT.


Thanks for the info.
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eric monkmanUser is Offline
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14 May 2014 06:06 PM
Agilia = Liquid Head :-) and the plasticizer keeps it liquid for a very long time, so even 4 ft lifts are dangerous. That's beside the point however.

Back to 4 inch....... we have good luck with it and we have done a couple 2 story jobs, no problems.
So my plan is to take a 6 inch core block and reduce the core to 4 inches by using the insert (on the inside face)
EPS @ R 4.5 per inch by 7.25 inches thick makes R 32.625

Interesting comment on the STC rating for 4 inch core , was that tested in the configuration I am intending to use ?


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