Hello All, I have been looking into ICF for a home to be built on a waterfront lot on Santa Rosa Sound near Pensacola Fl. The price looks like it will knock that option out as the best quote I have so far is about $240/sqft. That is WAY more than the 10% to 15% above normal construction cost usually mentioned. I have found a builder using precast concrete panels. I asked about the construction of the panels and he told me that the form is laid down, steel studs are placed at 16" oc, conduit run, foam is placed between the studs, and the remainder is filled with 5000psi concrete. The total wall thickness is 6" after drywall is put on. This seems thin compared to other tilt up walls and such I've looked at. I can't find much about this type of construction on line but maybe I'm not entering the right search queries. Can anyone tell me if this is a decent form of construction and if these wall thicknesses seem right? How would a home constructed of this type of material (precast concrete at 5 1/2") compare to other methods such as ICF and SIP's as far as strength and inslation go? Thanks for your help. C

I'd question how airtight typical tilt-up is and the thermal bridging effect of the steel studs. I'd also look into SCIP (shotcrete on foam) construction. I've seen it work very well in similar climates. And both interior and exterior cladding is unnecessary.

$240/SF based on floor or wall area? Either way it sounds excessively high... You might find this interesting/useful information:

http://www.icfmag.com/articles/features/real_costs.html

Posted By ghost95 on 24 Apr 2014 10:43 PM
Hello All, I have been looking into ICF for a home to be built on a waterfront lot on Santa Rosa Sound near Pensacola Fl. The price looks like it will knock that option out as the best quote I have so far is about $240/sqft. That is WAY more than the 10% to 15% above normal construction cost usually mentioned. I have found a builder using precast concrete panels. I asked about the construction of the panels and he told me that the form is laid down, steel studs are placed at 16" oc, conduit run, foam is placed between the studs, and the remainder is filled with 5000psi concrete. The total wall thickness is 6" after drywall is put on. This seems thin compared to other tilt up walls and such I've looked at. I can't find much about this type of construction on line but maybe I'm not entering the right search queries. Can anyone tell me if this is a decent form of construction and if these wall thicknesses seem right? How would a home constructed of this type of material (precast concrete at 5 1/2") compare to other methods such as ICF and SIP's as far as strength and inslation go? Thanks for your help. C

ghost95,
Our turnkey pricing for SIP construction in the Tampa area is $100 - $140 sq. ft. depending on size and finish of project,
not sure how that relates to the Pensacola area which is about 7 hours from us

Thanks to all for the input. I thought the ICF price was high too.

How does the panel system I described sound. 4" of concrete and only 1.5" of foam sounds thin compared to others but I am really just getting into this so I'm not sure.

Thanks, C-

Posted By ghost95 on 26 Apr 2014 09:00 PM
Thanks to all for the input. I thought the ICF price was high too.

How does the panel system I described sound. 4" of concrete and only 1.5" of foam sounds thin compared to others but I am really just getting into this so I'm not sure.

Thanks, C-

Is the foam at least continuous through the panel?i.e. no concrete edges?
How are the two concrete layer tie together? Does this cause a large thermal by-pass?

The foam is only on the inside of the panel. From what I can tell there is a 4" panel of reinforced concrete with steel studs, then the 1.5" of foam put between the exposed section of studs on the inside, and then the 1/2" drywall is hung on the studs inside of the foam.

This was the design I was talking about. I think this will explain it better than me. The wall I am talking about is the one with a total of 6" thickness. C-


http://concretebuildingconcepts.com/images/PrecastWall.pdf

We are looking to do something similar for our home. My father did one years ago. In our method we formed up the walls onsite and laid a 1.5 inch thick sheet of EPS over the entire area (minus windows and doors). We then took 3 inch thick pieces 2 feet wide and 8 inches shorter than the walls and glued those to the 1.5 inch piece so that they were spaced 4 inches from the top bottom and sides of the form and 4 inches apart from each other.

We then put in electrical boxes and other wiring in areas where we didn't have the 3 inch pieces. We laid down some rebar in the troughs of the foam. Then we poured concrete until level with the 2x6 forms. Concrete was 4 inches thick around the edges and between the larger pieces of foam and 1.5 inches thick over the bulk of the wall.

While wet we laid down a brick patter stencil that imprinted 'mortar' lines on the concrete of the appropriate depth and sprinkled a powder based concrete die on the panels. Removed the stencil after dry and had a fairly convincing brick pattern. We rented a crane to come set up the walls and put up 'dryvit' siding over the seams and corners. The panels ranged in size with the longest being 26 feet long. It has been 15 years and only one crack has formed. We left the 2x6 forms in place on the windows and doors to be the rough opening (ya I know its a thermal bridge but so much easier). Left 2 inches of 3/8" rebar sticking out of the bottom of the walls and drilled mating holes in the foundation to lock walls in place. J-bolts on the top were used to adhere a 3 layers of overlapping 2x6's for a triple header to tie all the walls together and give us something easy to attache roof too (ya I know, another thermal bridge). Sheet rock was then glued directly to the exposed EPS foam on the inside being nailed to wood on header and window and door openings where available. Not sheet rock has become loose in the last 15 years.


We did much of the work ourselves with the aid of regular concrete crew. The die was really the only new thing for them. My in-laws recently visited house for first time and later I asked them what they though of my parents home and what siding they thought it had - they looked at me confused and said brick and didn't understand why I was asking.

My father used standard wood trusses on top of the walls and is very happy with his heating a cooling bills.

I plan on doing something similar and using Metal sips for a shed roof. I also plan on using 2x4s for the door and window openings with concrete coming over the edge. I will do a dropped ceiling from the Metal sips to cover the double header and insulate it on the outside.