I am an Architect designing an ICF home in North Carolina near Camp Lejeune. I'm getting into the final planning and detailing, trying to figure out how to best preserve the opportunity for competitive bidding, yet get into the details of the house.

Overall wall thicknesses among manufacturers seem to vary significantly, optimum form lengths, etc.

My question is, once I have the structural core design calculated, what's the best way to move ahead with final design dimensions and detailing?

Bid the Schematic Designs out to ICF manufacturers and then work with 1 mfr?

Find out the local GC's preferences in the area? ( will be bidding out the job to a few GCs)

Or do you hold the interior wall dimensions and allow the exterior wall to 'float' the few inches that allows multiple manufacturers widths? Obviously that doesn't allow me to 'optimize' the layout based on the ICF module.

Any recommendations or experiences would be appreciated.

BG,

What I would do is interview and investigate your GC now. Find out what form they like to use, some may use several forms. Choose a form before you design, this allows you to design to the strengths of the form you are using. This will reduce waste and increase the speed of installation. This does not mean you can't build any design with any form it is just a better methodology to reduce waste, increase speed, which inturn reduces costs. Then send it out to competitive bid if you are not yet set on your contractor.

ICF Contractor

PS It is always a great idea to have your ICF contractor involved in the design phase to help reduce cost and increase the efficiency of the project.

But there's also a simpler way, especially since you as the design team "leader" is on the hook for the design parameters, including design strength complying with the area you are building in.

That simpler way would be to review the IRC 2003 code, which you may very well function under, because it has sections on ICF foundations and above grade walls. Assuming your design can be built within "typical" code extrapolations ALREADY done for you, you only need to spec the size of the core wall OR specify one or two or three different manufacturers who have a block system which meets your criteria.

Now the mfg have no interest in bidding from plans, they are interested in selling product to someone who will bid it for you. You just need to determine the products available to you, and then peruse the information about them.

To simplfy even further, most ICF work is done with 6-6.5" core ICF products, please ignore the 4" core for reasons you can further investigate by searching on this forum. So now that there are selected mfg, the dimensions of the block are immaterial because you are dealing with a core size and a building size. If you let the block size determine your building size, it shouldn't take more than 15 minutes to divide length of wall by length of block, once you delete a corner compensation.....BUT, to me it's a waste of time and money to do so beyond a cursory check to try and minimize a series of short cuts.

The other issue you run into is whether the walls should be built in different thichnesses for ledgers. I don't use an 8 on the bottom and then go to 6", some do, but I feel they do it for the wrong reason. They do it because they don't understand some of the ledger brackets we have available from sources like Simpson String0tie, who has developed these lvl brackets for our industry....no, what you wind up with is the tail waggin the dog, where the mfg or the distributor "suggests" you use 8 to 6 and sometimes, heaven forbid, then 6 to 4, because they don't have a competant carpenter crew or site project manager explaining how the systems work.

I'll suggest a better approach for you.....Buy one of VanderWerf's books on ICFs called "Insulating Concrete Forms, Demand, Evaluation & Technical Practice" or "Insulating Concrete Forms for Residential Design and Construction". These books can quickly get you up to speed about the whole process, and it will make your life easier!

Sorry Jim, I usually agree with your postings but this time I would have to go with ICF Contractor. As and engineer, architect, and builder I think it is critical to know what materials you are going to build with and design the structure accordingly. Despite what most architects claim, the dimensions of a structure are somewhat arbitrary and what appears to be a minor change in design could make a big difference in construction. One example I run into a lot is the inside corner or “pop-out”. Often the designers around here will make this dimension 4’-0” regardless of building material. If the wall is a SIP, this works well. However, a popular ICF product out here is 11” wide and the corner units have a 1” (or 25”) turn to keep the outside wall dimension on a 24” grid. This will make the dimension 4’-1” if full units are used so 1” needs to be cut from the blocks. By designing for the block, these cuts are eliminated. Another case is the flat SIP roof. The maximum panel length of 24’-0” can span only 23’-9” due to the bearing requirements but I often run into designers with 24’-0” wide rooms.

In our case, we work with the owner and GC during the design development stage to determine what products are going to be used. If it is an ICF product we create 3D units in our CAD system and “build” the walls on the computer. It is so much easier to take them down and rearrange them at the cyber site than the actual site. A structure that is designed to use full units is so much easier to layout, has less potential for blowout, and is less expensive.

Brian

P.S. Your comments about the core sizes and ledgers are good and should be considered in the decision of which block to use but architects and designers deal with exterior and/or interior dimensions.

Brian
I think we're saying the same thing, albeit somewhat differently. I do think getting the gc or at a minimum the installer involved would help, and yes, there are dimensions and corners and bends that need to be considered. My comments were based a little more toward getting some background info, so the architect has an idea of what they are discussing. How it impacts his design(dimensions) and how it impacts the installer. You see, at this stage, the architect isn't even sure of the product or sizes he wants to use, that is why I suggested the IRC code for a generic start!

I've done the corner thing before, and usually keep an eye on the dimensions; I don't think I could convey all the important info in a simple post. That is why as each of us posts to a question, we usually cover all the bases!