I have a very specific question.  I am getting differing opinions (including engineers) on what ICF block sizes to use.  I will be building in Maine a 2 story house ICF to roof.  Basement will be about 9' below joists, and about 8' - 8 1/2' for first floor and second floor.  House is 28' x 50' with non-straight walls.  Basically a 28' x 38' colonial with a 12' wide mudroom on it then a 32' x 40' two story attached garage.

I am trying to determine what size blocks to use.  Here are the suggestions so far:

8", 4", 4"
6", 6", 6"
8", 6", 4"
8", 6", 6"

All 6" can't actually be done because code requires at least 8" in basement.
One engineer feels the 8" to 4" transition is a week point as it will have two stories on it.

I feel going 8" to 6" to 6" is a conservative size and paying more engineers to disagree with each other isn't my idea of fun.  The code officer doesn't seem to care as long as the basement is 8".

I have helped friends use NUDURA and I prefer that over the others I have used so I am likely to go with them.  I will build myself.

Any suggestions on what you have built and what size blocks you have used for a two story home with basement?  I realize the wider I go the more concrete will cost, but I really don't care.

While I am at it, anyone done the concrete floors?  I will likley conventional frame them, but I am intriqued by the concrete floors in two story homes.

If this cost of concrete is not a concern, why not just use 8" all the way up? NO more eng. costs.

You make a very good point.  I would like to keep the extra 4" that I would have with 6" over 8", but I certainly can't argue with your point.  Personally, I am satisfied that 8" basement and 6" for the two stories is overkill especially if I use hight PSI concrete and excessive rebar.

I am wondering what people have built as I have not seen a two story ICF home yet, only a one story.

Thirteen, what code in Maine requires a 8" basement? Don't they folloe IRC there!

Dave

Town of Richmond, Maine code enforcement officer.  I think he makes it up as he goes along.  Frankly, I am fine with 8" basement so arguing with him would be dumb.

No arguing required, just show him the code and see what he says. Anytime you transition from a wider to narrower block it will dictate exact floor heights that are not necessary if you stay the same width. Also doesn't work real well when you have a exterior wall staircase. Don't let the BI dictate you, this can be handled real easily.

Dave

How close to Bangor?

Using 6 NUDURA 8" blocks in basement gives me a ceiling height of just about 8' 7 1/2" which is fine with me. I can adjust this easily with the first course anyway. The other two are an issue, but if the 1st and 2nd floor are the same size block there is no issue. NUDURA also has height adjusters. I agree changing block sizes can dictate ceiling height, but that does not appear to be a real issue in my project.

The problem with telling the inspector he is wrong in a small town is he can just not show up for an inspection or delay the project just to be a jerk. I don't need that.

I am about 1.5 hours south of Bangor.

Sorry, but most think BI are bullies and most just don't no their own codes. If you approach him with the "your the god and this is what I found in the code book" he will say yes this is correct and you can use 6" as I read it. It is tough for them to look you in the face when you plead ignorance for them to say well I just don't follow the code and I say you need an 8" wall. Further more this will be your only 8" level and block counts will need to be less accurate if you go 6-6-6 or 6-6-4.

Dave

That is a good idea. Bringing the code and pleading ignorance will likely work.

I've got a couple questions regarding the code(s).

1) If following the IRC, can someone specify the code which states that the basement only has to be 6", 4", etc?

2) Doesn't a local building dept (city, county, etc) have the right to over-rule a specific building code (IRC for example) and be stricter? That being the case, I'd expect them to have this info available in writing at the local building dept, pamphlets, guidelines, etc. (and yes, I did read that Thirteen said the BI makes it up as he goes along)


Thirteen, what have most basements in your area been built to?

Also, of the 4 suggestions you stated, are all those from your local engineers, or did a couple come from friends, associates, etc? You also stated high psi concrete and "excessive" re-bar schedule. Is this your desire, the engineers, or a local thing? Has an engineer spec'd out the re-bar schedule or is that still in the works? 8" block gives you a LOT more room to work with in getting your bars in and the concrete to flow around them IMO.

I don't have all the answers. I will check with the architect and local engineer. Most basements I see are 8" for two story homes, but 6" is allowed for single story homes.

As for the "experts": I actually have 8 sibblings that are engineers and a lot of info. is from them. But, none of them live in my State so I have a paid engineer that actually lives in my town. I think they are all probably right, even though the answers are the same. Some are being more conservative than others. I think I will just have to keep working this out and will probably just pick something on the conservative end.

The higher PSI concrete and excess rebar comes from the various people - all engineers, but only one in my State.

Thirteen;

Excessive rebar is not necessarily a good thing. Rebar has to be designed and calc'd for the project/area of wall, sometimes just arbitrarly adding additional rebar can imped the structural requirement and do more harm i.e. lintels

Nudura's rebar spec's are designed for Siesmic Zone 4 (It's a blanket that has fail safes in it), having an independent engineer review that may save you money since your siesmic may be less.

An engineer doing your design can spec. something and wet stamp it releasing the building department from any liability.

I would go for 6,6,6 most common size and easy to work with, 4" saves concrete but difficult to pour and vibrate

James,

You ask a great question that actually confuses many designers, Architects, engineers, and building officials. If you are in a state that has adopted the IRC and the IBC here is the difference in the codes. The IRC is a perscriptive path that requires no further engineering. Anybody can build a building out of the IRC, it is very conservative and restrictive, but it is a path you can follow without using an engineer. The IBC is the code used by the engineers to actually engineer the building. This code is more flexible and allows the engineer to think outside the box to get the job done. The issue with the IBC is that all of their calcs must be shown to prove their work. It is my opinion that an engineer should be able to save you the value of their bill in lower building materials cost and a more efficient design. That being said my opinion is if you go to an engineer and they are quoting the IRC then they are not doing their job. They are taking the easy way out by quoting you a code you can use yourself without them.

Now the problem in my area is that we are in a siesmic zone. In the IRC we are in D2 which is the most restrictive and if you try to build a house with more than 4 corners out of concrete it does not conform with the perscriptive path of the IRC. In the IBC we are in zone D which still is the most restrictive but your engineer is allowed to come up with their own design, concepts, and solutions. Just as long as it calcs out. Many engineers will blend the codes for what I guess is the ease of getting the job done faster. It has been my experience that this sometimes does or does not equate to savings in the build or the engineering fee.

The way this ties into this thread is by using the IBC I can build a basement 10' with a 6" core with #4 bar 16" horizontal and 16" vertical in siesmic zone D. Heck currently we are doing a 4 story condo project in which the back wall is back filled for 3 stories and it is done out of 6". Now the IRC will allow me to build a basement in seismic zones A,B,and C not ICF (R 404.4.1) but will allow me to build a conventional basement in zones D1 and D2 with many restrictions and has to be 8" (R 404.1.4). What I find interesting is the IRC allows a wood build basement. Oh well nobody said it ever makes sense.

The answer to your second question is yes. Many jurisdictions will amend the IBC to fit their specific needs and will enact them into their jurisdictional ordinances. In Seattle they have amended the IBC and it is now know as the SBC (Seattle Building Code)

For what it is worth

ICF Contractor

Thanks for all the replies. A friend found me an Engineer that actually specializes in houses, concrete and bridges. I sent him my plans this morning and for $75.00 per hour it looks like he will answer my questions and stamp the plans.

Hmmmmm, what does that say about me, an engineer using the IRC to build my own ICF house? If I were to charge myself a few thousand could I save a few thousand too? 

Forget it, I just couldn't resist!!!

Actually, I have done some calcs like footers and floor joist sizes. But making sure I comply with the IRC (shhh, don't tell anybody but the BI gave me a permit even though I exceed the 60' IRC limit on plan size!!) I figured it would save me a lot of potential hassle with the BI. And I've never done concrete design on the scale of a house so decided to play it safe. Plus I don't have a PE stamp so I'm not in a whole lot better position than any other DIYer!

But I agree with your comment. If you truly engineer the project rather than just 'cookbook' it you probably will save a fair amount of material. However, you'd probably be surprised just how much engineering is 'cookbook' engineering. There's very little original engineering work performed out in the world, especially on well established routine type jobs.

Seismic region? 8"-8"-8". Optimization possible.
Concrete floors? Need to be designed.

Actually, I don't agree with all the comments regarding code use above, however, this is not the thread to belittle our use of codes.

The IRC, by the way, has a defined ICF section both for walls and foundations for single family and 2 fam dwellings. Even an archie can use the IRC and still be doing their job :-)

Thirteen
If you need one of the most knowledgable ICF people around, he lives about 30m SW of you. Both ICF manufacturer AND still selling and installing. I did all my original training with him back in 96.

Contact direct if interested.