My sister and her husband are planning to put a 9' basement under their existing home and one of the builders they were getting a quote from told them that all 9' basements need to be engineered and that an engineer would not touch a 9' basement made with ICF.  Local codes aside, is it the case that engineers steer away from 9' basements made with ICF's?

Zad.

Local codes aside, is it the case that engineers steer away from 9' basements made with ICF's?

No. The builder must be saying he, personally, has no experience with it. Stay away from him as a sub contractor for this one.

Look into using Insuldeck for the floor above and make sure to design an irregular foundation with corners and interior support walls so that the ICF walls have additional bracing. In other words, building a box with long straight walls might cost you more in the long run than giving yourself a few more corners.

Be very careful with the final design of those tall walls for the simple reason that you don't want to end up with your walls an inch higher than a single piece of sheetrock, necessitating extra pieces and therefore, expense.

9' ICF basement walls are easily doable. How high will the backfill against the wall be? Another way to say it is how much of the 9' ICF basement wall will be exposed above final grade level?   How thick will the concrete portion of the wall be?  6", 8" or ?,  Also, what will the backfill material be?  Crushed stone, gravel, sand, sandy soil, or clay?  All of this makes a difference in the amount of steel reinforcement needed.  All of this is covered in HUD's "PRESCRIPTIVE METHOD FOR INSULATING CONCRETE FORMS IN RESIDENTIAL CONSTRUCTION" Second Edition.  It covers basement walls up to 10' high with up to 9' of backfill.

Here is an example of a basement replaced with ICF that appears to be 8'8" tall if I counted the ICF courses correctly (13 x 8" = 104"=8'8"):

https://picasaweb.google.com/LiteFo...lashalbum#

If your basement wall will require a lot of vertical steel reinforcement, you might want to consider using a knock down type of ICF block such as LiteForm or Quad Lock or other similar ICF since the vertical steel can be put in place first, then the ICF walls assembled around it.  This would be an advantage if you are building the ICF basement walls underneath a home suspended above like in the above photos.

ICFHybrid, Could the extra height in tall walls be covered at the floor level with a baseboard. In fact, I usually try to keep the drywall from touching a concrete floor. In my area I also have designed above grade-walls slightly taller than stretched drywall (54") to avoid problems with uneven floors. Since the drywall is installed horizontally from the top down, the crack is near the floor which is easily covered with a baseboard. What am I missing here?

Could the extra height in tall walls be covered at the floor level with a baseboard.

That may have been our backup plan had we screwed up. There are "interior design" ramifications, however.

Here is an example of a basement replaced with ICF

I don't know anything about LiteForm....are those window bucks in photo 7 inside the wall or some kind of bracing? Is there a reason they aren't treated lumber?

Posted By ICFHybrid on 21 Aug 2011 01:33 PM
..are those window bucks in photo 7 inside the wall or some kind of bracing? Is there a reason they aren't treated lumber?

It does appear to be window bucks and it does appear to be untreated lumber.  I would most likely use pressure treated (PT) lumber in that case, but I don't know the particulars of that job.

As far as code goes, I don't think PT lumber is required as long as the lumber is >8" above ground level.  Also, that project may have used an impervious moisture barrier between the new ICF foundation wall and the existing footing.  That would mitigate the concern of moisture wicking up from the footing to the wood bucks.

Posted By arkie6 on 21 Aug 2011 01:56 PM

As far as code goes, I don't think PT lumber is required as long as the lumber is >8" above ground level...

Previous discussions on the topic here:

http://www.greenbuildingtalk.com/Fo...fault.aspx

http://www.greenbuildingtalk.com/Fo...fault.aspx

Here is the code discussion on the topic:

http://www.irccdd.com/building_division/R319.pdf

No, your 9' is okay, my building code says anything greater then 8' for a basement must be engineered. We do a lot of over 8' basements and they are all engineered.

Chris, are you in the US or Canada? Is your code requirement that basement walls >8' be engineered due to seismic requirements for your area?

I'm back in Canada now, Part 9 of the Ontario Building Code says we can use an 8" wall WITHOUT rebar upto 8', maximum backfill 6'~~, If we use ICF (even 8") it is an engineered product and it must have rebar (Nice Eh?, if you can figure the logic in that I'll buy you a beer) but in the same breath if 6" ICF fits into the right criteria (Per Manufacturers Tables) I can use that. However if I exceed 8' in height it must be engineered, conventional pour-in-place or ICF are the same rule. Now here's the best part, when we exceed 8' basement wall, pour-in-place always gets engineered to 10", I can remain with 8" ICF which keeps me competitive (Taking into account framing and insulation).

Formerly I was in California for 5 years and everything required engineering...even a dog house if built with ICF.

How hard would it be to do a 8' poured (edit: was ICF) wall with some type of joist spacer that brings the actual ceiling height to 9'?

How hard would it be to do a 8' ICF wall with some type of joist spacer that brings the actual ceiling height to 9'?

Why select ICF and then do ...something else.... at the end to make it more difficult? Is that to avoid engineering?

I am really confused...

Chris - where do you find the 8 foot limitation in the code for ICFs???

This table clearly means that you do not need an engineer for a wall height of 3 meters???

Baldwin, Apply to your local building department and tell them you are doing 8" ICF to 8' high and tell them you are not putting in rebar...let me know how far you get!

One of the first things they are going to look for is the CCMC report for the ICF product, since it is an engineered product and then they are going to look for the rebar tables.

Hmm... I disagree. They should and will and must follow the code.
Let me explain how it works:

Below grade construction - use the Code or CCMC - it doesn't matter which you use. The code is probably better - less questions about waterproofing (in some cases).
Above Grade - use the Code for cities that have Seisimic Spectral Acceleration response Sa (0.2) below 0.4.
For the Above Grade you can also use the CCMC report which does away with the above seismic limitation.

I am saying this because i have built basements in Ottawa without the CCMC report. No problems. But I do need the CCMC for above grade stuff as Ottawa has its Sa(0.2) = 0.6... which is over the 0.4 limit for the code.

All I want to convey to potential ICF builders that there is no hassle when it comes to 9' high ICF walls. It's right in the code... wanna a tad bit on rebar? use the CCMC report from your ICF manufacturer. But quite honestly i would build just build out of the code. CCMC is meant for new products and raises questions and you don't want questions. This is a code accepted construction technology. very much mainstream...

But i do agree that some building inspectors may not know enough about ICF's... call up your ICF and ask them to help you out...

I have not worked in Ottawa in better then 15 years.

However, throughout the GTA and stretching up into central Ontario no building department is going to allow an 8" ICF without rebar, much as we wish, and believe me we have all tried.

The answer is always the same, it's an engineered product and requires engineering, agree or disagree, it's the way it is. I learned a long time ago, know which battles to fight...and this isn't one of them.

But we all agree 9' ICF walls are permissible, most major ICF manufacturers have supplied stamped engineered details in their installation books, most local building departments will accept them at face value.

poured a 9 ft deep with 9 ft of backfill here in western washington last year, tf systems and full west coast seismic
engineer called for a 10 inch wall with 5/8 rebar vert every foot and hort at 18 inches to give the op an idea of what it takes

called for a 10 inch wall with 5/8 rebar vert every foot and hort at 18 inches

Hmmmm...we just did a 22 foot high wall with 11 feet of backfill and it called for 6" wall with #5 bar 16" vert and 16" horiz in Western Wash for above code seismic. If I had to do it again, I would look into seeing how steel helix additive might change it.

seismic category  d2  and the 9 ft retaining wall is 5/8 every foot also with a 4 foot wide footing
went back and looked at the drawings and i stand corrected as it is 5/8 bar @ 12 inch vert but 16 inch horizontal instead of 18 that i previously misstated
regardless, it's poured and i'm satisfied with it