Is it cost effective to ICF all the way up to the roof line? My builder normal goes 9'6 then wood/spray foam...Fox Block 6 inch Phx, AZ. Thanks..

One story? Two story? What are we talking here....normal roof trusses or some kind of a wood pony wall after 9'6"?

Posted By dford1 on 17 Feb 2013 09:07 PM
Is it cost effective to ICF all the way up to the roof line? My builder normal goes 9'6 then wood/spray foam...Fox Block 6 inch Phx, AZ. Thanks..

Are you taking gable end?

IMHO, the only way to do ICF correctly is to run it up to the gable end. It makes no sense to stop and then wood frame out the gable end. Might as well just do it entirely out of wood frame and forget the ICF.

What is his reasoning behind stopping? Too complicated to do a gable end in ICF?

above = LAME




above = the right way to do it (that is a 12/12 pitch gable)

You only benefit from ICF gables if you have a cathedral ceiling

Posted By Chris Johnson on 17 Feb 2013 10:40 PM
You only benefit from ICF gables if you have a cathedral ceiling

How so?

According to engineers, a homes gable end can see some of the highest structural stresses out of the entire wall assembly. Why go to wood?

From an insulation standpoint with a typical flat ceiling the ICF is not necessary

From a structural point of view, the non-gable walls are carrying the brunt of the load, last time I looked the gable was dispersing about 90 lbs per l/f along the bottom chord, the ends of a typical truss are much higher and I have had girder trusses exceeding 16,000 lbs.

In your first picture, the gable in the front appears to have a flat ceiling (from what I see expanding the picture), but the gable on the right appears to be higher as it seems to show a small cathedral or tray ceiling. In your second picture, based on the height of the windows I would say it will have a cathedral ceiling which ICF gables are the obvious choice based on the examples you provided.

Posted By Lbear on 17 Feb 2013 10:20 PM

What is his reasoning behind stopping? Too complicated to do a gable end in ICF?

Not too, but more. In my case I determined that a uniform wall height all around and using trusses was the easiest, and overall, the smartest way to go. No potential issue for mismatching the ICF roof pitch with the trusses caused by mis-matching factory built components with site built components. The gable trusses were built at the right size to accommodate the lookouts, and with the exact same angles at the rest of the trusses. Everything fit quickly, easily, and perfectly. Six inches of spray foam on the inside of the gable wall and it was sealed as good as the ICF. It could easily have taken half as many manhours to build the ICF gables as it took to install the entire roof trusses and sheathing. Installing gable trusses probably added no more than 5% to the roof assembly time. Plus, it was easier to install the siding on the gables since we didn't have to fit everything to the webs.

In the lower of the two pictures above the far gable wall should have been frame. The high ratio of window area to wall area negates the greatest benefits of ICF, insulating and tightness.

According to the engineers I spoke to, gable ends are usually the first to fail in a high wind event. Gable walls are usually the highest walls on most houses so they are exposed to the highest wind loads. There are both negative and positive pressures being applied on a gable end. According to the FL code:

R614.3 Wood frame gable endwalls above concrete, masonry, or ICF walls.

This condition is not permitted unless there is a ceiling diaphragm in accordance with Figures 3.7a and 3.15 of the AF&PA Wood Frame Construction Manual for One- and Two-Family Dwellings.

In addition:

... balloon framing and is one of the best ways to make a very strong gable end wall. The masonry alternative to balloon framing is to continue the masonry wall all the way up to the roof and to install reinforcing in the wall that extends throughout the height of the wall.

Article from JLC about the weakness of wood gable ends:: JLC Gable Ends

There is a valid reasoning behind that code. Gable walls take a huge brunt of force in high winds and doing them ICF makes them bulletproof.




Masonry wall structure survived but the wood framed gable end failed, causing a snowball failure effect of the rest of the roof structure. 

If you're building in a high wind area, going ICF all the way up makes sense. Where I'm building in SC, the wind factor is very low. That, coupled with a low pitch means my gable ends won't be subjected to that much force. What I don't get is why they run the gable studs the flat way. I always add studs at a 90 degree angle to the gable studs for a very strong L-shaped stud. I think that's code in FL now. I also had my trusses built to a higher wind rating, had more anchor bolts than code, used thicker sheathing than code, and used the biggest hurricane ties I could get. Living in FL will do that to you. I had to get my H-10 hurricane ties in FL, as they didn't have them in SC.

It's interesting to note that in the first picture, the gable end fell out, and the panel itself doesn't appear compromised. It let go at the top, where it is connected to the roof. I also don't see the sheathing that it would have been attached to. Maybe the sheathing wasn't attached adequately? That was an old bugaboo in FL, with sheets of sheathing found in the aftermath of hurricane Andrew with only a few nails in them. Even with ICF gable ends, if the sheathing or trusses aren't adequately secured, the roof will still be compromised. I used the FL code on my sheathing, with 4" edge nailing and 8" field. What's a few more nails while I'm up there?

Proper back bracing and adequate inspections can help prevent those issues.

But yes based on hurricane type winds are going to destroy wood framing long before a concrete wall. I'm not trying to promote wood framing at all here, I promote ICF to the fullest but from a costing perspective and to keep ICF as feasible for most consumers you should frame your gables in non insulated areas

Posted By jdebree on 18 Feb 2013 07:50 AM
If you're building in a high wind area, going ICF all the way up makes sense. Where I'm building in SC, the wind factor is very low. That, coupled with a low pitch means my gable ends won't be subjected to that much force. What I don't get is why they run the gable studs the flat way.

Most of the tract/spec homes, for the gable ends, they just install a truss. So the gable studs are laid flat like any other truss. This makes for a VERY WEAK horizontal plane (negative & positive pressure). This type of gable end is NOT allowed in high wind areas and WILL fail in high winds. I've personally experienced a failing gable end, it wasn't a catastrophic failure like in the previous photos but a failure due to side-to-side movement in high winds.

If one stick frames the gable ends, then the studs can be laid sideways which is stronger but still not up to Florida code. Florida codes require additional bracing to prevent the gable from failing.

Here is more info on it: Gable Bracing

Posted By Chris Johnson on 18 Feb 2013 07:51 AM
Proper back bracing and adequate inspections can help prevent those issues.

But yes based on hurricane type winds are going to destroy wood framing long before a concrete wall. I'm not trying to promote wood framing at all here, I promote ICF to the fullest but from a costing perspective and to keep ICF as feasible for most consumers you should frame your gables in non insulated areas

It doesn't require hurricane force winds to cause problems. I personally experienced a failing gable with just thunderstorm force winds 50MPH -75MPH. It wasn't a catastrophic failure like in the photos but the gable end began to compromise due to the wood framing not being able to resist the negative & positive wind pressures.

Further north of me, they weren't as lucky and this was the result of poorly constructed gable ends:



I figure it is best to capitalize on the strength of ICFs and use them for the gable ends, especially on 2-story applications where the gables will be subject to intense wind loads during thunderstorms or other severe weather. Once a gable end fails, it's all downhill from there, as the rest of the home will begin to collapse. I'll take a concrete ICF gable over a wood framed gable any day.

First off you are the exception to the rule in most cases by using ICF for non insulating purposes (your gable). Secondly, are these actual gable trusses or a standard truss like the rest of them? A proper gable truss will have vertical studs 16" o.c. And is dropped 3.5" lower then the regular truss.

With the verticals at conventional spacing tying back properly should prevent any blow out. The 3.5" drop allows the lookouts or ladder to be tied back to the first truss, again helping lock it all together as well as preventing sag on the overhang.

I'd say poor installation techniques were used if a 75 mph wind is causing such failures, in my neck of the woods we design and build for snow load and wind load. I watched complete roofs blow off intact during our F4 tornado, it wasn't a gable failure it was the windows blowing out and the strong breeze sheering the connection from the top plate.

Posted By jdebree on 18 Feb 2013 07:50 AM
What I don't get is why they run the gable studs the flat way. I always add studs at a 90 degree angle to the gable studs for a very strong L-shaped stud.

Two reasons, ease of manufacturing and the grip area for the connector plates. On the flat they are run through the press rollers just like all the other trusses to set the connectors. Also, you need quite a bit of area for the connector plates to bite into. You don't get that with the 2x's perpendicular to the truss plane.

It is simple enough to add reinforcement to those flat gable studs in the field by attaching additional 2x4s perpendicular to the flat 2x4s. This detail is shown in many if not most truss manuals.

Posted By arkie6 on 18 Feb 2013 12:18 PM
It is simple enough to add reinforcement to those flat gable studs in the field by attaching additional 2x4s perpendicular to the flat 2x4s. This detail is shown in many if not most truss manuals.

The additional white colored studs show how to retrofit and brace a gable end. It requires both vertical and horizontal bracing on the top and bottom of the gable wall.

99% of builders will do code minimum, which usually means a flat truss gable wall.

Again, the point of all of this is that if you already have an ICF wall, why not complete the stack at the gable in ICF? A steel reinforced 6" concrete gable end will be much stronger.

Your not taking costs into consideration

You need to run 'kickers' down on a ~45 degree angle and tie to the bottom chord

Posted By Lbear on 18 Feb 2013 12:58 PM
Again, the point of all of this is that if you already have an ICF wall, why not complete the stack at the gable in ICF? A steel reinforced 6" concrete gable end will be much stronger.

Plain & simple, time and money, especially if you're not in a hurricane or tornado area, which is what, 70% of the country? From what I remember seeing of your drawings you've posted, and seeing the pics and drawings of what nd96 is building, it appears to me that cost is a secondary consideration for both of you. Keep in mind most ICF houses are built by guys who are going for the best they can on a tight budget. Why overbuild when ICF is plenty pricey as it is? Up north in Idaho, Montana, Minnesota, etc., you don't build a roof for high winds, you build it for high snow loads. There's a difference, a big one!

You build what makes sense for the location, and the budget.

Posted By Chris Johnson on 18 Feb 2013 02:19 PM
Your not taking costs into consideration

You need to run 'kickers' down on a ~45 degree angle and tie to the bottom chord

How much price difference are we talking about to do a gable end out of ICF vs. stick frame (reinforced & spray foamed)?