Another thing I don't know why it's not used more often, cantilever trusses. I didn't know what they were called when I wanted them, but the bottom cord of the truss goes over the wall to the plumb cut for fascia. I takes the right combination of roof pitch and eve size. Done this way is much stronger and no need to build that soffit BS. I am getting ready to insulate the garage to r60 and r74, nice to have the extra energy heal.

I like the look of the HGAM10 if the truss layout is difficult, and most seem to be, otherwise the LTA2.

Foundation.

- Contractor should care about the foundation. Our ICF contractor insisted on forming and pouring the footings and concentrated on level and square. He spent quite a bit of time on plumb, square and level of the walls prior to the pours.

- To prevent moisture wicking up through the footings, we installed Fastfoot fabric in the forms and wrapped up and over the top to the ICF. After the walls were poured, the peel and stick then overlapped the top of the footing. With the moisture barrier under the basement slab our basement is dry as a bone.

Bucking. Ensure rough opening requirements are accurate. We provided wrong number for one door, our mistake. Rest of openings were spot on.

I am an engineer, not a contractor and am building a rather complicated ICF castle in Oregon. I could not afford to contract it out, so am building it myself. I have learned a lot about ICF construction and here are the things I would definitely do differently:

1) Integral ICF w/footing. A lot of sources recommending pouring the first two courses of ICF along with the footings. The only advantage to this that I can see is placing the first cold-joint up inside the ICF, which could make the walls more vermin and moisture proof, although it was also claimed that it made for straighter walls. I tried to do this and lt was a giant PITA. We constructed a freaking FOREST of 2X4 risers & cross ties, hanging the ICF over the footing forms with tie-wire. I could not see any other way to do it. We did manage to get everything lined up perfectly but when we poured, the concrete would sometimes build up on the rebar and plastic webs and the weight of that concrete deformed the ICF downards out of vertical plumb. My first two courses were nice and straight horizontally, but in many cases sagged vertically as much as 1/2". I would not do it this way again and would not recommend it to anyone. Make the nicest, levelest footings you can, and make hangers for the rebar verts to keep them exactly in position. We did these in many places during wall construction where we had contiguous rebar that had to extend well past the top course being poured at the time by running a 2X4 horizontally a few feet above the ICF and lined up accurately, then we located the rebar in the footings and fastened them to the 2X4 with short strips of 3l8" plywood screwed to the 2X4. This set all the rebar exactly in the right places and held them firmly so they did not shift during the pour. Trying to stab them into the footings and hope that they still line up with the ICF and horizontal rebar is a no-win. Don't stab your pins...locate them and clamp them and you will be very glad you did.

2) watch your wall plumb when you pour. The mud will cause the walls to move and you really need to use turnbuckle braces so you can adjust them before the mud sets up. Keeping your walls plumb and straight will make things vastly easier later when building the roof and internal walls.

3) keep your wall cavities CLEAN! My house is set among some fir trees and we had to cover the ICF walls with 2' wide strips of black plastic to keep fir needles and other debris from getting in there. We did not do this on the first pour after the footing and had to go back and grout some places where the cold joint was packed with 1/4" of fir needles, creating an air space between the wall concrete and the top of the footing. Any snow, ice, leaves, and foam debris that get into the wall cavities will play havoc with your concrete integrity. You cannot wash it out with water, although we tried. The only thing that worked for cleaning the walls out by pouring water in them was to fill a 55 gallon barrel with water and dump the entire thing into one end of a wall using an excavator. This created enough of a tsunami to flush most of the crap out the end of the wall. Even dumping multiple 5 gallon pails simultaneously would not do it. The best we found was to vacuum the walls with a shop vac and a piece of 1" pvc pipe as a thin nozzle extender (sometimes we had to go 8' long). It is a major PITA to vacuum out your wall cavities but, IMHO, it is one of the most important things you can do. Fixing gaps in the cold joints is way, waaaay harder.

4) along the same lines, make sure you consolidate the mud properly...this means sting the hell out of it while pouring and make sure your stinger gets all the way to the bottom of the pour. My first wall pour after the footing, the G.C. who sold me my ICF suggested that I let him and his 'expert crew' come down and run the first wall pour for us, as we had never done it before and they were 'experts'. Sounded good to me so ok. Down they came and they ran through the pour very quickly. Later, we discovered that their stinger operator was only plunging the stinger about 2' into the walls! Everything below that was unconsolodated and the cold joints looked like they had a 1/2" layer of pea gravel separating the wall joint from the footing. I had to cut out about 150' of ICF, dig out the unconsolidated gravel, and hand grout the entire thing. To say I was pi$$ed off would be a gross understatement. We did every pour ourselves after that and they came out great, having learned that lesson the hard way. Also, the contractor that ran my first pour massively fuxxored up some formed concrete columns we had built to support a clerestory wall, and on either side of three big garage door openings. When we stripped off the forms, the exposed concrete looked like it had leprosy, all due to sloppy and incomplete vibratory consolidation. We had to jackhammer two of these columns out and re-do them, and grout the heck out of the rest. Did I mention I was pretty mad about all this?

5) Buy and use a hot knife. Do not cut openings in the ICF with a saw, no matter how tempting. You will fill your wall cavities with styrofoam dust and chunks of ICF than will be a B-ey-tch to get out later, and if you leave it in, you WILL have problems with walls that are, well, lousy with voids and defects. This, I understand, is the #1 problem with ICF construction and is a blight on the technology. But if you are conscientious, prepare beforehand, and take the time to do it right, you will have excellent, monolithic concrete walls.

6) Use a better spec of concrete than what the structural engineer specifies. My guys spec'd 3,500psi, 3/8" aggregate, 5 ~ 7" slump for all walls. That stuff was not easy to pour because it was stiff, and the mixer drivers would add too much water and it was just a mess. Not having any prior experience, I just went with what the structural engineers said. However, when I got ready to pour my clerestory wall, 20' in the air, I decided on my own to up the concrete spec. I ordered 4,000psi with a 8 ~ 9" slump, hot water, no air, and some admix & superplasticizer. Man, this stuff poured GREAT! We practically did not even have to sting it (but we did). It flowed like a dream into the walls and tested out at over 5,200psi 28 day. Man I wish I had thought of doing this sooner, especially before we poured all of the formed concrete beams & columns. It did such a better job, the finish was better, the pour went faster & smoother, the consolidation...sheesh. Way better and it only cost me about 4% more for the mud. IMO, I made that 4% back in spades with less labor and a better product. I recommend going beyond that the structural engineers spec to everyone, especially the higher slump and superplasticizer. That wet, slippery mud went into the walls like a wet dream and cured to well beyond strength specs. It was ALL good.

7) Mark on the walls where you have vertical rebar before you pour. We went around and marked with a sharpie, then with some black latex paint (which was more durable and visible) where every vertical rebar was in the walls. Now no surprises when adding holes, pass thrus, supplemental anchor bolts for internal supports for things like TV mtg. brackets & cabinets, etc. If you know where your verts are, you also know where your horizontal rebar is so you know exactly where you can drill without hitting steel.

8) If you think you have enough bracing on T-walls, transitions between ICF and cast-concrete beams & columns, and around door & window bucks, think again and add more bracing. Blowouts and bulges suck to repair, especially when you have mixers & pump trucks waiting for you to patch things up. We found it was very helpful to screw 2X4's across door bucks to extend across the ICF on either side at least a few inches to hold the ends of the cut courses in place. This was mainly a problem where the ICF was short, like 8 or 16" because occasionally, near the end of a cut, the plastic web would pull out of the foam and now you have a blow out. It's easy to slap some extra bracing on things...much harder to fix it afterwards.

9) pre-placed pass-thrus. Much was made of what a great thing it is to install ABS or PVC pipe thru the ICF before you pour to make pass thrus for water lines, electric, etc. After building this thing, I call BS. It's a PITA to do this, generates a lot of dust & debris that have to be cleaned out (if you are an ethical contractor), and you have to figure out where everything goes before hand. Screw that...just get a big hammer drill and after the walls are cured, it only takes a minute to drill a 1-1/4" hole thru 6" of concrete, and it's easy because you marked where all your vertical rebar is so you never have to worry about hitting steel, right? :-)

Well, that's enough out of me for now and I have to get back to work. I hope these tips are useful. If I ever did another ICF structure I would do everything I recommend above in a heartbeat.

You must have softer aggregate in your walls. The stone in my concrete mix is HARD. Even with a proper hammer drill (not a regular drill with a hammer function) I found drilling to be a major hassle.

Good point about debris in the forms. I used a leaf blower to push it into one area, then sucked it out with a shop vac. I was able to consolidate it near a window buck, making it easy to access. I cut all of my large openings by cutting the blocks, then putting them in place, so no dust, but there was some from drilling holes. It got cleaned out with the pine needles and leaves. Do all of your cleaning out before the rebar is placed, if possible.

Things I learned I had a builder do my house as I was overseas at the time. 1. make sure any holes that need to be in the walls for oil tank fill(northern Maine)air exchange ducts, direct vent boiler duct work if using one, sump pump pipeing etc is WELL PLANNED OUT and sleeves are installed prior to the concrete poor. My builder did not and it was a PITA to drill 6 inch holes after the fact and no need to if properly planned out. 2. Outlets. plan plan plan where you want your outlets as adding after the fact is not that easy. although with wireless ones now it is simpler. 3. spray foam and caulk around all windows very good prior to installing the final trim. 4. buy an appropriate size air exchanger, very important and make sure the installer actually knows how to BALANCE it. mine did not and I did it my self with a magnehilic gauge I bought, plus mine was sized 4 times to large for my house. Make sure he installs a back draft damper on it also. 5. I had the heat and air exchanger on for a couple of months prior to finishing the inside to help with the moisture issue in the walls. huge amount of water. my house is 100 percent knotty pine and it was also in the house uninstalled during this time to help it get "climatized" as you would. 6. enjoy the insulation benifits as I do. I live in northen Maine and use way way less heating oil compared to other new houses in my area. Larry

Hmmm- Let's see if I can figure out how to attach pics. To describe what I did- I planned on mounting my windows on the outside. For 6" Fox ICF, I used standard 4-1/2" window returns. I made my bucks 5-1/2" per side oversize, for a total of 11" wider than the window rough-out. After pouring, I made sub-frames for the windows, and angled everything 45 degrees. Once all of this stuff was in place, I used a SawZall to trim the interior ICF foam to 45 degrees, using the subframe as a guide. I left it a little 'fat', and used a SurForm rasp to get it perfect. The angled return is covered in drywall. I trimmed around the window with 1X angled to fit. Because of the sub-frame, I had a large step in my windowsills, so I framed the front with a 1X, and fit 2" foam to fill it in. This was covered with a wide board on top for finish.

First pic is a section view of the wall/buck detail:



Sorry all of the little details aren't labeled. From the buck, there is a 2X, then a gap filled with 1" rigid foam, then another 2X. The final 2X is the actual frame the window mounts in. On the outside, there is a piece of 5/8" plywood to help hold things together, then 2" rigid foam as a thermal break. I used construction adhesive and long timber screws through the entire assembly to make it strong. The drawings is a bit obsolete, as I didn't use the block of wood that goes horizontally near where it says 'outlet'.

Here's a pic of the unfinished window:



And finished:





I don't have any closer pictures of the windows, but can upload some of you want, and I also have some pictures of the process. I just need to upload them to photobucket. You can see how it makes the windows seem bigger and let's more light in.

Those look great! The outlet is a neat touch, now you have a convenient place to plug in your "leg in stocking" lamp I am doing something similar but my wall plan includes an interior stud wall. My windows also have a deeper return(6 1/2") so are more near the middle of the 6" fox blocks. Because of this my 45 degree bevel will start further into the room. I am going to trim off the inner corner of the buck at 45 degrees and continue that line out thru the stud wall framing... That can be the problem with a thick wall. All the windows look like tunnels unless you go really big on the window size. I think the flared openings really open up the apparent view and enhance the light distribution...

The outlet location is for the kitchen windows. I wanted the outlets in the window returns so they wouldn't be in the way on the countertops. I asked the inspector if they were OK like that, and he said, "Well, I would approve them, but that's not saying another inspector will." Apparently, they were OK, as nothing more was said. I used 6-1/2" deep windows in our basement, where the walls are 8" Fox Blocks. You can't see it in the pic, but the window returns in the kitchen have beadboard panels to match the cabinet doors.

I am planning to use flooring on the lower sill return as the size and height make them a natural place to sit, especially for the animals...

So what is the worse case R value between the interior and the concrete in the center of the ICF (window sill, top, etc)?

Posted By jonr on 05 Jan 2016 07:57 PM
So what is the worse case R value between the interior and the concrete in the center of the ICF?

For my wall? R25...

I suppose with just plain ICF, about R-12 or 13. I went around with a surface thermo to check surface temperatures once the house was heated, but not yet finished. The exposed concrete where the window sills are now was 55 F. during the coldest part of winter. What I don't know is whether the entire core was 55, or if the exposed concrete was being heated somewhat by the room temperature. That's why I insulated under my windowsills; to create a thermal break. I've been meaning to drill into the core and check the temperatures throughout the year. Our climate in upstate SC is pretty mellow. We've seen a range from +3 F to 107 F.(!) but the un-conditioned walk-out basement stays between 60 to 78 F. Yesterday was the first time this season we used the heat on the main floor. ICF seems to really perform well in our climate. We just went 3-1/2 months without using HVAC at all. We'll run the heat for a few months, and then get a few 'free' months before summer really sets in.

we left a thermometer stuck in second story closet wall of one of our last houses we finished. Was 53 degrees 18 feet above grade. Maintained year round. No bad for a bunch of foam legos.