Posted By jeepster on 04 Jun 2011 09:11 AM
Last Thursday I poured my first ICF basement.  This is my own house, so I get to live with any consequences.  I'd say it went 85% OK.  But honestly, I think it would have gone 95% OK if I didn't have the block rep that gave me crappy advice.  I still have the next level to pour, and I don't think I'll invite him over. 

Here is a list of things that didn't go so well:

1.  Many of my walls are bowed in.  One is bowed in up to one inch, and yes, it's the wall that everyone will see pulling up to the house.  My rep came and cranked in those braces way too much.  The theory is that the wall will flex to the outside and it's hard to pull the wall back into alignment.  I originally had the level bubble favoring the inside line, but he loosened up those braces and said it's easy to push the wall into alignment.  The wall obviously didn't move that much, if at all.  The pump truck operator (who used to build ICF houses) said they pull the walls in a max of 1/2 inch. 

2.  We waited way too long to adjust those braces.  When that concrete starts to sets up, it's next to impossible to make those walls move.  I figured if I'd get one wall to move, it would be a 28' wall with 4 windows and a 6' door opening.  All my braces did was bend the rebar stakes when I adjusted the turnbuckles . . . I decided to make a potentially dangerous move and I hooked my truck up to the top of the middle brace with a chain and pull.  Letting the truck pull downhill in neutral didn't make it budge.  Putting it in 2wd and giving incremental gas until the wheels spun didn't make it move.  Finally putting it in 4wd and spinning the wheels got me about 1/4" of movement.  Mind you this wall was the wall with by far the least amount of concrete.  Long and short, waiting until the end of a pour to true the walls was horrible advice.  I asked him after the first lift if we should plumb the walls, and he said just wait until we are done, that was VERY poor advice.  It's going to be a lot of work to make siding look good on that wall.

3.  He told me to not bother tap conning the braces to the footing.  I did anyway, but on about 5 braces where I had to move them because of window strapping interference, I didn't bother re-tap conning.  Not tap conning the bottom of the brace allowed the brace to move up the wall while adjusting instead of hinging on the footing.  You simply cannot expect #10 screws anchored into plastic to hold the brace against a wall that weighs at least 40,000lbs.  This was only an issue with the braces that I moved, but it was poor advice, none the less.

4.  Putting the rebar in the corners for the wing walls after the pour was complete.  I got one piece of rebar in.  The rest I'll have to drill because the concrete was set up too firm.

5.  Lift heights.  The pour was 10'6"  The first lift went about 5'; the second lift went about 4'6", and the last lift went about 1'.   I feel this was responsible for a lot of bulges.  The mix was obviously wet and coupled with the vibrator and the height of the lift, I'll have more rasping and trimming to do than I think I should have.  If you're going around the wall three times, might as well make the lifts shorter to relieve some of the pressure, right? 

6.  I didn't have any blowouts, but I almost did.  Once corner end joint broke out about 2", but it didn't spill any concrete.  My rep told me to simply spray foam the bottom course to the footing and that would be enough to hold back the pressure.  That might be true if we were pouring shorter lifts, but it obviously wasn't at the lift height we were pushing.  If the corners are the most susceptible, then go ahead and screw 2x4s to the footing to hold the form.

Things that I will/would do different:

Mind you that my footings were spot on and my forms were high-end.  The type that click together (trying no to drop brand names), so given a do-over:

Pre-pour:
-tap con braces to footing to prevent brace lift during adjustment
-if you have a large amount of fill that you are staking the braces too, either go down to virgin earth or pour mini- pads for your braces.  This would help prevent your stakes from bending.  I had about 6" of fill above the basement grade, and it allowed the rebar to bend when adjusting the turnbuckles.  I don't think this would have mattered, because my walls were too set up anyway.
-Big one! Tilt the walls in no more than 1/2 inch.


During pour:
-monitor the movement after the first lift.  If there was no change, then have someone start plumbing the walls while the concrete was still fluid, or at least split the difference.
- pour all the lifts 3-4 feet
- if you need rebar sticking out of the corners for wing walls, do it once the concrete stiffens, but don't wait until the end of the pour.

I didn't want to pour without the block rep on site, since I didn't have any experience at it.  He reportedly had over 50 pours under his belt so I was really relying on his advice.  I think If I went at it alone with the education learned here and the advice from the pump truck operator, I wouldn't be writing this email and I'd be sitting happy with a pour that went well.

Posted By BrucePolycrete on 05 Jun 2011 11:42 PM
Eric, my friend. Do the homework. Withstands over 1,600 lbs per sqft of lateral pressure. At 2,000 lbs, the testing machine broke. Nothing else comes close. This ICF functions on a scale that others can not even conceive of. Look at the pictures -- they don't lie. How strong is your preferred form? By the way, this wall as shown is 8 ft tall.

Posted By eric monkman on 06 Jun 2011 10:58 PM
I'll take Logix, Amvic, Nudura, Fox, Buildblock, Superform, Greenblock etc anyday over your dinosaur.
Take another swig buddy.

How much vibrating did you do? overvibrating can create alot of hydraulic pressure

Posted By jeepster on 07 Jun 2011 08:42 PM
I discovered something else while measuring for floor trusses today.  Notice the gaps between the corner blocks and the flat blocks.  Those gaps weren't there before the pour.  The hyd pressure in the walls really pushed the outer section of the corners out.  The inner section of the corners look good.  This is more evidence that either the slump was too high, or the lift was poured too high.  I'm going with the lift was poured too high.

My rep said I only had to zip-tie the top block to the adjacent block. After this, I think it would be wise to either tie all the corner pieces to their adjacent blocks, or run some strips of wood from the corner pieces to the adjacent blocks.