Editor’s note: Kent Earle and his wife, Darcie, write a blog called Blue Heron EcoHaus, documenting their journey “from urbanites to ruralites” and the construction of a superinsulated house on the Canadian prairies. Their previous blog on GBA was called Let Construction Begin. The blog below was originally published in June 2015. (A complete list of Kent Earle’s GBA blogs is provided in the “Related articles” sidebar below.)
While we attempted to work out the problems with site work, the foundation work continued to move forward. I wrote earlier about our decision to use the Nudura One Series of insulated concrete forms (ICFs). We were quite excited about this product for a number of reasons.
First, basements are generally boring. By using this system of ICFs we could have a finished interior wall of concrete immediately, which would look aesthetically pleasing and be something of interest, something unique, for our basement. No need for any extra framing and drywall.
Second, in terms of energy efficiency, this system should perform better than conventional ICFs. With this system, you are not insulating the walls of the basement from the house itself. (Standard ICFs and standard poured-concrete basement walls have insulation on the inside and cannot get any benefit from the thermal mass of the basement walls.) Since we have a huge thermal mass in the walls and floor of the basement, the concrete can store a lot of heat (heat collected from sunlight or simply added by the in-floor hydronic heating system) to radiate to the rest of the house — essentially functioning like a giant battery.
The forms were delivered about a week before they were needed. There was an incredible amount of insulation that was stacked in the shop. And the day following our stresses with the septic system, Taylor and Curtis got to work building the basement forms. They had budgeted about four days to get the forms up and one day to pour. “ICFs go fast,” they said.
Nudura forms are slow going
But not these ICFs. This basement was a massive pain in the ass. After one day, the guys only had one of seven rows done. There was no simple way to attach the forms and keep them locked in place. You see, with standard ICFs, the blocks are basically like Legos. There are little grooves on the inside and outside that line up and attach to the corresponding little plugs on the other block. Snap snap snap — it goes together. Easy.
Assembling Nudura forms was not easy. The little Lego grooves and plugs were only on the outside of the blocks, not the inside, as the plywood slabs simply butted together, creating big seams and gaps. (Wouldn’t tongue-and-groove plywood have made sense, Nudura!?)
Frustrated at the lack of progress, Taylor called the Nudura sales rep, who came out to the site. Amazingly, he had never seen the Nudura One series before. Like, never ever. As they all worked together to try to troubleshoot this problem, they eventually decided to call the technical support team at the head office in Ontario, Canada.
They suggested making 2Ã—4 L-brackets to support and anchor the forms. (Uh, that’s part of the plan?) Oh, and as for the gaps in the plywood — where concrete would completely burst from when pouring? Well, just use Tuck tape, they said. Tuck tape!?? (I suppose it’s slightly more classy than using duct tape.) Jeez Louise.
Unfortunately, after building a bunch of the 2Ã—4 L-brackets and bolting them onto the forms, the carpenters realized that this was not going to work at all. These brackets did nothing. If anything, they made the problem worse by pulling the forms further inwards, causing even greater warping of the walls. Thanks for the “technical support”!
(You’d think they’d never sold this product before. We later found out that they had never actually used these forms in a residential application.)
Over the following four days, Taylor and Curtis grudgingly put the forms together and stacked them higher and higher, eventually reaching the top, at 10’6″. They put an absolute ton (perhaps 2 tons) of rebar in the ICFs, both vertically and horizontally, to reinforce the high walls and provide the structural support for the beams, joists, and double walls that would sit upon the foundation.
Seeing the forms go up was pretty exciting, but just don’t look too closely or right down the line of the wall…
Because that ain’t straight.
I have to admit, I was more than a bit worried. I wondered, how the hell were they going to straighten these walls?
Taylor and Curtis had also eaten through their projected timeline and still had to try to straighten the walls. After four days, the walls were not even stacked, let alone straight and ready for concrete. Over another three days, all they did was straighten and adjust the walls, using large bracing and strapping to make them level, straight, and even. When Taylor finally told me they would be pouring concrete the next day, I had to run over and make sure.
Praise the Lord! (This whole process is making me become very religious, it seems.)
The following day, the pumper truck arrived, pumping a buttload of concrete into the basement walls. Now was the real test of the untested Nudura One walls and the MacGyver skills of the build team.
I was nervous that day at work, just waiting for the phone call from Taylor explaining that there had been a catastrophic failure, when the walls of the forms burst under the pressure of the concrete, causing the walls to break apart and concrete to fill our basement.
But that call didn’t come. Relieved, we drove home at the end of the day. The walls were still standing and they were filled to the brim with concrete!
The next day we would pull the plywood off and see what magic laid beneath.
P.S. Nudura has offered to cover at least some of the extra time of the build team for Research and Development of the Nudura One series.
Concrete wall reveal
The day following the placing of the concrete, we were ready to pull off the plywood forms and see what lay beneath. Leaving the plywood on for more than a day would cause the plywood to adhere too firmly to the concrete and make the sheets extremely difficult to remove. We were a bit nervous. We had been pegging a lot on how these walls would turn out — they would be, after all, our finished interior walls — so I really hoped they wouldn’t look like crap.
First we had to remove all of the exterior bracing that the builders had spent four days installing, tweaking, leveling, and straightening.
They had done a great job. The walls were perfectly straight and square.
We started unscrewing the plywood forms, and — cha-ching!
They looked frickin’ awesome!
As we removed the forms, I had to chuckle, because the builders, who had for the previous week been cursing the Nudura One system, said (as they saw the finished look) that they would “use it again.” I guess that, from time to time, looks do make up for a bad personality.
We spent about two hours removing all of the forms. As we got towards the base of the floor, we crossed our fingers, hoping that it had all settled nicely to the bottom without any “honeycombing” of the concrete that would need to be parged. Impressively, it looked excellent all the way from top to bottom.