Let’s Talk ICF For Our New Off-Grid Home – Part 1

There are any number of construction materials and methods a person can use to build their new home. The traditional method is stick frame using conventional framing lumber. That’s the method we chose for our last 2 off-grid homes. As many of you already know, we opted for a different method this time. Let’s talk ICF for our new off-grid home.

Lugging Buckets of Rocks Out

ICF (Insulated Concrete Forms)

ICF is short for Insulated Concrete Forms. Although the concept is not new, it has taken some time for this construction method to really catch on. I knew absolutely nothing about ICF until someone mentioned it in passing. It sounded interesting but working with concrete is not one of my strong points. I’ve done very little with it other than mix some stuff by hand a few times.

I did some research on ICF and found many manufacturers, each touting they had the best product. How do I sort out the best manufacturer and supplier? A friend had visited a trade show recently with an ICF booth and subsequently, we went and talked to the representative who gave us samples of the forms and form corners to play with.

Nudura and Bird Stairs Ltd.

An acquaintance suggested another company to check out, Bird Stairs Limited. Bird Stairs (http://birdstairs.ca/) is a company I had not heard of before. Not surprising since they only have a presence throughout the Atlantic Provinces and we’ve only been in Nova Scotia since spring. The brand of ICF they carry is Nudura. My suggestion to anyone considering ICF is to physically look at as many different brands as you can before deciding on what block you will use. I looked at 3 different blocks that were available in my area and it was an easy decision to go with Nudura.

That decision was made all the more easy by the customer service experience I had with a couple of the Bird Stairs sales guys. There’s nothing more aggravating to me than to ask a series of questions from a company and get partial responses or glossed over answers. So when Jeff Pineault and John Connely out of the Halifax/Dartmouth Branch office not only answered the questions thoroughly but offered suggestions and alternatives I might consider for our project, I knew I could count on these guys if need be. Jeff, a trained Nudura installer, even came out personally to demonstrate the building blocks and leave some samples to work with. After using the block and being well under way on our project, I’m confident we picked the best product and support team to help us along the way. If you are in the Atlantic Provinces and are thinking about ICF for your building needs, I highly recommend talking to either Jeff or John in Halifax sales. I’m confident you will get your questions answered and they’ll point you in the right direction for service in your particular area.

Johanna and I are the hands on type of people and are not afraid to tackle the toughest of projects. We have considerable experience from building our previous homes as well as camp construction. Having said that, I would not have attempted to build our ICF home without first reading the Nudura’s installer manual to get familiar with the techniques as well as having an experienced professional advising and overseeing us along the way. It is imperative that it be done right!

If it has required paying somebody for their time, we have done that to insure we were building a high quality home. There are also installer courses that I would have taken if it had been available prior to starting my project. I still may take one as there seems to be a demand for qualified ICF installers.

The bottom line is unless you have previous construction experience and understand the mechanics of proper home construction and unless you have professional oversight, it is best to hire the pro right from the start to build. I would get references and personally talk to previous customers of any contractor you would consider hiring for your new ICF home.

What is ICF?

So what is this ICF system? It’s pretty clever engineering. In the case of Nudura, it consists of roughly 2 ⅝ inches of expanded polystyrene insulation, EPS (think Styrofoam which is a Dow product) per side with hinged plastic web ties joining the panels spaced every 8 inches on center in the interior. In our case, we chose a 6 inch concrete core wall so the void between the 2 pieces of EPS foam panels is 6 inches wide which will be filled with concrete. So in essence, we will have an insulated 6 inch reinforced concrete wall with 2 ⅝ inches of EPS board on each side of it which not only acts as the concrete form but is also the air and vapor barrier.

ICF Being Delivered

The hinged webbing allows the blocks to be shipped flat and then at the job site, it is very easy to open up the forms so each side is open and parallel. Each of those webs is spaced every 8 inches and has a tough high density plastic (polypropylene) flange 1 ½ inches wide that acts as a stud. When it’s time to finish the interior and exterior, I know I have a well marked pattern on the surface of the EPS showing the fastening locations across the entire wall.

The Makings of Our House

My understanding is that Nudura makes the largest ICF block in the world so each piece I put up builds 12 sq. feet of wall. Each block comes in 8 foot lengths and is 18 inches tall. That’s the standard building block. Then there are corners shaped in an “L” pattern with one side longer than the other. This allows each successive course as we build to overlap and lock the course below. There are precise lines on the face of each EPS side. The top and bottom of the blocks have protruding nubbins that securely interlock with the courses above and below to provide additional stability and strength during the concrete pour. It’s like building with lego blocks.

If we do some simple addition we get a very interesting and useful number. 2 ⅝ + 2 ⅝ + 6 = 11 ¼. The width of a standard dimensioned 2 X 12 is exactly 11 ¼. We built what are called window and door bucks which are essentially rectangular boxes made out of 2 X 12 that we will fit our doors and windows into. The width of the 2 X 12 is the exact width of our wall. Pretty neat! Because these window and door bucks will be touching concrete, they must be made from pressure treated lumber.

Johanna Placing Form Lock

At the time of this writing, we have 6 courses up and filled with concrete which is a wall 9 feet high. Because the overall height of our walls will be 15 feet, it was deemed safer to fill the walls in 2 pours instead of one big one. Keep in mind, the walls are containing a tremendous amount of volume and weight of viscous concrete and although uncommon, there is at least a small potential of a “blowout” if a person does a poor job or weakens an area with careless workmanship.

Lesson learned

A Good, Level Footing to Start With

I can’t stress enough how critical it is to build a level footing, since it sets the stage for building a level wall above. We were able to lay our first course of blocks and continue on without shimming. However, I did make it harder on myself than need be. I poured the foundation and then went on vacation figuring this was a good opportunity to let the concrete harden. I didn’t realize that ideally, I would need to fit a wooden shoe around the outside perimeter of the first course of blocks and secure the shoe to the footing. That wooden shoe required pounding concrete nails. I found out it is near impossible to pound a concrete nail into 45 day old concrete.

Here’s what I did. A few days after my footing was poured, the concrete was set. I removed all the wooden forms and cleaned the concrete residue off all the lumber as best as I could. Then I stacked the lumber so it wouldn’t warp. That lumber will be perfect as scaffolding once the walls are braced. More on bracing in my next post.

A couple of times a day, I sprinkled water on the footings to slow down the drying rate. Concrete gets stronger with less shrinkage if it can cure slowly. Then I said “arrivederci”, “cheerio”, “sayonara”, tata, exited stage right and got out of dodge.

What I should have done at this point is hit the breaks and spent a couple more days at home. I should have run chalk lines down all 4 footings to create a visual line for where to place my blocks. The chalk line would have been a visual reference that our walls are straight and true. Then I would have measured my diagonals to insure they are equal signifying a square building. Next I should have laid out the first course of Nudura building block. In theory, those blocks would be right on the chalk line all the way around the perimeter of the building. At this point, I should have taken some 2 X 4’s and nailed them around the outside base of the first course on the footing with concrete nails so that there would be no way the walls could move outward. All of that is what I should have done before leaving for vacation.

Getting Started

Once we returned home from vacation, the concrete was hard and I spent a great deal of time bending concrete nails. For every nail I was able to pound partially in, I bent 2. Quite frustrating! So the lesson learned is if I need to drill or nail something in concrete, it’s a lot easier when the concrete is “green.”

One last note for this post. The dimensions of our house are 36 X 44 feet. As it turns out, that is a perfect utilization of the Nudura block. Virtually no cutting. The blocks are 8 feet long and the 2 corners that make up a wall are 4 feet. At the time Johanna designed the house, we had no idea we would use ICF or that the Nudura blocks and corners would match our dimensions perfectly; we happened to luck out on that. It made building with these blocks a little easier since everything just lined up properly right from the start and the next course, which overlaps the joints on the previous course, fit together properly.

In my next post, we’ll continue building from the first course. Although it’s a simple building technique, a lot of careful thought and laying out is required. This is concrete after all. Best to do it right from the beginning. Keep in mind, things like water and electric have to get through that concrete wall. Osmosis doesn’t work here.

Until next time, keep the dream alive! We wish you a great day!

Ron and Johanna

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