The foam that the ICF blocks are made of is fairly vulnerable to damage from impact (e.g. getting hit by a board or rock) as well as from UV damage.  Nearly all of it will be covered by the siding on the outside or drywall on the inside, but there is a small strip just above the grade that will be left exposed.  This is by design, as even though we are using cement fiber siding it is not advisable to fill up onto the siding and thereby bury the bottom edge of the siding.

In order to protect this strip, we started applying a product called Dryvit. I’m not sure about the chemical makeup of Dryvit, but you mix together a half of a bucket of Dryvit with 1/3 of a bag of Type I/II Portland Cement.  This creates a fairly workable mix that can be spread with a trowel.

To apply it, we spread strips of it vertically every 18 inches or so along the surface to be covered.  Then a strip of fiberglass mesh 24″ high is stretched out along the wall just above the ground and embedded in the strips of wet Dryvit.  Pressing the mesh into the surface with a trowel serves to hold it in place, and then you go back and cover the whole area with Dryvit, smoothing with a trowel as you go.

It sounds a bit easier than it is, and since it is a cement-based product, the length of time since it has been mixed and the temperature makes a big difference in how difficult it is to apply and smooth out.

One very important step is to remove the top layer of foam to make sure there is a clean surface to adhere to.  This can be done with a long handled broom or something similar.  The reason I know this is important is that I forgot to do it on the first wall that I did unsupervised by Doug, and he was able to easily peel it off a few days later as a result.

This is not terribly difficult to do, but is fairly difficult to do well so that the surface is smooth.  I can’t remember too many house projects that I’ve done so far that have made my arms quite so tired.  We still have quite a bit left to go, and it will need to be completed before the house is wrapped with Tyvek and the siding is put up.

One of the constant background projects we have is extending the concrete driveway toward the house. We try to keep roughly sixty feet of forms set up at any given time so when the opportunity comes up we can extend it. Forming a driveway is about as simple as it gets, but it takes a little practice.

The first thing we did was stretch a string line down the North side of the driveway. One stake was driven at the top, and another down the hill with a string stretched tightly between them. This provides a visual reference for keeping the side of the driveway straight. Then another metal stake is driven so that the center of the board will line up with the string, and a 2×4 is nailed to the stake at the desired height. Each 20 ft. board has three or four stakes to support it, and to connect two together you just hold the ends together and toenail them.

Once one side is straight, we take a spacer board whose length is the desired width of the driveway, and stake and attach the boards on the opposing side in the same way, making sure that the distance between them matches the length of the spacer board.

The distance of driveway poured is determined by the amount of concrete as well as the thickness of the slab (the higher the form boards are raised, the thicker the driveway will be). The spacer board becomes a floating end which is dropped in where the concrete runs out.

Doug has a magnesium screed board that is rested on top of the forms and dragged along to create a level surface. Having the right amount of concrete is a bit of an art, as trying to drag too much wet concrete with the screed board will wear you out quickly.

Once the surface is relatively flat, a bull float is run over the surface to smooth it out. This also reduces the surface area of the driveway, which will slow down the drying time and give you a bit more time to work with it. When it is still a little wet, we run an edging tool around the top of the forms to soften the top edges of the driveway, and cut joints every 10 or so feet with a handheld jointer. The joints give the driveway a natural surface to crack as it cures and shrinks, in order to prevent ‘unplanned’ cracks in the surface.

The final step is to broom the surface with a large flat broom head. This adds some texture to the surface to keep it from being too slippery. Once the concrete sets up (generally by the next day) you strip the forms, pull the stakes, and extend the string line if needed and set everything up again at the end of the slab.

The degree of difficulty is influenced quite a bit by the consistency of the concrete, and concrete that is too dry can be really hard to move around.

So far we have done about 150 feet with several hundred to go. Here are some pics of what we have so far.

On Tuesday my friend Grant came by to say hello and check in on the progress at The Casa. He made a comment along the lines of ‘that doesn’t look like any framed house I’ve ever seen…’ Since I have heard that several times since starting the project I thought I would take a minute to explain what Insulating Concrete Forms (ICF) are and how they work.

Although it is not yet widespread in our area, ICF represents a whole new set of options for new buildings, including residential construction. ‘Stick built’ or wood framed construction is still the prevailing choice, and it seems that most of the subcontractors are so accustomed to working with wood framed walls (read: they can do their work very quickly without a steep learning curve) that they don’t want to do anything but that. There have been some very welcome exceptions to that to be sure, and I’m sure in time more of the trades will continue to focus on this new building trend.

Even construction with brick or stone, like my father’s house, is essentially a facade applied over walls constructed out of (mostly new growth) timber. This is necessitated by the relatively low insulating value of brick or stone on their own. They are all fairly good thermal conductors, meaning that temperature changes on one side of the wall will be relatively quickly transmitted to the other side. The use of fiberglass or foam in the stud cavities of wood construction allowed houses with masonry construction to improve their insulation factor.

Decades ago a primary limiting factor for the use of concrete was aesthetics. While construction with concrete reinforced with steel was fairly cost effective and enjoyed more longevity than the average wood framed house, overcoming the ‘ugly’ factor was an issue. More common in commercial construction, penetrating the residential market was difficult when the primary option was to paint the concrete walls (or leave them bare). Couple this with the fact that concrete alone is also a very good thermal conductor, and it is no surprise that there remained relatively few concrete houses.

These insulation and aesthetic issues are both soundly addressed through the use of ICF construction. There are a number of different manufacturers of the blocks (Logix, Fox, Nudura) but all employ an elegantly simple approach. Instead of a single-layer concrete wall, or a layer of wood frame covered with a brick or stone veneer, Insulating Concrete Forms consist of three layers. A standard steel-reinforced concrete wall is sandwiched in between two layers of rigid foam insulation. The materials themselves are cost competitive with standard construction, and the systems are arguably more simple to construct than standard stick-built homes.

The standard building block (in our house at least, built with Nudura) is shown above. It is 8′ long and 18″ high. The inside and outside is made of rigid foam between 1 1/2″ to 2″ thick. The top and bottom of each form has teeth (like Legos) that allow them to easily fit together to build up the wall. In the space between the two sheets of foam are rigid plastic webs that space the forms apart in addition to providing an easy place to snap in the steel reinforcement (rebar). At the top and bottom of each plastic web are small plastic teeth that click together when you assemble the forms. These teeth keep the forms from ‘floating’ apart when they are filled with liquid concrete. These straight pieces are combined with corners and t’s (all with the same interlocking components) to essentially form the negative wall space. Once the forms are assembled (an incredible variety of shapes and configurations are possible by combining different forms) you literally pour in concrete from the top to form the core of the wall. The foam remains in place and becomes a permanent component of the structure of the building, providing a huge insulation boost among other benefits.

Concrete construction that doesn’t use ICF involves building the forms, pouring the concrete, and removing the forms once the concrete has cured - which adds labor to the process and takes away from the r-value of the finished product. So regardless of the system you choose, you wind up with a simple mechanism to build the forms (anyone who can assemble legos can put blocks together), great insulation for the walls, a good vapor barrier to prevent moisture from coming into the house, as well as ideal surfaces on the interior and exterior to attach siding or drywall. I can’t speak for the other systems, but Nudura has a nailing strip that runs vertically every few inches, and acts just like a stud in a wood framed house - allows for trades to drive nails or screws.

There is a great deal of information about and discussion on the benefits of ICF construction just a Google search away, but there are a few that helped us make the decision, including the low cost of heating and cooling, sound insulation provided by the thick walls, and best of all no wood to decay and need replacing down the road. Additionally, while the expansive pale green walls may look a bit odd to folks like Grant right now, by the time the construction is complete and the siding is applied the house will be virtually indistinguishable from a traditionally constructed home.

Hopefully that is helpful in understanding ICF construction, please don’t hesitate to ask if you have any questions or I can clarify anything.

It has been something of a slow week at our Concrete Casa while we waited for the main level floor to cure before being polished.  We arrived at the site yesterday and met briefly with the HVAC guy to strategize on the location of returns, etc. and checked out the floor in the master bedroom.

It is incredibly flat and has no visible defects after curing for just under two weeks.  The floor over the basement is much thinner (2″ vs. 5″) so is a little more prone to cracking - there are two that have appeared so far.  That is very much par for the course, they will just be filled with epoxy before polishing.  If all goes according to plan Micah and his crew will be there early next week.

I also checked out my concrete stair treads - Doug popped them out of the forms and they looked a lot better than I anticipated.  As I thought, the corners are a little rough and the shape isn’t quite perfect given the hastily constructed forms.  I don’t think they will make the cut for the stairs, but would be great to make a walkway outside somewhere.  I’m planning to build some new forms as I mentioned, I just need to get some materials and carve off a little time.  I’ve also been reading up on another technique called GFRC - Glass Fiber Reinforced Concrete - that allows for the construction of much thinner panels for concrete countertops, etc., without the need for steel reinforcement.

We are going to work on some admin tasks this weekend and perhaps start building some forms for the driveway so the next time Citywide calls with some scrap concrete we will be able to put it to use.  I spent some time last week looking into cabinets (Ikea entered the race) so we will probably mask off areas on the floor for the cabinets and kitchen island to get a sense of the flow through that area.

The only other news is I think we killed the idea of using stone on the exterior of the house.  The panels and the silver roof lean much more to the modern while the faux stone is a lot more traditional.  We are going to replace the stone around the entryway with cedal planks, similar to the look you see here courtesy of ‘hotfunk.’

After all the prep work on the floor the prior day I hung around to watch the flatwork. I got to the house about 6:30 to put expanding foam in some of the cracks in the foam and cut some strips of metal lathe. Zane and Robert arrived shortly afterward, and the four of us double checked a few things and waited for the concrete truck to arrive.

‘Bob’ got there right around 8am, and backed the truck up to the bedroom window. I didn’t have any boots, so my role was relegated to handing tools and a few other miscellaneous tasks. As the concrete began to roll into the space, Doug and Zane used their ‘come along‘ tools (like a rake without teeth) to level out the concrete. It was pretty amazing watching them take the fluid mass and level it out out perfectly up to the chalk line. I followed them around, pulling up on the metal mesh to get some concrete under the pex tubing so it would be embedded closer to the center of the concrete rather than on the bottom adjacent to the foam.

Across the transition from the main floor we dropped in the strips of metal lathe to give the concrete a little support across the bigger drop.

It only took them a few hours to get everything smoothed out, and Zane and Robert left, and Doug continued to work on the floor with a bull float. The truck had about 3/4 of a yard of extra concrete, and between the scrap lumber, the extra concrete, and a plethora of tools the temptation was nearly irresistible.

Doug gave me a quick form building tutorial, and I built two quick forms out of plywood and 2×4’s in the shape of the stair treads. I worked in some of the still-wet pile of extra concrete, and went to work with the trowel and edger. When it was starting to set up, we sprinkled in some color hardener to shore up the surface and add a few experimental shots of color. The corners were a little rough and I’m not terribly confident in the integrity of the forms (especially since they are now curing sitting on the uneven driveway) but it was a very fun experiment. I read Concrete Countertops by Fu-Tung Cheng a few months ago, and it was great to see some of the concepts in action.

Now that I have a little experience (and relatively easy access to extra concrete, it would seem) I’m going to build some real forms and try to make another version of the treads. The ones I did today were right side up (with the showing side of the tread up) but I think It would be easier to keep everything smooth if I made them upside down, with the face of the stair inside the form. More on that later.

With the gravel subfloor leveled and all of the plumbing and ductwork installed, it was time to prep the floor for radiant heat. The idea is fairly simple, you embed closed loops of tubing (called pex) in the concrete slab, heat water, and circulate it through the floor to bring it up to the temperature you want.

We spent quite a bit of time getting the transition from the main floor, separated by a form partially filled with concrete from the pour of the main level walls, to the lower gravel subfloor cleaned up. That just involved breaking off the foam, cutting the plastic ties, chipping out some dried concrete and smoothing everything off to avoid any sharp drops that could stress the concrete.

Once that was ready, we laid sheets of extruded polystyrene foam flat on the gravel, cutting out notches and knockouts around all the plumbing and vents. The primary purpose of the foam is to prevent you from heating all the gravel in the subfloor, and keeping the heat in the concrete slab where you can feel it. Compared to everything else it was surprisingly easy, and within about an hour and a half it was all covered. To provide a surface to attach the pex tubing to we then cut strips off of a giant roll of rusty metal mesh. These each had to be bent backward to straighten them out so they would lay flat. Once they were laid atop the foam sheets, we just unrolled the bright orange tubing and attached it in two loops in rows about 18″ apart with plastic zip ties.

After clipping off all of the zip tie ends, the last step was to get the floor lights (a chain of three of them underneath the master bedroom hallway window) installed. We got quite lucky in that the lights were at the perfect height (level with the top of the floor) when they sat on extruded polystyrene foam boards. To hold them in place, we ran the plastic conduit underneath the metal mesh with the light boxes sticking up.

It sounds like a fairly straightforward process, but I’m quickly learning that most tasks take about thrice as long as originally expected. By the time we finished it was about 10:30 and we were working in the light cast from some temporary lights. The concrete trucks were coming first thing the next morning, so it was definitely worthwhile.

Jill and I went back down to Springfield this past weekend to take some boxes and see if we could lend a hand with the construction process. Additionally, we were supposed to meet with Jeff from Summit Roofing to confirm the color selection and put down the deposit for materials.

Jeff called last week to check on our schedule and to let me know that the silver color we chose for the standing seam metal roof had a four week lead time. I let him know that there wasn’t any problem with that due to the cure time for the concrete before it could be polished (and subsequently the walls and roof deck framed). He persisted, saying that it would be hard to tell which color we really liked, and that the galvalume would be very nice. I was a bit nonplussed, but figured it couldn’t hurt to see it in person before signing up.

We arrived on Saturday and went to the house to check out the floor, and before going to meet Jeff we were scheduled to meet with a siding contractor. He seemed competent if not a little odd (asking ‘So, what can I do for you today?’ after we described all the work we wanted done), and didn’t have any concerns about our plan for using the hardipanel siding. I asked about using some kind of J-Channel flashing between the sheets, and he asked if it was just for aesthetic reasons. I said that it was primarily to prevent from water coming in between the panels and he immediately insisted that was not necessary because the foam was waterproof. I’m no expert but I’m fairly certain that getting water underneath the siding is not a recipe for long term success. We’ll see if we can get that little mystery resolved.

We left to go meet Jeff, and as we were driving out I got a voicemail from him saying he couldn’t meet as planned due to his girlfriend taking him to Oklahoma unexpectedly.

Tired of contractor oddities we got some beer and sat on our new floor drinking them. That can never be a bad idea.

Sunday morning we got up early and met Doug to get our hands dirty. The area under our master bedroom / closet / bath was filled nearly level with gravel, and had all the plumbing for the vanity, tub, shower, and toilet installed. The ductwork for the HVAC that we got is plastic, and looked like large diameter sewer pipe. Using metal ducts under gravel isn’t a good idea as it tends to rust over time, collapsing and filling with gravel and probably leading to a whole host of nasty issues. To get the tubes in, I went to work with a shovel digging big trenches in which we laid the pipes and glued them together. It took quite a while as the pipe (which we had to special order) was just a few inches too short to be placed ideally and reach through into the basement. We made some…ahem…field modifications to extend the pipe and got everything put together before pushing the gravel back over the top of it.

The whole process was pretty tiring, and we topped it off by adding some additional gravel to get the floor up to level. By the end of the day we were ready to move on to finishing the preparation of the floor but out of daylight so we called it a day.

Jill finally got in touch with Jeff slightly annoyed by his ruse about the color change and told him just to order the silver that we originally wanted. It all became clear when I went in on Monday to drop off the deposit and sign the paperwork. I asked if he had a sample of the silver color on metal so we could use it to match with the siding, fascia, etc. and I heard him tell one of the office girls that they didn’t have it around ‘because that is a specialty color, and costs $.30 / square foot more than galvalume, that is why I tried to talk them out of it.’ I guess when you consider the fixed bid and the fact that that $.30 is coming out of their margin (and likely his commission) who could blame him. So it goes.

When you are building with Insulating Concrete Forms your cladding options are virtually unlimited, the smooth surface makes it easy to attach any type of stone, brick, stucco, or other siding.

Here is a link to a post on LiveModern.com, where Jill has found a number of good design ideas. We have been going back and forth between lap siding or HardiPanel, and have always liked the look that ‘Splatgirl’ has on her house exterior. If you look around a little bit you can find a lot of blogs where homeowners mention using this material.

Here are a few other images from an Architect’s site:

I think you would have to be careful not to look too industrial, but if done correctly I think this could look great on the exterior of our concrete house.

Micah and his crew came yesterday and poured the floor on the main level. This will cure for three weeks before polishing. If you look closely you can see the knockouts where the lights will be.

The last picture also shows the pillars that will be used to support the deck. Sweet.

Here are some pictures of the walls on the main level. I have to say that I continue to be impressed with the ICF system, the concrete walls are going to be incredibly durable and energy efficient. Our concrete house would probably hold up well to a tornado strike, although I’d prefer to never find out.