Crestone Domes

After we got the foundation done, it was time to build our ICF stemwall.
ICF blocks are 8′ long and 18″ high. They can be used inside out or upside down, so they are easy to work with. The only thing to watch out for is that the webs must match. If you look at an ICF block, you’ll see a row of diamond patterns every 8″. These are the nailers that you can use for sheet rock, hanging cabinets from and so on. So, all the webs have to be aligned on top of each other. If you don’t align them, the whole project can become a nightmare.

The other thing to watch out for is that if you need to make cuts, try to cut on a cut-line. Up against the windows, you don’t have to worry about that, but if you have to use smaller pieces of block somewhere, they will snap together without problems if you cut them on the cut lines.

Third thing to watch out for is to alternate the corners every row. The corners have one short and one long side, so on every row, you should have one corner with a long end, and one corner with a short end, and on the next row, you switch them so they are always staggered. This is what holds your structure together.

Fourth thing is to make sure the blocks are snapped together properly. If they aren’t, you can get blow-outs and uneven walls, so knock each block with a hammer to make sure it snapped together properly with the block below it.

To start your first row, just line the blocks up next to eachother. Put your number 4 rebar into the clips inside the blocks and make sure that they overlap 20″. On our stemwall, we put the rebar in the outer clips all the way around.

On the second row we put our formlock in. Formlock is a piece of metal grid made to fit into the blocks and stiffen and straighten the wall. It is a major pain in the butt to put it in, but if you can do it, it does make a difference. Try to plan it so you’ll end up with a form lock row under the windows, and also at the top of the wall. They should go in every 2 rows, while the rebar goes in every row.

Putting in formlock is definitely not a girl’s job. A big heavy guy might be good for the job, or a big heavy hammer. Push, squeeze and knock until you get it in.

The stemwall was supposed to be 3′ high (2 rows). But we built it 3 rows high, and filled it half way up the third block so the join would be inside the block.

Before we could pour the walls, we attached a special ICF bracing system that can hold the walls straight when they are being poured. DON’T try to pour the walls without this system – if it starts to lean when filled with concrete, there is nothing you can do to rectify it. With the support system in place, however, adjusting the walls is easy. You just turn the legs, and the wall will move in or out as needed.

You also need to put in vertical rebar every 2 feet. We drilled the rebar into the slab before we built the ICF wall. Tie it to your horizontal rebar with rebar ties so they don’t move when you pour the concrete.

And last, but not least, all the seams between the blocks were foamed with special ICF foam, and also foamed to the floor. Diagonals were checked, and OSB bracing were put along vertical seams at the top of the wall. Lots of work!

And, if you want to save yourself some grief later, make sure you cover the tops of the walls with feltpaper and duct tape. You don’t want those knobs full of concrete if you are planning to build the rest of your walls in ICF, too. Keep them clean, and you’ll be glad you did…

Tags: Building with ICF

The first thing to do is to calculate the concrete. If you are mathematically inclined, you can do it yourself with a simple calculator. Just remember to calculate everything in feet, so if your slab is 4″ thick, that is 1/3′. If this doesn’t appeal to you, CLICK HERE to get access to a concrete calculator that will do it for you.
Before calculating the amount you need, you have to try to get the pad as level as possible. We actually got down on our knees with a large level and scraped and raked until it was as flat as we could get it. A little over the top? Not really. If you are trying to calculate the concrete for a 42′x42′ square, and you are 1/4″ off on your measurements across the whole pad, that adds up to 1.4 cu yards! It doesn’t take more that a 1/4″ discrepancy to screw up your calculation!
This is why people end up either short, or they’ll have 2 yards of concrete sitting somewhere on their property, and I tell you, 2 yards of concrete is hard to hide!
Anyway, on our pour, we ended up with half a bucket left over! We did the measurements as accurately as we could, after flattening everything with a level, and then we added about 1/2 yard to that, and it worked great!

Tags: Concrete pour

The foundation pad was very big, 42′x42′, and we wanted to do it ourselves to avoid paying to have a full crew. So, we came up with the idea to section off a 10′ outer ring, and do the ring one day, and the center the next. We made some temporary forms, level with the outer forms. Finally ready to pour!

Tags: concrete preparation

This is what it looked like before we put the plastic on top.

After all your plumbing trenches have been filled in and the ground has been somewhat flattened by machines, it is time to check your levels. If you take the time to rake away the high spots and filling in the low spots, it will be much easier to calculate the amount of concrete needed. So, whatever time you spend leveling is well spent.

Here, we used a long level to move the dirt around with. Dig up any rocks that are in the way, as long as they are of a managable size, and leave whatever you can’t move.

After we flattened the ground, we put 2″ of gravel on top and buried a 4″ pipe with a t-piece on the bottom into the gravel. This will become a passive radon system later. In Colorado, the radon levels can be very high in places, and putting a pipe in under your slab, with a vent going through your roof, makes all the difference in the world. Then the gas can simply get out from under the house, without actually going into your house. It costs a few hundred dollars in gravel, and a bit of labor, but it is well worth the hassle.

Around the edge, we suspended 3 rows of number 5 rebar. We simply made up some u-shaped piece of rebar that were knocked into the ground, and tied the rows on rebar on top of theses. Don’t forget to put an L-shaped piece of rebar in for the electrical grounding!

In Colorado, you have to ground your electrical panel, and any copper pipes, to the rebar rings in your foundation. So, what you need is an L-shaped piece of rebar tied to all three rings, sticking up from the concrete enough that you can tie ground wires to it.

After spreading the gravel in an even layer, we covered everything with thick black plastic, taped together, to keep the radon gas from entering the house.

After marking the foundation with stringlines, the forms must be made. Nigell likes to make solid, elaborate forms where he puts 2×4 lumber on the top and bottom and OSB on the side. Then he puts small blocking pieces on the inside, so you can actually walk on the forms without crushing them or changing the angles. But, from what I have seen others do, this is probably a bit over the top. Normally, people put 2×6 or 2×8 lumber in place and secure them to metal stakes at the right level all the way around.

Anyway, however you choose to create the forms, remember to double check all your measurements, especially the diagonals. After the forms are in place, you should also redo the stringlines that mark the interior walls that have plumbing pipes in them, to make sure that the plumbing pipes are still coming up in the right places.

In our case, we are making a 3′ crawl space under the house since Colorado code no longer allows plumbing pipes in the attick, so we’ll run electric, phone and gas pipes under the finished floor at a later time. But, if you don’t plan on doing a crawl space, you must also make sure that the main electrical wire and the phone line comes up exactly where they are supposed to be.

Tags: forms, foundation preparation