Today we finished making forms along the top of the channel block and filled them. This brought everything to a perfect level (okay, 1mm over 20′) with the poured wall all the way around the tiny cottage. By doing this we’ll have all our windows set at even heights and the block walls that follow will also be starting on an even, level height. This channel beam also increases the strength of the entire building. Up at the top of the walls we’ll do another one, locking the whole house together with a ring bond beam.
We made the forms using 2″ pink board insulation and toggles we made from screws and wire. This was a simple and easy way to quickly setup forms a little above the height of the channel block. Just wrap a wire around a screw, or a nail or what ever. It takes three toggles per section of pink board across the block wall. Get the foam form level and then stick the pointy end of the wire through the foam – getting that at the right hieght, just over the block, is the hardest part of this easy process. On the other side, use a stick with a hole in it, or in our case we had wiper blades from toner cartridges, and twist it to pull the wire tight. This locks the foam up tight against the block wall.
Here’s the toggle in use as well as one that is ready to use. Once it was in place we double checked all our levels, poured cement into the channel, floated it and inserted anchor bolts. In a day or two it will be ready for us continue raising the block wall.
That was the morning’s work. While we let that cure we spend the afternoon getting blocks organized on the slab for building more wall. Then we mortared up the initial course of the first two interior walls with partition blocks (4″x8″x16″). Working with the tall, thin partition blocks was a new experience. Standard Concrete Masonry Units (blocks or CMU’s) are very stable. Partition blocks are not nearly as stable. I will not be dry stacking these but instead will mortar the entire wall. Additionally we’ll add rebar vertically and tying to the outer wall after we take the insulation off of the inner walls.
If you look very carefully at the large photo of the work site at the top (click on it) you’ll notice that the mortared initial course of the partition block does not touch the outer wall. That is because I left a gap for utilities such as wiring to go behind the wall. Once we get above the first course I’ll join the partition with the outer wall. This makes it so I don’t have to worry about plumbing, electrical, data, etc right now and can just focus on concrete work. Never do now what you can put off until tomorrow – you may get better ideas!
The last thing I did at the end of the day was cut a key into my beautifully floated channel block surface. I had spend a fair bit of time floating the cement to practice getting it smooth. This is a skill for floors and other surface that will be visibile – something this will not be. But such a smooth surface is not good for bonding the next level of blocks. To improve it’s bonding ability I took a stick and cut a groove down the middle of the surface where blocks would lie. This is called a key – it resists shear forces.
In addition to the key we do have the rebar as you can see in the photo at the top – that goes from bottom to about 6′ up the walls. I can’t have the rebar go any higher as I’m not tall enough to lift blocks higher and over it when building the upper wall. I’m trying to avoid using a step up for as long as possible. We’ll extend the rebar, overlapping 18″, when we get to the top blocks that are over the 6′ mark.
Tomorrow we’ll do more partition block as well as start laying up the upper wall block on the poured wall. I’m hoping for continued summery weather…