Jill and I went down on Friday of last week to square away all the financing with CBOR. Everything went off without a hitch, and they were encouraging us to borrow even more money, surely due to the paucity of construction loans right now.
I had been dying to get out to take a look at the site, and we spent most of the rest of the weekend lending a hand and trying not to get in the way too much. The pump truck was scheduled to arrive at 7am on Monday morning, and there were a lot of details to get wrapped up before it arrived.
Here are some of the things we worked on:
- Stacking in the blocks from roughly rows 4 on up. The long straight runs were pretty easy, you just snap the blocks together like legos. The challenging parts were when they didn’t fit exactly right, especially in corners and wall T’s.
- Laying in the steel reinforcement. Most layers got a single row of horizontal rebar, which snaps right into the webbing between the blocks. The horizontal pieces are alternated in terms of their orientation toward the front and back of the wall, to leave a spot to weave in a horizontal rebar every 4′ or so. Additionally, there are straighteners in the top of select rows. These look like little steel ladders, and the (mostly) snapped into the top rows of blocks to keep them straight across blocks.
- Assembling the bracing. As you can see from the photos once the blocks get to a certain height, you can attach an upright brace. Onto the uprights attaches an arm that holds planks to make a walking surface, and 2×4’s to make a railing.
- Filling in cracks with foam. In places where the blocks don’t come together exactly or have imperfections due to rough handling, you can fill in with a can of expanding foam. Nudura of course has their own special brand of expensive foam.
- Taping off the top row of teeth on the blocks. To keep the concrete from filling in the recesses in the top of the blocks, we covered them with masking tape all the way around the top row once it was complete.
- Covering the window knockouts with waterproofing material. Doug had pre-assembled the window knockouts, and we wrapped the outside of them with a roofing membrane.
We had an army of helpers including my parents lending a hand wherever we could, and got everything wrapped up in time to start the pour on Monday.
The pump truck has an enormous boom, over 100 feet long, and each concrete truck backs up and dumps their load in. The nozzle is roughly 8″ across, and concrete comes blasting out at an alarming velocity.
We got off to a little bit of a rocky start as about 15 minutes in Ray, the Nudura rep from Alandson’s, was manning the hose on the back corner of the house where the guest bedrooms are. The conventional wisdom says to pour slowly and not fill any one section up too high with wet concrete to minimize the pressure on the bottom row of blocks. Owing either to arrogance, inexperience, accident or some combination thereof, Ray got too much ‘mud’ in the wall and my heart sank as I saw the corner block literally rip into pieces and a river of concrete came pouring out.
Apparently this isn’t terribly uncommon, and was fairly easily repaired by clearing the spilled concrete, re-attaching the broken pieces of the block, and securing the whole thing with a plywood band-aid. That whole process was completed in a matter of minutes, and we then proceeded to strap every piece of wood we could find onto areas of potential weakness.
Just as the first truck ran out of concrete, we got word that the Citywide plant had broken down and there wouldn’t be any more trucks for a while. Right about then we noticed that the concrete wasn’t coming up underneath the window knockout as expected. Each knockout has four circular holes drilled in it, and in theory the concrete should be wet enough to flow up underneath and start to come out of the holes. We were several inches shy, and didn’t have any more concrete due to the plant breakdown.
We first tried to fill it ‘naturally’ by filling a kitty liter bucket with the spilled concrete from the blowout, passing it up to Doug on the scaffolding, and pouring it in while tapping the walls to try to vibrate the wet concrete into place. After 6 or 7 buckets we realized that wasn’t working, so Doug chopped out larger square holes in the offending knockout, and we proceeded to fill it directly through those holes.
After about an hour and a half the trucks started showing up with greater frequency, and the whole operation started to wind down around 2 or 3 in the afternoon.
When the walls were full of still wet concrete, Zane Luzater - a wizened concrete oracle with a mean eye for straight lines - walked around telling us which way to turn the braces to push a wall a half inch here and let it out a quarter inch there. They also used a trowel to take off the concrete that had pushed out of the top of the inner walls that had a tapered edge. This edge is where the thickness of the concrete steps down from 8″ to 6″, and the difference is used as a ledge for the floor joists to sit on.
I was bushed from all the action over the weekend, and packed it up and headed back to KC. It was great to get my hands dirty and I learned a great deal about the construction process along the way.
Here is a great glut of pictures, with more to come in the next few days that will have more details on the blocks themselves. It is a great system, and makes it easy to snap everything together.
