Construction> A Case Study  A Good Old Fashioned Barn Raising (Part 2) Day 3 – Against the Wind We had not planned on using bracing but a storm front came in pushing (30+ mph) winds through the hill country canyon. Since the wind was forecasted to blow for the next several days, we spent the majority of day 3 bracing the walls. This kind of bracing is not typically needed. Grid-Wall itself does not require bracing to hold the concrete pour like the EPS-only products do. The only bracing that may be needed is to hold the door and window buckings in place, but you do not need to support the blocks while they hold the curing concrete.  We used four braces on the 80’ long back wall and three on the south wall and two on the north wall as the wind was blowing north to south. We made Grid-Wall sandwiches using 2x4s held together with 2 pieces of all-thread in holes drilled through the wood and solid portions of the blocks. We also put some braces on the inside of the structure to guard against possible changes in wind direction. These we attached to the 2x4 sandwich being used by the outside braces, secured inside with angle brackets anchored to the slab. We still managed to stack some blocks on day 3, going 9 courses high (12’) on the two sides and the back wall.
Inside on- the- slab bracing		Brackets used to anchor bracing to slab
Day 4 – Working on the front, the arches over the garage doors, and preparing to pour We focused next on the front of the building and the arches over the garage doors. This required the normal steps used to install Grid-Wall plus setting the steel frames in place for the garage doors. The forklift was handy for this job. Not a lot of block stacking was required between the doors, but some time was spent securing the frames and insuring that they were plumb to the slab. (arch pictures) We then stacked the front 9 courses high to match the rest of the building. Since they get removed after the pour, the blocks under the arches were stacked loosely just to support the weight above, and were not glued (note the double 2x4’s sitting in the door frame – used to support the solid sections of these blocks). As soon as the blocks were high enough to allow the whole arch to be drawn, an electric chain saw was used to cut a slot 8” into the 10” thick blocks. A 10” wide strip of thin press board, such as Masonite, was then inserted into the slot. During the pour, the press board will stop the flow of concrete along the arch line. After the pour, the support blocks are pushed out, the press board is removed, and the last 2 inches of the slotted blocks are cut away, forming the final shape of the arch. 20’ rebar was cut to extend 32” beyond the 12’ stacked wall height. It was then inserted vertically taking care to place the rebar inside the PVC rings that had been set over the slab rebar on day 1. This helps keep the vertical rebar centered in its column. The 32” extensions were to accommodate the final 2 rows of blocks on the back wall, while the side and front rebar were cut to extend approximately 40” allowing for the next 2 courses and 10 inches of rebar overlap with the next phase of stacked blocks. Debris from sliding the blocks across each other during the stacking and leveling process accumulates inside the wall at the slab. It is important to wash this out so the concrete poured into the wall can bond with the slab. Drain holes are cut from the blocks on the bottom course to allow debris to be flushed out. Keep this cut out piece from getting lost by screwing it with a deck screw to the wall above the hole it came from. This will make it easier to plug the hole again before the pour. Just insert the plug back into its hole and spot glue it into place. (picture of drain holes).   Day 5 – The first pour Check out the specifics of what you need for the concrete. We started pouring under the windows to insure that we had no entrapped air. We did this by cutting a hole in the sill of the window buckings (best to do this before bucking installation) and poured until we filled the blocks under the window. Smaller window buckings do not require this whereas larger ones may require one or more. After we poured under the windows, we used the scissor lifts in tandem and played a game of leap frog as we poured the walls. The bracing on the slab cut up our nice 40’ and 80’ walls, forcing us to frequently reposition the scissor lifts.  We did two passes or two laps pouring the 12’ high wall with no blowouts except where our garage doorways met the arches. The breaks were quickly repaired with some plywood and some deck screws, and then we continued to pour that section. We had caused the blowouts by positioning the block fragments with no material in place to hold back the concrete. We corrected that on the next three arches and had no issues. We had no blowouts at the holes we cut to flush debris from inside the blocks, or on any other blocks, including those that had been repaired.  We poured on a Tuesday and decided to allow the walls to set for a few days and went back on Friday. Day 6 – Arches, Arches, and more Arches Two courses were added to the back and the two sides bringing the back to the finished height. Time was also spent on the front of the building covering the next two arches in Grid-Wall. When working at this height and with arches, the installation rate does slow down.
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