Tornado Shelter Block Layout
I mentioned last post that I had gotten started laying out the block for the tornado shelter. Here is a closeup of that layout. The left side wall I will call the interior wall, the right side the exterior wall. You will notice all the blocks on the interior wall have been cut down to 3.5” height. Add the 4” slab thickness to that and you’re back to the height of the full-sized blocks on the right side (exterior wall).
Cutting down concrete blocks isn’t all that blog-worthy by itself, but how I got them all leveled and to the same elevation is. There is a stringline over the exterior wall that is used to set the correct elevation and location of everything (footers, block walls, floors, etc). I don’t have a stringline over the left side blocks and didn’t want to take the time or effort to rig one up. So, I just took a long, straight piece of galvanized fence pipe (leftover from another project) and put my level on it. It was long enough to reach all the way across from one wall to the other. I figured I would prop up the end of the pipe with wood blocks until it was level, then use that block height to measure and cut my blocks. I had a 2x4 piece close by, so I tried that first. When I put the pipe and level on top of the 2x4, low and behold, it was perfectly level. I am never this lucky on the first attempt, so something has to be wrong. So, to be sure, I took it all apart and put it back together again. Checking it again yielded the same result. So I cut the concrete block to 3.5” height and moved on to the next one. In the end, all five blocks were cut to this height.
These block I didn’t actually mortar to the floor because, 1.) they were already level (on top) and to the exact height desired and 2.) each block has a piece of vertical rebar in it. When concreted in place, the rebar won’t let them move. In the first block in the pic I stuffed some mortar to kind of hold it in place.
It was only after getting them all layed down that I finally realized why the 2x4 worked as the exact height needed. At first I reasoned that the 4” slab thickness plus the 3.5” block height added up to 7.5”. But full sized concrete blocks are 7-5/8” tall, so somewhere I’m off by 1/8”. But, then I realized none of the full sized blocks on the exterior wall were in fact full sized. They had all had at least an inch cut off them because of irregularities in the surface of the concrete footer. So now, mathematically nothing adds up right or makes any sense. But, in the end, the tops of the blocks are level and to the desired elevation so I’m going to stop worrying about it and leave it up to you, the reader to figure out. As before, you got any ideas, I’m all ears.
P.S. The first diamond blade is about used up. I probably made a hundred cuts with it, but I’m not believing the 200x printed on the side of the blade means it will last 200 times longer than a regular masonry blade. I bought a new Skil brand diamond blade at Walmart for $14. It only says 50x, so we will see how long it lasts.
P.S.2. The two cut down block in the front of the pic haven’t been leveled yet, but that’s where they will go eventually. There are no blocks placed yet which will make up the back wall. That’s next.
Cutting down concrete blocks isn’t all that blog-worthy by itself, but how I got them all leveled and to the same elevation is. There is a stringline over the exterior wall that is used to set the correct elevation and location of everything (footers, block walls, floors, etc). I don’t have a stringline over the left side blocks and didn’t want to take the time or effort to rig one up. So, I just took a long, straight piece of galvanized fence pipe (leftover from another project) and put my level on it. It was long enough to reach all the way across from one wall to the other. I figured I would prop up the end of the pipe with wood blocks until it was level, then use that block height to measure and cut my blocks. I had a 2x4 piece close by, so I tried that first. When I put the pipe and level on top of the 2x4, low and behold, it was perfectly level. I am never this lucky on the first attempt, so something has to be wrong. So, to be sure, I took it all apart and put it back together again. Checking it again yielded the same result. So I cut the concrete block to 3.5” height and moved on to the next one. In the end, all five blocks were cut to this height.
These block I didn’t actually mortar to the floor because, 1.) they were already level (on top) and to the exact height desired and 2.) each block has a piece of vertical rebar in it. When concreted in place, the rebar won’t let them move. In the first block in the pic I stuffed some mortar to kind of hold it in place.
It was only after getting them all layed down that I finally realized why the 2x4 worked as the exact height needed. At first I reasoned that the 4” slab thickness plus the 3.5” block height added up to 7.5”. But full sized concrete blocks are 7-5/8” tall, so somewhere I’m off by 1/8”. But, then I realized none of the full sized blocks on the exterior wall were in fact full sized. They had all had at least an inch cut off them because of irregularities in the surface of the concrete footer. So now, mathematically nothing adds up right or makes any sense. But, in the end, the tops of the blocks are level and to the desired elevation so I’m going to stop worrying about it and leave it up to you, the reader to figure out. As before, you got any ideas, I’m all ears.
P.S. The first diamond blade is about used up. I probably made a hundred cuts with it, but I’m not believing the 200x printed on the side of the blade means it will last 200 times longer than a regular masonry blade. I bought a new Skil brand diamond blade at Walmart for $14. It only says 50x, so we will see how long it lasts.
P.S.2. The two cut down block in the front of the pic haven’t been leveled yet, but that’s where they will go eventually. There are no blocks placed yet which will make up the back wall. That’s next.
posted by Tony @ 6:25 AM
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