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Concrete corrective surgery

August 18, 2008

Last weekend my neighbor got the framework for his building up, and though I helped on Sunday, I decided not to blog it, as the project wasn’t mine.  This past weekend, I got started on my project only to find that my concrete slab was out of square, or more descriptively, “out of rectangle”.  Instead of the desired 40 x 60 rectangle, I have a 40ish x 60ish parallelogram.   When I formed and poured it, I thought “close enough” – that I could locate a control point and establish all the critical points from that to facilitate layout and construction after the pour.  I was technically correct, however…

It turns out, that the building has a piece of angle trim at the base that captures the wall siding, and projects 1-2 inches below the top of the slab.  As a result, I really needed to get the concrete into true 40 x 60 shape.

After much measuring and snapping of chalk lines, I found myself trueing up the long sides, and then trimming away reciprocal pie wedges on either of the short ends to convert my parallelogram into the desired rectangle.   Were this an Olympic event, I seem to have just entered myself into the “men’s 100M freestyle concrete sawing”.  My times are miserable.   

While more cutting remains, I’ve done the critical areas, and so we were able to establish the layout of the bolt plates.  One can embed ‘L’ shaped bolts in the concrete or drill and epoxy in threaded rods after the slab is poured.  Wisely not trusting the accuracy of my forms, I decided against the embedded approach, and so am now having to drill in the 32 bolts that will anchor the steel to the slab.

Jim, stopped by to lend a hand, and so I quickly handed him the drill, the chalk box, measuring tape and the plans.  Practicing my delegation skills you see…

We drilled the holes oversize – 3/4″ holes for 5/8″ bolts, and 1″ holes for 3/4″ bolts so that we would have plenty of room for the epoxy.  The epoxy is about $20 a tube, and we’ve used 2 tubes to do the 5/8″ bolts and I expect we might use 3 tubes to do the 3/4″ bolts.  The threaded rod was close to $100, so this approach will cost about $200 in total.  The embedable “L” bolts were about $45 by comparison.

So, I’ve learned a few things which I should have already learned by now many times over.

(1) Almost anything can be fixed with more money and time. 

(2) As a corollary, it is more effecient to do it right the first time.  In this case, the extra time spent to ensure the forms were accurate would have saved me the hours of time re-sawing the slab, and drilling all those holes, and it would have saved money in materials as well.


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