Saturday, August 13, 2011

Deepening and Widening the Column Excavations

Over a week ago I worked on this No. 1 excavation... widening it on each side, to get the maximum possible footing size.  Then I twisted my brain around how best to layout the rebar.  To go straight with the world here didn't work as good as going straight with the biggest rock.

Each bar has been drilled into the rock on one end and after blowing out the hole with an air compressor I put a generous amount of epoxy in and then pushed the rebar into the hole.

The number "1" is on a stick that I set up to guide me in knowing when there is enough concrete to make the concrete footing 12 inches thick.

In most footing preparations one sets up forms at the proper height.  If you want 12" deep footing you make the forms 12" high.  But here there are no forms except the earth walls of the excavation, and no easy way to know when the concrete is deep enough.

So I came up with a simple tool to help me.  As I am placing the concrete in the hole the bottom of this stick is 12 inches off the bottom of the excavation... 16 inches below the garage floor.  I can move it around all sides easily to check when placing the concrete to insure I have the right thickness of footing.

Ritchie Smith. Hoel Engineering, told me that I needed to make hole No.2 a little wider and deeper than I had already.  So, I made it a full foot wider than he told me... and an extra 6 inches deeper.

There was this rock in one corner that was too big for me to lift out with the tractor.  Trust me I tried... but then decided that it would be easier to leave it there and just pop off the top of the rock.

So with my 12" rock saw I made a series of cuts about 2-1/2 inches apart.

It almost looks like sliced bread... however the rock doesn't cut as easy as most bread!

I then take my heavy rock hammer and one inch chisel and break each slice of rock off.

Once that layer is removed I did another series of cuts and this picture shows breaking the final layer off.

I was able to take off a full 8 inches and now can run the rebar grid each way right into the corner without any hassle.  The horizontal white board gives me the top of footing guide again, making it easy to get the concrete 12 inches thick overall.

I appreciate having an engineer who explains the reasons for criteria. This gave me the choice of going a little deeper and wider, which is better able to withstand the uplift and twisting in the event of an earthquake.
Hole no. 3 was such a hard dig to just get it 22 inches deep initially, I soaked the bottom of this hole a couple of times.  It made the digging a lot easier... but it seemed like it made the rocks grow!  Ritchie asked me to increase this hole to 4 feet by 6.5 feet and 36 inches deep.  

I needed to use the tractor at least 5 times to lift heavy rocks out of this hole... and you can see I was working pretty late in the day as Shirley had to use flash to capture this shot.

There were also lots of smaller rocks that I could dig up and lift out by hand... some will be used in future rock walls and rock facing.

I never realized when I started how deep that this hole would finally end up.  I just kept digging and kept pulling out rocks until I reached one rock that was bigger than my John Deere could even budge.

I drilled into the rock and pounded in a short rebar to prevent my chain from slipping off the rock... but this was just too much rock for either of us to handle.  So I ended up digging lower and was able to set a full pattern of rebar at about 52 inches below pavement.  This will now tie the huge rock into the footing, providing more weight to the foundation.

My next task was to build the rebar columns that will be poured full of concrete. We tackled the toughest one first... this one had 16 vertical bars, 12 horizontal wraps 11 inches square and 13 -  4" x 11" wraps in between.

Here the engineer specified the rebar layout showing the difference between pad 3 and pads 1, 2 and 4.

To bend the horizontal wraps I needed to make this jig by welding a couple of short rebars to an angle iron and attach it the workbench.  I was lucky to have guests coming from Victoria who brought me a new package of welding rods since I could not buy any here on Mayne Island.

With a stop set at 11 inches it is easy to make all the square wraps the same size using a short piece of steel pipe as a bending handle.

We learned how to tie rebar in Mexico, so made a couple of these hooks out of 1/4 inch scrap wire I found at Home Hardware here on Mayne Island.

I doubt that there are very many women in this country who know how to tie rebar... but Shirley's help was much appreciated this week.

There is more than 240 wire ties in this single column... and we have another three to make up next week.

With this column weighing over 240 pounds, it would take more than me and Shirley to lift it into the hole.  Enter John Deere to the rescue!

Once in the hole I tied the hooks on the bottom to the footing rebar and then plumbed it and braced the column both ways. This one is now ready for concrete.... but I first must get my building permit and get the Regional District Building Inspector to give me a green light.

1 comment:

  1. Boy howdy, you rock! (Get it?) Seriously. Way to go with those holes and that rebar! Now for the never-ending-concrete-making session...