New Water Tank (Page 2 / 3) -- May, June 2004
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The shed for the water tank is built on six pressure treated 6 x 6 posts resting on concrete footers poured below the frost line, which is around 6 feet in our area. Two tripled-up 2 x 10's form the support rails, and a floor of 2 x 10's, 12 inches on center form the floor. Plans for the floor appear in the image on the right, and a PDF version can be viewed by clicking on the image.
The work started by digging two trenches down about five feet. The biggest challenge was trying to find room for all the dirt being excavated. The house, dog yard and oil tank are all in the way of the excavation, and you can see the water line running through everything.
Unfortunately, the ground was still frozen at a depth of about 3 feet in the outer trench, so I had to chop thorough about two feet of frozen soil to reach a depth of just over six feet. I used a pick axe and a wood-chopping axe for most of the ice chopping.
After reaching a depth of six feet, I dug three footing holes and set forms in the bottom which were then filled with concrete. A U shaped post holder is set into the concrete and the posts are be affixed to the holder with a long bolt. This helps keep the posts anchored should there be any frost heaving.
I used two 80 pound bags of pre-mixed concrete for each footing. They are 16 inches square and 8 - 10 inches thick. I mixed the concrete in a wheelbarrow and then we shoveled the concrete down into the forms. I don't have a concrete vibrator to shake the bubbles out of the concrete so I banged on the sides of the forms with a sledgehammer.
The photos at the bottom show me mixing concrete, Andrea shovelling concrete into the footings, and a shot down the trench after the first footing was poured. You can see the other two forms, and the bracket that will hold the posts that support the shed.
Another weekend of work and the footings and rails are complete. After getting the pilings plumb and in line with each other, I braced them with some 1 x 2 boards and started filling the trench back in. The first image below shows the first trench about half full. The second is a shot down the outer trench with the pilings attached and leveled.
Like the first set of pilings, I used boards to stabilize the pilings plumb so they'd be in the correct position when the trench was filled. The third image shows me getting them plumb. Buddy and Snoopy came to see what I was up to.
Finally after a day of shovelling and smoothing all the piles of dirt all the trenches are packed down and filled, and the soil slopes away from the garage and house. The pilings were levelled using clear vinyl tubing filled with colored water and cut off with a hand saw. The rails supporting the floor are three 2 x 10's nailed together toe-nailed into the pilings. Hurricane straps also connect the rails to the pilings so they won't move. We're in earthquake country, so it's important to take rapid ground movement into account when building.
I built the floor on the rails, upside-down so that I could attach a layer of 1/4 inch plywood on what would become the underside of the floor. It seemed like it would be easier to put the insulation into the floor, and keep the squirrels out if plywood covered the bottom. As it turned out, this was a big mistake because the floor was much heavier than I expected and I was unable to easily flip it over.
After struggling for hours with the floor on the ground, I finally decided that the only way I was going to get the floor flipped over was with some mechanical assistance. I used a winch, attached to one of the roof joists on our house, to lift the floor on it's edge, and then pushed the bottom of the floor while Andrea lowered the floor back down. This procedure was fairly safe because it didn't require either of us to be under the floor at any point, and the winch was carrying whatever weight wasn't resting on the rails. The image on the right shows the floor about halfway over.
Once it was finally flipped, I muscled it into position, filled the cavities with fiberglass insulation batts, tacked down 6 mil plastic vapor barrier and covered the joists with 5/8 inch plywood.
At this point our water tank was close to empty, so I emptied it the rest of the way. Andrea and I tipped the tank onto it's side, rolled up up a ramp to the platform and flopped it back down onto the floor. The next morning the water company came to deliver water -- 1,600 gallons, or 6.7 tons resting on the pilings, rails, and floor I built!
The image on the left shows the tank, completely full of water, in it's final location. The floor creaked and groaned as the water was going into the tank, but there's no obvious deflection of the floor, and the pilings haven't shifted at all. I can see that the rails have compressed slightly because the hurricane straps aren't flush with the rails and pilings any more, but compression is to be expected with that amount of weight on the beams.
Next up is building the shed walls and roof to enclose and insulate the tank. To continue the story, click: Next page.
[ Last updated Sunday June 13, 2004 ]