We have a water tank in our yard, to store and purify water from the well. It uses a filter that bubbles ozone through the water, which causes minerals to precipitate out, and disinfects the water. It’s a very cost-efffective way to have clean, clear water. It just means every month or so I have to clean the filter.
Cleaning the filter has meant climbing up a ladder to get on top of the tank, open the hatch, pull out the filter on its chain, and hang the filter over the outside of the tank, where I can hose it off.
My goal was to build a permanent scaffold so I could access the water tank filter without using the unsecured ladder.
I designed a 3D model for the scaffold, showing a sturdy raised platform adjacent to the water tank, with a railing and a fixed ship’s ladder. This seemed within my skill to build.
I bought lumber and hardware for the project.
I got my friends Kevin and Jay to help. We had such a good time building my footbridge last summer that they wanted to construct something together again. This seemed like a good sized project, so we scheduled it when they would be out in California for this year’s summer vacation.
The first step was to clear the ground where the scaffold would be built, and dig some holes for concrete footings. The posts would form a 4 ft square. The holes didn’t have to be terribly deep, just about 18 inches.
Six bags of concrete seemed like enough to get started. I also got some pieces of #3 rebar to help hold the concrete together, and J-bolts to embed in the concrete so post bases could be fastened down.
Then we mixed up the concrete in a tub and started shoveling it in. We used fast-setting concrete, which certainly does start hardening quickly!
It turns out six bags only filled three of the holes, so we searched my garage and found some older bags of concrete. But they seemed like they had hardened. When you store concrete too long, the moisture in the air can cause them to cure, at least on the outside. But I found a YouTube video about how to loosen and use hardened bags of concrete. This worked! We were able to recover enough concrete to fill the fourth hole.
Now we had four footings with threaded J-bolts set in them.
The post bases were fastened to the J-bolts, using strings to make sure they were placed within a 48 inch square. I didn’t have a socket driver large enough for these nuts, so we ended up using a wrench to tighten them. It was a little awkward, but we only had to do four of these, so we decided to grin and bear it.
Very quickly we positioned the 4×4 posts on top of the post bases. We made sure each post was plumb using a post level. Thanks to Jan for making a new piece of elastic for my post level, since the original rubber band that came with it had broken.
In some cases, the post base was not quite level, so we shaved a bit off of the bottom of the post until it rested on all four corners.
We braced the posts with 2×3 boards fastened to stakes in the ground, so they’d remain plumb while we attached the joists.
We cut the tops of the posts so they were level, and fastened edge joists on top.
The joists were held firmly in place with special hardware. The weight-bearing is directly onto the posts. The hardware just holds the corner together.
Near the tank, the joists were cantilevered, so they get closer to the water tank. This required a different type of hardware.
The whole structure was given a lot more rigidity by adding a diagonal member on each side. These made a huge difference. The frame was much more solid once these were attached.
The trickiest cuts we made were bevel cuts on the ends of the joists, so the cantilevered end kind of followed the curve of the tank. We had to toenail some screws, because there isn’t enough space next to the tank to drive screws from the outside. We considered using joist hangers, but I only had joist hangers for perpendicular joists.
The joists were 16″ on center to support the decking. We used joist hangers.
After we put joist tape on the tops of the boards, we moved on to decking. I used an inexpensive composite decking board, whatever they had in stock at Home Depot. 2 1/2″ composite decking screws go right into this material, so we made quick progress.
We found it helpful to use a light hammer to tap the point of a screw into the decking, so it would stay put as we used the impact driver.
We got into a good rhythm, raising a decking board to be measured, then bringing it down to the sawhorse to be cut, then fastening the properly cut board in place.
The Craftsman Portable Craft Center again proves its worth!
As we added more decking, we could fully climb up and work on the platform to finish the rest of it. Here’s another angle, showing a bit of the joist tape.
Finally we completed the platform! It took about 12 hours of work, over three days. Plenty of time around the project for vacationing.
That was as far as we got while Kevin and Jay were visiting. I’ll continue to work on the railings and building a permanent ladder.
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