Friday, August 9, 2013

Pond Bridge Replacement – Part 1

After over a decade of use and being exposed to the elements, the bridge over the stream leading to my garden pond (see second photo in link) had a structural member give out. Unfortunately the same design was not available. In fact, I was not enamored of most of the designs I found online and the one local place that used to do custom fabrication that I knew about was no longer doing so. Luckily I finally found a couple of styles that had potential at Fifthroom. We opted for the Red Cedar Eden 1/2 Picket Rail Bridge, had it pre-stained and shipped to us. It was going to be a bit wider than the old one but luckily we had just enough room to accommodate it. (This style has three support beams instead of the two of the previous bridge.) As with our previous bridge, it was sent as a kit for us to assemble.

I learned a few things putting in the first bridge that meant my prep time before placing this bridge would take longer but the extra effort should ensure the bridge lasts even longer than its predecessor. While I did plan for footings when placing the first bridge, I did not make sure they were all level with respect to each other, nor did I check for square before we hauled out the assembled bridge. The sides of the stream looked like I should be able to measure off them to place the footings. I had also not realized that there was still a fair amount of slope to the sides in that portion of the stream. That meant that when we placed the first bridge, I had to quickly shift some footings. As I was getting close to finishing this, the bridge shifted some under its own weight to settle onto the adjusted footings. Since it didn’t look like it sheared or torqued too much, we decided to leave it alone instead of taking it off and doing anything more to the footings.

This time I was determined to have the footings in the correct locations, at the correct height to be level with respect to each other and level themselves. I used some large cardboard pieces to fashion a rectangle the size of the footprint of the bridge. I laid this across the stream so that I could place the footings such that they would be under the ends of the three support beams and avoid the larger rocks that we had placed along the stream banks. Once the footings were in place based on the cardboard mock up and we had the framework of the bridge assembled, we test fit the beams and the footings. After making a couple of minor adjustments, we pulled off the bridge framework so that I could level the footings completely.

The footing, as you look at the first photo, at the near left corner was going to be the one that set the height for the rest of them. This is because it was the only one that would be resting on the pond liner. Because it was upstream, I selected the shortest rock footing that I had and placed the tallest one at the near right because that was the lowest elevation where I needed to place a footing. While I worked on a footing to level it, I outlined its placement with some flags so that as I removed dirt to properly set the elevation and level of the top surface, I wouldn’t lose the proper placement. I used a carpenter’s level to check the level of the individual footings and I used and 8 foot metal straight edge and the carpenter’s level to level between footings. Once I had everything looking good, we placed the bridge frame on the footings to check and I’m happy to report that no more adjustments were needed.

(The conclusion to the bridge installation was posted a few weeks later as promised and can be found here.)

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