Small Upcycled Garden Bridge for a runoff

Small Upcycled Garden Bridge

If you live in North Carolina you know we have had a bit more rain than usual. We have three fields that are separated by runoff and tree lines. The fields are cut off during these rainy periods. We always said we will just build a bridge but it seemed to always dry out enough and the bridge can wait. Well, it is finally time to start the Upcycled Garden Bridge

Upcycled parts

I had been saving scrap metal for various projects around the property and came across two pieces of extruded aluminum that are the same. They are both arched perfectly for a small footbridge but also strong enough to drive over with the lawnmower.

Extruded aluminum
Extruded aluminum

The extrusion is five feet long giving me plenty of span for the open culvert that leads to the middle field.

The arches are lag bolted to 4″x6″ ground contact pressure-treated wood. We would have made the bridge 36″ wide for walking but I also needed to be able to ride the mower back there. So we made the bridge 48″ wide.

The next step is applying the pressure treated deck boards. We had made a ramp for the shed with pressure treated deck boards so I took a quick measure of those to figure out how may I would need. The ramp boards were 5.5 inches wide so for a span of 60″ I needed 11 boards at 48″. Since this bridge is 48″ wide I purchased 6 boards @ 8′ plus 2 extra boards to add at both ends which when installed will support the dirt or gravel and prevent it from washing out under the bridge.

In order to secure the boards to the aluminum, I used self-tapping deck screws. Due to the thickness of the Aluminum, it was necessary to pre-drill all the holes first. The deck screws hold like iron in the Aluminum

deck screw
Deck screw

With all the holes pre-drilled it was time to secure all the boards. Starting from the center and working my way down both sides.

Re-enforcing the structure

The bridge is extremely strong but due to the span, the center seemed to have a little bounce to it. The bridge is turned up on its side and I place a deck board from end to end so the curve can be traced. I used some old scrap deck boards to double up the thickness and cut the curve on the band saw. I placed the support in the center and screwed it into place and now the bridge is completely solid.

Small Upcycled Garden Bridge
Bottom of Bridge


Boards will be attached to the 4×6 to hold back the gravel or dirt below each end of the bridge. Another option would be to pour concrete abutments on either end but that seemed a little extreme for a small bridge.

The bridge is complete. However, the ground is too soft and I am not able to place the bridge in it’s no home.

We completed the bridge and had a break in the weather long enough to move around some stone and dirt. We leveled the dirt on either side of the runoff area and used stone we collected from the front field as a base. Once the stone was compacted down we laid 3 60 pound bags of concrete on top. We left the concrete in the bags.

This technique makes a solid easy base and is used for retaining walls for landscaping and erosion control. Now that the base has been installed it was a simple step to set the bridge in place. With the bridge in place, a piece of pressure-treated decking was screwed in to prevent the stone and topsoil from washing out. With the boards in place, more stone was added and compacted and then topped off with soil for now. It will not be a high traffic bridge but we may install pavers on either end depending on if there