The end of our driveway crosses a small stream to connect with the street. The bridge consists of 3 metal I-beams, firmly attached to the banks, across which are laid oak planks (4" x 10" x 12'). Some of the planks are beginning to chip and crack and I would like to replace them. A local sawmill estimated $4000 to replace the planks.
I was thinking that if I bolted together some pressure-treated lumber planks to the dimensions of each of the oak planks it would look better and would be a fraction of the price.
The question is strength. Would my idea support our cars as they cross the bridge?