To build a garden bridge, begin by measuring the area where the bridge is to sit, which is also the length of the support beams. Next, take two curved beams between 4 and 8 inches wide and ensure the beams are parallel and the appropriate distance from each other to suit the width of the desired bridge.
Use a circular saw to cut cross planks to fit the width of the bridge. Cut as many planks as needed to stretch the length of the bridge. Once they are cut, line the first plank up to the outside edge of the beams and secure the plank to both beams with four deck screws. Line up the next plank flush with the first plank and secure. Repeat this until the bridge floor is in place.
Create handrails by measuring the desired height of the rails and cutting at least six 4-by-4-inch posts to size. For six rails, place three rails on each beam and space them out in equal distance and parallel to the other beam's rails. Drill 1/2-inch holes with a 12-inch drill bit into the bottom of each rail and into the beam where each rail stands. Hammer 12-inch bolts that are 1/2-inch in diameter into the hole on the post and beam and then thread a washer and nut onto the bolts and tighten with a 1/2-inch wrench. Add 2-by-6-inch hand rails onto the top of the posts in the appropriate length using two 2.5-inch deck screws in each post.
If desired, stain or paint the wood. If staining, use an oil brush and clean excess stain with a rag. Give the wood time to dry before using.