Having a garden with a pond is one thing -- adding a bridge takes the pond to an entirely different level of enjoyment. Guests will be impressed, children will enjoy taking a journey to cross it, and as the owner and bridge builder, you will enjoy your garden even more. While you can certainly hire someone or buy a kit to build a garden bridge, neither will top the sense of accomplishment and pride you will have by building your pond bridge yourself.
Select a style for the bridge, specifically whether the bridge will be a flat footbridge or a bridge with an arch. Measure how long, how wide and how tall the bridge will need to be.
Decide whether you want to create a bridge with or without rails. Simplify the project by making a bridge without handrails if the bridge is just going to be a short accent piece, such as over a small koi pond. Add railings for safety if the bridge will be 2.4 m (8 feet) long or more and will be used by children, the elderly of those with physical limitations. Think about adding a middle rail for decorative purposes, and options such as rope instead of wood for the rails to give the bridge a rustic look.
Determine how many posts you will need and the height for each. Take careful measurements for the posts. Allow posts for every 1.2 to 1.8 m (4 to 6 feet) in length. Factor in the extra height you will need for posts that will be underwater, versus the height for posts that will be at the ends of the pond, and for posts that will be attached to an arch for a rising bridge (if you choose that type of design).
Draw a simple sketch for the bridge. Identify where the posts will need to be placed, and the railings, if you are going to have them. Include the measures on the sketch. Keep in mind that the posts for the centre of the pond will be underwater and will need to be longer than the posts at the ends of the bridge. Think about additional decorative elements such as end caps or balusters to your design and indicate them on your sketch.
Take a digital photo of the site for the bridge as a reference for yourself and whoever assists you at the timber merchants or wood department of a DIY centre.
Choose a wood that will withstand the climate where you live and can withstand being underwater. Consider different types of wood for bridge and rail versus the posts placed underwater. Get the timber merchants to cut the wood for the bridge to meet your needs and specifications, including the arch piece if you are creating a rising bridge. Be open to any advice given on adjusting wood types and materials.
Use common deck braces and brackets to install the posts under water. Paint the end of each post that will be submerged into the water with 5 to 10 cm (2 to 4 inches) of black bitumen paint to minimise water from seeping into the posts. Take care not to cut the pond liner during the installation of the posts.
Use wood decking screws to drill the cross bearer pieces of long wood, or the arch (if you are making a rising bridge) to the posts. Drill wood pieces on top of the posts for connecting the walking path wood pieces. Add balusters for bridges with handrails, and a middle rail.
Stain or paint the bridge. Varnish the bridge or add a waterproofing sealant for extra protection. Decorate with boulders or heavy cement urns at each end, and to give the bridge extra reinforcement. Add flowers or ferns for an extra decorative element.
Keep a saw handy to make adjustments to the height required for the posts. Study pond bridge styles closely to settle on your final style. If you're going for an Asian look, consider painting the bridge in a vivid, deep red, cinnabar colour.