How to Build a Backyard Creek Bridge

Do you have a creek running through your backyard? If so, adding a bridge can add some extra character to your yard. It’s a great way to make the most of your natural landscape and it’s not as difficult as you might think! In this blog post, we will discuss the steps you need to take to build a backyard creek bridge. You will be adding something that will increase the esthetics of your backyard. So, if you’re ready to add a little bit of whimsy to your yard, keep reading!

We believe you shouldn’t have to worry about water flowing over the banks of your creek and that you don’t need a permit for your project but we know that isn’t always the case. If this isn’t the case, before you go any farther, consult with your local permitting agency and possibly an engineering company.

What you need to build a 4-foot-wide by 12-foot-long backyard creek bridge

Nails made of galvanized metal with a thickness of 10 millimeters
Deck screws that have been galvanized or otherwise treated at least 3 in long should be used.
Deck screws 2¾ in long galvanized or otherwise treated (for attaching to the curb)
Galvanized lag bolts that are 1/2″ x 8″ in size
Brackets and metal hangers
If you’re going to pour the footers, make sure they’re made of concrete or metal forms (8-inch diameter minimum).
All wood should be dimensionally stable, contact-treated dimensional timber.
Steel rebar 6-in. minimum diameter and 10-in maximum, or concrete reinforcing bar (for footers)
(8) 2 X 10 X 12
(9) 2 X 6 X 14 (Cut into 25 4’ deck boards plus the bottom support in Step. 9)
(2) – 2 X 4 X 12

How to build build the bridge

Place your bridge on terrain that is flat and at approximately the same height. For our example, we’ll use a 7-foot creek bed and a 12-foot bridge length. The extra length is needed to ensure that the foundations are at least 2 feet away from the creek’s edges.
Consult your plat maps or any other records you may have to ensure that your planned bridge site is free of buried pipelines and cables. You can call 811 (Call before you dig) line to ask for them to send someone out to mark the area. Level the locations where you want your bridge’s ends to settle.
Measure, square, and stake a rectangle that is 4 feet by 12 feet long and positioned lengthwise over the creek. Just inside the four corners of your designated region will you lay concrete or wooden footings.
With a tractor, drill four 8-inch-diameter (or bigger) holes completely inside the triangle’s corners at least 3 feet deep. They need to be deep to be sure to hold even if the ground gets saturated. Then fill with concrete or an 8-inch-diameter post. If you’re using concrete, make sure each pair of footings is at the same level—slightly above grade is best; if possible, look for a form that will work. Trim the posts level after you’ve backfilled the holes if you’re using them.
Using 10 penny nails staggered every 8 inches or so, attach the two ground-contact treated 2″ x 10″ x 12′ dimensional boards together along their length. This results in a 4″ x 10″ x 12′ dimensional timber. Place the timber on the edge across the gap, with the footers acting as supports at both ends. Set the center of the timber over the centerline of the footer.
Place the two timbers side by side on top of the existing footers. Repeat step 5 and place the timbers along with the other set of footers. The timbers should be parallel and square, so adjust their position as needed.
Cut four pieces of 2″ x 10″ material to that length and make two left-angle crossbeams with the sections. To make crossbeams, nail two 2″ x 10″ lengths together in pairs to create them (three 8-inch lag bolts per corner of the bridge), and rest them centered on the footers. Attach timbers and beams to concrete or wood footings using brackets and screws appropriate for each type of foundation.
Attach two 2′′ x 10′′ x 12′’ treated dimensional boards to the crossbeams with metal hangers and galvanized screws at two points that are roughly one-third and two-thirds of the distance between the timbers, respectively (similar to floor joists).
Cut a piece of 2′′ x 6′′ treated lumber to length and set it atop the bridge halfway across the span, attaching it to both outer timbers and the two interiors “joists” to prevent them from spreading or curving.
Cut a total of 2” x 6” x 4′ lengths (about 25) of treated timber crosswise down the length of your existing superstructure. Fasten the decking to the outer beams and joists with screws, leaving a half-inch space between them. On each side, the deck planks will stick out beyond the outside timbers by about 2 inches.
By screwing a 2″ x 4″ x 12′ treated dimensional board flat on top of the decking, flush with the deck end planks or 2 story storage shed, you can create a curb on each side of the bridge. This will keep the deck ends even and prevent warping, as well as reduce the incidence of automobiles rolling off the edge.
Consider the ways to transition from ground to decking and make it as seamless as possible. If you need to elevate the elevation by more than a few inches, use crushed rock rather than dirt. This will help with drainage and prevent erosion. If the grade is only slightly higher on one side, use a ramp rather than stairs to make it easier for people and animals to get on and off the bridge.