Wednesday, December 28, 2011

How to Build an Arched Footbridge:Part 1

(click on the images for a larger view)
using a jig saw to cut out the bridge Making an arched footbridge out of lumber can be fun, hard work and also quite rewarding. Following is the plan for how to build an arched footbridge with or without rails. If you take your time and have modest woodworking skills you can easily build this type of bridge.

This arched footbridge can be built out of either Western Red Cedar or Redwood, using 2x4s or 2x6s for the floor planks and 2x12s for the support stringers. It will take some practice for you to get the proper arch needed for your own particular footbridge. Be careful not to make your arch too high for safety concerns especially if you live in an area where you get rain or snow on your bridge or people may slip and fall because of the steep slope.
Garden Bridge Plan Diagram:
drawing the arch for the  bridge

Cutting out the Top and Bottom Arch of the Bridge

drawing the arch for the bridge stringer Find the center of the stringer (2 x 12), as shown above in the bridge plan diagram, and determine the amount of arch you want by tracing the arch at the bottom with a pencil as shown on the image to the left.

You should leave 15 to 18 inches from the end of the boards on the bottom cut so as to have plenty of support on the stringers for the weight of the bridge as shown on the image to the right.

One way to determine the amount of arch is to use a tack and string to make the arch or use a compass or just carefully free-hand trace the arch.
leaving 18 inches on the end of stringer


cutting out top of bridge stringer After you have cut the bottom piece from the stringer you need to make an arched cut on the top. An easy way to do this is to just take the piece you have just cut out and attach it to the top of the stringer with a bead of wood glue and 3 inch wood screws. Put them in from the underside so they will not show. You could also cut out the top arch by tracing an arch across the top of the stringer with a pencil and cutting it out with a jig saw. This option requires more skill and practice

If following the 2nd option make sure you leave 1 1/2 inch thickness at the ends so you will have enough wood to attach the floor planks. After doing the first stringer, just use it as a template and trace it on to the other 2 x 12 to save time and work.
two bridge stringers side by side


Attaching the Floor Planks to the Bridge Stringer

Use the 2x4s or 2x6s for the floor planks by cutting the boards to the length you want. If you want the footbridge to be 36 inches wide cut the floor planks to 36 inches long.

After cutting the floor planks, the next step would be to place the 2 support arched stringers 32 inches apart straight and level. Start at one end of the bridge. Place the first plank square at the end of the bridge and overhanging the end of the stringer by 2 inches.
attaching the floor planks to the bridge stringer

Pre drill 2 holes on each end of the boards all the way through the stringers and put in the 2 inch stainless steel screws and tighten. Work from one end of the bridge to the other. Space each plank by using a carpenters pencil between each plank to get an even space between each floor plank.

Finished Arched Footbridge

finished 5 foot arched footbridge

You could build a 5 ft. bridge without rails in just 2 hours.

If you would prefer to have posts and rails on your bridge continue onto:

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