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Build a decorative backyard landscaping bridge
Dear Ms. Builder: There is a narrow gully near my flower gardens. I always thought that a small bridge, flat or arched, over it would look beautiful. Can you tell me the basic steps to build a simple bridge myself? - Paula R.
Dear Paula: Building a decorative bridge by your garden can be a stunning addition to your landscaping. It will become the focal point of your garden and one of your favorite spots to chat with guests when entertaining.
Although everyone falls in love with arched bridges that they see in all the gardening magazines, building one is beyond the skill level of the beginning do-it-yourselfer. It is difficult to make all the pieces fit properly for a solid bridge. If the bridge is at all wobbly or springy, people will feel uncomfortabe standing on it to view your gardens.
Building a flat bridge is probably your best bet at this point in your do-it-yourself skill development. With ornate handrails, the proper selection of woods and the orientation of the decking, a flat bridge can be very attractive and look like a professional installation.
Before starting to build your bridge, first consider all the ways you plan to use it. If the gully is deep and you plan to use the bridge to roll your lawn mower or wheelbarrow over, make sure to plan it wide enough. Making it wider usually requires just a little more materials and perhaps an extra center support joist.
If you are not going to use it just for a walking bridge and not roll anything over it, you can have a small step up to it. In this case it is basically a long narrow deck. To roll things over it and for a more professional look, make each end flush with the ground level.
First stretch some strings from the beginning to ending points for your bridge. Although it is not critical, it will look much better if the bridge is level from end to end. It is critical that you make it level from side to side or it will look really odd and feel strange to walk on. Use a string-type hanging level on the taut strings to check for the proper end positions.
The best foundation method to use is a concrete grade beam. Other than a sore back from digging a trench (grade beam) and a few post holes (supporting piers), it is not particularly difficult. Make sure the pier holes extend down below the frost line in your area. Taper them out at the bottom to eliminate any chance of frost heave.
Before the concrete is set, insert 1/2-inch anchor bolts and make sure that they extend about two inches out of the beam. They should be located 32 inches on center and start in about eight inches from one edge of the beam. The lumber sill plates on each end, which the actual bridge is built on, is bolted to these anchor bolts.
If your bridge is less than eight feet long, 2x8 joists on 16-inch centers (or less to space them evenly across the bridge width) should be adequate. Up to 12 feet long, you should use 2x10's and up to 18 ft., use 2x12's. Any longer than this and you will need an intermediate support beam.
Now, all you have to do is install the decking and handrails. Since you prefer an ornate one, you might consider cedar or heart redwood. You can also trim the side of the bridge with matching lumber to hide the pressure-treated joists. Using turned cedar or redwood spindles for the railing, can give the bridge a finished look.
Tools and materials required: level, tape measure, saw, hammer, post hole digger, shovels, trowel screwdriver, drill, nails, string, various sizes of pressure-treated lumber, finishing decking, spindles and railing
Send your questions to Ms. Builder, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com/msbuilder.