Past Articles Library | How to Build a Garden Bridge
Many years ago, I learned the importance of functional but decorative elements to a landscape design. This lesson started with a rainy spring that just would not quit. Creeks flooded, and areas that had normally did not have standing water filled up with moisture. What made it worse was the fact that the soil in my area is high in clay. In doing so, when it gets saturated it stays that way for a long period of time.
Prior to this wet spring, handmade stepping stones had been laid out. While these did work for awhile, the moisture just seemed to pop out of the ground every time someone stepped on the ground. Another approach that was used was gravel. Yes, that did work but it created a look that I was just not happy with. What to do, what to do?
Well, the answer came to me when I went and visited a favorite haunt of mine and that is Bernheim Forest. While there I saw this beautiful garden bridge and thought that is the answer. Yes, this bridge was over a small pond but there are other locations in a landscape that could warrant a garden bridge without looking out of place or overdone. Here are some suggestions that you may not have thought of. How creating a garden bridge that goes over a small stream, which is a traditional use for a garden bridge. What about using a garden bridge to deal with an uneven terrain or a low spot in your lawn? Or, how about building a neighborly meeting place between two properties that are separated with a drainage ditch but that are brought together by a garden bridge.
Now that you have read about how useful, beautiful, and functional a garden bridge is, are you ready to build one? Well, to get you started I have provided directions for a bridge that spans 8 feet 4 ½ inches long.
7 pieces of pressure treated 2 x 4 by 8 foot wood
6 pieces of pressure treated 4 x 4 x 8 foot wood
5 pieces of pressure treated 2 x 8x 8 foot wood
6 pieces of pressure treated 1 ¼ x 6x 12 foot wood
2 pieces of pressure treated 1 3/16 x 3 ½ x 12 foot wood
1 box (16d) galvanized finishing nails
1 box Phillips outdoor wood screws 2 ½ inch long
8 3/8 x 4-inch lag screws
200 pounds of all purpose sand
200 pounds of all-purpose concrete mix
1 box (4d) galvanized finishing nails
1 box Strong-Drive wood screws
24 2 x 4 fence rail brackets
Optional, 6 4 x 4 copper high point postcaps
Exterior stain and/or paint
- Cut the following pieces: joists (4 pieces at 96 inches long), floor beams (2 pieces at 46 inches long), posts (6 pieces at 64 ½ inches) cleats (14 pieces at 3 ½ inches), decking (18 pieces at 48 inches), rails (12 pieces at 42 ½ inches long), handrails (4 pieces at 42 ½ inches).
- Square off the end of each board after cutting.
- Lay out the joists so that there is a 13 inch space between them. Attach one floor beam to the end with 16d galvanized finishing nails. Repeat with on the other end with the other floor beam.
- Using a framing square, check to make sure the “box” is square.
- Next, measure off the area where the garden bridge is going to be located. Place flags where each post with located. All four posts need to be 94 ¼ inches apart in length and 44 ¾ inches in width.
- Where the flags are located, dig a hole that is 12 inches square and 22 inches deep.
- Place 18 inches of sand in each hole.
- Put one post in the hole and check to make sure that the post is level. Add dry concrete to the hole until the post is stabilized. Repeat with the remaining posts.
- Mix enough of the concrete with water to fill each hole. Push down and level off so that the slope is going away from the posts in all directions. Let dry overnight.
- Once the concrete is dry, attach the joist/floor beam box that was created in step 3 to the posts. Prior to securing with 16d galvanized nails and leg screws, check to make sure that each post is level with the joist box.
- Using a framing square, draw a line on each post where the top of the joist box attaches to the post. Repeat for each post.
- Place a cleat on each line making and secure with construction adhesive and 2 ½ inch outdoor wood screws.
- Lay one piece of decking board on one end of the joist box. Mark where each post hits the decking board.
- Using a jigsaw, cut out a 3 3/8 notch along the mark from step 13. Repeat this process with the other end.
- Attach this decking board to the joist box with 2 ½ inch outdoor wood screws.
- Repeat this process with the remaining decking boards. Please note that every time you come to a post you will need to repeat step 11. Also to keep the spacing even, attach 16d nails between each decking board.
- Once all decking boards have been placed, remove the spacers (16d screws) from the joist frame.
- Measure and mark each at 8 inch, 19 ½, and 31 5/18. All measurements need to come from the top of the decking boards upward.
- Place a mark on each post that indicates the center.
- Utilizing these marks, attach the fence rail brackets to the posts so that the bottom of each bracket is on the lines made on the posts in previous steps.
- Attach to the posts using strong-drive screws. Repeat with each bracket.
- Place one rail up and measure it off to make sure that it will fit in its particular place. It is not uncommon for the posts to be off a little bit and in doing so adjustments need to be made. Cut and adjust accordingly. Repeat with all rails but to keep from getting confused, make sure to mark them where they are supposed to go.
- Attach railings to each bracket using three strong-drive screws.
- Fasten the handrail to the top of the railing with 16d galvanized nails.
- Apply a protective finish such as exterior paint and/or stain.
- Optional: place a copper postcap on top of each post and secure with a little construction adhesive and 4d galvanized finishing nails.
*Please note that while this plan is just for a simple garden bridge, you may need a building permit before you can construct it. In doing so, check with your local building inspector to see if a permit is required before purchasing your wood. Also, keep in mind that this bridge is only for pedestrian traffic and will not hold lawn equipment.