Red Cat
On-and-off member
Update: It appears the Welcome Amiibo Update has changed the requirements for placing bridges. This guide may no longer be useful for updated versions of ACNL.
Thanks to jokimori for writing this bridge space requirement guide. It inspired me to look further into the bridge mechanics of Animal Crossing New Leaf. The main reason I wrote this guide was correct some mistakes in the previous version on this site and add some additional information.
Thanks to spacejamcrossing from tumblr for this well-written and thorough guide detailing the space requirements for vertical bridges. She(?) got the space requirements for vertical bridges right and got me thinking about how the space requirements for horizontal, vertical, and diagonal bridges are all related.
Thanks to viva-monteor from tumblr for this guide on diagonal bridges. It's not completely accurate, but it gave me a starting point for thinking about buffer zones for diagonal bridges.
Warning: This guide is very long in its entirety. The reason it is so long is because I know that a lot of misinformation about Animal Crossing New Leaf mechanics gets spread around, so I wanted to thoroughly explain what the space requirements for bridges are and also to explain why they are different for the different types of bridges. Most of my theory is based off of actual testing, so I expect my guide to be correct for every possible bridge. I certainly don't want to spread any more misinformation, so I tried to make sure I was being specific and precise whenever possible. If you don't want to read all of this and you just want to trust me, then just skip down to the "Can I put a bridge here?" section.
Note: If you are colorblind and can’t understand the diagrams I use in the “Can I put a bridge here?” section, please let me know. I thought red and green would be logical colors to use, but I may have messed up doing it that way. If it is unreadable for colorblind people, I’ll change the colors.
2nd note: If there are grammar errors or something is written in a way you don’t understand, let me know. I want this guide to be as readable as possible.
3rd note: I’ll add a section in the guide for bridge buffer zones after the bridge is built. It may be useful to help people plan, but remember you can always build a bridge first and then test putting another PWP nearby and then just demolish the bridge if it gets in the way of the other PWP.
Thanks to jokimori for writing this bridge space requirement guide. It inspired me to look further into the bridge mechanics of Animal Crossing New Leaf. The main reason I wrote this guide was correct some mistakes in the previous version on this site and add some additional information.
Thanks to spacejamcrossing from tumblr for this well-written and thorough guide detailing the space requirements for vertical bridges. She(?) got the space requirements for vertical bridges right and got me thinking about how the space requirements for horizontal, vertical, and diagonal bridges are all related.
Thanks to viva-monteor from tumblr for this guide on diagonal bridges. It's not completely accurate, but it gave me a starting point for thinking about buffer zones for diagonal bridges.
Warning: This guide is very long in its entirety. The reason it is so long is because I know that a lot of misinformation about Animal Crossing New Leaf mechanics gets spread around, so I wanted to thoroughly explain what the space requirements for bridges are and also to explain why they are different for the different types of bridges. Most of my theory is based off of actual testing, so I expect my guide to be correct for every possible bridge. I certainly don't want to spread any more misinformation, so I tried to make sure I was being specific and precise whenever possible. If you don't want to read all of this and you just want to trust me, then just skip down to the "Can I put a bridge here?" section.
Note: If you are colorblind and can’t understand the diagrams I use in the “Can I put a bridge here?” section, please let me know. I thought red and green would be logical colors to use, but I may have messed up doing it that way. If it is unreadable for colorblind people, I’ll change the colors.
2nd note: If there are grammar errors or something is written in a way you don’t understand, let me know. I want this guide to be as readable as possible.
3rd note: I’ll add a section in the guide for bridge buffer zones after the bridge is built. It may be useful to help people plan, but remember you can always build a bridge first and then test putting another PWP nearby and then just demolish the bridge if it gets in the way of the other PWP.
Many people who play ACNL know about the "buffer zones" PWPs and buildings have. For most PWPs, the buffer zone is every space adjacent to the PWP (including diagonally adjacent). For houses and other buildings you can enter, it's a little more complicated because of the "entrance spaces" which you cannot place items on, dig holes on, etc. Buffer zones prevent structures from being too close to each other. A structure's buffer zone cannot be on the same space as another structure's buffer zone at any point. For most PWPs, buffer zones require buildings and PWPs to be at least two spaces away from other buildings and PWPs. As too many poor souls have found out, bridges have an abnormally large and mysterious buffer zone and they have a larger buffer zone when you are trying to build them than they have when they are already there. This is why sometimes when you delete a bridge and then try to build another one in the exact same spot, Isabelle won't let you do so.
For those who have a town they can afford to experiment with and have the time, bells, and desire to constantly build and destroy PWPs to test exactly what Isabelle approves of, the challenge of figuring out bridge buffer zones has been that the buffer zones appear to be different for the different angles of bridges. Vertical bridges have wide buffer zones that stretch far East to West, but are not very long North to South. Horizontal bridges appear to have square buffer zones on each side. Diagonal bridges have not been tested or written about much due to the difficulty of finding a suitable location for one and then trying to make sense of a rectangular buffer zone for a diagonal object. All three bridges have buffer zones which are connected in a fairly simple way as you are about to see.
Research is in quotes because I'm just doing experiments in a video game. I'm not finding the cure to cancer, but I hope I can at least save someone's town from permanently losing a bridge. Anyway, the reason I did this is because I have a diagonal suspension bridge in Catopia which I want to replace with a wooden bridge, but the bridge is near both a house and the police station, but not right next to them. Once I bought my second copy of the game, I created a temporary town to do experiments in while I think of what I eventually want to do with that copy. I wanted to figure out exactly what the buffer zone for a diagonal bridge was so I'd know if I could replace that bridge in Catopia. After the painstaking process of finally getting Paula to move out so I could start building diagonal bridges on the river bend, I started the process of building more yellow benches than I could count.
I went off of viva-monteor's guide because it seemed like a logical start. What particularly interested me was her use of the "anchor space", the full space on the land which touches the center of the end of a bridge and how she based the buffer zone off of it. I placed yellow benches to test her buffer zone and I found out that the buffer zone in her guide wasn't correct. After moving the benches around some, I found out that I could place one bench just three spaces North of the northwest anchor space and Isabelle would have no problem with it, but I if I placed another bench four spaces west (and two spaces north) of that same anchor space, then Isabelle would not let me build one there at all. The bench which was a problem was clearly further away than the bench which was okay. The screenshot below shows the situation:
You would think it would be logical to have a square buffer zone with a diagonal bridge, but this isn't the case. As a matter of fact, this problem showed up on both sides of the bridge. I could have benches fairly close north of the anchor space connecting to the north part of my bridge, but they had to be a long distance away west of the anchor space if they weren't far enough away north of it. Furthermore, a bench had to be very far south of the anchor space if the bench was not far enough west of the anchor space as shown in this screenshot:
This was especially confusing since the bridge itself was going East from the northern anchor space, so even if I applied the same buffer zone to every space which the diagonal bridge occupies, including the half-spaces, the buffer zone was still extending into spaces which could not be explained by any space on the bridge itself.
After analyzing the dimensions of the buffer zone on both sides of the river, I came up with a "footprint" theory to explain it. Since every other PWP besides the diagonal bridge is rectangular, it makes some sense to base the buffer zone for a diagonal bridge off of a rectangular footprint which it occupies, even if not every space in the rectangle is occupied by the bridge itself. Sure enough, when I looked at the 5 by 5 square which the diagonal bridge is contained within, the buffer zone could be created by expanding that square three spaces horizontally in each direction and one space vertically in each direction.
I looked back at the buffer zones for horizontal and vertical bridges as explained by jokimori and spacejamcrossing, and I figured out that if you draw the rectangular footprint for each of the bridges which includes their anchor spaces (think of the anchor spaces like entrance spaces; they are part of the PWP even if it isn't completely apparent) and then stretch those footprints by 3 spaces horizontally in each direction and one space vertically in each direction, you get their buffer zones too. I independently tested their buffer zones to verify that they were correct and they were, so I strongly believe my footprint theory accurately describes why the buffer zones are the way they are for each of the bridges. That explains why the vertical bridge has a wide rectangular buffer zone on each end, why the horizontal bridge has a square buffer zone on each end, and why the diagonal bridge has an asymmetric rectangular buffer zone. I don't know why the developers made it that way because it doesn't make much sense in my opinion, but that's the way it is.
I have one last thing to say about my testing. I did tests with the cobblestone and suspension bridges and got the same results for all of the times which I tested both. I didn’t have any of the other bridges unlocked in the town which I did the testing, but I have no reason to believe the type of bridge makes any difference on the buffer zone.
I went off of viva-monteor's guide because it seemed like a logical start. What particularly interested me was her use of the "anchor space", the full space on the land which touches the center of the end of a bridge and how she based the buffer zone off of it. I placed yellow benches to test her buffer zone and I found out that the buffer zone in her guide wasn't correct. After moving the benches around some, I found out that I could place one bench just three spaces North of the northwest anchor space and Isabelle would have no problem with it, but I if I placed another bench four spaces west (and two spaces north) of that same anchor space, then Isabelle would not let me build one there at all. The bench which was a problem was clearly further away than the bench which was okay. The screenshot below shows the situation:
You would think it would be logical to have a square buffer zone with a diagonal bridge, but this isn't the case. As a matter of fact, this problem showed up on both sides of the bridge. I could have benches fairly close north of the anchor space connecting to the north part of my bridge, but they had to be a long distance away west of the anchor space if they weren't far enough away north of it. Furthermore, a bench had to be very far south of the anchor space if the bench was not far enough west of the anchor space as shown in this screenshot:
This was especially confusing since the bridge itself was going East from the northern anchor space, so even if I applied the same buffer zone to every space which the diagonal bridge occupies, including the half-spaces, the buffer zone was still extending into spaces which could not be explained by any space on the bridge itself.
After analyzing the dimensions of the buffer zone on both sides of the river, I came up with a "footprint" theory to explain it. Since every other PWP besides the diagonal bridge is rectangular, it makes some sense to base the buffer zone for a diagonal bridge off of a rectangular footprint which it occupies, even if not every space in the rectangle is occupied by the bridge itself. Sure enough, when I looked at the 5 by 5 square which the diagonal bridge is contained within, the buffer zone could be created by expanding that square three spaces horizontally in each direction and one space vertically in each direction.
I looked back at the buffer zones for horizontal and vertical bridges as explained by jokimori and spacejamcrossing, and I figured out that if you draw the rectangular footprint for each of the bridges which includes their anchor spaces (think of the anchor spaces like entrance spaces; they are part of the PWP even if it isn't completely apparent) and then stretch those footprints by 3 spaces horizontally in each direction and one space vertically in each direction, you get their buffer zones too. I independently tested their buffer zones to verify that they were correct and they were, so I strongly believe my footprint theory accurately describes why the buffer zones are the way they are for each of the bridges. That explains why the vertical bridge has a wide rectangular buffer zone on each end, why the horizontal bridge has a square buffer zone on each end, and why the diagonal bridge has an asymmetric rectangular buffer zone. I don't know why the developers made it that way because it doesn't make much sense in my opinion, but that's the way it is.
I have one last thing to say about my testing. I did tests with the cobblestone and suspension bridges and got the same results for all of the times which I tested both. I didn’t have any of the other bridges unlocked in the town which I did the testing, but I have no reason to believe the type of bridge makes any difference on the buffer zone.
For horizontal and vertical bridges, find the spaces on land where your bridge or potential bridge will be connected to. These allow you to find the edges of the “footprint” of your bridge and from there use the diagram below for the direction your bridge is in as a guide to lay out patterns on every space in the buffer zone (except the river spaces obviously).
dark gray = bridge
light gray = bridge footprint
blue = river
dark red = bridge buffer zone (cannot have any rocks, houses, or PWPs in this area including entrance spaces)
light red = cannot have houses, PWPs, or their entrance spaces in this area, but rocks are okay
green = okay to have houses, rocks, and PWPs in this area including entrance spaces
If any building or rock prevents you from laying a pattern in a space within the buffer zone, then you can't build a bridge there. If your pattern layout is touching any PWP or building, including the entrance space, then you can't build a bridge there. If the pattern layout is touching nothing or a rock, then you can build your bridge. Here are screenshots with examples of bridge locations which are allowed:
Notice that in the screenshot of the vertical bridge, it doesn’t matter that a rock is touching the buffer zone. This is because rocks don’t have their own buffer zones, so they can be one space closer to bridges than PWPs and houses.
For diagonal bridges, finding the footprint is more difficult and requires some visualization because two of the corners of the footprint are in the river, so you can't just start marching off spaces from those spots. I have diagrams for each of the four possible directions of the river bend. Find the one which corresponds to your river bend which you want to place a bridge on. Use the diagram below and your anchor space on the outer curve of the river as a point of reference to find a space which is directly North, South, East, or West of the corner of the bridge's footprint. Figure out where that space is in relation to the corner of the footprint (again, use the anchor space on the outer curve of the river as a point of reference), and from there you should be able to figure out where to place patterns to visibly show the buffer zone.
dark gray = bridge
light gray = bridge footprint
blue = river
dark red = bridge buffer zone (cannot have any rocks, houses, or PWPs in this area including entrance spaces)
light red = cannot have houses, PWPs, or their entrance spaces in this area, but rocks are okay
green = okay to have houses, rocks, and PWPs in this area including entrance spaces
Once you have laid out patterns on every space of the buffer zone, the same rules apply as with horizontal and vertical bridges. If any building or rock prevents you from laying a pattern in a space within the buffer zone, then you can't build a bridge there. If your pattern layout is touching any PWP or building, including the entrance space of houses and some PWPs, then you can't build a bridge there. If the pattern layout is touching nothing or is only touching a rock and no PWPs or entrance spaces, then you can build your bridge.
dark gray = bridge
light gray = bridge footprint
blue = river
dark red = bridge buffer zone (cannot have any rocks, houses, or PWPs in this area including entrance spaces)
light red = cannot have houses, PWPs, or their entrance spaces in this area, but rocks are okay
green = okay to have houses, rocks, and PWPs in this area including entrance spaces
If any building or rock prevents you from laying a pattern in a space within the buffer zone, then you can't build a bridge there. If your pattern layout is touching any PWP or building, including the entrance space, then you can't build a bridge there. If the pattern layout is touching nothing or a rock, then you can build your bridge. Here are screenshots with examples of bridge locations which are allowed:
Notice that in the screenshot of the vertical bridge, it doesn’t matter that a rock is touching the buffer zone. This is because rocks don’t have their own buffer zones, so they can be one space closer to bridges than PWPs and houses.
For diagonal bridges, finding the footprint is more difficult and requires some visualization because two of the corners of the footprint are in the river, so you can't just start marching off spaces from those spots. I have diagrams for each of the four possible directions of the river bend. Find the one which corresponds to your river bend which you want to place a bridge on. Use the diagram below and your anchor space on the outer curve of the river as a point of reference to find a space which is directly North, South, East, or West of the corner of the bridge's footprint. Figure out where that space is in relation to the corner of the footprint (again, use the anchor space on the outer curve of the river as a point of reference), and from there you should be able to figure out where to place patterns to visibly show the buffer zone.
dark gray = bridge
light gray = bridge footprint
blue = river
dark red = bridge buffer zone (cannot have any rocks, houses, or PWPs in this area including entrance spaces)
light red = cannot have houses, PWPs, or their entrance spaces in this area, but rocks are okay
green = okay to have houses, rocks, and PWPs in this area including entrance spaces
Once you have laid out patterns on every space of the buffer zone, the same rules apply as with horizontal and vertical bridges. If any building or rock prevents you from laying a pattern in a space within the buffer zone, then you can't build a bridge there. If your pattern layout is touching any PWP or building, including the entrance space of houses and some PWPs, then you can't build a bridge there. If the pattern layout is touching nothing or is only touching a rock and no PWPs or entrance spaces, then you can build your bridge.
Wow, that was a lot to write. Thanks once again to the people whose guides I listed above. I wish the game developers would have made bridge mechanics make more sense, but we just have to deal with what we have. Hopefully this guide will be helpful to people. Have fun building bridges everyone!
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I never had any problem placing a bridge, I guess I was very lucky if it's as tricky as you show us.
