[2022] Building Mechanics

There are six significant things to understand when building in 7DTD.
1: Vertical support, IF there is an unbroken line of blocks (terrain included) from bedrock, is effectively infinite; Horizontal support is finite.
2: Horizontal support begins at the nearest valid vertical support.
3: Horizontal support strength is rated off the support values at the vertical-horizontal connection point, and at each horizontal->horizontal connection; And is still limited by the material being horizontally supported.
4: Everything has mass. Player included.
5: Every material type can only support so much material horizontally, based on the mass mentioned in #4
6: No matter how much mass vs support you have, you cannot extend more than 15 blocks out. And the 15th block in most cases will not support the weight of anything; player included.

So, Because of #1, You can build a 1 wide pillar to the maximum build height with no issues. It will never collapse because it's support is infinite.

However, because of #2-6, Making modifications to portions of a base that are horizontally supported can be dangerous.

For example, Wood has a horizontal support of 40 and a mass of 5, while steel blocks have a support of 300 and a mass of 20.

If you use wood as your vertical->horizontal connection point, and then attempt to place steel blocks on it, you can extend 2 steel blocks out- The third will collapse, because 60 exceeds wood's support of 40. Reverse things, however, And you can extend 8 wood blocks out from a steel connection point- Only 8, because of #3; despite steel being able to support 300, wood still has a limit of 40, and so can only support 8 blocks (5x8=40)...

And because of #6, even if you, for example, extended out 13 blocks of steel and then tried to place 8 more blocks of wood ((13x20)+(8x5)=300), you would only be able to place 2 blocks more in that straight line; You could however place 6 more wood blocks pretty much anywhere on the extension- Just not in a way that will make it extend more than 15 from the vertical support.



Now, There are some odd idiosyncrasies to the way the game calculates distances- Namely that you can use angles and specific placement patterns to build more than you should really be able to build. If you've pushed your build near limits of support, when you break something and the game recalculates stability, even if the broken thing SEEMS like it's non essential, it could turn out to have been painfully imperative for that piece to be there.

For some visual aid, Here's a way you can use angles to build more than you should really be able to-

https://steamcommunity.com/sharedfiles/filedetails/?id=2867307076
In this picture, I have two examples. One is a steel pillar on the left for vertical support; the other is a wood pillar for vertical support.

And all of the horizontally supported material is wood. By functionally using wood blocks as a 'supporting beam', I have extended the 'vertical connection' point of wood 7 blocks out, from which I then extended 8 full wooden blocks.

Now, You might realize here that this is in direct contradiction to the statistics labeled earlier- Wood has a mass of 5, and a support of 40. So this shouldn't technically be possible. In fact, you can even do this with only wood- You dont need the steel pillar- In the right example I've made wood support 75 mass despite its actual support capping out at 40

But it's there; Fully buildable. You just have to start from the bottom and build upwards. Now, important to note here is that the final block of the 8 block extension cannot support a player; It has reached the mass support of 40 that wood can hold, and any additional mass, player included, causes a collapse. You could, however, build a 14 block extension in this same way, meeting in the middle and have a span of 28 blocks between 2 vertical pillars with nothing but wood as your material.
Here's a wooden bridge spanning 28 blocks Fully supported of course. :)
https://steamcommunity.com/sharedfiles/filedetails/?id=2867312970


Now for example 2:
https://steamcommunity.com/sharedfiles/filedetails/?id=2867308035
This was done by making the whole thing solid, and then removing blocks layer by layer starting at the top and from the end closest to the extension- NOT to the vertical pillar. Doing it in pretty much any other way will cause a collapse. In doing this, the 15th block is no longer placeable- capping out at 14. However, this is again, buildable; And fully supported. You can walk along the full 14 block beam and not collapse any of it.

Let me be clear, this is technically stable- But beware when using it. It's much better to have the full solid version if you have the choice.


Now, the reason all this matters is that, if at any time your modification to a build causes some segment to either A: Pass over it's mass limit in a way that isn't idiosyncratically supported, or B: makes a part of the build exceed 15 blocks in length, it will collapse.


This video here is several alphas old, and the specific Mass and Horizontal Support values listed for materials in the video may no longer be accurate- Be sure to check descriptions in game for up to date values. However, the Mechanics of structural integrity haven't really changed since; So you can learn a fair bit about SI mechanics from this video.
https://www.youtube.com/watch?v=7hq_HxCqgyU&ab_channel=MaxFox


Two final notes.

One, As #4 says- Everything has mass. Player included... This means zombies too. And furniture. And falling rubble from a collapsing structure as well as the permanent rubble it occasionally becomes- If you're building on the bleeding edge of support/mass values, A collapse can very easily propagate and destroy much/all of your build.

And two... If you're making changes to your build, Use wooden frames to build temporary vertical support pillars- Vertical support is basically infinite, regardless of material type. So it's easy to quickly shore things up just in case; and with frames, you can just pick them back up after with ease. Doing this and providing adequate additional support can prevent your entire build from collapsing.

Edit: might be some mistakes in phrasing and formatting; Apologies if so. Was written in bits and pieces as I found time, and rearranged twice.
Edit 2: Fixed some silly typos.

Originally posted by Macdallan: @Shurenai - Wow, nice post! That's probably everything they need all in one place.

Hopefully!

One thing I forgot to mention is upgrading things; When you upgrade things, the support/mass values change since the material is different now. So it's important to upgrade your vertical pillar first (most importantly at the vertical->horizontal connection points), and then upgrade outward from there so you don't accidentally put more mass on a supporting structure than it can support.

This isn't usually super important if you build within reasonable tolerances- But it is important to keep in mind. :)