Upgrade Floors & Walls
It’s important that you know how to upgrade your floors and walls in Last Day on Earth: Survival. Whilst it’s not super important in the game right now due to there being no official multiplayer, you should still do it.
As you’re aware, to build standard walls in Last Day on Earth it costs 1 log per item. You can build them using the construction icon located in the top right under your minimap. However once you start to reach higher levels, certain objects such as chests can only be built on Level 2 floors.

How to upgrade Floors & Walls in Last Day on Earth
Upgrading Floors & Walls in Last Day on Earth is easy. Start by making sure you have at least the 1st level floors and walls. Head into building mode by selecting the construction icon located under your minimap.
Now choose a wall or floor piece, and a small tool tip will pop up. You can see the materials that are needed to upgrade each part. If you have them in your inventory, the arrow will be green and you can press it to upgrade. In this tool tip, you can press the far left icon to destroy floors and walls and remove them from your base.
To upgrade Level 1 Floors to Level 2 costs 5 Limestone and 5 Pine Planks. Upgrading Level 1 Walls to Level 2 costs 10 Limestone and 20 Pine Planks.

Now, upgrading from Level 2 Floors to Level 3 costs 10 Stone Bricks and 5 Iron Bars. Finally, upgrading Level 2 walls to Level 3 will cost you 20 Stone Bricks and 10 Pine Planks.

Actually upgrading floors and walls are very expensive. Also, Zombies will still tear down Level 2 walls pretty easy. Make sure to check out our guide for surviving a horde attack and to also check our Last Day on Earth tips & tricks.