In this tutorial I have Open for Business installed and I make use of the indoor foundation tool. This tutorial will still work if you don't have OfB but the method will be slightly different.
Ok, lets get started.
1. First of all choose where you want a corner of your house to be when it is finished. I have chosen the back left corner. It doesn't matter which you choose but make sure if you choose a front corner that you leave room for adding stairs later. Now raise that corner square by FOUR clicks.
2. Next, using the level terrain tool, drag out the size of your house from the raised square. This doesn't have to be a box shape, I've just done it for simplicity.
You should end up with something like this:
3. Now grab the foundation tool and drag over the raised area.
Let go of the mouse and you will have placed your foundation.
4. Switch back to the level terrain tool and, starting from a piece of ground at the original height, drag across your foundation.
Release the mouse button and the ground will be levelled leaving your foundation at its taller height.
5. Now this is the part where the tutorial will differ slightly depending on if you have OfB installed or not.
OfB users do this: Select the indoor foundation tool that came with OfB and drag a small box out from the regular foundation.
This is what you should end up with:
Non OfB players: Instead of using the indoor foundation, simply use the regular foundation. The only difference is that your lower part will NOT be able to touch the existing foundation so make sure to leave a one tile gap inbetween. If your newest foundation addition does touch the existing foundation then it will just raise itself to the match the taller one.
6. Now its just simply a case of connecting the different levels together with connecting stairs.
Then you can add some railings and walls to your house:
7. Finally all that's left to do is to decorate it nicely. I'm sure you can all do a better job than I have. I just did this quick for this tutorial hence why the house has no roof.
8. Smile contently at your creation and enjoy playing it.
