Addon: Vertical Slabs
Author: PurpleByte
Small changes to block geometry can transform a facade or interior. Upright slabs and corner pieces give builders extra control over wall thickness and architectural edges.

Building shapes
Use vertical slabs for slim walls, room dividers, facade detailing and structural accents. Corners add horizontally oriented stair geometry, giving you another option for joining edges and shaping architectural details. The forms suit modern interiors as well as medieval buildings.
An included guidebook explains the new blocks and shows how they can be used in builds. Both singleplayer and multiplayer worlds are supported.
How to install the add-on
Download the .mcaddon or .mcpack file, open it with Minecraft and wait for the import to finish. Then enable the resource and behavior packs in the world settings. If the add-on requires experiments, turn them on before launching the world.