ArchitectureCraft Mod allows you to not only have sloped roofs but also blocks sloping in any direction, create round corners, arches, and other rounded structures, and give your windows nice-looking frames. This is a revamped and expanded version of Greg’s Blocks.

Detail and Download here : ArchitectureCraft Mod 1.8.9/1.8

See also : Minecraft mods 1.8