... the cottage() example function, and found that the blocks.stairs.birch behave differently than {brick, cobblestone, jungle, nether, oak, quartz, sandstone, spruce, and stone} when used with the prism0() function to build the rooftop. It was surprising, but perhaps it's known that birch stairs are a bit different? Basically the alignment of the birch stairs is not correct, so the rooftop doesn't get built correctly.

https://groups.google.com/forum/#!topic/scriptcraft---scripting-minecraft/JNaelBfoNYQ