Houses are being built in the nether out of furnaces and doors. The builders /cprivate the blocks and effectively have protected areas in the nether because the LWC protected blocks can't be broken by anyone but the owner. In the past, I've dealt with /cprivate'd blocks in the nether with TNT, but I tried using TNT recently and it seems that it doesn't work in the nether anymore.
Example of such a house:
Example of such a house: