Shiva Purana
गृहाद्दूरं ततो गत्वा बाह्यतः प्रवृतस्तथा । उदण्मुखः समाविश्य प्रतिबंधेऽन्यदिण्मुखः 1-13-१० ।
It must be in a place far off from the house. It must be a covered place. He shall sit facing the north. If it is not possible due to any obstacle he can sit facing other directions.
english translation
gRhAddUraM tato gatvA bAhyataH pravRtastathA । udaNmukhaH samAvizya pratibaMdhe'nyadiNmukhaH 1-13-10 ।
hk transliteration by Sanscript