It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When you disagree about a road, leave it seven cubits wide; and whoever constructs a building should support it on his neighbour's wall."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلح / 11380