Plentiful, easy to work, strong and an excellent barrier to heat, sun-dried mud brick was one of the most common construction materials in ancient Egypt.  Straw and other debris added to the bricks gave them better tensile strength.  Plaster, woven straw coverings and stone foundations often protected mud brick walls from the elements.  Stone was used preferentially for monuments and tombs because it would better survive the elements without such protections, lending a material immortality to the intended spiritual immortality of the nobles and notables buried therein.