All persons and association of persons, including corporations, performing labor upon or bestowing skill or other necessary services on, furnishing materials or leasing equipment to be used or consumed in or for a work of improvement of real property, except Public Works, shall have a lien upon such property as security for the payment of the value of such labor, materials, skill or equipment so furnished, whether performed orfurnished at the request of the owner or of any person acting by his authority or under him as contractor or otherwise. For the purposes of this Chapter, every contractor, subcontractor, architect, builder or other person having charge of work of improvement or a portion thereof shall be held to be the agent of the owner.