"79-3603. Tax imposed; rate. From and after the effective date of this act, for the privilege of engaging in the business of selling tangible personal property at retail in this state or rendering or furnishing any of the services taxable under this act, there is hereby levied and there shall be collected and paid a tax as follows:
. . . .
"(p) a tax at the rate of three percent (3%) upon the gross receipts for the service of installing or applying tangible personal property which when installed or applied is not being held for sale in the regular course of business, and whether or not such tangible personal property when installed or applied remains tangible personal property or becomes a part of real estate, except that no tax shall be imposed upon the service of installing or applying tangible personal property in connection with the original construction of a building or facility or the construction,reconstruction, restoration, replacement or repair of a bridge or highway. The tax imposed pursuant to this subsection shall not be applicable to said services which were rendered on and after the effective date of this act pursuant to a written contract for a fixed price and not subject to negotiation or alteration entered into prior to May 15, 1977.
"For the purposes of this subsection:
"(1) `Original construction' shall mean the first or initial construction of a new building or facility. The term `original construction' shall include the addition of an entire room or floor to any existing building or facility, the completion of any unfinished portion of any existing building or facility and the restoration, reconstruction or replacement of a building or facility damaged or destroyed by fire, flood, windstorm, hailstorm, snowstorm, lightning, explosion or earthquake, but said term shall not include replacement, remodeling, restoration, renovation or reconstruction under any other circumstances;
"(2) `Building' shall mean only those enclosures within which individuals customarily live or are employed, or which are customarily used to house machinery, equipment or other property, and including the land improvements immediately surrounding such building . . . ."