It would appear that both are taxable:
http://www.window.state.tx.us/taxinfo/taxpubs/tx96_259.html
Non-residential real property repair, restoration, or remodeling
All charges for labor and materials to rebuild, replace, alter, modify or upgrade existing non-residential realty. Non-residential real property repair, restoration and remodeling do not include the addition of new usable square footage or scheduled and periodic maintenance. Non-residential real property includes commercial establishments such as manufacturing facilities, restaurants, offices, and hospitals, but does not include property used as a family dwelling such as apartment complexes, nursing homes, and retirement homes.