The Texas sales and use tax rules surrounding contractors and other construction-related work are incredibly complex. Additionally, the rules are structured to have broad application and thus impact many industries, including general construction, oil and gas related services, demolition, and more. The application of these rules is a fact-intensive undertaking and should be performed on a case-by-case basis, but I have outlined a basic overview of these rules below.
What is a “Contractor”?
The Texas Comptroller defines a “contractor” as a person who performs one or more of the following real property improvements and who, in making the improvement, incorporates tangible personal property into the real property being improved: 
Building new improvements to residential or nonresidential real property; or
Completing any part of an uncompleted new structure that is an improvement to residential or nonresidential real property
“Scheduled and Periodic Maintenance”
Making improvements to real property as part of periodic and scheduled maintenance of nonresidential real property 
“Residential Repair & Remodel”
Repair, restoration, maintenance, or remodeling of residential real property
Work performed by a “contractor” also specifically includes the initial finish-out work to the interior or exterior of an improvement to real property , and the addition of new usable square footage to an existing building. 
Is Work Performed By a “Contractor” Subject to Sales Tax?