Texas tenants are legally entitled to rental property that meets basic structural, health, and safety standards and is in good repair. If a landlord fails to take care of important maintenance, such as a leaky roof or a broken heater, you have several important legal rights, including the right to "repair and deduct"—that is, to hire a repairperson to fix a serous defect that makes a unit unfit (or buy a replacement part or item and do it yourself) and deduct the cost from your rent.
Before you can use the repair and deduct remedy, make sure that the circumstances justify you paying less rent and that you comply with state legal requirements on things like notice you must provide your landlord. Check Texas state law (see resources below) on the following:
For an overview of Texas landlord-tenant law, including your rights to habitability, see http://texastenant.org/repairs.html.
For state law on repair and deduct, see Texas Property Code sections 92.056 and 92.0561.
For state law prohibiting landlord retaliation, see Texas Property Code section 92.331.
See the Laws and Legal Research section of Nolo for advice on finding and reading statutes and court decisions.
Also, check your local housing ordinances for any city or county rules that cover tenant rights when it comes to repairs. Contact your local building or housing authority. To find yours, call your mayor or city manager's office or check your city or county website.