Do I need a permit for residential demolition in Dallas County (Unincorporated)?

Most likely yes. Residential demolition usually requires a permit in Texas. Confirm the specifics with Dallas County (Unincorporated).

Section R105.1 of the 2012 International Residential Code, which Texas cities enforce under Local Government Code 214.212, requires a permit to demolish a building or structure. The Texas Department of State Health Services states that one private residence is not subject to the federal asbestos NESHAP rules and that no state notification is required before demolishing it. Texas law excludes a private residence from the definition of public building (Occupations Code 1954.002), so the asbestos survey that a city must see before permitting demolition of a public or commercial building (Section 1954.259) does not apply to a single home. Older homes can still contain asbestos, so a survey is a sensible precaution. This job demolishes a home or a structure with active water, sewer, gas or electrical service. Utilities normally must be disconnected and capped by the utility or a licensed trade before demolition, and departments commonly require proof of that before issuing a demolition permit. Ask your department and your state environmental agency whether an asbestos or lead survey is required before demolition, and whether a sewer cap inspection applies.