The building department monitors new building conditions and construction, and oversees the maintenance of older multi-family structures. Also enforces the state and local building codes, housing standards and ordinances, to the review of applications for permits of new buildings, repairs, alterations, signs, and rooming houses, in addition to electrical and plumbing work. The building department accepts complaints from tenants about conditions the landlord fails to resolve.

Provides anti-litter education programs in Islip as well as materials and equipment to effect hands-on clean-up and beautification. Also offers Adopt-A-Highway/Adopt-A-Spot program, Junior Commissioner and KIC Curriculum educational programs, Clean Teams, Earth Day events, Beautification projects, Anti-Graffiti campaign and a Commendation Letter Program.