Medical and dental space is among the best cost segregation material in commercial real estate, because so much of the fit-out exists to serve equipment rather than the building. The governing idea comes from Reg 1.48-1(e) and runs through the IRS Cost Segregation Audit Techniques Guide: a plumbing line or electrical circuit whose sole justification is a specific piece of machinery is personal property, 5- or 7-year MACRS, while systems that keep the building habitable stay at 39 years.
The systems that reclassify
In a dental practice, each operatory carries chair-side water, drain, vacuum, and compressed air lines that exist only for the delivery units; those runs, plus the central vacuum pump and compressor, are classic 5-year property. Medical suites add medical gas piping, dedicated circuits and transformers for imaging equipment, lead-lined walls and doors installed as x-ray shielding, nurse call wiring, and reinforced casework. Built-in cabinetry throughout clinical space typically reclassifies, as do decorative lighting, millwork, and removable flooring in reception areas. Sterilization room plumbing and the dedicated exhaust serving lab equipment follow the same logic. What stays long-life: the general HVAC conditioning the suite, restrooms, the primary panel, fire protection, and everything structural.
A worked example
A periodontist buys a $1,600,000 office condo in mid-2026 and spends $900,000 building out 6 operatories, a surgical suite, imaging, and sterilization. On the $900,000 build-out, suppose a study allocates $330,000 to 5- and 7-year property, operatory utilities, vacuum and air plant, imaging electrical, shielding, and cabinetry, and another $420,000 to 15-year qualified improvement property under IRC section 168(e)(6), since the work is interior improvement to a nonresidential building placed in service after the building. Only $150,000 remains at 39 years. With the project acquired after January 19, 2025, OBBBA's permanent 100 percent bonus under IRC section 168(k) makes $750,000 of the build-out deductible in year 1. The $1,600,000 purchase (less land) can be screened separately for its own component split.
Owner-occupants have an extra angle
Many practice owners hold the real estate in one entity and the practice in another. The self-rental and grouping rules under section 469 affect whether accelerated losses can offset practice income, and section 179 expensing, capped at $2,500,000 with a $4,000,000 phase-out under OBBBA, can apply to qualifying personal property and certain nonresidential improvements where bonus is less attractive for state purposes.
Where the answer is weaker
A plain-vanilla medical office with no clinical fit-out behaves like ordinary office space. Leased space raises the ownership question: the party that paid for the build-out depreciates it. And every reclassified system needs the equipment-service rationale documented, because this is precisely the boundary the Audit Techniques Guide tells examiners to test. Amadae's cost segregation screen gives practices a screening estimate of the split before an engineering study is commissioned, and Amadae prepares the return, or the Form 3115 catch-up for build-outs already sitting at 39 years.