Converting a Retail Space Into a Dental or Medical Clinic: What the Change of Occupancy Triggers

Modern Northwest · Published September 25, 2026

Turning a store into a dental or medical office is a change of occupancy: retail is Group M under the Oregon building code, and dental offices and outpatient clinics are Group B. In Portland that change needs a permit even if you remodel nothing, ends with a new Certificate of Occupancy, and brings the space up to the rules for its new use. The items that usually grow the scope are restrooms (1 per 25 occupants for the first 50 in a clinic, against 1 per 500 in retail), accessibility, ventilation, and, if the practice sedates patients, the jump to an ambulatory care facility.

Former storefronts are some of the most attractive spaces for a new practice: street visibility, parking, and a big open floor. They are also where the most expensive surprises come from, because a store was never designed for plumbing at every room. We build dental and medical offices across Portland and Southwest Washington, and this is the list we check before a client signs a lease on a former retail space.

Is converting retail to a dental office a change of occupancy?

Yes. The 2025 Oregon Structural Specialty Code, based on the 2024 International Building Code and in force from October 1, 2025, puts the two uses in different groups:

Occupancy groups and fixture ratios from the 2025 OSSC. The occupant load factors are from the 2021 IBC table, which the Oregon code follows closely; confirm against the adopted edition for your permit.

The code defines a change of occupancy as any change in the occupancy classification of a building or structure. Under OSSC Chapter 34, which is where Oregon puts its existing-building rules, the change cannot be made until the building official has issued a certificate of occupancy. Under the prescriptive compliance path, the building has to be made to comply with the new construction requirements for the new use.

What does Portland require for a change of occupancy?

A permit, even with no construction. Portland Permitting and Development states that a permit is required to document a change of use or change of occupancy classification of a building, even where no alterations are planned or required by the code. When it is approved you get a new Certificate of Occupancy. The same city page notes that a change of use can also bring system development charges, which are fees for the added impact on city infrastructure, so ask about them early.

A dental conversion is never a no-alterations project in practice, so it will also carry the building and trade permits covered in what permits a dental office build-out needs.

Is a dental office allowed where the store was?

Usually, but check the zone before the lease. Portland's zoning code puts medical and dental clinics in the Office use category, not Retail Sales and Service. In the commercial and mixed use zones, Office is allowed outright in CM2, CM3, CE and CX, and allowed with limits in CR and CM1, where each individual office use is generally limited to 5,000 square feet of net building area. A former store in a CM1 zone can still work for a small practice, but not for a large one.

Why restrooms are the first scope item

Retail needs very few toilets. Oregon's fixture table requires 1 water closet per 500 occupants in a Mercantile space, and 1 per 25 for the first 50 in a Business occupancy, a row Oregon applies to outpatient clinics as well as ordinary offices. The Business occupant load is lower per square foot, so the difference is not a straight twenty to one, but a suite that got by with one restroom as a store often needs more, or needs its existing ones rebuilt to accessible sizes. The Chapter 34 rules say a change of occupancy subject to different fixture requirements must comply with the intent of the plumbing chapter. Our commercial bathroom requirements guide walks through the counts.

The plumbing the store never had

A retail floor usually has plumbing in one corner. A dental office wants water, drain, vacuum and air at or near every operatory, which means cutting the slab in a building that was never laid out for it. Whether the slab can be cut, where the lines can run, and where a vacuum and compressor room can sit are the questions that decide whether a storefront is a good dental space. The specifics are in our dental office plumbing and rough-in guide.

Ventilation changes with the use

Mechanical systems are sized to the occupancy. The International Mechanical Code's outdoor air table uses different rates for retail sales and for office spaces, so a store's system is not automatically right for a clinic. Treatment rooms are their own question: the IMC sends ambulatory care facilities to ASHRAE 170, the health care ventilation standard. In a dental office the sterilization area and any nitrous use add exhaust needs on top. Plan on the HVAC being redesigned rather than reused as-is.

Sedation changes the whole classification

This is the question to answer before any drawings. The IBC defines an outpatient clinic as a facility providing care to persons who are not rendered incapable of self-preservation. An ambulatory care facility is one where patients are rendered incapable of self-preservation by the services provided, which is what general anesthesia and deeper sedation do. Under Section 422 of the 2021 IBC, once four or more care recipients are incapable of self-preservation, the space needs separation by a fire partition, and ambulatory care facilities carry their own sprinkler and fire alarm requirements. A practice that plans to add sedation later should design for it now.

Accessibility comes with the alteration

Under the 2010 ADA Standards, an alteration that affects the usability of a primary function area also brings the path of travel to it, meaning the entrance, restrooms and routes that serve it, up to the point where that work would cost more than 20 percent of the alteration. Portland notes that Oregon goes further: state law requires that up to 25 percent of the value of the total construction costs be spent removing existing architectural barriers. In a former store that often means the entrance, the restrooms and the route between them.

The pre-lease checklist for a retail-to-clinic conversion

• Zone confirmed, and the office use size limit checked in CR or CM1
• Sedation plan settled, so the occupancy is outpatient clinic or ambulatory care from day one
• Restroom count run for the new occupancy, and existing restrooms checked for accessible size
• Slab and plumbing path checked for water, drain, vacuum and air at the operatories
• Mechanical room location and HVAC capacity for the new use
• Entrance and path of travel checked against the accessibility spend
• System development charges asked about before the budget is set

All of this is answerable in a walkthrough before you sign, and it belongs in the lease negotiation. The dental TI allowance guide covers how to make the landlord's money fit this scope, and the dental build-out timeline covers the calendar.

Frequently asked questions

The bottom line

A store becoming a clinic moves from Group M to Group B, needs a Portland permit and a new Certificate of Occupancy even before any construction, and has to meet the rules for its new use: more restrooms, real plumbing to the treatment rooms, new ventilation, accessibility, and a different classification again if the practice sedates patients. None of that rules out a storefront. It just has to be priced before the lease, not discovered after.

Modern Northwest builds dental offices and medical offices in Portland and Vancouver, WA. Reach out for a free walkthrough of the space before you sign.