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Residential vs. commercial roofing: the Arlington County test, then the code differences
In Arlington the line is not drawn by what a building is used for. The county asks two questions: is it a detached one- or two-family dwelling or a townhouse, and is it no more than three stories above ground level? A yes to both means the residential permit path; anything else is commercial, even an apartment building people call home. This guide starts with that test, then sets the two Virginia code paths side by side, using the county pages, the Virginia construction codes, the Code of Virginia and federal fall protection rules. To talk through your own building, book a phone consultation.
- Two tests, both required: one- or two-family or townhouse, and three stories or fewer
- Three or more dwelling units: the county calls the building commercial
- Slope limits follow the covering, not the building type
Which permit path does the county assign?
Before anyone compares shingles with membranes, the county sorts the project. It says the permit type is set by the International Code Council standards used to review the permit, not by whether the building is a home or a shop. The residential permit needs both answers below to be yes.
- Detached one- or two-family dwelling, or a townhouse? Single-family houses, two-family houses and townhouses meet the first standard.
- No more than three stories above ground level? Height is counted as the Building Code defines it, not by how the building looks.
- Did either answer fail? The county says any project that does not meet the residential standards takes the commercial building permit.
The county gives apartment buildings with three or more dwelling units as an example of residential property that the Building Code treats as commercial. The Virginia Construction Code draws the same line in its occupancy groups: Group R-2 covers more than two dwelling units, and Group R-3 covers no more than two.
The county pages are uneven on roofs. The residential page prints a re-roof table, which the Arlington hub guide walks through. The commercial permit page lists new construction, additions, interior alterations and demolition, and the text of the page never uses the word roof. For a building on the commercial side, the answer to "does my re-roof need a permit" comes from the Permit Arlington Center, which the county lists at 703-228-3800 on its residential page.
Side by side: where the two code paths differ
The Virginia Construction Code says the residential code applies to detached one- and two-family dwellings and townhouses as set out in its Section 310, and the building code covers the rest. Each has a roof chapter. The table sets them side by side, from the 2021 texts as a third-party site publishes them.
| Topic | Residential path (Virginia Residential Code) | Commercial path (Virginia Construction Code) |
|---|---|---|
| Roof chapter | Chapter 9, Roof Assemblies. Its sections run from General to Reroofing. | Chapter 15, Roof Assemblies and Rooftop Structures, sections 1501 to 1512, which add a section on rooftop structures. |
| Drainage | R903.4: roof drains at each low point unless the roof slopes to drain over its edges. Secondary drains or scuppers where the perimeter would trap water; overflow inlets sit 2 inches above the low point, and scuppers are three times the drain size with a 4 inch minimum opening height. | 1502: drainage follows Section 1502, Section 1611 and Chapter 11 of the International Plumbing Code. Secondary drains where the perimeter traps water. Section 1611 designs each portion of the roof for rain load, using the 100-year 15-minute rainfall or approved local data. |
| Fire classification | R902.1: Class A, B or C roofing where the law of the jurisdiction requires it or where the roof edge is less than 3 feet from a lot line. | 1505.1: a minimum class set by Table 1505.1 according to the building's type of construction. The table notes allow non-classified coverings on Group R-3 and U buildings with at least 6 feet of fire-separation distance. |
| Replacing a covering | R908.3: replacement removes existing layers down to the deck. Recovering over the old covering is permitted in listed conditions. | 1512.1 sends reroofing to Chapter 15 and to sections of the Virginia Existing Building Code. The existing-building text applies Chapter 15 to recovering or replacing a covering. |
Sources: Virginia Residential Code 2021 chapter 9 and Virginia Construction Code 2021 chapters 1, 3, 15 and 16, UpCodes copies; Virginia Existing Building Code 2021 chapter 6. Opened October 26, 2026.
Where the two agree on a recover
Both the residential text and the existing-building text bar a recover where the base is water soaked or too deteriorated to carry more roofing, where the existing covering is slate, clay or cement tile, and where two or more applications are already on the roof.
An exception for old flat roofs
The existing-building text says a replacement or recover of an existing low-slope roof need not meet the one-quarter-in-12 minimum, nor add secondary drains, where the roof provides positive drainage. Existing secondary drains may not be removed unless replaced by compliant ones.
The pages read for this guide do not say which family of text a building official applies to the re-roof of an existing house. Ask the Permit Arlington Center, and have the scope name the code chapter.
Does building type change the slope limits?
A common idea is that houses have steep roofs and businesses flat ones. The codes do not say that. In both roof chapters the minimum slope belongs to the covering, and the numbers match.
| Covering | Minimum slope in both chapters |
|---|---|
| Asphalt shingles | 2 in 12 (17 percent) |
| Lapped, nonsoldered metal panels without applied lap sealant | 3 in 12 (25 percent) |
| Built-up roofing | 1/4 in 12 (2 percent); coal-tar built-up 1/8 in 12 |
| Modified bitumen | 1/4 in 12 |
| Thermoset and thermoplastic single-ply membranes | 1/4 in 12 |
| Sprayed polyurethane foam and liquid-applied roofing | 1/4 in 12 |
Source: Virginia Residential Code 2021 section R905 and Virginia Construction Code 2021 section 1507, UpCodes copies. Design slope for drainage is the wording the codes use for the membranes.
Both chapters require coverings to be applied per the manufacturer's installation instructions, so those belong in the written scope. See the flat roof, TPO, EPDM and metal roof pages for how those systems are built, and the materials overview for the wider list.
Who prepares the plans?
Residential side
- For a new house, the county says plans prepared by a Virginia-registered design professional must carry the original signature, seal and date.
- Code of Virginia section 54.1-402 lists single- and two-family homes, townhouses and multifamily dwellings of up to three stories among plans that need no architect or engineer license, if the plans show the author's name, address and occupation.
Commercial side
- For new commercial construction the county asks for construction documents that include a cover sheet with the scope of work and a code analysis.
- The same page points to a seal chart for the question of whether a design professional's seal is required under section 54.1-402.
- That section also lists business and mercantile buildings up to 5,000 square feet or three stories, and factory and storage buildings up to 15,000 square feet or three stories.
The state section lists who may prepare plans without a design license. It does not say what a re-roof needs, so ask the county whether your work needs drawings.
On the roof: the slope line OSHA draws
One federal rule does turn on slope. The federal fall protection standard defines a low-slope roof as 4 in 12 or less and a steep roof as more than 4 in 12, and it gives roofing work on each its own paragraph. Roofing work, in its definition, includes hoisting, storing, applying and removing roofing materials.
On a low-slope roof, the standard lists guardrails, safety nets, personal fall arrest systems, or a warning line combined with one of those or with a safety monitoring system. On a steep roof it lists guardrails with toeboards, safety nets or personal fall arrest systems. A separate paragraph for residential construction asks for guardrails, nets or arrest systems and presumes they are feasible. Which paragraph covers a job is for the employer and the regulator, so ask how the crew will be protected.
Nine questions to put in writing before you sign
- Which permit path does Arlington assign my address, residential or commercial, and who confirmed it?
- Which roof chapter does the scope follow, and for which edition of the code?
- What is the covering, by name, and what design slope does the roof have?
- How does the roof drain: over the edges, through drains, or through scuppers, and is there a secondary path for overflow?
- Is the work a tear-off to the deck or a recover, and which condition of the code allows it?
- What fire classification does the assembly carry, and how far is the roof edge from the lot line?
- Are drawings needed, who prepares them, and are they sealed?
- Which manufacturer instructions does the scope follow, and are they attached?
- What is the contractor's Virginia license number, class and specialty?
Which Arlington guide fits your building
Roofers of Arlington installs, repairs and replaces roofs, flat and metal systems included, in Arlington and nearby. The Arlington hub guide holds the permit table and historic review rules; these guides take one building type each.
- 1940s subdivision roofs: houses that meet the residential standard.
- Columbia Pike garden apartments: multi-unit buildings and who decides.
- Clarendon and Lyon Park flat roofs: low-slope membranes on apartment buildings.
- Condo and co-op roof replacement: the association path.
- Slate roofs on historic buildings: what the nominations record.
For the work itself, see commercial roofing, roof replacement and roof repair. If you would like to describe your building by phone, book a phone consultation. We would ask for the address, the stories and dwelling units, and what you can see.
Every document opened for this guide, with dates
All opened October 26, 2026. Arlington County pages are blocked to automated downloads, so the county text comes from archived copies with the capture dates shown. The code texts are third-party copies, so confirm the edition your building official applies.
- Arlington County: Residential or Commercial? (archived copy, January 29, 2026)
- Arlington County: Residential Building Permit (archived copy, December 30, 2025)
- Arlington County: Commercial Building Permit (archived copy, December 30, 2025)
- Virginia Residential Code 2021, Chapter 9, Roof Assemblies, UpCodes copy.
- Virginia Construction Code 2021, Chapter 15 and Chapter 16, section 1611, UpCodes copies.
- Virginia Construction Code 2021, Chapter 3, occupancy groups and Chapter 1, scope, UpCodes copies.
- Virginia Existing Building Code 2021, Chapter 6, Alterations, UpCodes copy.
- Code of Virginia 54.1-402, further exemptions for architects and engineers.
- 29 CFR 1926.500, fall protection scope and definitions and 1926.501, duty to have fall protection, Electronic Code of Federal Regulations.
Questions people ask
Is my Arlington condo building a residential or a commercial roof?
Under the county test, a building is residential only if it is a detached one- or two-family dwelling or a townhouse and has no more than three stories above ground level. The county's residential permit page gives apartment buildings with three or more dwelling units as an example of a commercial building. A condo building with three or more units therefore falls on the commercial side of the permit test.
Is a townhouse roof treated as residential or commercial?
The county names townhouses in its residential standard, alongside detached one- and two-family dwellings, with the same limit of three stories above ground level. The Virginia Construction Code says the residential code applies to those building types as set out in its Section 310.
Do flat roofs only belong on commercial buildings?
No code text read for this guide ties a roof slope to a building type. The slope limits sit with each covering. Thermoplastic and thermoset single-ply, modified bitumen and built-up roofs each have a one-quarter-in-12 design slope in both the residential and the commercial roof chapters. A house can carry a low-slope roof, and the same limits apply to it.
Does a house need overflow drains the way a commercial building does?
The Virginia Residential Code asks for secondary drains or scuppers where roof drains are required and the roof perimeter would trap water if the primary drains backed up. A roof that slopes to drain over its edges is outside that sentence. Whether a particular roof falls inside it is a question for the roofer and the building official.
Can a new covering go over the old one?
The code text says recovering is allowed in listed conditions and not allowed in others: a soaked or deteriorated base, slate, clay or cement tile underneath, or two or more existing applications. A replacement removes existing layers down to the deck. Which provision governs an existing building is something to confirm with the Permit Arlington Center before the scope is signed.
Who has to draw the plans for a commercial re-roof?
The Code of Virginia, section 54.1-402, lists work whose plans may be prepared without an architect or engineer license when they carry the author's name, address and occupation. The list includes homes, townhouses and multifamily dwellings up to three stories. The county's commercial page points to a seal chart. Neither source says what a given re-roof needs, so ask the county.
Why does the slope of the roof change the safety rules for the crew?
Federal fall protection rules draw a line at 4 in 12. A low-slope roof is at or below it and a steep roof is above it, and each has its own paragraph in 29 CFR 1926.501. The low-slope paragraph allows safety monitoring alone on roofs 50 feet wide or less.
Talk through your roof with Roofers of Arlington
Share the address, what you are seeing on the roof and the decision you need to make. We will tell you what to expect before anything is scheduled.