TPO roofing in Alexandria, VA: who decides, and how the sheet is held on

Owners, renters and building size in the City

The American Community Survey (2024 five-year estimates, opened October 20, 2026) counts 76,096 occupied homes in the City of Alexandria. The tenure split is the first fact that matters for a membrane roof, because the person who signs for it is different in each column.

Source: Census Bureau ACS 2024 five-year estimates, table B25032, City of Alexandria; owner share computed here. Mobile homes and other types make up the remainder.

Census counts homes, not roofs, and not offices or shops, so it cannot say how many roofs are flat or what covers them. What it does show is the era of the larger buildings, which is when the structure went up and not when the roof was last replaced.

• 1939 or earlier. 1,124 homes in buildings of 5 or more units.
• 1940 to 1959. 6,282 homes.
• 1960 to 1979. 17,674 homes, the largest group.
• 1980 to 1999. 8,959 homes.
• 2000 to 2019. 10,694 homes.
• 2020 or later. 773 homes.

Source: ACS 2024 five-year estimates, table B25127, buildings of 5 or more units, owner and renter homes added together (45,506 in all). See the Alexandria roofing guide for the City's wider housing mix and storm record.

Who decides a TPO roof, by building type

The City's permit page defines the sorting. Townhomes and rowhouses of up to three stories sit in the residential category. The commercial list names professional offices and retail, and it names multi-family buildings of three or more dwelling units, apartments and condominiums.

Rowhouse or townhouse

The owner is the usual signer for 11,727 owner homes in attached buildings, though a homeowners association or an easement may add a step. Sorted as residential by the City. If the street is in a historic district, the Board's roofing sheet applies, covered below.

Condominium

The association decides for the common roof. The permit page lists a Condominium Alterations Memo among its documents, so ask Code Administration whether a TPO replacement comes under it. Census does not separate condominiums from rentals in the 5-or-more columns, so the 10,682 owner homes there are a ceiling.

Rental apartment building

The landlord decides, and tenants rarely see the scope. With 34,824 renter homes in buildings of 5 or more units, this is the largest group in the City. The City treats the building as commercial.

Office, shop or mixed building

The owner decides, within the commercial category. No Census housing table describes these roofs, so nothing here counts them. A TPO sheet on such a roof falls under the commercial code sections read below. See also commercial roofing.

Fasteners, adhesive or stone: three ways to hold the sheet

The guide explains why. Wind creates localized suction above a roof, and where the layers below are not sealed, air leaking up from inside can make a mechanically attached membrane flutter and fail. It says the tightest layer, usually the membrane, takes the greatest wind load. Its remedy is a fully adhered sheet with sealed deck seams.

The same guide notes that fluttering pumps interior moisture into the roof assembly in cold and mixed climates, and that failures once limited to cold climates now occur in mixed ones as membranes turn light-colored. It was written for hurricane-prone regions and the IBHS Fortified program.

How an adhered bond gets tested, and where to find the listing

1. The adhesive meets the board. A fully adhered sheet depends on the bond between membrane, adhesive and the board stock beneath, such as insulation, cover board or plywood.
2. A peel test measures it. A SPRI article describes the TDP-1 test: a strip of membrane 2 inches wide is pulled off its board at 2.0 inches per minute, and the lab records the peak load and the way the bond failed.
3. Listings carry the result. The article says the test helps qualify components for listed roof assemblies and reduces the need for large assembly tests.
4. A directory holds the data. A second SPRI article points to DORA, the Directory of Roof Assemblies, for wind and impact data on tested assemblies, and notes that some specifications ask for more than the code minimum.
5. Your quote names one. Ask which listing, component list and fastener or adhesive the quote relies on, and whether the written scope matches it.

SPRI's standards page lists ANSI/SPRI RP-04 and ES-1 beside TDP-1, and says ANSI accredits the process rather than writing the standards.

What the Virginia code attaches to each method

The 2021 Virginia commercial code splits wind design by method. The text below was read on the UpCodes copy of the Virginia edition, so confirm it with Code Administration.

Two more lines bind every method. Section 1507.1 says coverings are applied under the manufacturer's installation instructions, and section 1507.12.1 sets a design slope of at least 1/4 in 12 for drainage. For the full list of single-ply standards, the commercial roofing page holds the code table; this page does not repeat it.

On permits, the state exemption list frees an unlimited amount of roof covering replacement in groups R-3, R-4 and R-5 where the design wind speed is not over 100 mph, and 100 square feet or less in any group. A rowhouse owner may land inside the first clause. A building the City counts as commercial starts outside it. Ask the City before assuming either.

Where the historic sheets stand on flat roofs

For addresses in Old and Historic Alexandria and Parker-Gray, the Board of Architectural Review's roofing chapter (amended July 16, 2025) draws a line by visibility.

The chapter also says visible replacement roofing needs staff review, and that the Board recommends light colors on flat roofs to reduce air conditioning loads and the urban heat island effect. The Parker-Gray chapter pictures single-ply membrane among local materials. Neither chapter names TPO. Staff judge visibility, so the first call is to preservation staff, then to the Permit Center. See the Alexandria guide for the district maps.

What a written attachment scope should name

• Who owns the roof: one owner, an association or a landlord, and who signs the agreement?
• Is the building residential or commercial in the City's sorting, and which code chapter does the quote cite?
• Is the sheet mechanically attached, fully adhered or ballasted, and why for this building?
• What lies under the sheet: deck, insulation, cover board, and how are the joints sealed?
• Which tested assembly or listing does the attachment rely on, and does the quote name its wind rating?
• If ballasted, which stone standard, and has an engineer confirmed the roof can carry it?
• Does the address need a permit, staff review or an association vote before work starts?

Book a phone consultation to talk through an Alexandria TPO roof: have the address, the building type and what you can see from the street. See TPO roofing, flat roofing, roof replacement, materials and services, or call (571) 397-6072.