EPDM Roofs in Great Falls, VA: The County Load Sheet
Great Falls has no town hall and no sheet of its own. Fairfax County Land Development Services publishes a single table of local design loads, and an EPDM flat roof here inherits it. This page reads that table line by line and marks where it stops.
The table
What does each line of the county sheet hand a flat roof?
The sheet is headed “Local Design Load Criteria” and sits on the county’s Codes and Standards page. It covers the whole county, so no row is specific to Great Falls.
| Line on the sheet | What it prints | What it leaves to someone else |
|---|---|---|
| Ground snow load | 25 psf (pounds per square foot) | Snow on the ground, not on a roof. The designer turns it into a roof figure using the roof’s shape and exposure, and the sheet gives no roof figure. |
| Ultimate wind speed, three risk categories | 105 mph for Category I, 115 mph for Category II and residential, 120 mph for Category III | Which category a building falls in, and how the speed becomes an uplift force at a roof edge or corner. |
| Ice shield underlayment required | “yes” | No note says which roof types the line reaches, so whether it touches a low-slope sheet is a question for the office. |
| Frost depth, winter design temperature | 24 inches; 17 degrees F | Our reading: these steer footings and heating, not a roof covering. The sheet does not say. |
Nothing on the sheet names EPDM, a membrane or any roof covering. It sets conditions, and the roof has to meet them whichever sheet goes on top.
The note under the table
Why does the county say its own snow figure may not apply?
The ground snow load posted on the website is valid if the design team uses the figures in the 2021 Virginia Construction Code and must comply entirely with ASCE 7-16. If the team uses ASCE 7-22 instead, the posted ground snow load “won’t be applicable.”
Paraphrase of the guidance printed beneath the table on the county Codes and Standards page, opened 2026-10-12. The quoted words are the county’s.
For an owner this changes one habit: do not copy 25 psf into a quote request. Ask the designer which edition the plans use. A flat roof over a new rear addition is the case where it comes up, because that work is designed and permitted, not simply re-covered.
Order of questions
Who answers what about an EPDM roof, and in what order?
First: Land Development Services, 703-222-0801
Is this work on the permit side at all? The residential list names shingle replacement as work without a building permit and roof repairs as work with one. A membrane re-cover is named on neither side, and the commercial list exempts only replacement of under 100 square feet of roof covering.
Stop here if the office says no permit applies to your scopeSecond: the designer, if the flat roof is new or reshaped
Which snow standard edition, which roof snow figure, and what slope toward which drain. A snow load that sits on a roof also melts onto it, and a trade bulletin on ponding lists melting snow and ice among the ways water stays on a low roof.
Third: the membrane tests named in the code
The model building code asks that fully adhered or mechanically attached single-ply systems be tested to FM 4474, UL 580 or UL 1897. Ask the roofer which one the chosen system was tested to, and have it written into the scope.
Fourth: the roofer, for how the sheet is held and edged
The wind speed above becomes a fastening and edge-metal question at the perimeter. Ask for the attachment method and the edge details in plain words before anything is ordered.
The county prints one, the state rule uses the other
The state text on ordinary repairs lets a house have an unlimited amount of roof covering replaced without a permit provided the area’s “nominal design wind speed” is not above 100 miles per hour. The county sheet prints ultimate speeds. They are different named quantities, and neither page converts one into the other, so do not set 115 against 100 yourself. Ask the office whether the exemption reaches your address.
Questions
Load sheet questions from Great Falls owners
Does 25 psf mean my roof carries 25 pounds per square foot of snow?
No. It is a ground figure. The roof figure is worked out by a designer from that number and the roof itself.
Why are there three wind speeds on the sheet?
They are keyed to risk categories. Houses fall under the second line, and who assigns a category to a building is the designer and the office, not the roofer.
Is there a separate Great Falls snow or wind number?
No. It is a county table, headed for the whole county, and it has no Great Falls row.
Does the county sheet mention EPDM?
No. It names no roof covering. The flat roof guide covers how the sheet is described and seamed.
Will the 25 psf figure change?
The county says the snow rows depend on which standard edition the designer uses and that Virginia is working on a correction. It gives no date.
Does a flat porch roof near Colvin Run Mill need a designer?
That turns on whether it is new work and whether the parcel is inside the district. The mill district page reads the guide, and the county offices decide the rest.
Nearby pages: the Great Falls hub, PVC roofs in Great Falls, EPDM roofs in Reston and EPDM roofs in the City of Falls Church, which prints a different table. General reading: the flat roof guide and the materials page.
Official pages used
Checked 2026-10-12: Fairfax County Codes and Standards, local design load criteria; Fairfax County, when a permit is required; 13VAC5-63-80. Code text from the 2021 International Building Code, Chapter 15, opened 2026-10-11, and the ponding bulletin of the Asphalt Roofing Manufacturers Association, October 2024.
Talk through the next step
Bring the flat section and the question
Tell us the street, whether the flat part is new or already there, and where you think its water goes. A short phone call sorts out whether the county or a designer answers first.
9220 Topaz St, Fairfax, VA 22031
Mon to Fri 7 AM to 8:30 PM, Sat 7 AM to 8 PM, closed Sunday