TPO roofs in Washington, DC: what the hail and wind rows say about a low-slope membrane

What the 431 rows are made of

The ten annual files for 2016 through 2025 hold 431 rows with the District as the state. Only a few types bear on a membrane roof:

Thunderstorm wind

149 rows, by far the largest group, on 73 separate dates.

Hail

19 rows on 6 dates.

High wind and strong wind

5 and 1 rows, none with a place label.

Tornado

4 rows on 2 dates.

Winter storm, ice storm and blizzard

4, 1 and 1 rows. Snow and ice loads are outside this page.

Flood types

163 rows across flood, flash flood and coastal flood. These are water at ground level, not roof rows.

The rest are heat, fog, frost, cold and lightning. The Washington, DC roofing guide covers permits and historic review; this page stays with the exposure record.

The six hail dates

Hail shows up in only four of the ten years. Sizes are inches, as NOAA records them.

• July 19, 20166 rows, 1.00 to 1.75 inches, at the Georgetown, Brookland and US Capitol labels. The 1.75 row is at the Capitol.
• April 21, 20173 rows, all 1.00 inch, at Brookland (two) and the National Arboretum.
• June 2, 20196 rows, 1.00 to 1.75 inches, at Georgetown, Tenleytown and the Lincoln Memorial. The 1.75 row is at Tenleytown.
• June 17, 20191 row of 0.88 inch at Tenleytown.
• August 20, 20192 rows: 1.75 inches at Tenleytown and 1.50 at the US Capitol.
• April 15, 20241 row of 1.00 inch at the Lincoln Memorial.

Eleven of the 19 rows came from trained spotters. The rest came from the public, a newspaper, National Weather Service staff, an emergency manager and a federal agency. A size is a reporter's measurement at one spot, so a membrane two blocks away may have met smaller or larger stones.

Place labels, hail and wind

NOAA attaches a place label to many rows. Twelve labels appear on the District rows, and they are reference points, such as a monument or a neighborhood, not the exact address of the event. Another 141 rows carry no label at all.

Other four: Bolling AFB, Dalecarlia Reservoir, Benning and Lincoln Memorial. Counted by the author from the NOAA files on October 20, 2026.

Read the table as a map of where reports were made. Labels with many rows may simply be where observers and instruments are. A label with zero hail rows does not mean it was spared.

The wind rows

What testing sources say about membranes

The question an owner wants answered is how a TPO sheet stands up to a 1.75 inch stone. The neutral sources opened for this page do not answer it directly, and the silence is part of the finding.

The same guide lists where collateral damage shows: air conditioning units, gutters, metal flashing and downspouts. On a rowhouse, the rooftop equipment and the coping are the places to photograph first. The Office of Planning guideline also lists single-ply (rubber) as a substitute for a flat membrane and tells owners to consult the Historic Preservation Division first; the TPO roofing guide covers the material itself.

Questions a rowhouse owner can put on paper

A rowhouse owner can make a quote answer the exposure record. These are questions, not claims about any product:

• The data sheet for the membrane names any hail or impact test it relies on, by standard and by laboratory.
• The sheet says what was tested: the membrane alone, or the membrane over a named insulation and deck.
• The scope lists the rooftop equipment and edge metal that the written price covers, since these are the places hail marks first appear.
• Edge, corner and parapet attachment is described in the scope, with the engineer or the Department of Buildings asked what wind value applies.
• The scope says whether the work is in kind, as the Department of Buildings uses the term, and who confirmed it.
• For a historic property, the written scope records that the Historic Preservation Office was asked about the substitute.

1. After any storm, photograph first. Roof edge, coping, air conditioning units, gutters and downspouts, with the date.
2. Check the dates. Compare the date of your photos with the NOAA rows above and with your insurer's weather report.
3. Call the insurance agent before repairs. The IBHS guide says to do this first; see the roofing insurance guide.

Book a phone consultation to talk through a Washington, DC TPO roof; the call starts with the address, the building type and what is visible from the street. For flat roofs in general read the flat roof guide, and see roofing materials, roof replacement and services. The District roofing hub sets out the permit and review path, and the commercial roofing page covers larger low-slope buildings.