PVC Roofs in Herndon, VA: What the Downtown Book Says
Herndon has one design document written for the buildings it wants downtown: the Downtown Pattern Book. We read its apartment, mixed-use, townhouse and garage chapters for anything about roofs. It speaks about parapets and roof lines. It never names a roofing material.
The document
What is the Herndon Downtown Pattern Book, and is it still on the Town's page?
Its cover calls it a guide for downtown development, prepared by Urban Design Associates for the Town and adopted by the Town Council on January 29, 2013. The Town's Downtown Redevelopment Project page still links it on October 15, 2026, beside the Downtown Master Plan the Council adopted on February 22, 2011.
Both were written for Herndon's downtown, not for every street in town. Neither is a permit rule for a house in a subdivision, and we do not treat it as one.
- February 22, 2011
The Town Council adopts the Downtown Master Plan, according to the date printed on the plan itself.
- January 29, 2013
The Town Council adopts the Downtown Pattern Book, the design guide quoted below.
The Pattern Book is the Town's own picture of downtown buildings.
Read with us
Where does the book say anything about the top of a building?
Mixed-use buildings can be two to four stories, not to exceed 50 feet. Parapets and other decorative features are permitted above 50 feet.
Herndon Downtown Pattern Book, Section C, Mixed-Use Buildings, step 2 (read October 15, 2026).
The top of the building should be articulated by varying roof and cornice lines.
Same chapter, step 4.
The roofscape and articulation of the top floor should vary to enrich the facade of the street.
Same book, Section C, Apartment Buildings, step 4.
Why a parapet matters
What does a wall above the roof edge change for a PVC sheet?
The book never links parapets to flat roofs. That link is our reading: a parapet is a low wall around a roof edge, and a roof ringed by walls has to send its water out through drains or scuppers.
The 2021 International Building Code, for new design, asks for secondary drains or scuppers where the roof perimeter rises high enough that water would be trapped if the main drains backed up. Where an existing roof is only replaced, the same chapter eases that rule for roofs that already drain positively.
As for PVC itself, the same code table lists it under ASTM D4434, and a roofing-association paper groups it with TPO as a thermoplastic whose sheets are fused by welding with heat. The neutral sources we opened give no PVC-only claim beyond that. On a downtown-style building with parapets, the open questions are the same for every single-ply: the drains, the turned-up edge and who inspects them.
Says and silent
What do the book's building chapters leave open for a roofer?
| Topic | What the pages we read say | Left open: ask the Town |
|---|---|---|
| Height | Mixed use: two to four stories, 50 feet. Apartments: three or four stories, 50 feet. | Where height is measured when a parapet is added. |
| Roof edge | Parapets and decorative features may rise above the limit. | Any rule on how a parapet is drained or capped. |
| Roof lines | Vary them. Townhouses and apartments list roof dormers among special elements. | Whether a flat portion is accepted behind them. |
| Garages | Screened by buildings where possible; facades vary parapet height. | The top deck, which the chapter does not describe. |
| Material | None named in these chapters. | Whether the Town reviews roofing material downtown at all. |
The market study, storefront and street chapters and the developer's plans stayed unread, so this table is not a claim about the whole book.
Is PVC your question
How do you check whether your building is a candidate at all?
Look up from the street
Is a wall rising above the roof edge, or does the roof slope away?
Find the parcel
The Town's Fairfax County property search page shows whether it is Town ground. See our Herndon page.
Ask what covers it
Get the roof's last report and the membrane on it today.
Ask about the edge
Who caps the parapet, and are the drains in the quote?
Background on sheets and drains: flat roof, roofing materials and single-ply roofing across Northern Virginia.
Questions
What people ask about downtown Herndon roofs and PVC
Does Herndon's Downtown Pattern Book say what a roof must be made of?
Not in the chapters we read. They cover heights, parapets, roof and cornice lines and dormers, and none names a roofing material.
How tall can a mixed-use building be downtown under the book?
Two to four stories and no more than 50 feet, with parapets and decorative features allowed above that line.
Does a parapet mean the roof behind it is flat?
The book does not say. Our reading is that walls around a roof edge make drainage a design question, and the building code text we opened asks for secondary drains or scuppers in that case for new work.
Where does PVC appear in the building code?
The 2021 International Building Code lists PVC single-ply roofing under ASTM D4434. Ask a quote to name the standard its sheet meets.
How are PVC sheets joined?
A roofing-association paper describes PVC, TPO and KEE membranes as thermoplastics, whose neighboring sheets fuse together when welded with heat.
Does the Pattern Book apply to a house outside downtown?
It was written for the downtown blocks. Ask Town Community Development which map covers your parcel before assuming it does or does not.
Nearby pages: PVC roofs in Reston, PVC roofs in Chantilly, and for the same town EPDM roofs in Herndon and metal roofs in Herndon. The Town-or-county test is on our Herndon page.
Sources used
Town of Herndon: Downtown Redevelopment Project page, the Downtown Pattern Book and Downtown Master Plan PDFs linked from it, all read October 15, 2026. 2021 International Building Code, chapter 15, and the roofing-association papers listed in our materials research, read October 11, 2026.
Talk through the next step
Tell us which building you mean
Give us the address, the number of stories and what stands above the roof edge. A short phone call sorts out whether a welded sheet is even the question.
9220 Topaz St, Fairfax, VA 22031
Mon to Fri 7 AM to 8:30 PM, Sat 7 AM to 8 PM, closed Sunday