Flat Roof Installation & Repair in Northern Virginia, DC & Maryland
TPO, EPDM, modified bitumen, and silicone-coating systems for additions, garages, row houses, and small commercial buildings — installed by crews who do this every week.
Flat roofs aren't actually flat — they require a minimum 1/4-inch per foot pitch toward drains or scuppers, and they need fundamentally different materials and detailing than pitched shingle roofs. King's Roofing installs and repairs single-ply membrane systems across the DC metro: TPO (most common new installs), EPDM (preferred on shaded roofs and behind parapets), modified bitumen (existing-roof repairs), and silicone coatings (cost-effective restoration of older smooth-surface roofs).
TPO Roofing: Our Default Recommendation for New Installs
Thermoplastic Polyolefin (TPO) has been the fastest-growing single-ply membrane in the U.S. for over a decade. We install primarily 60-mil and 80-mil GAF EverGuard TPO and Carlisle Sure-Weld TPO — both backed by 20-year manufacturer warranties and capable of 25+ years actual service life in DC-metro UV exposure.
TPO is bright white, which reduces summer cooling loads on the building below by 15–25% versus a black roof. Seams are heat-welded with a hot-air robot welder — when done correctly the seam is stronger than the field membrane. We pull-test every seam during install and again at the final QC walk-through.
EPDM Rubber: When We Recommend It Over TPO
EPDM (ethylene propylene diene monomer, aka 'rubber roofing') is the longest track-record single-ply membrane — installations from the early 1980s are still in service. It's black, so it adds to summer cooling loads — but on roofs that are hidden by a parapet (no visual benefit to white), heavily shaded by trees, or in northerly applications where winter solar gain is actually welcome, EPDM is the better choice.
We install 60-mil and 90-mil Carlisle Sure-Seal EPDM, fully adhered or mechanically fastened depending on substrate and wind-zone calculation. Seams are tape-bonded with primer (the modern method — far more reliable than the older liquid-adhesive seams that gave EPDM a leaky reputation in the 1990s).
Modified Bitumen: Repair & Patch Work
Modified bitumen ('mod-bit') is what's already on most older DC-metro flat roofs — granule-surfaced rolls fused with a torch or hot-mopped asphalt. We do not install new mod-bit (TPO and EPDM outperform it on both cost-per-year and warranty), but we repair existing mod-bit roofs extensively. Targeted patch work, seam re-flashing, and full restoration with a silicone coating system are all common.
If your mod-bit roof has reached the end of its service life, restoring it with a silicone coating is often half the cost of a full tear-off and re-install — and adds 10–15 years of service. We'll evaluate which approach makes more financial sense at your free inspection.
Silicone Roof Coating Restoration
Silicone coatings (we cover these in detail on our silicone coating page) are an excellent low-cost restoration for older flat roofs that are still structurally sound but losing surface integrity. The silicone forms a seamless, fully-bonded, highly reflective membrane over the existing roof. Properly installed, a silicone restoration carries a 10-year manufacturer warranty and routinely lasts 12–15 years in service.
Best candidates: smooth-surface mod-bit, BUR (built-up roof), and older TPO/EPDM that's intact but UV-degraded. Not appropriate: heavily granulated mod-bit (granules must be cleaned off), or roofs with serious ponding (silicone tolerates short ponding but not chronic standing water beyond 48 hours).
Common Flat-Roof Failures We See in the DC Metro
Top failure patterns on DC-metro flat roofs: (1) seam separation on older liquid-adhesive EPDM (now correctable via tape-seam retrofit), (2) ponding water at internal drains because of compressed insulation around the drain bowl (we add tapered insulation crickets to fix), (3) parapet wall cap-flashing failures (the cap-flashing transition is the #1 leak path on row houses in Capitol Hill, Georgetown, and Old Town Alexandria), and (4) penetrations — HVAC curbs, vent pipes, and conduit feet — that move with thermal cycling and tear the membrane around them.