Felt Flat Roof Edges Installation

Most Brooklyn flat roofs don’t fail in the middle-they fail where the field meets the edges and corners. After twenty-six winters watching homeowners chase leaks on felt roofs, I can tell you that 90% of those brown ceiling stains trace back to six inches of sloppy edge work at a parapet base or a rushed fascia corner. The field may be perfect torch-on felt with tight laps, but if the crew cut the upstand short or skipped the corner gusset, your roof will leak.

Edges and corners concentrate water, wind, ice, and movement. They’re where felts bend ninety degrees, where metal trims bolt to timber, and where two vertical planes meet the horizontal deck. Get these transitions right and your felt roof can last twenty-plus years in Brooklyn weather. Rush them and you’ll be patching within two seasons.

Know Which Flat Roof Edges You’re Dealing With

Before we talk installation, you need to identify what kind of edges your roof has. Brooklyn flat roofs present four main edge types, and each needs its own felting detail.

Parapet Edges

These are the masonry walls that rise around your roof perimeter-common on brownstones, multi-families, and older commercial buildings. The felt field must turn up the parapet over a smooth transition, then get protected by coping stone or metal flashing at the top. Shared party walls between row houses add complexity because the parapet may be old, cracked, or leaning.

Open Eaves and Fascia Edges

This is where your roof deck ends at a drip edge with a fascia below-typical on rear extensions, garages, canopies, and newer low-slope additions. Here, felt wraps over or terminates into metal edge trim that throws water clear of the fascia board. No parapet to hide behind; every seam and cut edge is exposed to weather.

Upstands Around Openings

Vertical surfaces around skylights, roof hatches, HVAC curbs, vent pipes, and bulkheads. The felt must dress up these upstands with reinforced corners and proper top terminations that tie into the unit’s own flashing system. Low-profile skylights sitting almost flush with the deck are a nightmare to detail correctly.

Internal and External Corners

Inside corners form where two parapets meet or a parapet joins an upstand-these collect water and debris. Outside corners jut into the weather and catch wind and mechanical damage. Both need shaped felt pieces and extra layers to prevent the splits and pull-aways that single-ply shortcuts always produce.

Core Principles for Felting Edges and Corners

Three rules govern every edge detail I install, whether it’s a Bed-Stuy brownstone or a Canarsie garage.

Always Turn Felt Up and Over, Not Just to the Edge

Felt should climb vertical surfaces to a minimum height-typically 150mm (6 inches) above the finished roof level for parapets and upstands. At open edges, wrap the felt over and onto metal drip trims or under capping pieces. Raw cut edges sitting right at the deck line will peel and let water creep behind.

Use Multiple Layers and Reinforcement at Stress Points

Corners, direction changes, and terminations get extra pieces-gussets, patches, reinforcing strips-under the main layers. These spread movement that would otherwise concentrate in one fold line and crack under thermal expansion. On a Sunset Park job last winter, we pulled off a failing felt roof and found every cracked corner was a single layer trying to bend both directions at once.

Direct Water Away from Joints

Edge felts and trims should make water drip clear, not run backwards into walls or seams. That means properly lapped felts, drip edges with enough projection, sloping copings, and correct grain orientation on upstands. If water can find a way to travel along a joint instead of off the roof, it will.

How to Felt Parapet Edges on a Flat Roof

Parapets are where I spend most of my time fixing other crews’ work. Here’s the sequence that actually keeps water out.

Build a Solid Base and Fillet

Check that the parapet masonry is sound and the roof deck is solid at the junction. Loose bricks, missing mortar, or sagging deck boards will undermine any felt detail. Install a triangular timber fillet (typically 50 x 50mm or 2×2″) at the base so the felt can bend gradually over the curve instead of folding at a sharp right angle. Some roofers form this fillet with mortar or fiber-reinforced mastic-either works if it’s smooth and won’t crack.

Dress Base Felt Up the Parapet

Your first felt layer runs across the field and continues up the parapet over the fillet to at least six inches above roof level. If you’re torch-applying, heat the deck and the wall surface, press the felt into the fillet curve, then work up the vertical with a firm hand roller. Laps between sheets should face away from prevailing wind and main water flow. On a Park Slope job with an east-facing parapet, we oriented every vertical lap so the top sheet faced west-kept wind-driven rain from lifting edges for twelve years and counting.

Add Corner Pieces and Second Layer

At inside and outside corners, bond small square or triangular gusset pieces first-grain running diagonally across the corner-before your larger strips. This prevents one piece from stretching thin as it tries to cover two planes. Then apply your second layer of upstand felt, staggering joints from the first by at least three inches. Each layer reinforces the one below and spreads stress from thermal movement.

Finish with Coping and Flashing

The parapet top needs protection. Ideally, install stone or precast concrete copings with a drip edge on both sides, and either tuck your felt into a reglet cut in the masonry (with counter-flashing over) or turn it over the coping edge under a metal cap. Many older Brooklyn parapets have crumbling brick tops with no coping at all-felt alone won’t fix that. You’ll need masonry work before the felting detail can function. I’ve lost count of how many times I’ve told a homeowner: “Your felt is fine; your parapet isn’t.”

How to Felt Open Eaves and Fascia Edges

Open edges are simpler in theory but less forgiving in execution. No wall to hide mistakes.

Install Drip Edge / Metal Trim First

Fix a metal drip edge along the roof perimeter before you felt. The trim should be aluminum or galvanized steel, lapped at joints (upper piece over lower), with a small kick-out nose-usually 10-15mm-to throw water clear of the fascia. Fasten into solid timber blocking or edge joists, not just into thin sheathing. A loose drip edge will vibrate in wind and work its fasteners loose within a year.

Lay Field Felt and Turn Over Edge

Bring your main felt layer to the edge, then wrap it down over the nose of the drip trim and dress it tight against the vertical leg. How far down depends on your system-some specs call for the felt to cover the full trim height; others use a separate edge strip. Either way, avoid cutting the felt flush at the deck; that cut edge will eventually peel. On a Bushwick garage last spring, we found felt cut flush and already curling back after just two winters-we re-detailed it with a full wrap and added an edge strip for good measure.

Add Edge Strips and Seal Laps

A reinforcing strip along the edge-typically a narrow roll of the same felt-covers laps and adds a second layer right where wind uplift is strongest. Torch or cold-bond this strip over your main layer and onto the metal trim, pressing out any voids. Air pockets under felt at an edge are invitations for water to creep horizontally along the trim.

Felting Around Upstands: Skylights, Vents, and Bulkheads

Upstands are mini-parapets. Same rules, smaller scale, more corners per square foot.

Create a Clean, Raised Upstand

Skylights and hatches should sit on curbs at least four to six inches above the finished roof. Lower profiles are fashionable but tough to detail-you don’t have enough height to properly lap and seal felts, and every heavy rain tests the limits of capillary action. Before felting, remove any loose debris, old caulk, or ragged edges from the curb faces.

Turn Felt Up and Past the Vulnerable Zone

Run your base felt to the curb base, then cut and apply separate strips up each vertical face. These upstand pieces lap generously over your horizontal field felt-three inches minimum. At curb corners, bond small gussets first, then wider cover strips over them. Trying to stretch one piece of felt around a ninety-degree outside corner of a skylight curb guarantees a thin spot that will crack. I’ve repaired dozens of these shortcuts on Flatbush and Crown Heights rowhouses.

Tie into Skylight/Bulkhead Flashing

The skylight or hatch manufacturer provides metal or plastic base flashings that should overlap your felt upstands by at least two inches. Sealant belongs in that joint as a backup, not as the primary seal. If you’re working with an old skylight that has improvised flashing-or worse, just caulk around the frame-consider replacing the unit or at least fabricating proper stepped flashing before you felt. A perfect felt detail can’t fix a leaky skylight frame.

Internal and External Corners: Extra Care Areas

Corners crack more than any other part of a felt roof. Here’s how to stop them.

Internal Corners (Inside Angles)

Cut small triangular or square gussets-usually 6×6 or 8×8 inches-and orient the felt grain to minimize stress, typically diagonally across the corner. Bond these first. Then run your larger upstand strips up each leg of the corner, overlapping the gusset and each other by at least three inches. Your final field layer goes over everything, staggering all joints. The result is three or four plies in the corner zone, spreading movement that would otherwise concentrate in one fold. On a Clinton Hill three-family, we rebuilt two inside parapet corners this way after years of cracking-no leaks in five winters since.

External Corners (Outside Angles)

External corners take more abuse. Add reinforcement that fully wraps the corner with generous laps on both sides-eight to ten inches is common. If metal edge trim or coping corners are involved, make sure they’re properly mitered and lapped; felt underneath should protect those metal joints, not rely on them. I once tore off a Gowanus warehouse edge where someone had just folded one sheet of felt around the outside parapet corners with no reinforcement-every corner had split within three years.

Common Edge and Corner Felt Mistakes to Avoid

Brooklyn-Specific Edge Details and Challenges

Local building conditions shape how we detail edges and corners in Brooklyn.

Old Parapets and Shared Walls

Shared masonry walls between rowhouses are often cracked, out of plumb, or capped with deteriorating brick. You can’t felt properly onto unstable masonry. On a recent Prospect Heights job, we had to rebuild eight feet of shared parapet top and re-point the base before we could even think about felting-and we coordinated with the neighbor because half the work was on their side. Good felt edge details often require masonry and carpentry work first.

Gutters and Scuppers at Edges

Felt around scuppers-those openings in parapets that drain to external gutters-must be carefully dressed and reinforced. I’ve seen more Brooklyn brownstone leaks from poorly detailed scuppers than from any other single cause. The felt needs to wrap into the scupper throat, not just butt up to it, and the metal liner or trim around the scupper has to overlap that felt correctly. External gutters hung off fascias need the felt and drip edge above them to direct water into the gutter, not behind it onto the wall.

Rooftop Foot Traffic and Deck Add-Ons

If your roof doubles as a deck or terrace, edge and corner felts near doors and around rail posts see constant flexing and wear. We add walkway pads, protection boards, and careful detailing where rail attachments penetrate or load the edge. On a Williamsburg penthouse roof deck, we detailed all perimeter edges with an extra protection layer and metal angles to guard the felt from furniture legs and foot traffic-still perfect after four years of dinner parties.

What You Can Check Yourself vs What Pros Should Do

Your Inspection Checklist

From a safe spot-or with a roofer present-look for these signs of correct edge work:

• Felts visibly turned up parapets and upstands, not cut short at the deck.
• Smooth fillets at parapet bases, not sharp right-angle bends.
• Neat corners with no obvious single-ply stretches or gaps.
• Drip edges with felt wrapped over, not cut flush at the deck line.
• Copings or cappings in good condition protecting the top of upstands.

Inside, map any ceiling stains or dampness and see if they align with exterior edges, corners, or parapet bases. Recurring leaks almost always trace to those transitions.

Work Left to Roofers

Torch-on and hot-mop work, cutting and shaping felt pieces at edges, reworking parapet bases, and coordinating with masonry trades should stay with experienced crews. Brooklyn pros also know how to stage safely at roof edges, handle fall protection on parapets, and pull permits when structural work is involved. Felting edges isn’t a YouTube-and-weekend project-it’s the most technical part of the roof.

Micro-FAQ: Edge and Corner Felt Questions

How high should felt go up a parapet wall?
Minimum six inches (150mm) above finished roof level, but eight to twelve inches is better and often required by manufacturer specs and code for high-wind or heavy-snow zones.

Can I just paint over cracked felt at corners?
No. Paint or coating over cracked felt at corners is a short-term cosmetic fix. The crack will reopen as the roof moves. You need to cut out the failed section, add reinforcement, and properly re-felt the corner.

Do I need metal trims on a felt fascia edge?
Yes. A metal drip edge protects the fascia, provides a clean termination for the felt, and throws water clear. Felt alone at an open edge will eventually peel and let water behind the fascia board.

What’s a fillet and why does it matter?
A fillet is a triangular or curved transition piece (wood, mastic, or foam) installed at the base of vertical surfaces. It prevents felt from bending at a sharp ninety-degree angle, which causes cracking. It’s one of the simplest, most effective details in flat roofing.

How do I know if my parapet edge felt is failing?
Look for lifting or bubbling felt at the base, visible cracks at corners, water stains on the interior wall just below the roofline, or damp patches after rain that dry slowly. Any of these mean your edge detail is compromised.

Prepare to Talk Edge and Corner Details with a Brooklyn Roofer

When you call a flat-roof contractor, bring these items to the conversation to get focused, detail-oriented proposals:

• Photos of parapet bases, corners, open edges, and around scuppers showing how current felt meets walls and trims.
• Leak history: dates, locations, and whether stains align with edge or corner zones.
• Roof age and layer count: how old is the felt, and can you see multiple layers at the edges?
• Usage notes: maintenance-only access or active deck/terrace, so the roofer can plan protective details.
• Planned facade or parapet work: if you’re rebuilding copings or repointing masonry, coordinate it with felt edge work for efficiency.

Ask contractors to describe, step by step, how they will rebuild your parapet bases, fascia edges, and corners-what materials, how many layers, what trims, and how they’ll handle inside and outside angles. If they talk about fillets, gussets, staggered laps, and copings, you’re in good hands. If they just say “we’ll throw another layer over it,” keep looking.

Get Flat Roof Felt Edges and Corners Installed Right the First Time

Careful felting at parapets, fascias, upstands, and corners often matters more than the brand of felt you chose or how perfect the field looks. I’ve seen expensive three-layer torch-on systems leak within a year because someone rushed the last six inches at the edges. I’ve also seen budget single-ply felt last fifteen years because a crew took the time to build proper fillets, cut correct corner pieces, and lap everything in the right direction.

A few extra hours spent on correct edge detailing saves years of leak-chasing and thousands in interior repairs. Show edge and corner photos to Brooklyn flat-roof specialists and listen to how they describe rebuilding those transitions. Choose the crew that talks details, not speed.