Install Dome Flat Roof Skylights Now

What would it feel like if that dark Brooklyn hallway or stairwell suddenly had daylight pouring in from above-without turning your flat roof into a leak risk? Well-chosen, properly flashed dome skylights are built for exactly this job on flat roofs. These raised, curved or pyramidal units-usually acrylic or polycarbonate-sit on curbs above your roof membrane, shedding water while they bring natural light into spaces that have never seen the sun. They’re different from the flush, glass roof windows you see on pitched roofs, and on Brooklyn’s flat roofs, proper curbs and flashing aren’t optional extras-they’re the only way to keep a skylight dry for the long haul.

Dome Skylights on Flat Roofs: What You’re Really Installing

Dome skylights for flat roofs are self-contained units designed to rise several inches above your finished roofline. That height is critical: it sheds snow, rain, and pooled water away from seams and fasteners. Most units use either acrylic (economical, clear, good clarity) or polycarbonate (tougher, better impact resistance for exposed roofs). They mount to a wood or metal curb that’s framed into your roof deck, and that curb is fully integrated with your existing membrane-EPDM, TPO, modified bitumen, whatever you have.

Common reasons Brooklyn owners add dome skylights:

• Brighten up interior hallways, stairwells, and windowless bathrooms.
• Bring natural light into top-floor apartments or loft spaces.
• Reduce daytime electric lighting in commercial or warehouse areas.
• Add a feature element in a renovated brownstone or mixed-use building.

This guide explains options, details, and the installation process so you can plan and hire confidently. It’s not a DIY manual-cutting through your own roof without proper training and permits is a fast track to leaks, code violations, and dangerous structural mistakes.

First Questions: Is Your Roof Ready for a Dome Skylight?

Dome skylights are easiest to add during a roof replacement or major renovation, but they can be retrofitted if the structure, membrane age, and interior layout cooperate. Before you pick out a dome online or call for a quote, run through this reality check. Some roofs are ready to go; others need prep work or a rethink.

Dome Skylight Options for Flat Roofs: Shapes, Glazing, and Operation

Dome skylights differ by shape, glazing material, number of layers, and whether they open or stay fixed. This matters because the wrong choice can mean glare, heat gain, or a venting unit that nobody ever opens because the controls are inconvenient. Framing conversations around these options with your contractor helps you avoid being steered to a default that doesn’t fit your needs.

Shape & Profile: Single domes are lower profile and economical. Double domes add an inner shell that dramatically improves insulation and reduces condensation-worth it in heated spaces. Pyramidal or multi-sided domes deliver architectural punch on visible roofs. Low-rise domes sit closer to the roofline, often preferred when the skylight can be seen from the street or neighboring windows.

Glazing Material: Acrylic is economical, optically clear or available tinted, and has good impact resistance for most Brooklyn roofs. Polycarbonate is stronger-better if you’re in a hail zone or under trees-but can yellow slightly over time depending on UV exposure. Glass-on-curb hybrids (flat glass mounted on a curb frame) exist, but they’re less common in the “dome skylight” category and usually discussed as an upgrade option for modern renovations.

Fixed vs Operable: Fixed domes are simplest and most common on commercial roofs and many residential installs. Manual or electric venting units can open to provide ventilation in bathrooms, kitchens, or lofts-great for air movement, but only if you can run wiring safely and the controls will actually be used. Motorized options need protected interior wiring and sometimes a rain sensor to close automatically.

System Anatomy: From Ceiling to Dome

A dome skylight installation is really a light well or shaft running from the dome down through your roof structure and ceiling. Understanding this stack helps you anticipate interior finishing work, framing changes, and where leaks might start if details are missed. Here’s the typical layer order from the top down:

• Dome unit (outer shell) attached to a curb frame with fasteners and sealant.
• Skylight curb flashing, integrated with the flat roof membrane, sloped to drain water away.
• Roof deck framing cut and headed off to create the opening, with double headers and joist support around the hole.
• Light shaft/shaft walls through attic or plenum space-insulated and air-sealed where code and comfort require it.
• Ceiling opening and finish (drywall, trim, optional diffuser) where daylight enters the room below.

Curb height above finished roof is a critical detail-too short and snow or future roof layers bury it. The shaft walls need insulation in conditioned buildings to prevent winter condensation on the interior surface. Every joint between these layers is a spot where air leakage or moisture can happen if details aren’t tight.

Step 1: Structural and Layout Planning

The first step in any dome skylight project is not picking a pretty unit online-it’s confirming the roof can safely accommodate an opening where you want it, and that the light shaft can reach the interior space cleanly. Skip this step and you’ll discover halfway through the job that a beam is in the way, or that the interior ceiling has ductwork exactly where the shaft needs to go.

1.1 Locate Joists and Beams: On a flat roof, you need to know joist direction and spacing. This usually means core cuts, probe holes, or reviewing existing plans if they’re available. Large openings-anything over about 24 inches square-will require double headers and structural framing around the hole, sized by an engineer or architect. In Brooklyn, many older buildings have 2×8 or 2×10 joists on 16-inch centers; cutting one or two joists is doable with proper headers, but cutting more than that starts to trigger bigger structural reviews.

1.2 Align with Interior Space: Coordinate the exterior skylight location with the room below. You want it centered over a hallway, stairwell, kitchen island, or bathroom-not awkwardly off to one side. Check for conflicts with ducts, pipes, sprinklers, and electrical conduits in the ceiling cavity. On a two-family in Kensington where the stairwell felt like a basement, we had to shift the planned skylight eight inches east to clear a cast-iron drain stack. That kind of discovery happens early or it happens expensively.

1.3 Check Loads and Codes: Structural changes to roof framing in Brooklyn fall under NYC Building Code. A licensed design professional should review framing changes, especially in multi-family or mixed-use buildings. Egress and fire separation rules may impact where openings can go-some interior stairs need to remain separated from attic spaces, and adding a shaft can complicate that. Get this review done before anyone touches a saw.

Step 2: Curb Design, Height, and Flashing Strategy

Dome skylights for flat roofs almost always sit on raised curbs-either site-built from treated lumber or factory-supplied metal frames. The curb is the heart of a leak-free skylight. It must be tall enough, insulated or thermally broken where needed, and fully integrated with the membrane so water runs away from the skylight, not under it. Get the curb wrong and you’ll have a beautiful dome above a wet ceiling.

Good curb design in Brooklyn:

• Curb height at least 4-6 inches above finished roof surface (check code and manufacturer specs-some require more in snow zones).
• Inside of curb insulated or thermally broken when the skylight is over conditioned space, preventing condensation on cold frames in winter.
• Curb sides sloped or detailed so water and snow can’t sit against fasteners or sealant lines.
• Membrane and flashing pre-planned with the roofer before carpentry starts, so curb blocking matches flashing requirements.

Typical curb mistakes: Short curbs that disappear under snow or when you later add tapered insulation or pavers during a roof upgrade. Nailing trim or siding through membrane flashing without metal counter-flashings or proper sealant. Leaving raw wood exposed to pooled water, leading to rot, curb movement, and failed seals. Installing the skylight frame out of level, making factory gaskets and seals work harder than they’re designed to, shortening lifespan.

Step 3: Integrate Dome Skylights With Existing Flat Roof Membranes

Integration details vary by membrane type-EPDM, TPO, PVC, modified bitumen, BUR. Getting this wrong is how many skylights end up leaking a year or two after installation. Each system has its own rules for flashing, compatible materials, and termination methods. Here’s what works with common Brooklyn flat roof systems:

EPDM (rubber): Use compatible EPDM flashing sheets or prefabricated boots and tapes at the curb. Avoid sealants that aren’t rated for EPDM-some will cause the rubber to swell or degrade. Adhere the field membrane up the curb sides and terminate under a metal counter-flashing or clamp bar that’s mechanically fastened and sealed.

TPO / PVC: Heat-weld membrane to prefabricated corners and curb flashings for a monolithic seal. Make sure the curb is wrapped with the same membrane type-TPO skylights on TPO roofs, PVC on PVC-because mixing the two doesn’t weld reliably. Corners are critical; use factory corners or carefully detail field seams to avoid peel points.

Modified Bitumen / BUR: Step-flash or wrap the curb with base and cap sheets, making sure laps shed water away from the skylight. Reinforce corners with extra plies and compatible mastics. These systems are very forgiving if done carefully, but they’re also easy to rush-and rushed bitumen details leak.

Metal Roof Sections: Use custom curb flashings that interlock with standing seam or flat-lock metal panels. Seal with manufacturer-approved sealants (butyl tapes, high-grade polyurethers). This work is best done by a roofer experienced with both metal and skylight integration, because the details are less standardized.

Cutting openings and installing skylights can void roof warranties if not done per the membrane manufacturer’s published details. Coordinate with your roofer and get sign-off in writing before cutting starts.

Light, Heat, and Glare: Performance Considerations in Brooklyn

Dome skylights change light patterns, heat gain, and sometimes sound in the space below. Brooklyn owners should consider orientation, size, and glazing performance to avoid overheating rooms or creating glare on screens and work surfaces. More light is not always better light.

Daylight & Glare: Larger domes bring more lumens but can create hot spots and harsh glare near desks or kitchen counters. Diffused or prismatic domes soften and spread light-better for offices, studios, and living areas. Multiple smaller units often give more even, comfortable light than one big one, and they’re structurally easier to frame in.

Thermal Performance: Double-dome units reduce winter heat loss compared to single-dome designs-worth it in heated spaces. Tinted or low-E coated options can cut summer solar heat gain on sunny, exposed roofs. Insulated light shafts and proper air sealing around the opening help prevent condensation on shaft walls and around the ceiling trim in winter.

Noise & Privacy: Rain drumming on domes can be noticeable, especially in quiet bedrooms or offices directly below. Glazing type and how you finish the shaft affect how much street noise filters down. Placement matters for privacy too-avoid locations where neighbors in taller buildings can see directly down into bathrooms or bedrooms through the skylight.

Brooklyn-Specific Constraints When Adding Dome Skylights

On a three-story mixed-use building in Park Slope, the owner wanted a dome skylight over the top-floor apartment stairwell-a space that had been dark since 1927. The roof was only two years old, TPO over rigid foam, in great shape. But the building sat mid-block with a four-story neighbor ten feet away on one side and a landmarked row on the other. We couldn’t put the skylight near the front parapet (landmark district rules), couldn’t go near the rear because of the neighbor’s direct sightline into the unit, and the middle of the roof had two old brick chimneys and a bulkhead. We ended up with a 30-inch square double-dome unit offset slightly toward the north side, sized and positioned to clear all the constraints while still lighting the stair effectively. That’s typical Brooklyn skylight planning: you’re threading the needle between structure, code, neighbors, and history.

Local factors that influence design and install:

• Landmark status or special historic districts restricting visible domes on front-facing or street-side roofs.
• Close party walls and parapets limiting skylight placement near building edges, leaving only narrow “safe zones” mid-roof.
• Existing roof equipment-HVAC units, vent stacks, solar arrays-occupying prime skylight locations.
• Stair bulkheads, roof hatches, and fire escape paths that must stay clear per code and insurance requirements.
• Noise and work-hour rules when cutting openings above occupied apartments or ground-floor retail-expect complaints if you’re sawing joists at 7 a.m.

Common Mistakes With Dome Skylights on Flat Roofs

Here are the most common reasons dome skylights leak, fog up, or disappoint owners. Avoid these and you’re ahead of half the installs I’ve been called to fix.

1. Cutting through the roof deck without properly framing and heading off joists around the opening-leads to sag, cracked domes, and membrane stress.
2. Using a curb that’s too low, then later adding tapered insulation or pavers during a roof upgrade so snow and water sit against the dome base.
3. Relying on caulk alone instead of proper membrane flashing at the curb-caulk shrinks, hardens, and fails; flashing lasts decades.
4. Installing domes directly in ponding areas without addressing slope and drainage-constant water accelerates UV damage and finds every weak seal.
5. Skipping interior air sealing and insulation of the light shaft, leading to winter condensation, staining, and mold on shaft walls.
6. Ignoring roof and skylight manufacturer instructions, voiding warranties on both systems and leaving you on the hook for repairs.

FAQ: Dome Skylights for Flat Roofs in Brooklyn, NY

Do I need a permit to add a dome skylight on my flat roof?
In NYC, new roof openings and structural modifications generally require DOB filings and professional drawings, especially in multi-family or mixed-use buildings. Even single- and two-family homes often need an alteration permit-cutting joists and changing roof structure is Alteration Type 2 work under the building code. Work done without permits can complicate sales, refinances, and insurance claims.

Are dome skylights more leak-prone than other options?
Any roof penetration is a potential leak source, but properly flashed, curb-mounted dome skylights are reliable when installed correctly. Poor installation-wrong curb height, bad flashing details, incompatible sealants-is the culprit, not the dome itself. I’ve seen 20-year-old domes that have never leaked and brand-new ones that failed in the first winter because someone skipped the membrane integration step.

Can I replace an old wire-glass or plastic bubble skylight with a new dome?
Many Brooklyn buildings have aging wire-glass or yellowed acrylic units installed decades ago. Replacement is often possible using the existing curb and opening, though you may need to upgrade the curb height, improve flashing, and possibly reframe if the old opening doesn’t meet current code. Sometimes it’s simpler to remove the old curb entirely, properly frame and flash a new opening, and start fresh with a modern double-dome unit or even a glass skylight.

How long do dome skylights last?
Typical lifespans run 15-25 years depending on material, UV exposure, and how well they were installed. Acrylic yellows and crazes over time; polycarbonate holds up longer but can also discolor. Failed seals between double domes show up as interior fogging. When you see significant yellowing, crazing, leaks around the frame, or constant condensation inside a double dome, it’s replacement time.

Can I walk on or put a deck over a dome skylight?
Domes are not designed as walking surfaces and will crack under foot traffic or furniture. If you’re adding a roof deck, skylights need to be protected with guards-wood frames, low curbs, or layout planned so decking and railings keep people and furniture clear. Some designers recess skylights into well openings in the deck; that works but requires extra framing, flashing, and careful drainage details.

Plan Your Dome Skylight Project With a Brooklyn Flat Roof Specialist

Successful dome skylight installs on flat roofs in Brooklyn depend on structural planning, proper curb height and flashing, membrane-specific detailing, and sensitivity to local constraints like landmarks, neighbors, and code. When those pieces are handled by pros who think like roofers and glaziers at the same time, dome skylights transform dark interiors without creating chronic leaks or regrets. Done right, you get a bright hallway, a sunlit stairwell, or a bathroom that finally feels like it’s part of the building instead of a cave-and a roof that stays dry through every storm.