Curb-Mounted Skylights in Buffalo: Installation, Sizing & Repair Guide

A curb-mounted skylight sits on top of a site-built raised frame, called a curb, that is typically 4 to 6 inches tall and attached to the roof deck before the skylight unit is set on top. The curb creates a raised platform that separates the skylight from the roof, and flashing is installed around the curb-to-roof transition to keep water out.

Curb-mounted skylights are the dominant choice for flat and low-slope roofs with a pitch under 3:12. In Buffalo, that raised curb height is especially important. The region averages 95 inches of snowfall annually, and ice dams are a common winter problem. A properly built curb keeps the skylight above melted water from ice dams, drifting snow, and ice buildup that would otherwise sit directly against the frame and cause leaks.

How Does a Curb-Mounted Skylight Work?

A curb-mounted skylight works through three connected parts: a site-built wood curb, the skylight glazing unit, and a flashing layer that seals the curb-to-roof transition. The curb is typically framed and fastened directly to the roof deck at the rough opening. The skylight dome or glazing unit then caps over the top of the curb. Flashing wraps the outside perimeter where the curb meets the roof. On flat and low-slope roofs in Buffalo, that flashing is most often EPDM or TPO membrane, while pitched roofs typically use step and counter flashing along the sides and counter flashing at the top.

The raised curb height is what makes this system perform well in a climate that receives heavy snowfall. The International Residential Code (IRC) sets a minimum curb height of 4 inches, but in snowy regions like Buffalo, 6 to 8 inches is the more common standard. That extra height directs melted snow, water runoff, and ice away from the glazing seal and prevents ponding at the base of the unit, which can cause leaks when the seal fails under standing water pressure.

One advantage of a curb-mounted skylight is that the glazing unit can be replaced without disturbing the roof deck. In Buffalo, where repeated temperature changes accelerate flashing wear, that means a damaged skylight unit or worn flashing can be addressed independently, keeping repair costs lower over time.

Curb-Mounted vs. Deck-Mounted Skylight: Which One Is Right for Your Roof?

For flat and low-slope roofs in Buffalo, a curb-mounted skylight is the right choice. Deck-mounted units are integrated directly into the roofing material and require a steeper pitch to drain properly, making them a higher leak risk where ice dam backup and snow load are regular concerns. Understanding the difference between curb-mounted and deck-mounted skylights comes down to how each unit sits on the roof and what conditions each handles well.

Cost alone does not tell the full story here. A deck-mounted skylight installed on a low-slope roof in Western New York will face repeated water and ice pressure at the glazing seal every winter, a design mismatch that leads to early failures. Homeowners with flat or low-slope roofs in Western New York should default to curb-mounted with a curb height of at least 6 inches to stay above melted snow and ice buildup. The replaceability advantage also matters: since the curb stays in place, a worn glazing unit or flashing can be swapped out without touching the surrounding flat roofing system.

What Curb-Mounted Skylight Dimensions and Sizing Should You Order?

It is crucial to avoid “rules of thumb” when calculating curb size and glass area. Every manufacturer builds their skylights differently. The required outside curb dimensions for a rough opening will vary depending on the brand you choose, as will the final square footage of the actual glass due to different frame thicknesses. Always consult the specific sizing and dimension charts provided by your chosen manufacturer before ordering a unit.

How you approach sizing also depends on whether you’re replacing an old skylight or installing a new one.

• Replacing an Existing Skylight: If you are swapping out an old unit, you must measure the exact outside dimensions of your current curb, including the thickness of the roofing material and flashing, and order a replacement unit designed to fit over that exact footprint.

• Installing a New Skylight: If you are installing a skylight where there wasn’t one before, you have the flexibility to choose the skylight size you want first, and then frame the rough opening to accommodate it.

For Buffalo homes built before 1960, older rafter spacing often requires non-standard curb sizing or structural headers, meaning that a contractor must verify load capacity before any unit is ordered. Pre-1960 homes make up a large portion of the Buffalo market, and framing that was never designed around modern skylight sizing can shift unexpectedly under added snow load. A licensed contractor should measure the actual rafter spacing on site and confirm whether headers are needed before the curb-mounted skylight dimensions and sizing guide from any manufacturer is applied to the job.

What Does Curb-Mounted Skylight Installation Involve and When Should It Be Done in Buffalo?

Curb-mounted skylight installation follows a six-step sequence, and in Buffalo, that work should be scheduled between late April and early October when temperatures are consistently above 40 degrees Fahrenheit. Following the correct curb-mounted skylight installation instructions is important, as skipping or rushing any step is the most common cause of early flashing failure and water leaks around the curb.

1. Cut and frame the rough opening: The roof deck is cut to size, and the rough opening is framed with doubled headers sized for the span. This step supports the structural load around the new opening.
2. Build the curb to meet height requirements: The curb must be at least 4 inches above the plane of the roof to meet the IRC requirements. In Buffalo, where snow loads average 95 inches annually, it’s recommended to build the curb to be at least 6 inches tall above the finished roof. 
3. Apply flashing integrated into the roofing system: On flat and low-slope roofs, EPDM or TPO membrane is extended and flashed to the curb. On pitched roofs, step flashing and counter flashing are standard. Sealants and roof membranes require a minimum temperature of 40 to 50 degrees Fahrenheit for application. Installation below that threshold increases the risk of adhesion failure at flashing seams.
4. Set and fasten the skylight unit over the curb: The glazing unit is positioned over the curb and fastened per the manufacturer’s specifications.
5. Apply sealant at the curb cap: Sealant is applied at the curb cap per manufacturer specs to seal the joint between the skylight frame and the curb top.
6. Inspect interior vapor barrier and insulation: The curb perimeter is checked from inside to confirm that the vapor barrier is intact and that the insulation is continuous. Gaps here cause condensation and interior damage over time.

New York State Building Code requires a permit for new roof openings in most municipalities. Buffalo-area contractors typically pull permits through the City of Buffalo Department of Permit and Inspection Services or the applicable town building department, with residential skylight permit costs typically ranging from $75 to $200. Scheduling installation between late April and October and pulling the required permit before work starts are the two steps most homeowners overlook, both of which directly affect the quality and legality of the finished installation. OConnor Contracting can handle permit coordination as part of the installation process for Buffalo-area homeowners.

Is a Curb-Mounted Skylight Worth the Cost, and How Long Should It Last?

A fully installed curb-mounted skylight costs $900 to $2,500 and typically lasts 15 to 25 years, making it a reasonable long-term investment compared to repeated flashing repairs that run $150 to $400 every 5 to 10 years. The table below breaks down each component so homeowners can see exactly where money goes and what lifespan to expect.

Major manufacturers offer product warranties of 10 to 20 years on glazing and 5 to 10 years on installation when a certified contractor does the work. In Buffalo’s climate, where temperature changes stress flashing seams every winter, inspecting flashing every 3 to 5 years is recommended, compared to the national standard of every 5 to 7 years. A properly installed curb-mounted skylight also delivers at least twice as much natural light as a comparably sized vertical window, and ENERGY STAR-rated units reduce solar heat gain in summer while improving winter solar gain. That seasonal balance makes an ENERGY STAR-rated unit the smarter long-term choice over a standard glazing unit at a similar installed cost.

How Do You Fix a Curb-Mounted Skylight Leaking Around the Curb?

Identifying the source of the leak before starting any repair is the difference between a $150 to $400 reflash and a $500 to $1,200 curb rebuild, and in Buffalo’s climate, picking the wrong repair wastes both time and money.

• Flashing failure at the curb base: This is the most common cause in Western New York. Temperature changes stress flashing seams every winter, lifting step flashing and membrane edges away from the curb. Water appearing at the curb base during rain points here first. This can be fixed by resealing or replacing step flashing and the surrounding membrane. 
• Curb cap seal failure: The sealant at the top of the curb where the skylight frame meets the wood degrades within 5 to 10 years under Buffalo’s sun and temperature swings. This can be fixed with a compatible polyurethane or silicone sealant rated for roofing applications.
• Condensation mistaken for a leak: An uninsulated wood curb framing interior creates a cold surface that pulls moisture from warm indoor air. This can be fixed by adding rigid foam insulation inside the curb framing to bring the surface temperature up.
• Ice dam backup: Melted water forces under flashing from below during warm spells after heavy snow. Fixing this requires improving attic insulation to R-49 to R-60, the range recommended for Buffalo’s climate, and improving ventilation before re-flashing the curb.

The triage rule is straightforward: water at the curb base during rain points towards flashing first; water appearing only in late winter or after snow melting points towards ice dam backup. These two causes require different repairs and sometimes different contractors. Ignoring a leaking curb for more than one season risks rotting the wood curb frame entirely, turning a simple $150 to $400 reflash into a full curb rebuild at $500 to $1,200. A residential roof repair professional can assess whether reflashing or a full curb rebuild is the appropriate choice before any installation work begins.

Ready to Add a Curb-Mounted Skylight to Your Buffalo Home?

Avoiding a full curb rebuild, which runs $500 to $1,200 compared to a $150 to $400 reflash, starts with getting the installation right the first time. OConnor Contracting works with homeowners to install curb-mounted skylights on flat and low-slope roofs across Buffalo, Cheektowaga, Amherst, Tonawanda, and surrounding Erie County communities. The late April to early October installation window fills fast, so scheduling early matters.

Request your free on-site estimate before the late-spring window opens, as slots between late April and early October book quickly in this market.

Not ready to schedule? Learn more about curb-mounted skylight installation.