Curb Mount vs. Deck Mount Skylights: What’s the Difference & Why Roof Type Matters

When it comes to choosing the right skylight for your home or project, most people start with aesthetics — natural light, clean design, maybe even a venting option for airflow. But there’s a behind-the-scenes decision that’s just as important: how that skylight is installed on your roof. In skylight terms, that comes down to curb mount vs. deck mount — and choosing the right one depends heavily on your roof pitch and roofing material.

Let’s break it down so you can make the right choice with confidence.

What Is a Curb Mount Skylight?

A curb mount skylight is designed to be installed on top of a site-built curb — essentially a framed “box” that sits above the roof deck. The skylight is fastened over this curb and sealed with flashing.

Best for:

• Flat or low-slope roofs
• Homes with existing skylight curbs
• Replacement jobs
• Roofs with thick roofing materials (like tile or wood shakes)

Why choose curb mount?
Because the skylight is elevated on a built curb, it creates extra height and offers added protection from water infiltration — making it ideal for flatter roofs where water drains more slowly. It also allows for flexibility in custom sizing and is often used in retrofits or skylight replacements.

What Is a Deck Mount Skylight?

A deck mount skylight is designed to sit directly on the roof deck without the need for a separate curb. It has a low-profile look and is sealed into place with step flashing and underlayment.

Best for:

• Pitched roofs (10°–60° / 2:12 to 20:12 slope)
• New construction or major roof remodels
• Homes seeking a sleek, flush appearance

Why choose deck mount?
Deck mount skylights blend cleanly into your roofing surface. They’re engineered for weathertight performance when installed on pitched roofs and are the go-to choice for most new Velux skylight installations on sloped homes.

Roof Pitch: Why It Changes Everything

Your roof pitch (also called slope) plays a huge role in what skylight type you should choose.

• Flat or Low-Slope Roof (0:12 to 3:12):
  → Use curb mount to keep water away from the skylight and ensure proper drainage.

• Standard Pitch Roof (4:12 to 12:12):
  → Go with deck mount for better aesthetics and simplified installation.

• Steep Pitch Roof (12:12 or more):
  → Deck mount still works, but installation must be precise — flashing kits become critical here.

Pro Tip:
Always measure pitch before ordering. Velux skylights are rated for specific pitch ranges, and using the wrong one can void the warranty.

Roofing Material: It’s Not Just What’s Under the Skylight

Different roof types also affect skylight selection and flashing requirements:

• Asphalt Shingles:
  → Compatible with both curb and deck mount; most common for deck mount installs.

• Tile (Clay or Concrete):
  → Typically requires curb mount plus custom flashing due to the thickness of the tiles.

• Wood Shake or Wood Shingle:
  → Best with curb mount to elevate above uneven or thick material.

• Metal Roofing:
  → Both mounts can work, but flashing kits must match the profile — some custom work may be needed.

So... Which Skylight Should You Choose?

Here’s a quick cheat sheet:

Still unsure? At Skylights2Go, we help you choose the right Velux skylight and flashing system for your specific roof — no guesswork, no risk. Whether you’re a DIY homeowner or a seasoned contractor, we make selection simple and installation stress-free.

Need Help Choosing? We’re Here for That.

If you're replacing an old skylight or planning a new install, reach out to Skylights2Go. We can help match the perfect product for your roof type, slope, and visual goals — and ship it right to your door.