Has your roofing contractor ever told you that your roof is “19 squares,” highly “cut up,” and needs a new “ice and water shield”? If you nodded along while secretly having no idea what they were talking about, you aren't alone.

Roofing has its own unique language. But when you're investing thousands of dollars into a roof replacement, you need to know exactly what you are paying for. Educating yourself on basic roofing terminology is the best way to ensure you aren't taken advantage of and that you get the best quality materials for your home.

Here is a breakdown of the 16 most common roofing terms you need to know before interviewing a roofing contractor.

1. Square

If a contractor says your roof is “19 squares,” they aren't talking about the shape of your house. A square is simply a unit of measurement used in the roofing industry. One square equals 100 square feet. Instead of saying your roof is 1,900 square feet, contractors will say it is 19 squares. This makes it easier to calculate and order materials.

2. Decking (or Sheathing)

Decking is the structural foundation of your roof. It consists of flat panels (usually OSB or plywood) that sit directly on top of your roof's trusses. Everything else — underlayment, ice and water shield, and shingles — is laid on top of the decking.

3. Eave

The eave is the gutter edge of your roof. It's the lower border that overhangs the exterior walls. Pro tip: A great way to remember this is that if you turn a capital “E” on its side, it looks like a gutter collecting water!

4. Rake Edge

While the eave is the bottom edge, the rake edge is the angled, sloping edge of your roof where two sections meet to form an upside-down “V.”

5. Style D Flashing (Drip Edge)

Style D flashing (often called drip edge) is a metal flashing installed along the rake edges of your roof. It features a small, one-inch lip that allows shingles to extend slightly over the edge. This prevents driving rain from seeping underneath the shingles and causing leaks.

6. Gutter Apron

Similar to drip edge, gutter apron is a metal flashing installed along the eave edges (above the gutters). It overlaps the back of the gutter, ensuring that water runs directly into the gutter rather than dripping behind it, which can cause wood rot and water damage.

7. Ice and Water Shield

This is one of the most critical components of your roof. Ice and water shield is a self-adhesive, waterproof membrane applied directly to the bare roof deck along the eave edges. In the winter, gutters often fill with water that freezes and expands, pushing meltwater up under your shingles. The ice and water shield prevents this water from penetrating your roof deck. Note: Local building codes usually dictate that this must extend at least two feet inside the exterior wall.

8. Synthetic Underlayment

While ice and water shield protects the edges, synthetic underlayment covers the rest of the roof deck. It is a massive upgrade from older, asphalt-saturated felt paper. Synthetic underlayment is highly durable, safer for workers to walk on, resists tearing, and provides a superior moisture barrier.

9. Valley

A roof valley is the internal trough created when two sections of a sloped roof meet at a downward angle. Valleys channel a massive amount of water off the roof, making them highly susceptible to leaks if not properly flashed and sealed.

10. Ridge & Ridge Vent

The ridge is the highest point on your roof, where the two sloping sides meet at the top. A ridge vent is an exhaust vent installed directly over this peak. Because hot air rises, ridge vents are the most effective way to allow hot, stagnant air to escape from your attic, regulating temperature and moisture.

11. Turtle Vent (Box Vent)

Turtle vents (or box vents) serve the same purpose as ridge vents — allowing attic air to escape. They are square, static vents (about 12x12 inches) installed lower down on the roof. While they are industry standard and effective, they are not quite as efficient as ridge vents. If possible, ask your contractor to upgrade you to a ridge vent and plug your old turtle vents.

12. Impact Rated (IR) Shingles

Impact-rated shingles are engineered to withstand severe physical hits, primarily from hail or falling debris. They are rated either Class 3 or Class 4 (Class 4 being the highest). While they cost a bit more upfront, upgrading to a Class 4 IR shingle (like the Malarkey Legacy) can often earn you significant discounts on your homeowner's insurance premiums.

13. Cut Up

This is contractor slang for the complexity of a roof's design. A simple, single-peak roof is not “cut up.” However, if your roof has multiple dormers, valleys, and different angled sections, it is considered highly “cut up.” A cut-up roof requires more labor and materials, which impacts the final cost.

14. Walkable

This term is exactly what it sounds like. A “walkable” roof has a low enough pitch that contractors can safely walk on it in warm, dry weather without the need for ropes, harnesses, or roof jacks. If a roof is too steep and not walkable, expect the labor costs to increase due to the safety equipment and extra time required.

15. Penetrations

Anything that punches through the roof decking is considered a penetration. This includes chimneys, sewer pipes, skylights, and vents. Every penetration requires specialized flashing and boots to prevent water from getting in, which adds to the labor cost of a roof replacement.

16. Starter Shingles

Every row of asphalt shingles relies on a strip of tar to adhere to the row beneath it. But at the very bottom edge of the roof, there is no row beneath to stick to. Starter shingles are a specialized row of shingles applied along the eaves to provide a secure, sticky base for the first visible course of shingles, preventing them from blowing off in high winds.

How to Use These Terms to Interview Your Contractor

Don't be afraid to show your contractor you mean business. When getting an estimate, ask questions like:

  • “Are the shingles you're quoting Class 4 Impact Rated?”
  • “Will you strip the roof down to the bare deck before installing the ice and water shield?”
  • “Do you use synthetic underlayment or old-style felt?”
  • “My roof is pretty cut up and has multiple penetrations — will you reflash the skylights and chimneys?”
  • “Can you upgrade me to a ridge vent and plug the old turtle vents?”

If a contractor stumbles over these elementary terms or can't give you a straight answer, it's a major red flag. A trustworthy roofing professional will welcome an educated homeowner and gladly walk you through their process.