Roof Anatomy 101: Every Part of Your Roof, Explained

From the Bottom Up

1. Rafters or Trusses

The skeleton. Rafters are individual angled boards; trusses are pre-built triangular frames. They define the roof's shape and carry every load above.

2. Roof Decking (Sheathing)

Plywood or OSB attached to the rafters. This is the surface everything else nails into. Damaged decking has to be replaced before new shingles can go on — often a $200–$800 add on a typical replacement.

3. Underlayment

A water-resistant layer rolled across the entire roof deck. Synthetic underlayment is now standard — felt paper is mostly obsolete. This is your secondary water barrier if shingles ever fail.

4. Ice and Water Shield

A peel-and-stick rubberized membrane installed in valleys, around chimneys and skylights, and along eaves. In our climate it's most critical in valleys where heavy water flow and hail damage often combine.

5. Drip Edge

Metal flashing along eaves and rakes that directs water into gutters instead of behind them. Required by Texas code. Read our drip edge guide.

6. Starter Strip

The first row of specialized shingles installed along the eaves. They give the field shingles something to seal against and prevent wind uplift.

7. Shingles (Field)

The visible layer. Asphalt is most common — see our shingle comparison guide.

8. Ridge Cap

The shingles at the very top of every ridge. They cover the seam where two roof slopes meet and often house ridge ventilation. Ridge cap is the most exposed part of the roof and the first to fail in high winds.

9. Flashing and Pipe Boots

Metal pieces that seal where the roof meets walls, chimneys, vent pipes, and skylights. Flashing failures are the single most common cause of roof leaks — far more common than "bad shingles."

Bonus: Ventilation

A balanced roof system has intake vents (in soffits) and exhaust vents (ridge or box vents). Bad ventilation cooks shingles from below and is the #1 cause of premature roof failure in North Texas. See our custom roof ventilation page for more.