Georgia Roof Guide

What does a ridge vent installation diagram show?

Short answer. A ridge vent installation diagram is a cross section of the roof peak: the rafters or trusses meeting at the ridge, the roof deck with a slot cut on each side, shingles and underlayment running up to the slot, the vent body centered over it, and cap shingles nailed through the vent into the deck. Arrows show air rising from the soffits, along the underside of the deck and out through the sides of the vent.

Reading the cross section from the bottom up

  1. Framing: two rafters meeting at a ridge board, or two truss top chords meeting at a point. Many diagrams show both, because the slot is measured differently for each.
  2. Roof deck: plywood or OSB with a gap at the peak. On trusses the gap is typically about 1 inch on each side of center; with a ridge board, it is measured from each face of the board.
  3. Underlayment and field shingles: run up to the edge of the slot without covering it.
  4. Vent body: a rigid plastic or fiber mat centered over the slot, with filter fabric at the outer edges and often an external baffle that kicks wind upward.
  5. Cap shingles: folded over the vent at the specified exposure and nailed through the vent into the deck.

The plan view

Many instructions include a top-down drawing showing where the slot starts and stops, usually about 6 inches short of each gable end and about 12 inches from walls, chimneys or junctions with other ridges. The vent itself runs the full length so the ridge looks even.

The airflow arrows

A complete diagram also shows intake: air entering through soffit vents, passing over insulation baffles at the top of the wall, and rising under the deck to the slot. If a drawing or proposal shows only the ridge, ask where the air is supposed to come from.

Use the right drawing

Go by the diagram printed on the packaging or the installation sheet for the exact vent being installed, since slot width, nail length and hip approval change by product. For the terms used, see roof anatomy explained and roof ventilation basics.

In depth

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