Roof Peak Layers
401 Oak Court · Roof

What sits on top of your roof peak

Three layers stack at the very top of the roof. The vent and the plastic strip are the same thing.

Ridge
The top line of the roof, where the two slopes meet.
Slot
A gap the roofer cuts in the wood along the ridge. Hot attic air gets out here.
Ridge vent
A plastic strip laid over the slot. Air gets out through its edges. Rain and bugs stay out.
Yours: Cor-A-Vent V-600, 8.5 in wide.
Cap shingles
Small shingle pieces folded over the strip to cover it.
Yours: CertainTeed Mountain Ridge, 10 in wide.

The three layers, pulled apart

3. Cap shingles, 10 in wide2. Ridge vent (plastic strip)Cor-A-Vent V-600, 8.5 in wideRoof shinglesPlywood roof deck1. Slot cut in the plywoodRafters and ridge boardATTIC
Looking at the end of the ridge. Bottom to top: the wood with the slot, then the vent strip, then the cap. Thicknesses are drawn bigger than real so you can see them.

How the roofer builds it

1. Cut the slot2. Nail the vent over it3. Nail caps over the ventOpen to the attic.Ridge board in the middle.Strip covers the slot.Air leaves at its two edges.Caps hide the strip.Each one overlaps the last.8.5 in strip10 in cap
Looking down on the same ridge in three stages. The vent comes in 4 ft pieces. When it is done, the slot and the strip are hidden. From the street you only see the caps.

How air gets out

Hot attic air risesAir outAir outRain lands on the capand runs off, away from the slotCap lip coversthe strip's edge
Hot air rises out of the attic, through the slot, into the strip, and out its two edges under the cap. The whole house fan pushes air out this same path, just much faster.

Why the vent has to match the cap

Your plan: V-600 + 10 in capCobra made for 12 in caps + 10 in capCap covers the whole strip,about ¾ in to spare each side.Red: about 1 in each side that a12 in cap would cover. Yours won't.Dashed: the 12 in cap it was made for
Each vent is made for one cap width. The V-600 is narrower than your 10 in cap, so the cap covers all of it. The Cobra you linked is made for 12 in caps. Under your 10 in caps, about 1 in on each side is left bare where a cap should sit. Cobra edges stick out past the cap on purpose. That is where its air comes out.

What “sits right” means

Crack at the foldGap: wind lifts it,rain blows inSits rightDoes not sit rightBends over the strip and liestight on top of it, end to end.Too stiff to bend. Stays flatterthan the roof and lifts at the edges.
Mountain Ridge caps are thick, about five layers. A good roofer bends each one over the strip so it lies tight. If they are too stiff for the strip's shape, they lift or crack. Your roofer will know from experience.

From the street

Dark shingle roof with a thin, slightly raised line along the very top of the ridge.
A computer-made picture of a roof like yours. The vent is the thin raised line along the very top. That is all anyone sees.

Ask the roofer

  1. Does my CertainTeed warranty need a CertainTeed ridge vent, or is the Cor-A-Vent V-600 fine?
  2. Have you put Mountain Ridge caps over a V-600 before? Do they lie tight?
  3. Please write down the feet of slot on each ridge, plus the box vents. We need 9.18 sq ft of vent in total.