Can a roof with a ridge vent to have two shingle layers?

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Can a roof with a ridge vent to have two shingle layers?

David S.
Rental Property Investor · Larkspur, CO · Member since 2018 · 198 posts · 179 votes

Hey all, I’m looking to put an offer on a home that’s part of an estate. The seller has no idea if there’s one or two layers on the roof and I couldn’t tell when walking the property (no ladder). But the house has a ridge vent. Does this make it far more likely it’s one layer, or do some homes with ridge vents still have two layers of shingles? 
Thanks!

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Nathan Grabau
Realtor · Longmont, CO · Member since 2021 · 577 posts · 631 votes
4y

I am a roofing contractor in Colorado. It should be pretty obvious if a roof has a second layer. I would not consider ridge vent to be that big of a sign either way because a typical residential roofing company, especially one doing a second shingle layer on a house, probably is not looking at the details enough to know what a vent roofing even does. If you do not need to replace the roof though, it venting or not venting and a second layer would not have a significant impact on my analysis of a property. (on a house at least) 

If you google pictures of roofs with multiple layers, you will feel better about it because it is not easy to hide. 

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  • Jared McClellan
    Member since 2022 · 3 posts · 3 votes
    4y

    A roof can have two layers and a ridge vent.  

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  • Austin F.
    Investor · MI · Member since 2015 · 227 posts · 478 votes
    4y

    Installation of a ridge vent is not limited by number of layers.

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  • JD MartinBusiness Member
    Moderator
    Rock Star Extraordinaire · Northeast, TN · Member since 2015 · 10k+ posts · 16k+ votes
    4y

    Likely one layer with a ridge vent if it's the continuous air vent type that comes in 4 foot sheets. Not impossible but difficult to install a second layer of roof ridge shingles over top of those. 

    Easiest way to tell is to go to one of the gable sides of the roof (unless it's a hip roof) and look at the edges of the shingles. If it's doubled it's going to likely have three shingles on the end (a continuous underlayment shingle, original exposed layer, second exposed layer. If you only have two layers, and they appear stuck together you likely have only a single layer. If you can get into the attic, it's another way to tell - look for excessive roofing nails coming through the sheathing. Most roofers will put 3 or 4 nails to a shingle, so if they doubled them you should see 6-8 nails in a 3 foot area. 

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  • Nathan Grabau
    Realtor · Longmont, CO · Member since 2021 · 577 posts · 631 votes
    4y

    I am a roofing contractor in Colorado. It should be pretty obvious if a roof has a second layer. I would not consider ridge vent to be that big of a sign either way because a typical residential roofing company, especially one doing a second shingle layer on a house, probably is not looking at the details enough to know what a vent roofing even does. If you do not need to replace the roof though, it venting or not venting and a second layer would not have a significant impact on my analysis of a property. (on a house at least) 

    If you google pictures of roofs with multiple layers, you will feel better about it because it is not easy to hide. 

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  • David S.
    OP
    Rental Property Investor · Larkspur, CO · Member since 2018 · 198 posts · 179 votes
    4y
    Quote from @JD Martin:

    Likely one layer with a ridge vent if it's the continuous air vent type that comes in 4 foot sheets. Not impossible but difficult to install a second layer of roof ridge shingles over top of those. 

    Easiest way to tell is to go to one of the gable sides of the roof (unless it's a hip roof) and look at the edges of the shingles. If it's doubled it's going to likely have three shingles on the end (a continuous underlayment shingle, original exposed layer, second exposed layer. If you only have two layers, and they appear stuck together you likely have only a single layer. If you can get into the attic, it's another way to tell - look for excessive roofing nails coming through the sheathing. Most roofers will put 3 or 4 nails to a shingle, so if they doubled them you should see 6-8 nails in a 3 foot area. 

    I believe this is the type you mean? May be hard to see, sorry. 

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  • JD MartinBusiness Member
    Moderator
    Rock Star Extraordinaire · Northeast, TN · Member since 2015 · 10k+ posts · 16k+ votes
    4y
    Quote from @David S.:
    Quote from @JD Martin:

    Likely one layer with a ridge vent if it's the continuous air vent type that comes in 4 foot sheets. Not impossible but difficult to install a second layer of roof ridge shingles over top of those. 

    Easiest way to tell is to go to one of the gable sides of the roof (unless it's a hip roof) and look at the edges of the shingles. If it's doubled it's going to likely have three shingles on the end (a continuous underlayment shingle, original exposed layer, second exposed layer. If you only have two layers, and they appear stuck together you likely have only a single layer. If you can get into the attic, it's another way to tell - look for excessive roofing nails coming through the sheathing. Most roofers will put 3 or 4 nails to a shingle, so if they doubled them you should see 6-8 nails in a 3 foot area. 

    I believe this is the type you mean? May be hard to see, sorry. 

    Yeah, so half of that roof is a hip roof and half is a gable (the hip is to the left). The gable is going to have the continuous vent if it's got it. You should have some kind of attic access somewhere, even a crawl hatch, if you can't tell by looking at the edges.
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