Asphalt shingles on Shiplap Roof

arnold

Hi guys, a contractor has hired me to reroof a 1200 square foot old house which has shiplap on it. The contractor has indicated to the owner that its okay to put the asphalt shingles on the shiplap and that it won't void the warranty on the shingles. The homeowner is going with the Highlander 30 year Malarkey shingles.

The house is 45 years old and the roof looks very decent. The old shingles were the 3 tab interlock shingles.

I wanted to get your guys input on this as I will be responsible for this job. I have only worked a few years and have dealt with new houses and have no experience with shiplap, though I do know it can expand and contract. Some of my colleagues recommend putting 3/8 plywood on top of the shiplap before using the asphalt shingles, others say don't worry about it.


Here are my questions:

What if the shiplap is not rotted and is aligned properly -would you just put the underlayment down and then shingle.

Would putting asphalt shingles on the shiplap void the warranty. I could not find anything on the Malarkey website.

Another thing I found after inspecting the house which the original contractor did not mention to the homeowner is that there are only 3 soffit vents and no roof vents. I am concerned that there may not be enough ventilation in the attic.

I was going to propose putting in more soffit vents ( 3 more ) and adding one or two roofing vents. Does this seem reasonable?

Would appreciate any feedback.

tinner666

Sounds like a plan. No need to put plywood down. That's for going over skip-sheathing and sheathing with 1/2" gaps, between the planks. If I hit a a crack, I raise or loser my nailing pattern, or even exposure accordingly. I'll drop the shingle 1/4" if necessary.

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tinner666

Oh yeah, somebody will disagree with that, but I don't mind.

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Ed the Roofer

I agree with Tinner regarding the roofing procedure and your ventilation question can not be accurately answered without square footage details and existing NFVA of the existing and proposed Intake Vents and Exhaust Vents, along with inquiring about the attic floor vapor barrier, if any.

Ed

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Interloc

When we roof over shiplap we re-nail deck into trusses and use 30# so the shingles will lay smoother, if the boards are wider then 6" we re-sheet with 3/8's.

rooferguy

do not sheet over shiplap ppl that say go ahead do not know what they are talking about not only do nails come back up but after a few years all the shiplap boards well show thru also 3/8 way to thin min we use is 7/16 are plywood.i will turn down jobs if the home owner wont pay for the resheet.as far as venting goes ridge vent is the way to go.

Interloc

3/8 is not to thin, lost count how many we've done that way and no problems,but you want to pay more for your wood, have at it...

rooferguy

may not be for a new deck but sure does not help to take out any dips in the roof iam not sayinf 7/16 osb is much better 1/2 plywood is the best deck overall and well help get rid of dips in the old roof deck just saying 3/8 is the thinest you can use not somthing i give my client

Interloc

1/2" ply OVER shiplap is overkill, and it won't solve dipping problems..

rooferguy

might be over kill but so what it will help take out dips way more than 3/8 would of course it wont take out all the big dips all iam saying is 3/8 is way to chessy to use and you should not shingle over shiplap it is wrong most of you know that cracks in boards lose boards broken boards it is just wrong