# Asphalt shingles on Shiplap Roof



## arnold (Jul 13, 2011)

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.


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## tinner666 (Oct 28, 2008)

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 (Oct 28, 2008)

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


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## Ed the Roofer (Sep 15, 2008)

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 (Apr 6, 2009)

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.


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## rooferguy (Mar 4, 2011)

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.


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## Interloc (Apr 6, 2009)

rooferguy said:


> 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.


 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...


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## rooferguy (Mar 4, 2011)

Interloc said:


> 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...


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


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## Interloc (Apr 6, 2009)

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


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## rooferguy (Mar 4, 2011)

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


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## Interloc (Apr 6, 2009)

It doesnt take out the dips any more then 3/8 does..


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## byoung (Jul 11, 2011)

Hello everyone. I am not a roofer but I would like to hear more of your ideas and opinions about the matter. How can I tell if my shiplap is really rotten? What should be the best measurement of plywood to take out dips? Are plywoods and other roofing materials expensive? I might encounter this problems one of these days. I want to know how to look at the situation if I will have to get my roof redone because I don't want to be scammed. A friend of mine had been fooled by a roofer and I don't want something like that to happen to me or to anyone. Your opinions and advises will not only help me but also other people who needs to be guided. Thank you

Byoung


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## oldroofer (May 10, 2011)

what do you mean by shiplap sheating


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## Interloc (Apr 6, 2009)

around here its 1"X 4" or 6" or 8" tongue & groove for decking..


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## oldroofer (May 10, 2011)

ty interloc,was not used much around here just ran in to it acouple time 1by4 t&g hardwood 2 layer tearoff with hotdip nails i still remember the back acke to this day,


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## tinner666 (Oct 28, 2008)

I just thougth I'd post some pix I took today. Regular plank sheathing. 3-tab shingles about 19 years old. As you can see, there are no ill effects of putting them on shiplap or other planks. This is typical. All the repairs on this roof have been done because of trees or tree limbs hitting the house. There has been no other damage.


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## tinner666 (Oct 28, 2008)

The only thing you run into is that repairs are cheaper and easier. The newest repair.

The other 3 attachments are just other pix. Fact is, planks are better.


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## Interloc (Apr 6, 2009)

not all..


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## vtroofing (Sep 27, 2009)

Straight from the Malarky site:
2.5.2	wood BoaRd decks
Wood board decks are composed of solid-sawn dimen- sional lumber.
Wood board decks should be constructed of seasoned, kiln dried or water-base treated lumber.
Wood board decks are to be level and even, and not af- fected by warping, cupping or bowing.
Wood board decks shall be supported, gapped and se- curely nailed to all framing members.
Remove and replace all split or cracked wood boards prior to installing Malarkey products.
Wood board decking should be protected to prevent the accumulation of moisture on its surface prior to the instal- lation of the roofing assembly.
Wood boards must be no wider than 8”.
CREoSotE tREatMEnt iS not CoMPatiblE With aSPhalt SatuRatED oR CoatED PRoDuCtS.
Cracks greater than 1/4” and all knotholes will be covered with sheet metal nailed securely to the deck.
on decks that have a consistent 1/4” or greater gap be- tween each wood board, Malarkey recommends a mini- mum 1/2” recovery board to provide a smooth surface for the roofing materials for low slope applications. on special cases, a heavy weight SbS base sheet or inverted cap sheet may be used, in lieu of a 1/2” recovery board. Con- tact Malarkey for details.
Square-edge boards are not acceptable unless the space immediately below the deck is enclosed with a solid, rigid ceiling to prevent positive interior air pressure loads being imposed on the roof membrane. (for example, warehouses or freight sheds and where windows or doors may be left open during high winds will permit positive air pressures which, combined with negative pressures, may cause blow- 

Also a informative link IMO: http://www.nachi.org/osb-plywood.htm

We more often use OSB on a re-deck. However we use plywood of various thicknesses to match on repairs.


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## calums (Jul 22, 2012)

This is what I gave my customers when it comes to shiplap decks. Obviously I disagree with putting shingles on shiplap decks. "Shiplap decks are common in some areas of the Lower Mainland. What has happened in the past couple of years is some fiberglass shingle manufactures Gaf & Malarkey) are allowing their shingles to be installed on shiplap decks while others (IKO &Emco) will not warranty or want their fiberglass shingles to be installed on these types of decks. What happens with shiplap decks is that over time they move. If you install a fiberglass shingle each shingle bonds to the one above and below it and when the shiplap deck moves ever so slightly the fiberglass shingles buckle and where this happens, water cannot flow straight down the roof and instead goes sideways causing leakage inside the house. The manufacture of the fiberglass shingles will say that they will warranty their shingle on a shiplap deck. But if the deck does move and the shingles buckle they say the fault is not with their shingle but is the fault of the deck. Thus your roof has to be redone complete and we have seen roofs from 6 months to 5 year old have to be redone with both the manufacture and roofing contractor failing to do anything for you. Now this does not happen with all shiplap decks but it is common enough for Canada's largest roofing manufacture (IKO) do not want (or warranty) their fiberglass shingles installed on shiplap. . Some contractors will say they will re-nail the deck but there are two things to be aware here. Will you be home to see that they in fact are re-nailing the deck instead of just saying that they have. But also the shiplap deck over time will loosen these nails allowing the above buckling to happen."


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## harojs (Mar 15, 2015)

*What to lay over ship-lap*

If laying say 7/16in t&g ply over shiplap and using std fiberglass quality thicker shingles for a Seattle home:

[Q1] What is the best type of ply?

[Q2] What is the best type/weight of underlayment?

[Q3] What is the best nail type?

[Q4] How far should nail go in? just past the 1/2in ply? or farther?


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## roofermann (Jul 7, 2012)

harojs said:


> If laying say 7/16in t&g ply over shiplap and using std fiberglass quality thicker shingles for a Seattle home:
> 
> [Q1] What is the best type of ply?
> 
> ...


You should start a new thread with these questions instead of hijacking one that is years dead.:blink:


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