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I have a shake roof (looks like the original from 1952!) with skip sheathing. Then an asphalt shingle re-roof over that (that makes 2 roofs in 60 years, thanks previous owners!). I have repairs and upgrades to make now and potentially would like to put a whole new roof on eventually.

Can I just strip shingles and shake, then put new decking ON-TOP of the skip decking (considering it is in good shape)? Or should I also rip out all the decking wood down to the rafters?

If I do put ply/osb over the skip deck, I'm guessing I should use longer nails and still try and fasten to the rafters? What is the advice there?

  • I'm not an expert on this at all, but this article may be useful: askaroofer.com/skip-sheathing-roofing-in-roseville-95678. It suggests you should be fine to add OSB over the skip deck. – Shimon Rura Aug 11 '15 at 18:34
  • @ShimonRura Hi. I read it before you even commented here, and the one comment on that page is from me ;) Thanks! – Wilbur Whateley Aug 12 '15 at 0:41
  • California Building Code (That's my state) doesn't specifically mentioned this issue, just mentions which roofing materials (shingles, metal, tile, etc) require which sheathing, most can be used with either solid or skip. The code also only mentions a minimum 3/4" fastener penetration into the sheathing. I'm going to get advice from the local building inspectors. – Wilbur Whateley Aug 22 '15 at 0:30
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Skip sheathing for shake roofs used to be really common around my area of the country and I've never removed it (or seen anybody else remove it for that matter). OSB or plywood over skip sheathing makes for a much stiffer roof deck, resists problems with expansion better, and obviously doesn't require all the hassle of removing it.

After you strip the roof, do spot repairs to the existing sheathing where needed, then go right over it. You'll want to use both longer sheathing nails and longer roofing nails. The sheathing nails should be long enough to give a good hold in the studs, and the roofing nails should be long enough to penetrate both layers of sheathing.

  • When you say I've never removed it (or seen anybody else...), do you mean in the course of doing roofing? Indeed, I can also confidently say I've never removed it or seen anyone else do it, but that's because I've never done any roofing. Have you personally done this? It's not clear from your answer. – Wilbur Whateley Aug 20 '15 at 23:37
  • @WilburWhateley - Yes, in the course of re-roofing. I've done more than my share of roofs through the years. – Comintern Aug 20 '15 at 23:38
  • My city building inspectors confirmed this, that new sheathing can go over the skip sheathing. However they recommended using the same framing nails, specifically 2 1/2 inch, no change there. – Wilbur Whateley Aug 24 '15 at 16:46
  • I've also done my fair share of roofing and have always put new sheeting right on top of skip with no problems, longer nails for the shingles were not required. – Ed Beal Mar 21 at 18:50
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The only skip sheathing I've ever encountered is that installed to support a tin roof. What I found, was that the sheathing was not a consistent thickness which made laying osb or plywood on top quite difficult.

Granted, these were in rural areas where the roof decking seemed to be made of the materials at hand, and not by a professional roofer, but before I lugged a sheet of OSB up a ladder, I would make sure the existing sheathing was a consistent thickness.

Additionally, what will you do if you find that one or two (or a dozen) of the existing planks are not sound and need to be replaced? Finding a 1x6 today that has the same thickness as one fabricated in 1952 will likely not be possible.

  • Really good points, although more of a comment than an answer, in fact you brought up more questions if anything ;) – Wilbur Whateley Aug 20 '15 at 23:35
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60 year old wood is strong, but dry. Dry wood does not like nails much and is more prone to splits and cracks, leaving your Shingles more susceptible to wind damage. Also, the nails will back out more over time, since the fastening holding ability is reduced.

Plywood is the best choice for floors and roofs. OSB is best for sidewalls.

  • This doesn't answer the question, which is about sheating over existing skip sheathing. – isherwood Mar 21 at 18:12
  • Many contractors use osb for roof decking, I won't use 1/2" but depending in the spacing will use 5/8 or 3/4. Never had a problem with nails backing out. – Ed Beal Mar 21 at 18:55

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