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Old 08-05-2011, 12:36 AM   #1
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Did not find OSB under my roof. Now what?


I recently have had an opportunity to replace my roof completely do to some rather horrific storms earlier this year. I have read all my how-to books on replacing a roof and eagerly started stripping away four layers of shingles the previous home owner either installed or covered over.

Much to my surprise I did not find any OSB or Plywood waiting for me underneath. That I did find has me a little confused about where to go from here.

The boards found underneath are rough cut and have spaces between them ranging between a quarter inch to two inches. With the shingles off I am able to see directly into my attic through the gaps.

Any direction from here would be appreciated!

Thanks,

Tim
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Old 08-05-2011, 07:12 AM   #2
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Did not find OSB under my roof. Now what?


That was standard practice until the 1960s.

I'm not a roofer but have installed over skip sheeting a few times.

Simply replace any defective boards and cover with felt--then start shingling---

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Old 08-05-2011, 07:33 AM   #3
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Did not find OSB under my roof. Now what?


Two inch gaps are way to big. We recently did a roof where they were all gapped 1 1/2 to 2 inches. We sheathed over the entire roof with osb. If there are only a few large gaps, just replace those boards with a wider board or plywood. If there are more than a few, sheath over the entire roof. Osb is pretty cheap.
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Old 08-05-2011, 05:34 PM   #4
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Did not find OSB under my roof. Now what?


You should check your gap measurements again.

They look more like an average of 1/2" gap, not counting where some edges have slightly broken off.

If you actually do find a continuous gap that is about 2" wide, you could install lengths of 1" x 2" from rafter to rafter for the entire gap length, but if they are mostly in the 1/2" range or less, then you "May" have to just slightly adjust your nailing pattern for some courses of shingles that align with the gapped area so that the nails do actually sink into the actual wood decking plank boards.

You should not have to encounter the additional expense of re-sheathing that entire roof deck, unless you want to.

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Old 08-05-2011, 08:20 PM   #5
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Did not find OSB under my roof. Now what?


Ed pretty much covered it.I have always liked that type of tear off spade.Your lucky to have felt under that Green roll.

I have had tear offs that they sealed that junk directly to the decking.Nasty.

IMO you might be over thinking the situation.When you start nailing you will know if your nail blows thru a seam.IMO its O.k to pull the shingle and replace it then nail a bit higher on the shingle.Or nail higher and seal the blow thru.

Are you counting 2 starters and 2 layers existing as 4 layers?,,,It looks 2 to me.If not that white shingle held its color well.
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Old 08-05-2011, 08:39 PM   #6
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Did not find OSB under my roof. Now what?


That looks like 2 layers to me.

1st is SIS, Seventeen Inch Selvage or 90# Roll Roofing in green color and the top layer is white 3 tabs.

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Old 08-05-2011, 10:06 PM   #7
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Did not find OSB under my roof. Now what?


It was odd. The layers went
1. Decking
2. Felt
3. A black rolled roofing with brown sand towards the felt
4. Green rolled roofing
5. 3 tab shingles. Grey I guess.

I think I have enough money in the budget to OSB the entire roof on top if the existing decking. "Start Fresh" if you will.
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Old 08-06-2011, 08:59 AM   #8
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Did not find OSB under my roof. Now what?


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Originally Posted by JetMech642 View Post

I think I have enough money in the budget to OSB the entire roof on top if the existing decking. "Start Fresh" if you will.
If you go this route, I recommend re-nailing the existing sheathing with 8 penny nails, then use a medium crown sheathing stapler to sheath with OSB.
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Old 08-06-2011, 09:48 PM   #9
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Did not find OSB under my roof. Now what?


Keep going.. I would fix some cracked or any knot holes larger than two inches. Spacing should be 1/2 to 3/4 of an inch. you should have a decent amount of wood repair with the three layers of nailing and cracked boards. To my knowledge there is no benefit to OSB over your 1x spaced decking. Just make sure if you have any nails blow through to pull them and re-nail as talked about above. I wouldn't re-deck it.
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Old 08-06-2011, 10:02 PM   #10
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Did not find OSB under my roof. Now what?


This maybe pushing your experience level but,,,why not pull the 1x's and install the O.S.B directly to the bones?


Just saying???

If need be,,, re brace/straighten then install your O.S.B,,,some H-clips and have a new roof assembly???

Last edited by Roofmaster417; 08-06-2011 at 10:05 PM.
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Old 08-06-2011, 10:07 PM   #11
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Did not find OSB under my roof. Now what?


Quote:
Originally Posted by JetMech642 View Post
It was odd. The layers went
1. Decking
2. Felt
3. A black rolled roofing with brown sand towards the felt
4. Green rolled roofing
5. 3 tab shingles. Grey I guess.

I think I have enough money in the budget to OSB the entire roof on top if the existing decking. "Start Fresh" if you will.

I might be mistaken but that brown sandy might be some old school base.
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Old 08-07-2011, 09:55 AM   #12
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Did not find OSB under my roof. Now what?


Quote:
Originally Posted by Omegaroofer View Post
Keep going.. I would fix some cracked or any knot holes larger than two inches. Spacing should be 1/2 to 3/4 of an inch. you should have a decent amount of wood repair with the three layers of nailing and cracked boards. To my knowledge there is no benefit to OSB over your 1x spaced decking. Just make sure if you have any nails blow through to pull them and re-nail as talked about above. I wouldn't re-deck it.
The benefit is that you get a warranty on the shingles. If that was here in MN, we would have to resheath it. We would go over it with 7/16" OSB.

Just looked at a job the other day where the roofer 10 years ago went over boards like that. It looks very rough already and there was shingles blown off. There were many other loose shingles also. The old boards move and loosen the shingles over time.
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Old 08-07-2011, 08:20 PM   #13
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Did not find OSB under my roof. Now what?


After your done tearing off go grab a handful of eight penny nails and nail nails down and beat new one into it. Pull any bad wood. I do these jobs all the time with no problems, well maybe a few.. But it can be done. I haven't heard about it not have a warranty, unless its was because the shingle that fell out on your friends wasn't nailed into wood.
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Old 08-10-2011, 08:56 PM   #14
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Did not find OSB under my roof. Now what?


the sandy layer is base roll for the green, its upside down and nailed so the green adhears to it. strip the roof"tighten" it up replace rotten with same 1" board. now to sheet you can drop to a lot thinner 1/4" ply or osb. i'd also advise you instal drip edge moulding, ice and water around your perimeter and a tar paper over the rest then shingle. check int to ridge vent all this takes is setting the depth on the skill saw and an old blade open the ridge ( u'll need @ 2 1/2" roofing nails to attach this vent)
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Old 08-11-2011, 08:57 AM   #15
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Did not find OSB under my roof. Now what?


Drip edge is a must if you are going to sheath over since you will be raising the plane of the roof substrate above the fascias thus exposing the edge of the new sheathing. This over a short time will cause rott if left exposed, so the drip edge would be a must if resheathing. The pic isn't the best, most guys in my area would roof right over it and I would lose the job because I would want to resheat. I'd go right over through, i wouldn't bother tearing off the 1x boards. I'd make sure my sheathing nails went right in through the 1x and into the rafters.

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The information found in this post is not to be considered legal advice. All information should be considered relative, not specific. Never attempt any repairs you are not comfortable with. Always maintain safety! The author of this post takes no responsibility for any losses that occur. Use at your own risk.
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