Hello,

I am looking at at 2 home that need re-roofing. I just had a quote done, and the job is going to cost more than I thought because the home has a layer of ashphalt shingles over cedar shake shingles, and the decking is 1 x 8 decking, with 2-3 inch spaces between them.

The contractor quoted me the cost to remove all of the cedar and replace the decking with 7/16 osb. My question is- does the new decking really need to be replaced? Can I fit 1x2s in between the decking that is currently there? Could I just roof felt and shingle over the existing decking?

Also- can you put the OSB over the existing 1x8 decking or do you need to take it right down to the roof trusses/rafters?

Finally- what would be the worst thing that happened if I just shingled over the existing shingles? I know that technically there are only supposed to be two layers. But, these are rental homes, they are really run down, and I do not want to spend a ton of money on the roofs since there is so much more that needs to be done.

Any thoughts would be appreciated. Thank you

 

Hi Noake, you packed a lot of questions into a short message. I'm sure you'll get some good answers. Here's mine:

In some areas, building inspectors don't count the layer of wood shingles the same as a layer of asphalt shingles... sometimes they consider the wood shingles almost like a layer of sheathing. So whether or not you can just shingle over your existing without tearing off is up to your local codes. In my area you "could" do it. (not that you would want to, but you could.)

The biggest problems you have when shingling over so many layers is that the shingles usually do not last as long... due to the thickness of so many layers they can be more difficult to flash (in certain areas where flashing is required), if the existing shingles are not perfectly flat, your NEW shingles will not be perfectly flat, which can potentially lead to leaks and/or missing shingles in high winds. And by not tearing off, you are postponing the inevitable. Picture putting those rentals up for sale in a few years when the roof needs to be torn off. No one in their right mind would consider buying them without considering the price of tearoff and replacement. If you can't tearoff due to budget reasons, that's certainly understandable, but those are the facts.

When roofs like yours are torn off, the existing 1x sheathing stays on, and new sheathing is laid over it. I doubt you will find any contractors who will fill in the 2-3" gaps in your existing sheathing. The boards used tend to be thicker than today's nominal 1x and the old boards usually aren't straight enough or of a consistent width to do that. If YOU wanted to take the time to do that, you probably could, but I don't think you will find many contractors who will.

There's plenty of roofers here who can chime in too. I just couldn't wait to get my 2 cents in. Beer 4U2

 

If you haven't gone up into the attic and thoroughly checked out the underside of the roof, I suggest you do it. Look for signs of previous leaks, mold or mildew. If you have any signs of the above, then a full shingle tearoff would be the way to go. I had a similar situation a few years back and even replaced some of the 1x8's before sheathing over them.
ALSO: A lot of debris falls through the cracks between those
1x8's, so you may want to lay down drop cloths in the attic to collect that debris. (I didn't, and still don't have all the crap picked up).

 

If you haven't gone up into the attic and thoroughly checked out the underside of the roof, I suggest you do it. Look for signs of previous leaks, mold or mildew. If you have any signs of the above, then a full shingle tearoff would be the way to go. I had a similar situation a few years back and even replaced some of the 1x8's before sheathing over them.
ALSO: A lot of debris falls through the cracks between those
1x8's, so you may want to lay down drop cloths in the attic to collect that debris. (I didn't, and still don't have all the crap picked up).

 

Thanks for the thoughts guys.

Any other thoughts? Am I just postponing the inevitable? Or would it be fine to shingle over the existing layers. Points all well taken on the debris, etc. The contractor who quoted me is willing to rip off all of the existing 1x8 decking and replace with OSB. I am kind of thinking that, although it is much more expensive to do this now, it will allow an easier tear and reshingle, or just a regular reshingle next time it needs it.

 

I advicate doing it right the first time!
1. If those 1x8's show any signs of deterioration or moisture, this could lead to a mold problem down the road.
2. Replacing the 1x8's w/ osb & only 1 layer will lighten the load on those old rafters.
3. You may even be able to find someone that wants to salvage those 1x8's. Think green & recycle!
Check with the mfgr of the roofing and read the fine print on the guarantee/warranty.

 

okay,1st leave the 1x8(which is usually 5/4 by 8-nominal 1" thick),don`t worry about the spaces,install Osb over the "1x8",add a drip edge to cover the perimeter height difference---if you remove the "1x8",you have to look at space between the rafters for proper thickness of sheathing(14 1/2" good for 1/2" plywood,22 1/2" you need 3/4" plywood,and the big issue is:These old homes typically have random rafter spacing,and often larger spaces than quoted,By keeping the "1x8",repairing it as necessary It gives added strength,and covering/sheathing it with 1/2" plywood will make it that much stronger