Roofing, Gutters and Waterproofing - Roof sheathing question

I am rebuilding a 1940 in-law house in my yard, it's going to be a shed. I just ripped of a metel roof only to find shingles underneath. I plan to rip them off soon. The shed roof it self measures 24 X 20 total both sides, which means I will need 15 pieces of 4x8 sheathing. I'm not trying to go bankrupt building this thing but I do want it to last. What thickness of sheathing should I go with to do a new shingle roof?

Another question is, I'm looking in some books and some books show felt under the shingles and some books just show the shingles being nailed directly to the sheathing. Which way is correct?

Before some ask me if the sheathing on the roof now is any good, actually it really isn't. It is over 60 years old and the nails are not gripping to the wood, plus i need to replace 2 joist. But I did get very luck, back when they built this in-law house. Who ever built it, used signs to do the roof. If you go into the shed and look up, all you see are 1940 Ice Cream signs from a out of business philadelphia Ice Cream company. I had an offer on the signs of $50.00 per sign. I'll probable sell them to help with the price of the rebuild.

2 more quick questions:

Do people usually match singles on the house and the shed? I'm hoping I can find the same shingles that are on the house but so far no luck?

Also is it expensive to get rid of asbestos, all the siding are those asbestos boards.

If you are in Colorado, 9/16" OSB (or 5/8" CDX Plywood)will do for sheathing. Check with you building dept. Sometimes old buildings are not framed good enough for modern requirements...especially snow loads. A min 15# felt underlayment with Ice & Water along eaves is required. The asbestos siding could be a HUGE problem. The rules are strict. Your local dump most likely won't take it. Must be class A dump. Giant fees. Must be bagged 7 tagged by certified contractor. Maybe best to leave it alone and just cover it up with new siding.
Jim

5/8 OSB, is all you should need to use for the plywood. Shingling without tarpaper is a very old way of doing thing. Use tht roofing felt And keep the signs, in a bout another 20 years the could be worth about a grand, you never now.

Thanks for the quick reply. When I lay the new sheathing down is it cool if I screw it down with galv. screws?

First place to check is with your local code office regarding minimum specs. Some localities DON'T allow OSB and almost all set minimum thicknesses. Some even require interim inspection to confirm that each nailed on piece of decking is marked "CDX" before putting on felt paper.

IMO the felt paper ONLY PROTECTS THE DECKING TO KEEP IT DRY PRIOR TO SHINGLING. I've seen people deck roofs (particulary notable with so much OSB), leave it exposed to heavy rains for a week or two, then put down the felt and shingles the same day. This is moronic. The OSB has absorbed lots of moisture and probably in a year or three will exhibit "windowpaning" where the outline of the decking becomes visible through the shingles. I would only use PLYWOOD for roof decking, I once fired and sent packing a contractor who had OSB delivered to a jobsite and started installing it even though our contract said "CDX plywood, minimum 5/8". He bi***ched and moaned but later admitted he screwed up and has since done other re-roofs for me.

Frank

Go with the 5/8 ply Dont see why the screws. See if code there calls for the H clip between roof rafters on the decking .15 lb felt drip edge then the shingles.

Id cover the old siding up and let it there under a new kind. It would sure save you a ton of money;) ED

Frank, i have thrown scrap cuts of OSB outside on a burn pile for months and have not seen any delamination/warpage/etc. OSB uses waterproof resin glues. I would not let it undercovered long periods on purpose, but its sure not the consistancy of particle board either. I have also used exterior grade plywood on stuff that delaminated within 2 weeks.