Home>Discussions>EXTERIORS>How best to replace old skip sheathed wood shakes with asphalt shingles?
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Konstantin
How best to replace old skip sheathed wood shakes with asphalt shingles?

I am in the process of replacing my wood shake roof with asphalt shingles. The original redwood shake roof was installed in 1980 over 1x6 inch pine skip sheathing. While I liked the look of wood shakes, fire code now prohibits their use in our area. Also seismic considerations now require plywood (or OSB) in place of the skip sheathing regardless of roofing material. We have decided to use asphalt shingles over plywood decking as replacement roofing.

The question I have is how best to re-roof while minimizing labor costs. Removing the old shakes is the first step regardless of how the plywood sheathing is applied. The question is how best to prepare the roof surface to add the new sheathing of plywood. The old shake nail heads will be protruding from the skip sheathing after removing the shakes that needs to be smoothed prior to attaching the plywood. We could 1) remove all the old skip sheathing, shakes and metal flashings at the same time we remove the shakes. Then attaching new plywood directly to the rafters. Or (2) remove the olds shakes and flashings alone. Then pound down and/or remove the shake nails from the skip sheathing. Plywood over the now smoothed skip sheathing, nailing into the rafters. (3) Any other ideas?

Alternative (2) is more labor intensive then (1). Thanks Konstantin

A. Spruce
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

The standard method that I have always seen and used is the shake and felt get pulled off, all nails and staples get beaten flat and then 1/2" plywood is applied over the top of the skip sheathing. Where the edge of the plywood falls into a gap, lay in a piece of 1x4 to support the edges OR use plywood clips.

OSB isn't good for anything, don't use it, use plywood, you'll have a much better finished product that will stay looking good throughout it's life. OSB has a tendency to warp, making your once flat and pristine roof all wavy, which can tear the felt under the shingles and cause leaks. It will also disintegrate if it ever becomes wet.

dj1
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

Yes, that's the way I do it too.

Timothy Miller
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

First call you home insurer see if you get a large discount if you change to a level 4 impact resistant asphalt shingle! on all future payments - its a big deal. Also they should reduce the costs once you no longer have shakes as you pay higher rates with wood roofs.
OSB is cheaper then plywood and is installed on thousands and thousands of roofs with out issues. the other posts issues are rare.. See what your code allows as you are simply overlaying spaced decking maybe 3/8" will be allowed. the spaced decking is quite strong! It performs very well. be sure if you use it that you get the roof underlayment on prior to rain if it gets wet let it dry a few days before covering it up. Be real sure you consider additional roof venting because shakes on spaced decking usually have no other roof venting. Consider installing a whole roof ridge cap vent when shingling and soffit or eve vents to allow air into the attic. Also consider the non roof felt underlayment it is less expensive then felt and 6 moths to 1 year exposure to sunlight . Lays flat, resists wind, and is getting very popular i use GAFs product.

HoustonRemodeler
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

That plywood with the shiny metal side costs 70 cents a sheet more and is an excellent radiant barrier. It gets installed shiny side down.

Mastercarpentry
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

I'd avoid 3/8 and any overlaying for two reasons. The 3/8 isn't rated for this and is far less resistant to warping than anything thicker. And if you use 1/2 or better, the skip-sheathing is redundant and just adding weight where you least need it. Here in the hot and humid south I've seen many 3/8 overlay failures even with good ventilation. Since you're going to have to do a tear-off anyway, removing the skip-sheathing isn't really that much more work or debris.

Based on the height and bracing layout, you might also want to consider laying plywood or walkboards on the ceiling joists for a work platform. That makes the job a lot easier and safer too, plus it will catch a lot of what would have otherwise fell into the attic insulation for easier clean-up. Just be sure that you can get them out before you close it all back in or you may have to leave them in the attic when you're done. Don't ask me how I know about that.

Phil

Timothy Miller
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

Removing spaced decking is a whole bunch more work then overlaying osb or plywood on it not to mention the time to then remove additional nails .... Big Howdy to Mastercarpenter great suggestions- to lay down some plywood in the attic might consider the blue tarps instead to catch the shingle debris but you cannot walk on the tarp in attic unless stepping on the ceiling joists.

Mastercarpentry
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?
Timothy Miller wrote:

"might consider the blue tarps instead to catch the shingle debris but you cannot walk on the tarp in attic unless stepping on the ceiling joists.

That's why I didn't suggest that. Even us experienced folks would likely have a mis-step with slippery plastic tarps and we're trying to not get hurt. It's a lot easier to just stay on the very clearly visible plywood. You're going to need that plywood to sheet with after the tear-off so doing it this way, the plywood is halfway there already too. Hey, I like doing things the smart way whenever possible since it's usually less work too!

One more suggestion: It might be easier to 'bash' the strips off with the head of a sledge applied from underneath versus prying them up with a crowbar, another reason to be working from the attic instead of from the top.

Phil

dj1
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?
Mastercarpentry wrote:

That's why I didn't suggest that. Even us experienced folks would likely have a mis-step with slippery plastic tarps and we're trying to not get hurt. It's a lot easier to just stay on the very clearly visible plywood. You're going to need that plywood to sheet with after the tear-off so doing it this way, the plywood is halfway there already too. Hey, I like doing things the smart way whenever possible since it's usually less work too!

One more suggestion: It might be easier to 'bash' the strips off with the head of a sledge applied from underneath versus prying them up with a crowbar, another reason to be working from the attic instead of from the top.

Phil

Instead of new OSB/plywood, can one use new strips to fill in the blanks?
I've never done this, but I have installed plywood on top of the strips.

Redecker
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

I work only with overlaid roofing replacements(composition shingles over cedar shake with skip sheeting)
.

Industry standard consists of removing wood shakes and laying 1/2 OSB over the existing skip shingles. Removing the skip shingles increases risk of the rafter layout getting thrown off and is not recommended. Radiant barrier decking is a solid upgrade for any market, especially Houston. Care should be taken not to let shingle debris into the furnace vents for the hot water heater or the furnace. An extra roll of Poly with the material drop will easily take care of the attic. Once in place, the attic should not be entered for any reason. When the job is complete, workers can go into the attic and carefully remove the rolled up plastic. OSB no longer has the issues that it used to have. It no longer warps or mushrooms. If the decking and a poly-based underlayment are installed correctly, the deck will never get wet. Roof leaks are always due to lack of foresight. Make sure you use Ice and Water shield in all of the manufacturers recommended areas and widths...Especially when it pertains to the install of the I&W around the pipes, roofers never make a diaphragm around the pipes like they are supposed to.

Sombreuil_mongrel
Re: How best to replace old skip sheathed wood shakes with asphalt shingles?

If you retain the 1x6's use 1/2" OSB; the old sheathing will not allow it to warp or sag. If you strip to the rafters, use 5/8" 7-ply fir plywood, the best stuff there is.
Casey

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