Comp shingles over wood shingles

Would the installation of composition shingles over wood shingles with no felt paper and no plywood (skip sheathing was used) be an acceptable installation?

Composition shingles can be installed over wood shingles BUT are not typically placed over wood shakes.

A typical installation would be skip sheathing, then wood shingles over that. With wood shingles you don’t use felt paper. Did not understand the comment about the comp being installed on skip sheathing.

Are you saying they had skip sheathing; wood shingles; more skip sheathing; then composition shingles over that???

It was skip, wood shingles, comp shingles. I thought there should at least be felt paper over the wood shingles, and question whether any manufacturer would say it’s okay to fasten to only wood shingles (since it’s unlikely you would always be nailing into the skip sheathing).

I think re-roof overlays are a bad idea, they are allowed under certain conditions and in today’s world we can’t get new roofs installed correctly.

What makes consumers think an overlay is any better?

Oh yeah, I saved a few hundred dollars to shorten the life of my new roof, if not damaging it upon installation.

I’m not familiar with the term “skip sheathing”.
What does it refer to?

Definitely would not be a problem here, but it might not be something that I would do in a place like your service area. Better in drier climates than rainy climates. However, if the wood was in good condition when it was overlayed then I definitely wouldn’t have a problem with it. Think of it like this: "Other than probably being uneven in places, what’s the difference between having plywood or board sheathing under the comp or having another type of wood, i.e., wood shingles, under the comp? None.

After reading one of the “warranty sheets” on a very well known batch of shingles, I doubt very much if the roof would have any warranty if installed over wood shingles. Heck, if you read those warranties, a gale force wind voids the warranty. Who doesn’t get 40mph winds a couple times a year. Some warranties are void if you walk on the roof. Huh? They will come up with anything they can to not pay out.

Matthew -

Your scenario is OK. Typical installation. Felt between is preferred if there was existing wood rot, fungus growth OR moisture deterioration that could affect the new comp shingles.

This’ll show you quicker than explaining.:wink:

Good looking job. Strip off is preferred, but not required.

Dan, when you say not required, can I assume not required by code?

My code advice, would be to remove it and do it right, or pay the consequences when you try to sell it and a NACHI Inspector shows up. ha. ha.
Have to remember, it might meet Code, but does not mean that it is right to the Building Standards of today.

Marcel :slight_smile: :wink:

I doubt any shingle manufacturer would even take a glance at them if told they were installed over wood shingles and a problem occured in the future.

Ditto what Marcel said…do it right…!!

Except for the uneven surface you eluded to causing premature horizontal cracking (failure) at the deflected (folding) areas of the shingles.

It would be required if it was My home for sure .

… Cookie

So would it be on mine Roy.

Look what I found here related to this subject;

[FONT=Arial, Helvetica, sans-serif][size=]Composition Shingle Roofing

[/size][/FONT]A. ROOF DECK:

  1. Roof deck must be solid sheathing, either plywood or original plank board construction. Any large voids must be replaced or covered with sheet metal.
  2. Fill in between existing spaced sheathing boards is not allowed.
  3. Shingle installation may not be applied directly over rigid insulation board.
  4. Up to two overlays of composition shingles are allowed over original composition or wood shingles if the roof is in reasonable condition.
  5. Shingle recovers over shakes or laminated composition shingles are not allowed.
  6. Ventilation should be improved wherever practical.

[FONT=Arial Narrow][size=3]B. UNDERLAYMENT:

[/size][/FONT]1. A minimum 15# felt underlayment is required. IRCC recommends 30# felt.
2. No underlayment is required when roofing over existing composition shingles when the pitch is at least 4/12. IRCC recommends a minimum 30# felt underlayment.
3. A minimum 30 # underlayment should be used over wood shingles.
4. A mineral surfaced cap sheet or two layers of 30# felt are needed in all valleys where shingles are used in lieu of a metal valley.
5. All sheet metal valleys shall receive a felt underlayment equal to the roofing underlayment.
6. Slopes less than 4/12 and greater than 2/12 should have a minimum double layer of 15# felt installed in shingle fashion. A single underlayment of 30# felt is not adequate. IRCC recommends a double layer of 30# felt installed in shingle fashion.
7. Application of asphalt shingles on slopes of 2/12 or less should be over an impermeable membrane where the shingles are installed for aesthetic purposes only.

[FONT=Arial Narrow][size=3]C. FASTENERS:

[/size][/FONT]1. Nails shall be EG type, 7/16” head, long enough to penetrate 3/4” into or through the sheathing board.
2. Staples shall be galvanized type, 7/8” crown minimum, long enough to penetrate 3/4” into or through the sheathing board.
3. Shorter fasteners are acceptable for use at overhangs and eaves to
minimize penetration of the visible underside.
4. Fasteners shall be located as to penetrate through all laminations and the selvage top of the underlying shingle, generally four fasteners per shingle.
5. Additional fasteners may be required in high wind areas. [FONT=Arial Narrow][size=3]
[FONT=Arial Narrow][size=3]D. STARTER COURSE:

[/size][/FONT]1. Starter may be 3 tab shingles or mineral surfaced cap sheet cut down to 9” width.
2. Starter may be fastened separately or with the first course of field shingles.
3. Low nailing of starter shingles is not recommended.
4. Supplemental spot sealing of first course over starter course is not required.

**E. VALLEYS:**1. 28 gauge, 18” wide, W type metal valley may be used. The shingles should overlap a minimum of 6” on each flange.

Metal Valley

  1. A “California Valley” consists of shingles lapped 12” past the valley center line and covered with a “bleeder strip” parallel with the center of the valley Shingles lapped from the other side are cut along the bleeder strip.[INDENT]

California Valley

  1. Shingles may be woven across the valley 12” onto the opposite side.


Woven Valley

  1. No fasteners may be installed within 6” of the center of any of these valleys.


  1. May be reused if in serviceable condition. When roofing over an existing roof, the base flange and step shingles should be lifted and installed into the new roof
  2. If counter flashing is replaced, it may be fastened to the chimney with concrete nails and sealed with a good exterior caulk.

Chimney Flashing

<B>G. ROOF JACKS AND PLUMBING VENTS:</B>1. May be reused if in serviceable condition. When roofing over an existing roof, flashings should be lifted and installed with the new shingles.
2. Plumbing pipes may be sealed to the flashing with flashing tape, rubber collar, or plastic cement.
3. Painting of flashing to blend with the roofing is desirable but not required.
4. Exposed galvanized nails in base flashing are acceptable.


  1. Edge metal is required to cover exposed edges of plywood.

  2. Edge metal is not required but is desirable to cover exposed edges of the original roof when overlaying an existing roof.

  3. Painting of edge metal is not required.

  4. When flashing against a vertical side wall:[INDENT]a. New flashings may be installed if feasible. If new flashings are installed on the exterior of the wall, the flashing should be counter flashed with wood or metal sealed to the wall with a good exterior caulk.
    b. The old flashings may be reused if in serviceable condition. The flashings shoulld be lifted and installed with the new shingles except in applications as noted below.
    c. When roofing over composition, the old flashing may remain in the old roof. The last 3” of the new shingle is embedded in plastic cement. A bead of plastic cement should be applied on top of the shingle against the vertical wall.
    d. When roofing over wood shingles, the old flashing may remain in the old roof. Install a 6” wide strip of mineral surfaced cap sheet next to the wall. Cover the strip with plastic cement and install the new shingles. Apply a bead of plastic cement on top of the shingles against the wall.


  1. Ridge should be installed with one nail on each side penetrating into the sheathing at least 3/4”.
  2. Blind nailing is recommended. If nails are exposed, they must be galvanized.
  3. Supplemental surface nailing in addition to blind nailing is acceptable and is desirable in high wind areas.
  4. Spacing of ridge shingles shall match that of the field shingles unless otherwise specified by manufacturer.

**J. BUILDING DEPARTMENT INSPECTIONS:**1. Pre-inspection of roof overlays should be required.
2 In-progress inspections should include spot checks of decking, plywood nailing, shingle application, and flashing installation.
3. Final inspections should be done from the ground if inspectors do not provide their own ladder.

I guess 4000 miles away the standards are different. ha. ha.
I wonder how many Roofing Manufactures would agree with all of this?

Marcel :slight_smile: :slight_smile:

Whaddaya think about that California Valley? Isn’t that the most beautiful thing you’ve ever seen?

Sorry RR; I think I will stick to the cut valleys of Maine. ha. ha.
It took me awhile to accept the cut valleys, but that is only because nobody left that knows how to weave them anymore and takes to much time. :slight_smile:

Marcel :wink:

Marcel or Others -

Sorry guys, you’re thinking new roof - its not. A re-roof by putting composition over wood shingles is totally acceptable and usually done when a wood shingle roof goes bad the 1st time. We use more wood roofs around here than even many places in Colorado or the North woods.

You’re right it would be my preferred choice to tear it off and start again, BUT unless your local code requires it, its not a code requirement. I don’t know a code inspector, insurance adjustor, appraiser or home inspector that would say it was required to tear off and do from scratch as its been described here.

I really thought this was a “no-brainer” and haven’t responded because I thought it would die a quick death.

Most codes allow for layering of materials. That does not mean it’s a good practice. In fact, it is considered by most professionals to be poor practice.

I know of no manufacturer (of comp-shingles) that will honor their material warranty after comp has been laid over wood-shake or wood-shingle. I can think of several reasons why. . .

I also thought this was a “no-brainer” and have been really amazed at the responses on this board. I’m outside of Kansas City. For the most part we use the IRC 2003; some use an earlier version; a few are on UBC; one is on IRC 2006.

You can go over wood shingles with a composition shingle 1 time per IRC 2003.

Last year, I had heard that you could only have 1 layer by IRC 2006 codes and that it would void a manufacturers warranty. So I wrote up 2 that way. I got jumped on bigtime by city code guys, roofer and insurance company - not to mention agents, seller and even buyer for running off mouth when not true in our area and creating a huge problem that did not exist.

So when I saw this post I was curious again, and started calling roofers, insurance adjusters, roofing suppliers, code departments, etc. I was once again assured that may be somebodies rule somewhere else - but not here.

So - for any new guys online, check your own area. When one of us says its not allowed and will void a warranty OR says its 100% OK and you write it up as gospel - you may or may not be demonstrating pure and total ignorance.