Asphalt shingles over wood shingles

Is it ever OK to put asphalt shingles over the original wood shingles? I did an older home (80+) that had two layers of asphalt shingles over the original wood. It has spaced board sheathing. Even though the current layer of shingles are only about 5 years old I feel the client needs to know the additional cost of having all this removed the next time he needs a roof. Because he will also need to have new sheathing installed over the spaced boards.

Certainteed requires beveled wood strips be applied to all existing wood shingle courses to obtain an even base. This is to ensure good anchorage for fasteners and also to prevent an uneven base from telegraphing through.

I see that quite frequently here. I have never seen ashpalt shingles over a shake roof, but over wood shingles is common.

I do make a comment that removal of previous layers and installation of sheathing will likely be required when reroofing.

Ralph’s right. Real important is that depending on jurisdiction, they may not allow re-installation of wood shingles or shakes. Most roof covering materials require a solid roof deck. That may mean ripping off spaced sheathing (usually boards) and replacement with OSB or plywood. This is a considerable expense and your client needs to know about it.

Down here many insurers will not write a new policy and have revoked policies in effect once they become aware of the comp over wood.

Never heard of tearing skip/spaced sheathing off we just overlay with OSB around here.

While I have heared of it, doing so is rare here, too, with roofers preferring to just overlay with OSB.

I am surprised the roof can support the additional weight with two layers of asphalt/fiberglass shingles. Average 400-500 lbs. per 10 Sq. Ft. for each layer, in addition to flashing issues when a roof is layered.

In Los Angeles, since 1989, it has not been permissible to install any type of roofing material (including one that is Class-A fire-rated) over a wood roof on spaced-sheathing. Spaced sheathing is more seismically vulnerable and also can allow a fire to draft more rapidly, and the fasteners of the latest roof will have a tendency to split the old and often dry wood shakes/shingles, which means that the roofing material will also be vulnerable to wind-damage.

Looks like you have 3 layers of shingles.
It would not be ok for 3 layers of asphalt shingles.
What is the difference?

2 layers, max.

John hit it right on the head!

Thanks for all the responses. I basically wrote what I saw. I did tell them that when it came time for a new roof there would be considerable expense in removal. And yes the spaced boards would stay and osb would be used on top. The roofing estimate with removal was $18,000.00. Thanks, Ken :slight_smile: </IMG>