Thread: Asphalt shingles over wood shingles?

Hi, I have a roof with wood shingles as a base layer, then half inch plywood over these shingles, then asphalt shingles over the plywood.
I would like to simply tear off the asphalt shingles and reshingle with new asphalt shingles on top of the plywood.
Is this an acceptable construction?
Does the plywood count as a layer? or would this be considered only two layers (wood shingle and asphalt shingle)?
I would save a lot of work an expense If I could avoid a complete tear off back to the 1" x 4" wood batterns.

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Originally Posted by jonathanteller

Hi, I have a roof with wood shingles as a base layer, then half inch plywood over these shingles, then asphalt shingles over the plywood.
I would like to simply tear off the asphalt shingles and reshingle with new asphalt shingles on top of the plywood.
Is this an acceptable construction?
Does the plywood count as a layer? or would this be considered only two layers (wood shingle and asphalt shingle)?
I would save a lot of work and expense If I could avoid a complete tear off back to the 1" x 4" wood batterns.

I believe you can do that and it would be considered two layers. The plywood is sheathing, not a roofing layer.

However. I recommend you bite the bullet and tear off to the strapping. It will make a better roof for minimal extra cost and a day or two of extra work. If there are rotten sections such as in the valleys of the original roof shingles, you will be cleaning that up. You will reduce the weight on the structure. The new sheathing will be fastened firmly to the strapping without the old water-soaked roof layer in between. You may be able to reuse a lot of the plywood so it won't cost much more to do a better job, and raise the value of the house as well.
All those cedar shingles in the attic are a fire hazard as well. Get rid of them.

Do yourself a favor and do it right, sleep well, and add value to the home.
By adding on top as was done before you are putting yourself into the stupid homeowner category and there are severe fines for that!!

I agree. Do it right this time, your home will be better and be worth more (some day)

Additionally, if you strip it and secure it to current code and have a wind mitigation survey done you can save some real $$ on your insurance !

Thats not to code here in New Jersey and I so can't imagine Tampa wind design criteria's accepting that. All fastening tables specify "to framing"

How and what would they have that plywood fastened every with. A #8 rosin coated nail going through a 1/2" layer of plywood, then the lapping of the shakes may be 1/2" thick with a minimum 3/4" thick slat installed perpendicular to the rafter leaves barely a 1/2" of fastener into the already dry timber.

I'm describing stripping to the rafters then securing and strapping to current code. True it's more work but the insurance savings could make it very attractive to do right in addition to some piece of mind if a storm comes.

Originally Posted by jonathanteller

Hi, I have a roof with wood shingles as a base layer, then half inch plywood over these shingles, then asphalt shingles over the plywood.
I would like to simply tear off the asphalt shingles and reshingle with new asphalt shingles on top of the plywood.
Is this an acceptable construction?
Does the plywood count as a layer? or would this be considered only two layers (wood shingle and asphalt shingle)?
I would save a lot of work an expense If I could avoid a complete tear off back to the 1" x 4" wood batterns.

It's a technicality to count "layers". The concept, among others, is roof loading.
the roof framing is designed to carry a certain dead load, the shingles do count!

Along with all the other reasons to "do it right", not doing so might void the warranty on the new shingles.

Wood shingles new air If you install a composition over the wood shingle what you will have is a mess in a few years...

Remove all of the old materials and install to the Manufactures spect...

Best

Ron

Originally Posted by jonathanteller

Hi, I have a roof with wood shingles as a base layer, then half inch plywood over these shingles, then asphalt shingles over the plywood.
I would like to simply tear off the asphalt shingles and reshingle with new asphalt shingles on top of the plywood.
Is this an acceptable construction?
Does the plywood count as a layer? or would this be considered only two layers (wood shingle and asphalt shingle)?
I would save a lot of work an expense If I could avoid a complete tear off back to the 1" x 4" wood batterns.

It will most likely be a mote point. All re-roofing must meet the requirements of the current Florida Building Code (permit required). Assuming the original shake/shingle roof is installed over wood battens the roof sheathing will not be able to be nailed to meet the minimum requirement for spacing. If the original roof is installed over a solid roof you could then nail the roof off to meet the requirements but will probably need to retain an engineer to specify the means of attachment and to perform loading calculations

Ok ,Ok I get it! Thanks for all the advice!

Also, call your local fire department and ask them why you should have no more than 2 layers and definately not what you have now.

"If you don't have the time to do it right... when will you have the time to do it over?" These guys are right. Take a little extra time and money now to do it right!

Andrew Constantine
InspectPro Home Inspections
Charlotte NC Home Inspections
Charlotte Home Inspections

Plus that's a lot of extra weight on your framing.
Did you need to calculate the loading?

JLMathis