Underlayments where should it be applied

Base on the written estimate my contractor gave me it said: supply and install 30lb roofing felt to eaves and 15 lb synthetic underlay to remainder of roof.
I’m having both garage and house re-roofed .
When they did the garage I only saw them install the synthetic underlay, should the roofing felt have been installed as well?
Or does the roofing felt only need to be installed to the house?

Both are considered “underlayment” felt is old school and synthetic is new hotness. Bonus point for getting the movie reference.

I assume they are installing the #30 paper felt to the eaves because of ice damming? I’ve also not heard Synthetic referred to as 15 lb. IMHO, the synthetic is a far superior product, not sure why they mentioned the #30 felt. If that was for code, IWS is required, felt won’t cut it.

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My guess was they installed ice and water on the eves and synthetic on the rest. Probably a case of a salesmen not actually knowing much about the roofing process.


What I’m asking is were they suppose to install both items on garage roof, because I only saw them install the synthetic underlayment.

Ice and watershield may not be required in your area by code if its not a section with living space. Codes vary all over the country.

I know in some western provinces organic felt is still common on the eaves. Saskatchewan I know for sure it’s common to do it this way. Ice and water isn’t required, but the way the building code is written only organic felt is allowed on the eaves of heated spaces.
As your garage is unheated, the felt wouldn’t be used on the bottom, as synthetic is a little more user friendly.

Unheated structures don’t need ice & water shield.


Hey Andy!
What others are saying is correct.
Detached garages or unheated structures are not of the same code.
So that upgraded black underlayment on the bottom is not required like it is on the house.


Andy,simple answer. No. You either install the 30# felt or you install the synthetic felt.

The contract you signed should be clear. If the roof is warrantied it will list the materials and the installment method. If the garage is excluded from the warranty or given a different material, it should specify that. If for example, the contract says “supply and install 30 lb roofing felt to eaves and 15 lb synthetic underlay to remainder of roof.”, unless it specifically says, “excludes garage”, you should get the same thing. What would the judge say in court?