On a new 4:12 asphalt-shingle roof, shingles are nailed directly to the wood structural panel deck with no underlayment, membrane or approved alternative assembly. Under 2021 IRC R905.2.3 and R905.1.1, what is the finding?
- AAccept because underlayment is required only below 4:12
- BAccept because self-sealing tabs eliminate the underlayment requirement
- The asphalt-shingle installation lacks required underlayment and needs a compliant correction
- DOnly a full-roof ice-barrier membrane can comply
Where to look it up
https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042182/2021_International_Residential_Code.pdf
Why C is correct
R905.2.3 requires asphalt-shingle underlayment complying with R905.1.1, which addresses material standards, application, attachment and alternative underlayment arrangements. The stated bare-deck installation supplies none. The correction must establish the compliant roof assembly; it cannot be approved merely because tabs seal. Ice-barrier provisions are a separate check and do not universally require one membrane over the entire roof. Do not extend this asphalt-shingle finding into a claim about every roof-covering material or prescribe a universal layer count independent of the applicable tables and alternatives. Source: https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042182/2021_International_Residential_Code.pdf