required fire protection for I-joists and roof sheathing

[Robert Ellenberg]

I am a builder/designer who strives to get it right and have spent many hours combing these forums and appreciate the sharing of knowledge.

I am working on a plan for a modern/contemporary style house with a section of flat roof. It will be framed with I-joists and insulated above deck with tapered foam covered in EPDM, short parapets all around with canales for drainage. We initially were going to split the insulation with some foam on top and R-38 batts between the I-joists but after concluding we could not comply with R806 ventilation requirement, we simply put all the insulation on the deck. Here is the question: since we no longer have any batt insulation, we are considering leaving off any finished ceiling and staining/painting the underside of the deck and the I-joists, leaving them exposed. Am I required to have a finished ceiling? R805.1 Ceiling installation states that they "shall" be installed in accordance with R702 requirements for wall finishes which states "Interior coverings or wall finsihes shall be installed in accordance with this chapter............

Does "shall" mean that is how you have to install them or does it mean you shall (meaning you have to) install them? I assume you don't have to since many commercial buildings paint the joists and underside of the decking and I have seen exposed rafters with decorative wood decking (Deck House out of Acton MA) but commercial buildings are usually steel but also have different fire resistance requirements than residential single family. I don't know if the exposed wood I have seen in house like a Deck House have special fire retardant on the wood.

Thanks for any help.

 

[Heaven]

Re: required fire protection for I-joists and roof sheathing

It seems that you are being directed back to the section below, and if that is the case just determine if the decking complies with the below on its own. If it doesn't, there are intumescent paints (clear even) that if used bring a material into compliance with the section below.

SECTION R315 FLAME SPREAD AND SMOKE DENSITY

R315.1 Wall and ceiling.

Wall and ceiling finishes shall have a flame-spread classification of not greater than 200.

Exception: Flame-spread requirements for finishes shall not apply to trim defined as picture molds, chair rails, baseboards and handrails; to doors and windows or their frames; or to materials that are less than 1/28 inch (0.91 mm) in thickness cemented to the surface of walls or ceilings if these materials have a flame-spread characteristic no greater than paper of this thickness cemented to a noncombustible backing.

 

[Coug Dad]

Re: required fire protection for I-joists and roof sheathing

Robert,

Welcome to the board. I do not have my codes at home so cannot look up that section. However, in a house of V-B construction, I do not see why a ceiling would be required.

 

[TJacobs]

Re: required fire protection for I-joists and roof sheathing

If you install a ceiling it shall be installed...

The bottom of the I-joists may require some kind of lateral bracing depending, plus make sure the tapered insulation gives you the R-value you need for your climate zone.