OK, my builder just had an inspector at the house I am building for the initial inspection of the mechanicals, electrical and plumbing. The inspector informed him that if the roof deck is spray foamed, it will need to be covered with a fire retardant (like drywall or fiberglass insulation). This seems to be a new "glitch" in what I have been reading regarding "hot roofs." Is this just a local code issue or have other people had this experience as well?

This is in the International Residential Code (IRC). My insulating company sprays a fire retardant paint on areas that won't be drywalled or otherwise legally covered. See www.contegointernational.com/

Posted By dolphin on 16 Mar 2010 04:53 PM
OK, my builder just had an inspector at the house I am building for the initial inspection of the mechanicals, electrical and plumbing. The inspector informed him that if the roof deck is spray foamed, it will need to be covered with a fire retardant (like drywall or fiberglass insulation). This seems to be a new "glitch" in what I have been reading regarding "hot roofs." Is this just a local code issue or have other people had this experience as well?

I've never seen fiberglass insulation touted as a qualified thermal barrier for foam- did he put it in writing? (IIRC it's not in the IBC that way!) But a quick google comes up with this qualification use of wet sprayed JM Spider and this sprayed rock wool  for use as thermal barrier for spray foam under roof decks.

Half-inch gypsum qualifies, as does almost any half-inch wood products (check the thermal ratings if there's a question.)   In spaces with no ignition sources and no ducts or air communication with conditioned space air the IBC relaxes the  requirement (3/8" gypsum).  In some instances if it's a fully enclosed dead space the gypsum of the ceiling below qualifies as an adequate thermal barrier.

I don't know if fiberglass is a "qualified thermal barrier for foam", but I do know that fiberglass batts with kraft paper or poly can be left uncovered. I have had kraft faced batts OK'd by building inspectors when it is in front of XPS on a basement wall. Probably would suggest this be verified with the local buidling inspector.

I understand where the inspector is coming from based on the IRC, however, I suggest you ask him to review the IBC Commentary, which takes a slightly different outlook on the foam covering. It is appropriate to use the IBC section for residential, based on using both books.

Keep in mind though, dana hit it pretty close, if there are mechanicals in the attic space, you will have to protect the foam. I did have one contractor build a "room" in the attic around the mechanical equipment with 1 hr walls and skipped the attic covering!

Dolphin:

What model is your state code based on?

Unfortunately, I don't know. I am in Iowa, if that helps.

Dolphin:

A quick Google told me that building codes in Iowa is a somewhat muddy issue as it is up the local AHJ (authority having juresdiction) as to what model code is adopted.  The following somewhat outdated document shows that most towns, citys, etc are on IRC for residential.  What version of IRC is the question, especially based on the fact that the document is 3 years old. http://www.dps.state.ia.us/fm/build...iction.pdf 

A simple phone call to your local AHJ will answer the question - ie the employer of the building inspector, although your builder should know this - and he should have the code book. 

I'm gonna refer to the IRC 2006 since this is a residential application and my guess is that 2006 would be the one in effect.  Also I don't have a IRC 2009 since our state hasn't adopted it yet.  There were changes between IRC 2003 and 2006.  2009 I don't know about.  The info regarding foam plastics is in Section R314.  So, as shown below, if your foam mananacturer can show that his product meets the R314.3 flame spred and smoke development indexes and has been tested per section R314.6 the product should be allowed to be installed without the drywall covering.  The supplier/installer of the foam should be able to help with this if he wants to sell his product and stay in business.

A word of warning... unfortinately when items are discussed with a building official, matters must be handled very delecately and diplomatically.  A lot of these building officials exist in their own little kingdom, and will be reluctant to reverse a previous dicision.

Here are the code sections.  I underlined the most improtant stuff: 

from 2006 IRC:

SECTION R314 - FOAM PLASTIC

R314.1 General. The provisions of this section shall govern the materials, design, application, construction and installation of foam plastic materials.

R314.2 Labeling and identification. Packages and containers of foam plastic insulation and foam plastic insulation components delivered to the job site shall bear the label of an approved agency showing the manufacturer’s name, the product listing, product identification and information sufficient to determine that the end use will comply with the requirements.

R314.3 Surface burning characteristics. Unless otherwise allowed in Section R314.5 or R314.6, all foam plastic or foam plastic cores used as a component in manufactured assemblies used in building construction shall have a flame spread index of not more than 75 and shall have a smoke-developed index of not more than 450 when tested in the maximum thickness of 4 inches (102 mm), provided the end use is approved in accordance with Section R314.6 using the thickness and density intended for use.

Exception: Foam plastic insulation more than 4 inches thick shall have a maximum flame spread index of 75 and a smoke-developed index of 450 where tested at a minimum thickness of 4 inches, provided the end use is approved in accordance with Section R314.6 using the thickness and density intended for use.

R314.4 Thermal barrier. Unless otherwise allowed in Section R314.5 or Section R314.6, foam plastic shall be separated from the interior of a building by an approved thermal barrier of minimum 0.5 inch (12.7 mm) gypsum wallboard or an approved finish material equivalent to a thermal barrier material that will limit the average temperature rise of the unexposed surface to no more than 250°F (139°C) after 15 minutes of fire exposure complying with the ASTM E 119 standard time temperature curve. The thermal barrier shall be installed in such a manner that it will remain in place for 15 minutes based on NFPA 286 with the acceptance criteria of Section R315.4, FM 4880, UL 1040 or UL 1715.

R314.5 Specific requirements. The following requirements shall apply to these uses of foam plastic unless specifically approved in accordance with Section R314.6 or by other sections of the code or the requirements of Sections R314.2 through R314.4 have been met.
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R314.5.3 Attics. The thermal barrier specified in Section 314.4 is not required where attic access is required by Section R807.1 and where the space is entered only for service of utilities and when the foam plastic insulation is protected against ignition using one of the following ignition barrier materials: 
- 1. 1.5-inch-thick (38 mm) mineral fiber insulation;
- 2. 0.25-inch-thick (6.4 mm) wood structural panels;
- 3. 0.375-inch (9.5 mm) particleboard;
- 4. 0.25-inch (6.4 mm) hardboard;
- 5. 0.375-inch (9.5 mm) gypsum board; or
- 6. Corrosion-resistant steel having a base metal thickness of 0.016 inch (0.406 mm).

The above ignition barrier is not required where the foam plastic insulation has been tested in accordance with Section R314.6.
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R314.6 Specific approval. Foam plastic not meeting the requirements of Sections R314.3 through R314.5 shall be specifically approved on the basis of one of the following approved tests: NFPA 286 with the acceptance criteria of Section R315.4, FM 4880, UL 1040 or UL 1715, or fire tests related to actual end-use configurations. The specific approval shall be based on the actual end use configuration and shall be performed on the finished foam plastic assembly in the maximum thickness intended for use. Assemblies tested shall include seams, joints and other typical details used in the installation of the assembly and shall be tested in the manner intended for use.

R807.1 Attic access. In buildings with combustible ceiling or roof construction, an attic access opening shall be provided to attic areas that exceed 30 square feet (2.8m2) and have a vertical height of 30 inches (762 mm) or greater. The rough-framed opening shall not be less than 22 inches by 30 inches (559mmby 762mm) and shall be located in a hallway or other readily accessible location. A 30-inch (762 mm) minimum unobstructed headroom in the attic space shall be provided at some point above the access opening. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics.

Thanks. I will pass it on to the builder.

try this flame retardant wood spray FL will solve all your problems!

a 2 year old post hopefully has been figured out already