Porch ceiling covering

[Alexbaldwin]

Hi everyone,

I am in the process of building a two story slab on grade with a porch that wraps part of the front and side of house. My local building department follows the latest IBC codes.

I am working on covering the ceiling on the porch and looking at the codes and am seeing that it says it needs to be covered in a non combustible material, an ignition resistant material or basically have type x sheetrock under anything else.

My question is, is that just required for a porch roof that connects to the main house roof. How do all these people use toungue and groove on porch ceilings? Ive seen it done on new construction houses I've worked on and I’ve never seen sheetrock hung first.

I was wanting to use T1.11 or something similar since it’s just under 8’ and 24” OC roof framing.

 

[ICE]

Wildland-Urban Interface Fire Area requires that.

T1.11 never looks good on a soffit. V-rustic isn’t bad as long as the joints are scattered. Blind nailed T&G pine is attractive.

 

[Alexbaldwin]

I am not in an area where wildfires happen and my closest neighbor is a quarter mile away.

I have thought about some tongue and groove as well, definitely is a good look.

 

[TheCommish]

Should you be in the IRC not the tIBC

 

[Alexbaldwin]

Yes the IRC my bad.

 

[ICE]

looking at the codes and am seeing that it says it needs to be covered in a non combustible material, an ignition resistant material or basically have type x sheetrock under anything else.

Where did that come from?

 

[bill1952]

Center and edge bead finished with spar varnish.

 

[Alexbaldwin]

Where did that come from?

I just typed it into google and it code 707A.7 came up but now I am seeing that its for California (wildfire risk I’m guessing).

So is there a specific code on what can and cannot be on a open porch ceiling?

 

[ICE]

So is there a specific code on what can and cannot be on a open porch ceiling?

I am not familiar with the codes in Minnesota. You could ask the local B/S office.

 

[bill1952]

For a one or two family dwelling, I don't think any ceiling is required. Could be open to roof deck. One near me used t&g boards for roof sheathing and it's quite pretty as well as open feeling.

Other than not using flammable materials - like foam - I don't know of any place ceiling materials are regulated by IRC except garages with habitable space over them, then 5/8 type x gwb or equal is required. WUI areas excluded.

 

[steveray]

R302.9 Flame spread index and smoke-developed index
for wall and ceiling finishes. Flame spread and smokedeveloped
indices for wall and ceiling finishes shall be in
accordance with Sections R302.9.1 through R302.9.4.
R302.9.1 Flame spread index. Wall and ceiling finishes
shall have a flame spread index of not greater than 200.
Exception: Flame spread index 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

 

[ICE]

R302.9 Flame spread index and smoke-developed index
for wall and ceiling finishes. Flame spread and smokedeveloped
indices for wall and ceiling finishes shall be in
accordance with Sections R302.9.1 through R302.9.4.
R302.9.1 Flame spread index. Wall and ceiling finishes
shall have a flame spread index of not greater than 200.
Exception: Flame spread index 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

That doesn't apply to a porch. A room has a ceiling .,, a porch is an appendage with a soffit.

Here's some information on wood flame spread: https://awc.org/wp-content/uploads/2021/12/AWC-DCA1-FlameSpreadPerformance-1906.pdf

 

[bill1952]

Always seems it eliminates exposed foam (polyiso exception) and some fabrics but not much else (in an IRC house).

 

[Paul Sweet]

Almost all woods & plywood have a flamespread less than 200.