Parapet Fire Rating: 705.11

[TatorTot]

Existing building is Type 1A, low-slope roof, parapets vary, but most are less than 30". Existing construction dwgs show FRT plywood on roof side of balloon framed steel stud wall/parapet. Existing roof membrane extends up and is adhered to FRT, lapping over top track, and then covered by wood blocking and metal coping (cladding is brick veneer on outboard side). No parapet is required per 705.11 exception 1 (fyi - I'm in Oregon, so OSSC). - (Note: I do understand the argument that a parapet <30" is not a parapet anyhow, but still unclear on my questions below)

We are re-roofing the building, and have some questions arising regarding fire-ratings and the parapet.

Questions:

1. Is FRT actually allowed anywhere on this parapet (even though it was designed and constructed this way originally) - either on roof-side wall, or as blocking under the cap?

2. Is there any fire-code justification for an owner request to install 1/2" gyp on roof-side of the parapet (my thought is no, since no parapet is actually required, and if parapet was required, no rating is required per table 602 - fire separation is >30ft).

3. How is the parapet cap treated (i.e. - like a small roof, then requiring 1.5 hr rating per roof construction in Table 601? - or as an extension of the wall rating?) - small roof seems crazy to me, but the code doesn't actually define "roof" anywhere (I'd love to be proven wrong on this one, but haven't been yet...)

4. I'm confused on the 705.11.1 requirement for 18" upper non-combustible face material - am I correct in assuming that this does not apply since no rating (or parapet, for that matter) is required (as it is a sub-paragraph to 705.11 Exception 1)?

5. If the parapets were actually over 30" but all other info above remained the same, would it make any difference to the answers for questions 1-4 in this scenario?

Much appreciate any help on these

 

[cda]

An engineer named tator tot,,,

Must be a story behind that.

Any way welcome to this humble forum

 

[cda]

Sorry I do not do parrots, give it a day or two, and you should get some faboulous answers.

 

[cda]

You might look through this commentary, if you do not have one, to see if it helps answer questions



http://diberville.ms.us/home/wp-con...C-Code-And-Commentary-Volume-I_Compressed.pdf

 

[TatorTot]

Thanks, cda.

Interestingly, IMHO, in the commentary, there seems to be direct contradiction to the 18" rule:

Code language 705.11.1: "...shall have non-combustible faces for the uppermost 18 inches..."

Commentary: "...interior wall covering facing the roof, including the flashing, shall be noncombustible to a height of 18 inches above the roof."

Which way are we measuring here, from top down, or from bottom up? Also - is a Class A roof membrane considered a "noncombustible facing"?

 

[steveray]

In noncombustible buildings FRT is allowed for blocking...IBC 601 or 602ish?

 

[Francis Vineyard]

Generally with roof repairs and membrane replacement on existing buildings can used like materials or reuse materials as applicable in Chapter 15. The Building Official should be consulted as to what is specifically required such as alterations to include upgrading insulation.

 

[steveray]

to include upgrading insulation.

Which may cause the roof structure to be evaluated to handle the additional snow load....

 

[Paul Sweet]

I'm probably oversimplifying, but I've always thought that type I & II (non-combustible) construction had to have non-combustible (gypsum) sheathing, and that plywood could be installed on the exterior side of the non-combustible sheathing.

 

[Francis Vineyard]

For example an existing building constructed under the 1996 BOCA, Type 1A, permits FRTW in roof and non-load bearing exterior wall construction where the fire resistance based on the fire separation is 1 hr. or less.

 

[steveray]

I'm probably oversimplifying, but I've always thought that type I & II (non-combustible) construction had to have non-combustible (gypsum) sheathing, and that plywood could be installed on the exterior side of the non-combustible sheathing.

Type II can have combustible sheathing as long as it is not structural...