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4 or 5 story wood framed apt?

BayPointArchitect

BayPointArchitect

Sawhorse
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Oct 19, 2009
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Lincoln
Hello again.

There is a little ambiguity with IBC Section 510.2 where the height in feet is clearly measured from the grade plan and it is limited to either 60' if the residential portion is sprinkled with the 13R system, or up to 75' if the residential portion is sprinkled with the full 13 system. But is the limited number of four stories for a 13R system measured from the grade plane or is it measured from the 3 hour fire-rated pedestal?

Here is an illustration of my question:

https://www.dropbox.com/s/wf9ywe1ebpgekkj/510.pdf?dl=0

With a 13R system for everything above the pedestal, are we limited to a total of four levels above grade plane or can we go up to five levels?

Thanks again!

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner
 
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510.2 Horizontal building separation allowance.
A building shall be considered as separate and distinct buildings for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type of construction where all of the following conditions are met:

1. The buildings are separated with a horizontal assembly having a fire-resistance rating of not less than 3 hours.
2. The building below the horizontal assembly is not greater than one story above grade plane.
Not that unclear I don't think...
 
Constructed per Code, the pedestal is a separate building. The R occupancy would be limited to 4 stories above the pedestal if using a 13R system, that limit is in the standard itself.
So a properly designed and constructed pedestal not exceeding one story above grade plane could have a maximum four story R occupancy above with a 13R sprinkler system. IMHO
 
Builder Bob said:
Look at the 2015 IBC code, i believe it really points you into the right direction;.
Click to expand...
The only real difference provided by the 2015 IBC is that the allowable height shown in Table 504.3 indicates that we are limited to 60' while using the NFPA 13R sprinkler and 70' while using the full NFPA 13 sprinkler. No misunderstanding there.

With regards to either four or five levels (including the reinforced concrete level immediately above the grade plane), I am still a bit foggy.

Steveray, is my "separate and distinct... number of stories" measured from the grade plane or the three-hour pedestal?
 
510.4 Parking beneath Group R.
Where a maximum one story above grade plane Group S-2 parking garage, enclosed or open, or combination thereof, of Type I construction or open of Type IV construction, with grade entrance, is provided under a building of Group R, the number of stories to be used in determining the minimum type of construction shall be measured from the floor above such a parking area. It seems as all of the references to this type of construction cite this, so that is what I would go with....

All this being said, I would have to look at the scoping for 13R to make that determination or the other pertinent sections...
 
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2009 Commentary....
7. The height of the combined buildings above and below the horizontal assembly is limited to the number of feet above grade plane allowed by Section 503 for the type of construction of the upper building. However, the charging language of Section 509.2 does not restrict the number of stories to the entire structure but only to that which is above the horizontal assembly. Thus, a Type VA building, protected by a NFPA 13R sprinkler system and containing a Group R-2 occupancy, can have four stories above the horizontal assembly, provided the overall height of both buildings does not exceed 60 feet (18 288 mm) above grade plane.


4 stories, 60' if you follow this..
 
steveray said:
All this being said, I would have to look at the scoping for 13R to make that determination or the other pertinent sections...
Click to expand...

NFPA 13R:

1.1* Scope. This standard shall cover the design and installation
of automatic sprinkler systems for protection against fire
hazards in residential occupancies up to and including four
stories in height in buildings not exceeding 60 ft (18 m) in
height above grade plane.
 
The provision allows the pedestal and stories above the pedestal to be 70 feet in height from grade plane to top of height measurement if using a NFPA 13 Sprinkler system.

If using an NFPA 13 R system, then the pedestal plus the # of stories is limited to 60 feet in height.

510.2 Horizontal building separation allowance.

A building shall be considered as separate and distinct buildings for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type of construction where all of the following conditions are met:

1. The buildings are separated with a horizontal assembly having a fire-resistance rating of not less than 3 hours.
2. The building below the horizontal assembly is not greater than one story above grade plane.
3. The building below the horizontal assembly is of Type IA construction.
4. Shaft, stairway, ramp and escalator enclosures through the horizontal assembly shall have not less than a 2-hour fire-resistance rating with opening protectives in accordance withSection 716.5.
This section does not include Building Height overall.....from grade plane to highest elevation for measuring a building height.
 
After a careful review of the 2015 NFPA 5000 Building Construction and Safety Code, we see that Section 7.5.2 and the associated appendix makes it clear that the four story limit associated with the 13R system must be measured from the grade plane rather than the 3 hour fire-rated pedestal.

Four stories measured above the grade plane.
That is the definitive answer that I was looking for.

Thank you everyone!

https://www.dropbox.com/s/c7oeke22tgo90s5/Pedestal-Buildings.jpg?dl=0
 
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steveray said:
How are you using NFPA 5000 and the IBC?
Click to expand...
I'm shaking my head over this one, I didn't think any jurisdiction had adopted the NFPA 5000, California's Building Standards voted to adopt it but the governor was recalled and the governor appointed a new Building Standards Commission that voted to rescind the prior vote and adopted the IBC.
 
Use a 13 system and get the fifth story. Not sure where NFPA 5000 came from...
 
If you still need wood frame AND you want to exceed 60' from grade plane, consider using fire-treated lumber on the exterior walls to get a Type III wood framed building. This is how those monstrosities are being built in downtown LA.
 
Yikes said:
If you still need wood frame AND you want to exceed 60' from grade plane, consider using fire-treated lumber on the exterior walls to get a Type III wood framed building. This is how those monstrosities are being built in downtown LA.
Click to expand...
Sounds like an expensive way to get a two hour fire resistant rating for load bearing exterior walls.....

602.3 Type III.
Type III construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code. Fire-retardant-treated woodframing complying with Section 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.

Although fire-retardant-treated wood (FRTW) does not meet the specifications of the code as a noncombustible material, it is permitted as a substitute for noncombustible materials for framing within exterior wall assemblies of Type III construction. The exterior surfaces of the walls must be of noncombustible materials. While the exterior walls are permitted to be either nonload-bearing or load-bearing, to apply the allowance for FRTW the required fire-resistance rating of the exterior wall must be no greater than 2 hours. FRTW is required to comply with the provisions in Section 2303.2.

Sounds like you might be in violation of 602.3 since the FRTW is not within the exterior wall assemblies.
 
With respect to the 13R limitation, where do I measure the building height? And I am only asking about the top of the measurement. Is it (A) floor level of the uppermost occupiable floor, or (B) average roof plan, or (C) top of the parapet?
 

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HEIGHT, BUILDING. The vertical distance from grade plane to the average height of the highest roof surface.


Regardless of whether a building does or does not involve a pedestal, NFPA 13R systems are always limited to structures that do not exceed 60 ft (18 m) in height above grade plane. Note that model building codes do not allow building height to be measured from the top of a pedestal. That allowance only applies to determining the number of stories. The 60 ft (18 m) overall height limit is consistent with limits established by model building codes for buildings of Type V construction. The height of a structure above grade plane is determined by model building codes, which base the height on the average height of the highest roof surface above grade plane. For further information on the building height story limits, see model building codes.
 
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