Construction Type Reclassification?

[JPohling]

So I thought I had this figured out, but I am running into some problems................

Existing commercial office building. 4 floors over partial mechanical basement. originally classified as Type II - 1 hour and is fully sprinklered. The original design was permitted under the 1982 UBC. The client is trying to remove the 1-hour rated lay in ceiling system that is installed across all floors to protect the bar joists and concrete filled metal deck.

Upon looking at the original shell plans and permit application it became apparent that the original designers used the fire sprinklers to increase the allowable area and then they just went with it. This building is separated on all sides by a minimum of 70 feet. My initial thinking was to use the yards for the area increase and then use the sprinklers in lieu of 1-hour rated construction. My intent was to reclassify under the 2013 CBC. Unfortunately everything was looking good except the shafts are all 1 hour rated per 82 UBC and the 2013 CBC would require 2 hour shafts...........I could trade out the rated ceiling system by adding an additional hour of protection on the shafts.........not what I had in mind. No shafts connect more than 4 floors.

Now I am wondering if I can reclassify the construction type back to the original 82 UBC. Have any of you building officials allowed something like that?

It calcs out ok under the 82 UBC as type II with the side yards and using sprinklers in lieu of 1 hour construction. I cannot understand why this was not done originally.

In any case your thoughts and possible other alternative solutions would be appreciated. Owner wants to have suites open to the structural deck because that is what they see being leased currently. "creative space" ha

 

[cda]

Not a BO but new work seems like it would have to meet present code

Can the deck be sprayed ??

Guess I should have added us 82 as proposal for alternative design under. CBC

 

[jdfruit]

As a prior BO;

Recalc per 82 UBC may be possible, you need to make contact with AHJ & get an opinion. Hopefully there is an old code book hanging around and maybe an old dinosaur still working that is familiar with the old codes.

Recommend you try the recalc per 82 code first. BO's are more comfortable with the codes they know but may accept old code if fully laid out and you can walk them through the format and code sections applicable.

You appear to have a rational approach to reclassify the building for compliance with most current code and that may be the way to go if the AHJ is difficult with recalc to old code.

 

[steveray]

Why not current IIB with sprinklers and no rating?...How big is the building?

 

[JPohling]

BO will not allow reclassification to old code. Need to use current code and then there are all sorts of issues. shafts would need to be made 2 hour from the existing 1 hour. Sprinkler system would need to be upgraded to current code if I want to use it to eliminate the 1 hour rated construction. On and on. Current thinking is to apply for "alternative methods and materials" We would propose removing the rated lay in ceiling system and in turn we would do things such as install quick acting heads, add seismic bracing, maybe increase the density, add emergency egress lighting, possible fire alarm system. those types of things.

 

[steveray]

New construction IIB should NOT require a rating for the structure....exits and shafts are another matter....Per table 601...

EDIT

 

[JPohling]

IIB only allows 3 stories, We are 4 over mechanical basement. way to difficult to get a 30 year old building to comply with current codes.

 

[cda]

Cannot talk to existing building code and forgot if CBC adopted it

That might be a route to go if adopted.

And guess it is a B before and wil be a B in the future

 

[mtlogcabin]

IIB only allows 3 stories, We are 4 over mechanical basement. way to difficult to get a 30 year old building to comply with current codes.

504.2 Automatic sprinkler system increase.

Where a building is equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1, the value specified in Table 503 for maximum building height is increased by 20 feet (6096 mm) and the maximum number of stories is increased by one. These increases are permitted in addition to the building area increase in accordance with Sections 506.2 and 506.3.

You can have 4 stories, The basement does not count

 

[steveray]

The basement does not necessarily count....Unless it can be considered a story above grade plane...

 

[JPohling]

It is a B now and B after. Four stories over basement. I think we can calc it to work as a IIB with yards and sprinklers getting us to where we need to be. The biggest hurdle to this is the darn existing 1-hour rated shafts. These will need to be 2-hour rated shafts. That is a huge undertaking. Anyone have any ideas on how to address the shafts? Perhaps the "alternative methods and materials" approach. I do not seeing adding layers of gyp to both sides of the shafts being plausible.

 

[jdfruit]

If you can't sell the 82 UBC, possible shaft alternate:

There are 2 hr rated shaft "boards", take a walk through the gypsum design manual or UL product assembly listings, or gypsum board manufacturer's sites/literature. May be possible to overlay with AHJ approval.

Another alternate; using 82 UBC, spray fireproof the floor frame & deck pans for one hour (thanks cda in post #2), then the old 1hr grid ceiling can be eliminated and shafts remain as existing 1hr. This may be an easier "sell" to the AHJ.

 

[JPohling]

thanks JD will look at the shaft liner products, but I think that we are moving towards a compromise...............removing the rated suspended ceiling in the suites we are improving and monokoting the bar joists and deck to maintain the one hour floor / ceiling assembly. Using a rated demise partitions to maintain the rating as it shifts from the rated suspended ceiling next door to the new and improved "creative space" ie open to the structure. No need to revisit the 82 UBC or upgrade to 2013 CBC needed.

 

[mtlogcabin]

You classify the building construction Type by height and area limitations and materials used and fire ratings of walls, floors and supporting construction. The ratings of the shafts are not part of the type of construction type.

A one hour shaft in an existing building is permitted under the IEBC

1012.7.3 Other vertical shafts.

Interior vertical shafts other than stairways, including but not limited to elevator hoistways and service and utility shafts, shall be enclosed as required by the International Building Code when there is a change of use to a higher hazard category as specified in Table 1012.4.

Exceptions:

1. Existing 1-hour interior shaft enclosures shall be accepted where a higher rating is required.

2. Vertical openings, other than stairways, in buildings of other than Group I occupancy and connecting less than six stories shall not be required to be enclosed if the entire building is provided with an approved automatic sprinkler system.

 

[JBI]

IF the EBC has been adopted that is an option.

For the rated ceiling removal though the answer is simple; Intumescent finish. Modern alternative to spray on fireproofing.

On the shaft ratings, from one hour to two hour is one layer of gypsum on each side (typically).

Since there is no change of occupancy classification, what exactly is triggering the shaft upgrade?

 

[mtlogcabin]

IF the EBC has been adopted that is an option.

The IBC authorizes the use of the IEBC without adopting it. I believe the 2015 does away with chapter 34 and references the IEBC

3401.6 Alternative compliance.

Work performed in accordance with the International Existing Building Code shall be deemed to comply with the provisions of this chapter

The IEBC also has a definition for change of occupancy that is different from what we normally understand a change of occupancy to be. This should help JPohling with be able to use the exception for the one-hour shafts

CHANGE OF OCCUPANCY. A change in the purpose or level of activity within a building that involves a change in application of the requirements of this code.

 

[JPohling]

https://law.resource.org/pub/us/code/bsc.ca.gov/gov.ca.bsc.2010.10.pdf

I do not see any shaft exception in the 2010 CEBC. The 2 hour shaft upgrade was being driven by trying to reclassify the construction type to the 2013 CBC. We are not pursuing that.

It will work out much better for the building owner to use the monokote or intumescent paint on a suite by suite basis and just maintain the existing construction type and maintain the 1-hour floor/ceiling assembly but just with a different method.

 

[JPohling]

cant you delete a double post?