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Re: Roof Gardens Live load[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Roof Gardens Live load
- From: "Gerard Madden, SE" <gmse4603(--nospam--at)gmail.com>
- Date: Thu, 24 Jan 2008 12:27:24 -0800
I'm working on a building with an "Inaccessible" garden roof.
There is one stair to the roof for a 100,000 sq. foot building. There are 3 other stairwells that do not go to the roof. The footprint is 30,000 sq. feet
A 100psf live load, blindly applied to this structure per your proposal would have major implications. What if the garden is only on certain portion, what do we do then?
My roof has a small 4 foot wide area of pavers for workers to access the irrigation lines. There is no way it could become a place of public assembly.
Why should I have to design for anything other than a 20 psf live load and the garden's self weight?
This is an interestingly timed question, because there are two code proposals for the upcoming ICC hearings in Palm Springs on this very subject to fix a conflict in the 2006 IBC. Table 1607.1, which essentially reflects ASCE 7-05 Table 4-1, reflects the 100psf for "roofs used for roof gardens or assembly purposes". In the 2007 interim cycle, a proposal passed to add a new section for landscaped roofs. That section, 1607.11.3, specifies a 20psf minimum live load for any roof with landscaping.
One of the two proposals makes Table 1607.1 specify a 100psf for roofs used for assembly purposes (including accessible roof gardens) and 20psf for "roofs used for roof gardens". The other fixes the new section to specify 100psf for any roof with landscaping, accessible or non-accessible.
Our proposal review group favored the option to set the live load to 100psf for all roof gardens, accessible or not. The general opinion was that there is enough going on with the typical landscaped roof (landscaping, waterproofing, rigid insulation, pavers/decking, curbs, etc.) that even if the roof is non-accessible (or has only limited access), the higher live load made sense. It allows a margin in dealing with the difficulty in, or uncertainty in figuring out exactly what the actual roof load is with all the "stuff" that goes into a roof garden.
Gary J. Ehrlich, PE
Program Manager, Structural Codes & Standards
National Association of Home Builders (NAHB)
1201 15th Street, NW, Washington, DC 20005
ph: 202-266-8545 or 800-368-5242 x8545
We do several jobs were we have live roofs (roofs with a gardens, not necessary accessible after construction). Based on ASCE 7-05 table 4-1, the live load should be designed for 100 psf. Can anyone clarify if this is only for roofs with gardens that is accessible.
Any help would be great.
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