Question: "What's everyone using for their downspout guideline?
I was following the one every 15' of gutter, but maybe taking it too literally, because I got a few comments that I had too many. If I had like a 32' gutter, I would put 3 d.s. figuring to divide by 15 and round up.
Let me know what I should do tomorrow AT THE TEST!"
Answer:
This subject has been discussed many times.
Two downsprouts at each gutter should be OK for this vignette. Any kind of rule of thumb is just some suggestions by third parties and not enforceable by NCARB.
There are NO specific requirements in the NCARB codes of the vignette, and no location of the project, so there is NO way for NCARB to enforce any rule of thumb numbers.
I just did a room addition project for one of my properties, and several rain gutter contractors who have been doing nothing but rain gutters and downsprouts for 30 years say one downsprout is adequate for a 32’-long rain gutter for our area because the rainfall is so little.
I ask them to put in two in case one gets clogged, and the other is still working.
You can look up the actual sf of maximum roof area for a certain size of the downsprout from Table 1106.2 of IPC .Here is the link:
http://publicecodes.cyberregs.com/icod/ipc/2009/icod_ipc_2009_11_sec006.htm?bu2=undefined
Gang
Chen, Author, AIA,
LEED AP BD+C
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