Mike Lamb Posted December 21, 2008 Report Share Posted December 21, 2008 I believe this was asked before but I couldn't find it. Why are chimneys in old house (70+ years) offset in the attics. To help prevent backdrafting? I see it so often. Click to View 38.4 KB Quote Link to comment Share on other sites More sharing options...
kurt Posted December 21, 2008 Report Share Posted December 21, 2008 So the chimney would exit at the peak, where it can be flashed so it doesn't leak. They'd offset the chimney base so it wouldn't run up directly through the center of the house, and take it out the peak in the attic. Or, so I've been told. Made sense to me at the time. Back then, folks understood about the high sides of roof penetrations leaking. Quote Link to comment Share on other sites More sharing options...
Bill Kibbel Posted December 21, 2008 Report Share Posted December 21, 2008 There are 3 different reasons a chimney may be offset: To penetrate the roof at the ridge so as to avoid having any roof slope above that would need to be diverted around the chimney (cricket) To avoid cutting and supporting a structural member Some architectural styles include chimney placement as part of the design. Quote Link to comment Share on other sites More sharing options...
Neal Lewis Posted December 21, 2008 Report Share Posted December 21, 2008 Mike, what's your guess as to the age of the house? Without a ridge, I'm thinking at least 125 years old. At least that's what I see around these parts. Quote Link to comment Share on other sites More sharing options...
Bill Kibbel Posted December 21, 2008 Report Share Posted December 21, 2008 I've posted this before in other threads: It's pretty accurate for the mid-Atlantic region. Quote Link to comment Share on other sites More sharing options...
SonOfSwamp Posted December 21, 2008 Report Share Posted December 21, 2008 Here in Middle Tennessee, I've seen plenty of 10s-20s houses with no ridge board. WJ Quote Link to comment Share on other sites More sharing options...
Mike Lamb Posted December 21, 2008 Author Report Share Posted December 21, 2008 Thanks. Sounds good to me. I'm not sure how old. According to Bill's drawing 100 years+. The 2Xs in the forefront are 1 1/2" so that was an add on, and behind the chimney a real 2". Quote Link to comment Share on other sites More sharing options...
SWagar Posted December 21, 2008 Report Share Posted December 21, 2008 In Portland this past summer, I inspected a house built in 1927 that had no ridge board. Quote Link to comment Share on other sites More sharing options...
Rob Amaral Posted December 22, 2008 Report Share Posted December 22, 2008 Other reason is optimal draft... stubby little chimneys exiting at the ridge are not prone to the same problems with wind... Quote Link to comment Share on other sites More sharing options...
msteger Posted December 24, 2008 Report Share Posted December 24, 2008 Yep, offset chimneys are pretty common around here in homes I've inspected from the 1700s and 1800s. I always figured it was to help flash it at the roof line to help prevent leaks. Quote Link to comment Share on other sites More sharing options...
belvedere Posted January 5, 2009 Report Share Posted January 5, 2009 Originally posted by SWagar In Portland this past summer, I inspected a house built in 1927 that had no ridge board. Our house was also built in '27 and has no ridge board. Quote Link to comment Share on other sites More sharing options...
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