I’m framing a large addition right now in Southborough, MA. Great looking design, funky elevations, wrapped in a mahogany deck…nice digs. Part of the addition includes taking the back of a 12 in 12 roof off, adding a shed dormer and raftering back up to the existing ridge. Kind of. I’m actually swapping out the existing 2 x 12 ridge out for an 11 7/8 x 3″ LVL ridge beam.
Only problem is the plans call for the ridge beam to be posted on one end and HUNG ON THE CHIMNEY on the other end!! Is this legit? Plans were drawn by a archi with town and engineers stamps on em. Has anyone ever heard of this? To my understanding a chimney was a “free standing” structure capable of supporting only it’s own weight. Am I wrong about this? The detail basically appears to be a piece of angle iron with Hilti quick bolts into the chimney. Should I aim for mortar or brick? Couldn’t I possibly puncture the liner? I’ve got the arch, GC, and engineer coming out in the morning anyway to poke their noses around, so I guess I’ll get my answer then.
Just curious if anyone else has seen anything like this before.
Replies
Chimneys in general are supposed to be independent with an inch or two of airspace between masonry and framing, depending on the local code. But the new one does allow for direct contact if there is a foot of masonry between the combustible and the flue or firebox.
But I wouldn't do it with bolts. They might handle the shear in concete but with varying materials in the CMU mass, I would fear pullout. Only on a new chimney with a beam pocket buiilt in and that would be rediculous for an existing.
Get yourself a detailing fromn the archy with a disclaimer (hold harmless clause) for your self.
Excellence is its own reward!
That's what's called a "clip" . (The angle iron) . Done it before but not on chimney. How many bolts?
If my memory serves me, it's two bolts. I haven't actually seen the bracket/hanger yet. Like I said, the archi and enginner will be around tomorrow. I'm going to ask to be walked through it very specifically.
Think I'll take Piff up on getting a disclaimer off of them. I usually trust my gut and this thing just doesn't seem right to me. The ridge hits within 3" of the outside corner of the outermost bricks...I wonder how long the bolts will have to be? What ever happenned to good old fashioned posts?
how about a threaded strap right around the chimney for pull out, and the bolts ( epoxied ) for shear ?Mike Smith Rhode Island : Design / Build / Repair / Restore
Reason I was asking is the job I recall doing that was a short beam, I think about 10', with the clips hung on concrete walls both sides, 4 1/2" bolts apiece, so I thought maybe for what you were doing , it a take 8. But I wouldn't know.
Just a stupid question to add to the gut feeling that you already have, but over time don't most chimneys lean towards the Sun as they age? How could typical framing stay in the proper position if one end is chasing the chimney? I am not a framer, but it does not sound like the best of ideas to me. Have fun with this one.
Dan
I remember a trip to Williamsburg Virginia. Spent a lot of time wandering around the old buildings. There are many newer ones but I concentrated on the old ones. While doing all this noticing I don't remember seeing any leaning brick work. While I realize that much of the older building have been reworked there are still many in original or just touched up condition.
In fact the only leaning structures were the smaller houses and, most notably, their chimneys. But these were not brick chimneys. They were daub and wattle, mud and sticks, chimneys were built to lean away from the house. Frequently you would see a single support leg opposite the house supporting the chimney. According to the literature these leaning chimneys were only fireproof as long as the mud stayed intact.
Chimney fires were common. The HO, upon finding that her chimney was on fire would run out and kick out the support. This would cause the leaning chimney to fall to earth away from the house. This saved the house and made fighting the fire easier.
Ok, met with the archy and engineer onsite yesterday...the connection's sole purpose is to use the chimney as a "post" for the structural ridge. The "connector" is simply a piece of 1/2" angle iron6" by 6" cut to 6" length. It "bolts" to the chimney via two 1/2" Hilti bolts with epoxy filled holes in chimney (block part, not brick) to form a "shelf" for the ridge beam. Then I am to drill up through the angle iron to run two 3/8" lags into the bottom of the ridge.
It all seems ok....I just had no idea the a chimney could be used as a structural bearing point. My butt is covered on paper, I had just never heard of such a thing.
I'd talk to your building inspector before proceeding too much further. The drawing may have the architect's/engineer's stamp, it may even have a building permit issued, but you of course know that won't keep you out of trouble.
True, true, however as I am just the framing sub on the job my liability is somewhat limited. In addition, I had the GC sign a "zero liabiltiy" statement that simply says that as long as I follow the arch/engineer's installation procedure, failure will be of no fault of mine. When the archy and engineer were on site yesterday, the engineer did a little sketch of how he would like it to be handled. That's in my glove box now.
Thank you for the reason that I waste all of this time here, I learn something every time. Never heard of "waste the chimney save the house" but it does make some sense. Thanks for the education.
Dan
Sounds pretty hokey to me...During our last good sized quake, half of the chimneys in the Valley fell over...even in Southborough, MA, EQs are a possibility.
I've fastened a lot of heavy fixtures to brick walls with Allthread and Epoxy, but still felt a little queasy about it. Brick is a fairly crumbly material to be relied upon to connect a major structural feature to. Or maybe it's t'other way round, perhaps the intention is to support the chimney...
Although the rafters would carry most of the weight, you're talking about the ridge here. If there were an EQ, there's bound to be some kind of major seperation, and major damage control afterwards.
Edited 3/28/2003 12:36:10 PM ET by Jencar