Chimney movement

[Marc M]

Anyone have an opinion on what degree of movement is acceptable for a precast chimney? My buddy, a 30 year chimney vet says 1 inch is acceptable. Just looking for another voice.

[Gunnar Alquist]

Anyone have an opinion on what degree of movement is acceptable for a precast chimney? My buddy, a 30 year chimney vet says 1 inch is acceptable. Just looking for another voice.

I do not see the precast fireplaces around here, but I will chime in with my thoughts. Masonry chimneys should have no movement. They should be solid as a rock. I would think that the precast fireplaces would be the same. This is a lot of weight and I believe they should not move.

[Bruce Breedlove]

I don't think you can go by a blanket acceptable maximum movement for a chimney. What does "1 inch is acceptable" mean exactly? One inch horizontal movement on a chimney how high? One inch is a lot more movement on a 15' chimney than it is on a 45' chimney.

The important thing is that the chimney should not have any openings where hot gasses can escape and cause a fire. I'm sure there have been plenty of instances where a crack in a joint of a precast chimney opened up with less than 1" movement.

[Marc M]

I should have been more specific. The chimney is about 25' with about 5' over the rake. The movment is at the base and it deflects .5" at that point. IMO, there should be no movment also, but I dont want to look like an ass when they spend $300 for that second opinion.
BTW, since this thread was started I checked with another sweep, he also said .5" was okay. Conventional wisdom would suggest otherwise however.

[Bob Harper]

If you're dealing with Rampart General precast fireplaces, why not ask the expert? Dale Feb knows more about these systems than anyone alive.He is based out of Moorpark, Ca. He has all the technical reports from the engineer who designed them, letters from LA County agreeing there is no approved field repair when the insulation plate cracks (as they all eventually do). Dale literally wrote the book on them--and a 2 day hands on training course. Click on the FIRE Service button on this site to contact him.

There are other precast systems out there but this is most prevalent and was based out of So. Cal. They were cast as a monolith at the plant then trucked to the site and stood up on a pad. They have several inherent defects that will cause failures not the least of which is from seismic activity. If you want to see how they are made, take his course as he has one in his shop which he uses for training. The chimney has been snapped off the top of the Fp so you can see the construction. It came out of his own house. His place is like a museum of fireplaces, hearth appliances and chimneys. The best there is.

HTH,
Bob

[Marc M]

Agreed. Unfortunatly, it's difficult to get a hold of them. I am actually taking that class in FEB, so I suppose I can write my report then...;)