[GeauxCajuns82]

I have a brick chimney that is in pretty bad shape with lots of mortar cracks and leaks. It is about 6 feet high. There is no framing on the inside, just a brick/mortar chimney with the metal pipe inside. I'd like to tear the whole thing down and replace it with a stud framed chimney covered with Hardie plank siding and a metal vent cap. Does anyone have any kinds of plans for constructing this? Here are my main concerns:

• How do I fasten the chimney framing to the rafters? And can i just attach it to the 2 X 6 roofing rafters or do I need to go down to the 2x6 horizontal rafters on the attic floor?
• What kind of spacing do I need to maintain between the wood framing and the metal vent pipe?
• 2X6 or 2X4 studs for the framing?
• how is the vent cap attached to the top? the vent cap cant contact wood or other combustible material, right?

I'll try and have some pictures soon.

 

[Wildie]

I have a brick chimney that is in pretty bad shape with lots of mortar cracks and leaks. It is about 6 feet high. There is no framing on the inside, just a brick/mortar chimney with the metal pipe inside. I'd like to tear the whole thing down and replace it with a stud framed chimney covered with Hardie plank siding and a metal vent cap. Does anyone have any kinds of plans for constructing this? Here are my main concerns:

• How do I fasten the chimney framing to the rafters? And can i just attach it to the 2 X 6 roofing rafters or do I need to go down to the 2x6 horizontal rafters on the attic floor?
• What kind of spacing do I need to maintain between the wood framing and the metal vent pipe?
• 2X6 or 2X4 studs for the framing?
• how is the vent cap attached to the top? the vent cap cant contact wood or other combustible material, right?

I'll try and have some pictures soon.

That metal liner isn't likely to be suitable for wooden framing!
You will have to replace it with one that is!
Most chimneys on the inside are good for many years! Its the exposed portion that fails most of the time.
In this case, its easier to rebuild the chimney from the roof on up. The bricks may be reused, if they are in good condition.

 

[Wildie]

how do you know whether the bricks are in good condition?

Take two bricks and bang them together, sharply! If they break when they collide, they are no good!

This test only works if you keep your thumbs from cushioning the blow!

 

[GeauxCajuns82]

It's a double walled liner. I have been researching this and it looks like a 2" min gap between the outside pipe and all combustible materials seems to be the standard. The chimney has several other problems besides the crumbling mortar. The seams at the roof flashing are leaking. There is no grating at the vent, just an open top with a cap, and birds love to hang out here. Every fall when I first open the vent door of the fireplace there is a ton of bird feathers that fall down. Also, the brick chimney is resting on the brick walls that surround the fireplace by way of angle iron. The points on the brick where the angle iron sits is starting to crumble so there is a structural issue as well.

I need to know if the wood framing needs to extend down to the attic floor or if it can be correctly supported from the roofing rafters. The distance to the chimney opening from the roof is 4' 6" on one side and 5' 8" on the other.

FYI, The house was built in 78' so the chimney is about 31 years old.

 

[Wildie]

It's a double walled liner. I have been researching this and it looks like a 2" min gap between the outside pipe and all combustible materials seems to be the standard. The chimney has several other problems besides the crumbling mortar. The seams at the roof flashing are leaking. There is no grating at the vent, just an open top with a cap, and birds love to hang out here. Every fall when I first open the vent door of the fireplace there is a ton of bird feathers that fall down. Also, the brick chimney is resting on the brick walls that surround the fireplace by way of angle iron. The points on the brick where the angle iron sits is starting to crumble so there is a structural issue as well.

I need to know if the wood framing needs to extend down to the attic floor or if it can be correctly supported from the roofing rafters. The distance to the chimney opening from the roof is 4' 6" on one side and 5' 8" on the other.

FYI, The house was built in 78' so the chimney is about 31 years old.

Its my opinion for what it worth, and I'm not a structural engineer, is that it should not be supported by the rafters as they are designed to carry the roof load not supplimentary structures.
You also have to consider horizontal forces from winds!
I would be more comfortable having the four corners made from 2X4's that are continuous from the attic floor all the way to the top!
The cost to do so, would be minimal!