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Our builder built a brick chimney. As per the Mason the brick chimney is resting on a 3-1/2 angle iron and over double 2x12.
There are about 900 bricks, limestone etc. on the top of the chimney
and I counted the weight could be approximately 5000 lb.
It is enough support for the roof? Can that weight collapse the building and how safe we are? I can't find my architect, he juswt does not answer the phone. Which specialist I have to invite to get an advice? What is the maximum weight can handle the roof with that support? Thank you.

Answer
Nur from New Jersey,
I am curious. Are you originally a Muslim from Turkey or some other Arabic-speaking country?
One of my favorite instructors for structural engineering is from Turkey.

Without seeing your existing conditions, I must first make a few assumptions.
Your fireplace opening is the typical 36 inches wide fire box.
Limestone is 171 pounds per cubic foot
Concrete is 150 pounds per cubic foot
4 inch thick brick veneer is 42 pounds per square foot
All of these materials are supported by a reinforced concrete foundation sized according to the soil bearing capacity.

All of the materials above the fire box is distributed around a 36 inch wide opening by 3-1/2 angle iron which is then supported by two 2 x 12's ? ? ?
I don't know why the 2 x 12's are part of the equation but I doubt that these two sticks are intended to support anything.
But if your total weight of 900 bricks, limestone and etcetera = 5,000 lb. over a 36" wide opening, then a pair of 2 x 12's is sufficient for 8,000 pounds of load.
But who would think of supporting anything related to a fireplace with combustible materials?  Who would knowingly design a dangerous building and then have two other people agree to build it according to those dangerous plans?

Let's consider two other important variables.
Your snow load ranges from 20 to 50 pounds per square foot - depending on where in the State of New Jersey you live.
What I need to know is how much tributary area of roof and floor are being supported by the brick structure.
I would guess that 500 S.F. would be the largest tributary area anyone could expect within a 2,000 S.F. footprint.  Imagine a fireplace centered in the middle of a square building.  In the worse-case scenario, the masonry column is supporting 25% (more or less) of the overall weight of the building.  

If your architect does not answer the phone, then I must ask
Why do you think that your architect does not answer the phone?
Just curious.
Ask both your Builder and Brick Mason what the tributary area is being supported and relay that answer back to me along with your local snow loads.

The "specialist" you are looking for would be any structural engineer licensed by the State of New Jersey.
He will likely determine that the corbel effect above the 36 inch wide opening equates to only 200 pounds being supported by the 3-1/2 angle.  The remainder of the brick and limestone is self-supporting.
The 3-1/2 x 3-1/2 steel angle may be only 1/4 inch thick.  If that is the case, then I believe that the section modulus is only 0.787 in^4.
But for the scenario based on my assumptions, the steel angle should be 5/16 inch or thicker for me to consider this piece of steel adequate to support a 36 inch wide distributed load of 5,000 pounds.

One of the basic principals of structural engineering is that the strongest materials (steel) support durable materials (brick) which then support materials that are subject to rot, decay, and termites (combustible wood framing).
Structural engineers will raise a red flag with regards to the two 2 x 12's supporting the steel that supports the brick masonry.
Something does not seem right in your description.

I hope to hear back from you.

Richard Burton, AIA
Registered Architect
ICC Certified Plan Reviewer
www.arrow-architecture.com

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Richard Burton AIA

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A combined total of 25 years experience with construction, architecture, and building code enforcement. Ask me about residential and commercial design. Ask me about design aesthetics, structural methods, and building something that will withstand severe weather conditions. Ask me my opinion about YOUR design ideas and I will tell you the merits of good design and challenge your thinking about practical issues. Ask me how to best find and work with your local architect and approach general contractors to get the most value for the least amount of headaches. You can ask me about improving your energy efficiency and things that are both green and practical. But don't ask me about solar panels and wind turbines unless you are currently paying your utility company 35 cents per Kilowatt. Otherwise the math does not justify the initial cost and return on investment. Ask me any building code question and how to get a building permit from the most difficult enforcement agencies.

Experience

Here in the midwest, we design and build "green" in ways that make sense. My construction methods prioritize weather resistance, ease of maintenance and durability. While a graduate student in San Diego, I taught drafting and history of architecture. After working ten years for other architecture firms, I have started my firm Arrow Architecture in 2008. More than half of my work involves commercial office buildings. But my portfolio of work also includes custom homes, residential additions, home remodels, and second story additions.

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President-Elect of American Institute of Architects - Lincoln, NE

Education/Credentials
B.S. Architecture - (Interior Design) University of Nebraska Lincoln 1997 Master of Architecture - (Urban Design and Professional Practice) NewSchool of Architecture - San Diego 2004 Graduated Summa Cum Laude ICC Certified Building Plans Examiner

Awards and Honors
AIA Henry Adams Medal and Certificate

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