25'X35' Flat-Roof - Built-Up Beam Okay?


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Old 12-31-04, 05:50 PM
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Cool 25'X35' Flat-Roof - Built-Up Beam Okay?

I want to tear down old garage and build new one. Dimensions 25' x 35'. Old garage had shed roof with metal poles in center to support rafter span greater than 16'.

Don't want metal poles/columns in middle. Want big/open room. Still want flat roof - actually slope 1/4" per ft.

Intend to have deck on top. Don't want to get expensive and want to do myself w/couple helpers. Don't want to use iron girders/cranes, etc.

Can I use built-up wood for 30' main beam construction down middle and tie rafters into it? If so, what size lumber? How many do I laminate (nail and glue) together to form the beam?

I am not aware of any span tables on this. Thanks for responses from you guys who have done this before.
 
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Old 12-31-04, 06:52 PM
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Ask your local municipality what code requires. You can probably buy glulam beams cheap enough to make it worthwhile not making it a DIY project. Plus you want a deck above it. That complicated the load bearing issues.
 
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Old 12-31-04, 09:49 PM
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No "Cheap" Answer

Even at the minimum 25' span, no glulam or roof truss or I beam will be 'cheap' or possibly even be able to meet the span requirements you wish.

While Hellrazor is correct in that your local community will need to engineer the design, I think he is being overly optimistic even still.

Personally, I don't think you can do what you wish and will almost surely need a center beam(s) to meet snow and wind sloads depending upon where you live.
 
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Old 01-01-05, 06:23 AM
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You might be right on the pricing, but i don't condone making laminate beams yourself either. He doesn't list where he is from, so either snow load or hurricane requirements also can come into play. Did i mention i hate flat roofing?
 
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Old 01-01-05, 06:02 PM
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25'X35' Flat-Roof - Built-Up Beam Okay

Here is a link to a product that will clear span;
http://www.apawood.org/pdfs/managed/Z725.pdf

You create the slope by increasing the height of an opposing wall.

Where you encounter the difficulty, and need the advice of an engineer, is the expanse and placement of the deck and its affect upon tributary loading.
 
 

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