Double or triple beams?

[Astrolopitec]

Hi

I'm building a 16X16' flat roofed extension to my roll-off roof astronomical observatory. It will serve as control room and cottage in snow country.

http://pages.videotron.com/astrolo/sitech/footings.jpg

It will rest on five piers. And I was wondering if I can build the floor girder box with 16', 2X12" double beams or do I need to go with triple beams ?


Thanks
Juan Herrero
://pages.videotron.com/astrolo/

[Don_P]

It looks to be 4 piers short at first blush, generally girders don't span over 8'. Is this one floor and a slightly sloped roof? Snow load per square foot? There is a ponding issue on flat and nearly flat roofs. If they begin to pond water this causes it to sag, which allows it to hold more water, which causes it to sag more, and hold more water, etc... until it hits the ground. Just some thoughts.

[Astrolopitec]

OK
You win!

hxxp://pages.videotron.com/astrolo/sitech/peer9

[Don_P]

Not really, I wish we had talked about that a bit more before it got framed.

[Astrolopitec]

Those six inches walls are too heavy to lift by only two persons, so I used a pair of come-along.
Although I can only work on weekends, the roof should be up before first snow which was my main concern. Once the roof is overhead I can continue to work on the inside finishing through the winter.

://pages.videotron.com/astrolo/buffer/wall

[Astrolopitec]

So here's the 16 feet central support beam for my flat roof. An actual 4X12 sistered with five layers of 3/4" playwood, 100 screws, 200 nails, and two large tubes of glue.

If this roof sags. I'll eat my shorts!

://pages.videotron.com/astrolo/buffer/beam2

://pages.videotron.com/astrolo/buffer/beam1

://pages.videotron.com/astrolo/buffer/beam4

://pages.videotron.com/astrolo/buffer/beam3