Author Topic: 30 foot beam  (Read 2615 times)

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Offline alaskamike

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30 foot beam
« on: August 25, 2015, 11:02:09 AM »
I am planning on building the cottage at mile 69 of the Richardson Highway in Alaska and still trying to find out how I can build the foundation at my permafrost location...

For the 20 x 30 one and a half story cottage I am wondering if it would be stronger for the 30 foot beams to use three 2x12's with two strips of 3/4 inch plywood or osb sandwiched between them instead of using 4- 2x12's.  I would use glue as well as nails to construct the beams.  So it would end up being 2x12, 3/4 plywood, 2x12, 3/4 plywood, 2x12.  Thanks much!

Offline MountainDon

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Re: 30 foot beam
« Reply #1 on: August 25, 2015, 12:47:39 PM »
The plywood in a beam is usually just thought of as a spacer to make it easier to use factory made brackets such as Simpson post to beam connectors.   The best beams will be all 2x material with all the joints staggered throughout the beam and located directly over the piers. An engineer will not count glue for any additional strength as they have no control over the application in the field. It save time and expense to simply forget about glue. With the 2x joints located directly over each pier the nails only serve to hold one 2x tight and straight against the adjacent 2x's. The simple act of using layers increases the strength of the built up beam over the strength of sawn timbers.

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline alaskamike

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Re: 30 foot beam
« Reply #2 on: August 25, 2015, 09:00:08 PM »
Thanks for the info!  I will plan the 4-ply 2x12s and make the joints over the piers.  Learn something new every day.  Much appreciated.


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