I built a lake house that is 28 wide and 34 long. I constructed…

Question

I built a lake house that is 28' wide and 34' long. I constructed a 34 foot long
center beam for the roof by using 2X12's, elmers wood glue, steel bolts with
washers and nuts. I glued 9 2x12's together and double bolted them 2" from the
edge every 18 inches. I offset the seams. Once cured I set it on top a 2X6 wall
top plate, spanning the 34' length of my house. I then placed two 4.5X6 inch
center poles from the beam to the floor. The beam cuts the house in half. The
beam supports 32 2X10's that span 14' each from the outter edge of each wall to
the beam in the center. The 32 each, 2X10's meet and are joined over the center
of the beam to make up 16 2X10 roof trusses. I will cover the roof with 7/16
OSB, tar paper, and metal roofing sheets. The roof has a shallow pitch, it is
12' to 10' tall shed roof. Is my 2X12 beam sufficient to carry the weight? Thank
you for your help, D Smith

StructuralEng · Accepted Answer

StructuralEng : I can help.
StructuralEng : Hi
StructuralEng : Give me a few minutes to read the question.
Customer:

Thanks for the help. I'd be happy to answer any additional questions, D

StructuralEng : Let me get back to you in about 20-30 min.
Customer:

I just noticed that I didn't tell you the 2X12's are triple layered, (three
thick) and 34' long. I'll look of ryou in 20 mins or so.

StructuralEng : You have three spans then - each almost 12'?
StructuralEng : Does it support the roof or just the joists for the attic?
Customer:

yes three spans, i cut one in half (6 feet) so I could off set the seams.

Customer:

It supports the 2X10's wich are also the roof trusses. The roof trusses are also
the ceiling joices, (one in the same).

StructuralEng : but the roof load is going to the exterior walls only, correct?
StructuralEng : There isn't a panel point in the truss over the beam, is there?
Customer:

correct, the roof load is going to the exterior walls only. It rests on the 2X6
wall top plate. I reenforced the the wall top plate with 4 2x6 studs directly
under the center beam.

Customer:

____________________

Customer:

revision - the roof load is split between the exterior walls and the triple span
2x12 center beam. the 2x12 center beam has two support poles aprox 1/3 spaced on
the beam.

StructuralEng : So this beam is supporting attic load only, correct?
StructuralEng : How is the roof load getting into the beam? Are there posts from
the ridge to this beam?
Customer:

the 2x10 trusses span from north to south exterior wall top plates, and are
supported half way across that span by the 2x12 center beam. The 2x10 trusses
span a total of 28 feet, with the 2x12 beam supporting them at the 14 foot
point.

Customer:

there is no attic. it's built like a lean two. the 2x10 trusses are visible from
inside the room, and have the roof exterior on the outside.

StructuralEng : But the beam isn't supporting the roof unless there are posts
from the ridge or s panel point at the beam
Customer:

the roof is basically flat (very low pitch) 12' to a 10' fall.

Customer:

not sure what you mean by ridge or S panel, sorry

StructuralEng : Are the joists the actual roof structure. That is not a truss.
Customer:

yes

StructuralEng : Can you please attach a sketch? Something is getting lost in
translation
Customer:

ok, they are joists, 2x10

StructuralEng : You can upload a sketch with the paperclip icon
Customer:

I do have sketches but not sure how to attach, looking

Customer:

can you give me an email to send them to?

Customer:

Can't find a way to upload attachment, any chance you can give me an email?

StructuralEng : there is a paper clip icon you can ise
Customer:

looking

StructuralEng : Yiu can also upload to mediafire and post the link here
Customer:

[//f01.justanswer.com/JACUSTOMERaokmdqq5/2011-11-16_175723_east_wall-1.jpg]
[//f01.justanswer.com/JACUSTOMERaokmdqq5/2011-11-16_175723_east_wall-1.jpg]Full
Size Image
[//f01.justanswer.com/JACUSTOMERaokmdqq5/2011-11-16_175723_east_wall-1.jpg]

Customer:

hows that?

StructuralEng : Great
StructuralEng : Is the beam supporting the high rafters AND the low joists?
Customer:

No just the 2x10 joists. The 2x10's will be skinned with the 7/16 OSB then steel
roof material

Customer:

again, I have two center supports under the 2x12 center beam, placed about 1/3
of the beam

StructuralEng : Ok, then it's not supporting any roof load and it's fine
StructuralEng : If you've found my answer helpful, please "accept" it. I'll be
happy to answer additional questions on the topic. If you could provide
feedback, I would appreciate it
Customer:

Guess I'm not being clear. The 2x10's are the roof support. The 2x10's are
supported by the exterior wall top plates, and the center beam. There is no
attic. I will be looking at the underside of the 2x10's from inside the house.

Customer:

sorry, I have to run to a meeting. be back in 50 min.

StructuralEng : You're not using terminology correctly then. The slopes members
high are the rafters. The horizontal members low are joists. You said it's not
supporting the high rafters earlier, but now you said it is.
StructuralEng : Also, let me know where you're located so I can look at snow
loading
StructuralEng : Also, just FYI - this is not a truss. It's just a monoslope
roof.
StructuralEng : Simple stick framing
Customer:

I'm back

StructuralEng : Great. Let me know where you're located and I'll check the beam
Customer:

Thanks for the education on the correct terms. I learned how to frame the house
by watching youtube videos. Hey my neighbors were impressed. The 2x12 center
beam looks plenty strong, I just wanted some peace of mind. But the education
and experience are great and much appreciated.

Customer:

I'm located in Eufaula Oklahoma. That's east-central Oklahoma about 60 miles
from Arkansas.

StructuralEng : Ok. Give me about ten minutes to run some numbers on it. Can you
verify how many 2x's are continuous for each of the three spans?
Customer:

First I laid three 12 foot long 2X12's end to end and spread the wood glue

Customer:

The middle row is a six foot long 2X12 at each end with two 12 foot 2X12's in
the center. This off set the seams. The other outside row was the same as the
first, three 12 foot long 2X12's.

Customer:

Of course that equals 36 feet, so I had to cut 2 feet off after it cured to make
my 34 foot beam

StructuralEng : Under a full design load, it's overstressed in bending.
StructuralEng : At a full design load, it probably won't collapse, but it has no
reserve capacity for overload.
Customer:

What can I do to correct it?

StructuralEng : Add a 2x12 to one side that is continuous between supports. Only
splice it over the support posts.
Customer:

How would you adhear the additional 2x12 ?

Customer:

Ok, great. Thanks a mil for the help. Lots-o-work for you aye. Greatly
appreciated. Happy Thanksgiving. D

StructuralEng : sorry. Use No. 10 x 3" long wood screws at 12" oc staggered
StructuralEng : Have a great Thanksgiving, too!

I built a lake house that is 28 wide and 34 long. I constructed…

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