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StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7143
Experience:  Structural Engineer
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I need advice on LVL and dimensional lumber sizing various

Customer Question

Hi, I need advice on LVL and dimensional lumber sizing for spanning various distances under 3 different circumstances. I'm in Louisville, KY.
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  StructuralEng replied 1 year ago.

Hello

Expert:  StructuralEng replied 1 year ago.

What are your conditions?

Customer: replied 1 year ago.
I purchased a home with an existing gable roofed 20'x20' room addition with about a 4 foot shed roof off the bottom left eave if looking from the rear. The roof pitch is about 10-12; the slope of the shed roof is very low (virtually flat), so probably less than 1-12 pitch. The front side of the room is stick framed and was the original exterior wall to the existing house. The other three walls are concrete block. There is an existing beam spanning 20' at the connection between the shed roof and gable eave which is two 10' long 2x6s sistered together with 2 more 10' long 2x6s and resting on a post (in the center of the beam/span) and carrying the load of the left gable and shed roof. The right gable is resting on the block wall. The ceiling joists were perpendicular to the roof rafters and not supporting any load and have already been removed. I want to a) remove the front wall and support the 16' span with 2 LVLs, b) remove the post and support the 2x6 beam (and left gable and shed roof) with 2 20' LVLs, and c) add three 16' western red cedar dimensional beams as rafter ties distributed evenly across 20' room. My 3 questions are what size LVLS for the 16' span and 20' span, and what is smallest red cedar beam that could work in given situation. Of course, if I'm way off on proposal, please advise. Thanks!
Expert:  StructuralEng replied 1 year ago.

Do you have a sketch or pictures that can provide a visual aid to your description?

Customer: replied 1 year ago.
Customer: replied 1 year ago.
the half wall is acting as "the post" in my description for what is holding up 20' 2x6 beam
Customer: replied 1 year ago.
the beam with angle iron was supporting roof joists only and adding load to 20' 2x6 beam ... it is removed as well
Customer: replied 1 year ago.
sorry, I believe the 2x6 beam is actually 2x8s
Customer: replied 1 year ago.
Also, I added the collar ties when I opened up the ceiling and saw the conditions
Expert:  StructuralEng replied 1 year ago.

Is the 16' span the gable end of the gable portion of the roof?

Customer: replied 1 year ago.
Expert:  StructuralEng replied 1 year ago.

Ok. Now that I have a good understanding of what you're looking for...it is typically one question per thread. I can answer two with this one, but the tie question should be asked separately. It's quite a bit more involved. Is that reasonable?

Customer: replied 1 year ago.
can I just pay more and do it all now?
Expert:  StructuralEng replied 1 year ago.

I can submit an additional service offer for you to consider to do it all here.

It will just be member sizes and checks, though, not connections. Unless you prefer to have the connections designed and detailed, too. Just let me know since it will affect the offer.

Customer: replied 1 year ago.
I don't need connections designed. Not sure what you mean by checks, is it referring to the span/load tables? Either way, yes to additional fee and no to connection designs.
Expert:  StructuralEng replied 1 year ago.

I will submit the offer for member designs without connection designs

Customer: replied 1 year ago.
Does the $120 offer take the place of my original $54 fee?
Customer: replied 1 year ago.
you want to charge a total of $174? If so, then I don't agree. Just give me the 20" LVL answer.
Customer: replied 1 year ago.
20'
Expert:  StructuralEng replied 1 year ago.

That was why I initially said that. Spacing out the ties makes the analysis of the eave beam more complex. I will assume load is vertical only.

What is the city and state so I can look at snow loading?

Customer: replied 1 year ago.
Louisville, KY
Expert:  StructuralEng replied 1 year ago.

A 7" x 16" 2.0E LVL will work for strength and limit total load deflection to about 3/8"

Customer: replied 1 year ago.
4-1.75" LVLs sistered together will work as well? That seems excessive, can you provide the source? I have 2007 IRC book and I assume LVL specs are online.
Expert:  StructuralEng replied 1 year ago.

The size is not controlled by strength, it's controlled by deflection.

Customer: replied 1 year ago.
You said you weren't considering anything but vertical load, so now i'm confused. What direction is the deflection?
Expert:  StructuralEng replied 1 year ago.

Deflection is how much the beam sags. I did consider vertical load only, but I still have to check the vertical deflection for that vertical load.

Expert:  StructuralEng replied 1 year ago.

You can use a 5.25" x 14" 2.0E LVL if you're ok with a little over 3/4" deflection under a full design load.

Customer: replied 1 year ago.
Ok. Please confirm sistering individual 1.75" LVLs is permitable. And, please provide your sources for my records. Thanks
Expert:  StructuralEng replied 1 year ago.
sistering multiple 1.75" pieces of the correct depth is acceptable.
The source is my caculations. I don't use tables
Expert:  StructuralEng replied 1 year ago.

Hello. Do you have any other questions for me on this topic? If you could rate my answer, I would appreciate it.

Expert:  StructuralEng replied 1 year ago.

If you could rate my answer, I would appreciate it.

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