Engineering - 4" x 12" beam span allowance

[tSmalls]

I am beginning a basement project and I have an engineering question for a span that I would like to create.

CONTEXT:
Currently half my basement is fully finished and the other half is a wide open semi finished space that was a workshop. A 4"x12" beam bisects the house and a framed wall separates the finished space with the unfinished space. There is a photo of a SketchUp model below for visual reference with the beam painted with a wood texture.




PROJECT:
The project is to convert the unfinished space into two offices/bedrooms. To achieve this with the most ergonomic layout, I plan to remove an existing wall in the finished space and move the entryway to the center and expand it from a standard 30" doorway to a 5'10" arch. There are photos of the planned work below.








QUESTIONS:
My questions are these...

• Is this new 5'10" span safe for the 4"x12" beam?
• Would standard king studs be sufficient to support this kind of span or would it be required to put some bigger posts in?
• Should I just get a structural engineer to come and take a look ;D?

I've seen some load bearing calculators around but I can't even begin to imagine how to determine the dead and live loads of my first floor and how much weight each joist is transferring to the beam.

Thanks in advance for all of your sage wisdom! 

[beenthere]

What is the load above this beam/floor?

[Don P]

What he said.

Egress windows or abandon that idea. Window wells is one way.

Let's see if the codebook girder tables will get you there. I believe you will be in table R602.7(2), read the whole section and the section in chapter 5 on floor girders.
CHAPTER 6 WALL CONSTRUCTION, 2018 Virginia Residential Code | ICC Digital Codes (iccsafe.org)

[tSmalls]

What he said.

Egress windows or abandon that idea. Window wells is one way.

Let's see if the codebook girder tables will get you there. I believe you will be in table R602.7(2), read the whole section and the section in chapter 5 on floor girders.
CHAPTER 6 WALL CONSTRUCTION, 2018 Virginia Residential Code | ICC Digital Codes (iccsafe.org)

Egress windows will be installed, so that won't be a problem. I'll give a look at the section now. Thanks for the reference!

[tSmalls]

What is the load above this beam/floor?

That's really the heart of my question, actually. I'm new to this so I'm not sure how to go about determining what the load is on the ground floor. Would this be in the building plans or is there another way to calculate this? 

[beenthere]

Can you explain what is on the first floor? Are there walls above the wall you are talking about? Is the wall you are referencing a support wall for the roof support above the first floor? or is there a second floor above the first and then the roof? Do you think there is a footing under that wall in the basement?

Where in this house do the utilities (plumbing and heating) pass through to the upper floor(s)?

[tSmalls]

Can you explain what is on the first floor? Are there walls above the wall you are talking about? Is the wall you are referencing a support wall for the roof support above the first floor? or is there a second floor above the first and then the roof? Do you think there is a footing under that wall in the basement?

Where in this house do the utilities (plumbing and heating) pass through to the upper floor(s)?

There are no walls built onto the beam on the first floor. there is a wall that runs parallel to the beam across half of the space but it's offset from the beam by two feet, so I can't imagine that being a load bearing wall. There's just open floor on the first floor where the span would be underneath. The outer walls that transfer the load from the roof go directly down to the concrete on the outside walls of the basement perimeter. 

[Don P]

Can you post a floor framing plan? (The joists, posts, load bearing supports of whatever kind... etc)

[wudshp]

When renovating my basement I removed some posts increasing the span beams similar in size to yours carried.  I contacted the local building inspector who I had dealt with before and he recommended a structural engineer that was in town.  The engineer walked into the basement looked around and walked out.  He had me add rebar welded to the flange on both sides of the web.  Charged me 200$ for the site visit, and the inspection after welding.  Was much simpler and cost efficient than I expected.  Bonus was the building inspector trusted the engineer so that headache was removed as well.  I also had to cut a piece out of the basement floor and add a footing for a post in a new location.  The concrete cutting and the welding were a huge mess but the post removal created a much more useful space. I usually try to figure everything out myself but in this case a solution I never would have found solved all my issues in about 10 minutes.     

[trees_are_good]

I would recommend going the structural engineer route. This is your house, don't try to DIY it since there can be complications. What the engineer would do is calculate, as you say, the load on the beam, by seeing what's above and what the dead load and live loads are on the flooring system just above the beam. You would also have to take into account the species of the beam because different species have different load-bearing properties (e.g. modulus of elasticity). There are also different formulas for beams loaded at one point, for uniform loads, and for two-point loads. It can be unclear which one to use. If you're interested, there's a pretty detailed explanation of all this in Tedd Benson's book "Building the Timber Frame House". I mean, it's possible one can learn enough from Benson's book to calculate what you want. The book is here: Building the Timber Frame House: The Revival of a Forgotten Craft - Tedd Benson - Google Books.

But better to just get an engineer in, consultations are not that expensive but a collapsed beam would be pricey indeed.

EDIT: I did some calculations, which you should not at all take too seriously since I'm not an engineer, but these might give you a starting point. Assuming a span of 6' and lateral length of 30', we get a loaded area on beam of 6x30=180 sq ft. Using strength properties for Eastern Hemlock and an 11.5x3.5 beam (height x width), and dead load of 10 and live load of 40, we arrive at a value of "D-max" (maximum deflection of beam) of 0.23373, which, per inch, is 0.00325, or around 1/308. Allowable deflection is usually taken to be 1/360, so your deflection is more than allowable. Similarly, your allowable shear comes to 167.70, which is more than the allowable shear for Hemlock, which is 155.00. So, for both the cases of deflection and shear, my quick calculation (which, again, is for illustrative purposes only) implies that the plan won't work and the beam might collapse.