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Calculations for cantilevered LVL Beam

Calculations for cantilevered LVL Beam

Calculations for cantilevered LVL Beam

(OP)
I am planning build a post and beam framed addition that started simple enough until I was informed that I cannot move some existing gas meters and need to leave some space for access. My structural design had to change to move the southwest post at least 3ft away from the corner to accommodate. How do I calculate this cantilevered beam to prove to the town it will support the load? The proposed posts are 6x6 douglas fir and beams are 5.25" x 9.25" laminated veneer lumber, but I am open to other suggestions. The rafters are running perpendicular to the main building face where the gas meters are. Thanks.

RE: Calculations for cantilevered LVL Beam

Who did the structural design for the original configuration? The most convenient solution would be to employ that person to complete the structural calculations (and stamp it) for the revised configuration.

Rod Smith, P.E., The artist formerly known as HotRod10

RE: Calculations for cantilevered LVL Beam

If the rafters are perp to the building, there is very little roof load on the beam... about 8" and whatever trim. Depending on your area, you could have a lot of snow accumulation on this roof.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Calculations for cantilevered LVL Beam

Structure is self supporting, not tied to existing building??
Blocking to fill space between beams at corner?? Huh?

RE: Calculations for cantilevered LVL Beam

(OP)

Quote (bridgesmith)

- I did the design, I am an architect, but I lack the ability to do full calculation to prove the beam will support the loads which are 50lbs/sqft (upstate ny)

Quote (If the rafters are perp to the building, there is very little roof load on the beam... about 8" and whatever trim. Depending on your area, you could have a lot of snow accumulation on this roof.)

- Thanks @dik, totally agree, however, the concern the town inspector has is when the beam parallel to the building face transfers load to the cantilevered beam, I need to prove that beam size with cantilever can hold it. I roughly calculated the tributary area and weight to be 750 lbs. Not sure where to go from there though, maybe look at the lvl beam design manuals??

Quote (Structure is self supporting, not tied to existing building??
Blocking to fill space between beams at corner?? Huh?)

- your questions are vague and not helpful.

RE: Calculations for cantilevered LVL Beam

Quote:

- I did the design, I am an architect, but I lack the ability to do full calculation to prove the beam will support the loads

Then you need an engineer who can do the calculations and stamp the design.

Rod Smith, P.E., The artist formerly known as HotRod10

RE: Calculations for cantilevered LVL Beam

So not attaching it to the house? How are you providing lateral stability? Looks like too many windows to make a 3-sided building work. Is it brick veneer or load bearing masonry?
Also, for gravity loads, you probably can make this work with dimensional lumber and save a bunch of $$.

RE: Calculations for cantilevered LVL Beam

Deflection of the cantilever comes at a location where drift loads will be maximum. The cantilever is virtually unloaded throughout its span, and its back-span with a point load adjacent to the existing house, so the upward deflection of the span will cause a sizable downward deflection of the cantilever.

To provide lateral stability for the addition, as mentioned by XR250 and to alleviate a nasty flashing problem, I would prefer to carry the new roof on a ledger attached to the existing house, assuming it is capable of carrying the additional load.

RE: Calculations for cantilevered LVL Beam

If we design a beam we can print out a design sheet for a building inspector. And we have the ability to get the design sealed.

So I'd suggest asking the company you're buying the beam from.

RE: Calculations for cantilevered LVL Beam

Stability of the top of the column seems like a concern. Probably more so than the 3 or 4 foot cantilever. Overall stability needs to be investigated, as XR250 states.

RE: Calculations for cantilevered LVL Beam

(OP)

Quote (Stability of the top of the column seems like a concern. Probably more so than the 3 or 4 foot cantilever. Overall stability needs to be investigated, as XR250 states.)

I was recently told I could strengthen this design using the PFH method of Braced Wall Panels to stiffen it. Any thoughts on this?

RE: Calculations for cantilevered LVL Beam

This project seems to be above your abilities . It is not even close to being easy. I recommend hiring a local structural engineer.

RE: Calculations for cantilevered LVL Beam

I'm not familiar with the term PFH but it is clear that the advice you are getting on bracing is inadequate.
As other have indicated:
The cantilevered beam you are asking about is doing very little work and (it seems to me) is the very least of the concerns that one should have with this configuration of things.
Stability of the beam and column line that is up against the house appears to be lacking completely.
There are a lot of openings in the walls of the addition. I wonder how any of it is stable.

I'd be curious about the age of the original house and how the existing exterior walls are built. Assuming that you will completely flash between the old and new, it seems that there might be an advantage to tying into the existing building. Since you are NOT doing that.... I'd want to know why that is. There may be perfectly valid reasons for that but without knowing more, it is harder to give useful advice.

RE: Calculations for cantilevered LVL Beam

I'm not familiar with it either, but I think it refers to Portal Frame with Holdowns. The proponents keep coming up with goofy acronyms which they expect everyone to be familiar with, then you search all over for some information.

Quote (Who knows?)

One method that is useful if you are using intermittent wall bracing is the Method PFH Portal Frame with Holdowns. This method relies on low-deflection holdown anchorage at the bottom, and substantial nailing at the overlap of the sheathing and the header at the top to prevent overturning of the narrow panel.

RE: Calculations for cantilevered LVL Beam

I think a structural engineer with residential design needs to do this. Weird design choices being made here, and there are a fair bit of concerns. If you are unable to verify the LVL beam's cantilever capacity, you are not qualified to do the rest of the (larger) design issues, IMO. Not trying to belittle - trying to make sure that the future occupants get a stable and safe structure.

EDIT: Also, with a nearly flat roof like this, and being in NY, snow drift is a real thing and this needs to be properly designed and verified.

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