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sizing beam for header

Posted by odo53 (My Page) on
Thu, Feb 2, 12 at 21:03

Hi,
We are opening up a wall to get more "open concept" between two rooms. The new opening we want is 9 feet 3 inches. This is on the first floor of a 2 story house, I assume it is a load bearing wall because there is another wall directly above.

I hear anecdotally that a 2 x 8, doubled up, is sufficient for an 8ft span and a 2 x 10, doubled up, is sufficient for up to 10 feet.

Can anyone point me to a table or a calculator or an equation where I can determine what size header I would need using traditional methods, and what I can use if I go with an LVL or some engineered solution? The things I find online are very confusing about live load and dead load and PSF vs PLF and deflection criteria and bearing resistance, etc. I just want a simple beam, supported by 4 x 4s underneath either end. Is a double 2 x 10 enough to hold up my house and meet code? Is a single (or double) LVL that is 7 1/4 tall enough?

I know ultimately it will come down to the building inspector's OK. I just want to be able to be somewhat informed before I talk with him.

Thanks Much!


Follow-Up Postings:

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RE: sizing beam for header

One detail I forgot to mention: the 4 x 4s holding up this beam go from the first floor's floor to the first floor ceiling. Underneath this (in the basement) there is a lally column directly under one 4 x 4 while the other 4 x 4 is attached to the wall so it has foundation wall supporting it. In other words, no worries from basement floor level up to this beam in question.


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RE: sizing beam for header

Excellent article I've referred to while figuring on the same problems:

http://www.mattsonmacdonald.com/documents/BearingWallRemoval.pdf

Based on this, ASSUMING your wall is a true load bearing wall supporting a second floor and roof, you will want a double 11 7/8 LVL.


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RE: sizing beam for header

To design a beam you must first determine the load on it. The anecdotes are most likely for exterior walls and assume a number of stories and width of span for the second floor so they would not apply to an interior beam.

The fact that there is a wall above it doesn't tell us anything. You need to figure out how the house is framed and then determine the load that the beam will carry to the posts and what load the posts put on the structure below, all the way to the foundations.

The beam span is not very long so double 2x12's will probably be large enough or they might be larger than necessary and decrease the height of the new opening unnecessarily.


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RE: sizing beam for header

The headers in the codes are for doors and windows.

You are well past that and the AHJ would be well withing their rights to want a stamped off plan form a professional engineer.


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also

If the beam supports 12 ft long 2nd floor joists on each side of it, three 2x12's or two 11 7/8" LVL's would be required. If the second floor wall carried a load from the attic or roof above, the beam would need to be larger.

Don't guess about structural elements, get someone to assist you who can look at the existing structure before you make a serious mistake.


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RE: sizing beam for header

I am supporting my 1 1/2 story 1906 house with a scaffold of LVLs and columns from the ground up to the 2x4 rafters. House footprint is 24x28'. The front room is 12 x24, joists running in the 24' direction (east west), the gable end wall is the 24' length (north). All joists and rafters run east west and all LVLs perpendicular (north south). The upstairs joists are 14' and 10' long above this room (a little longer because they lap). I've added 12' long double 9 1/2" LVLs 5 feet in from each side wall directly under the kneewalls/joists that carry some of the roof load above. Where the second floor joists lap I removed an old twisted timber (added in 1950s to replace a wall) and replaced it with a double 9 1/2" LVL. All LVLs supported in beam pockets and columns down thru walls. I jacked the floor above when putting in the LVLs and removed most of the sag from 100 years of no support. LVLs die on appropriately sized headers where needed above windows. A neighbor, who is a residential engineer, ran the numbers. I do have two sets of double 9 1/2" LVLs upstairs above the collar ties carrying some of the roof load down through the end walls and stairwell walls that bisect the house in the 28 foot (east/west) direction so all beams are sized throughout the house with relation to each other, house load, snow load etc. Since the original ceilings are 9' tall I will drop them to the bottom of the LVL--8'. There is a 2x4 plate on top of the LVLs to take up the distance of the plate at the top of the wall. I stripped the walls, so the LVLs end within the walls with new studs/beam pockets carrying the loads down to the foundation. All LVLs are glued and timberloc screwed or nailed together. You'll only pay a little more to oversize the beams though it is wise to get a professional assessment. The engineers with the computer programs can run the numbers very quickly.


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RE: sizing beam for header

Perhaps a computer generated spam message?


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RE: sizing beam for header

We need the same info for a 14' span. When I got the permit I didn't know what size, so the gentleman there quickly figured I'd need at least 3 12' beams together. He told me we would be able to change to an LVL. We will need to have it sized by the LVL supplier and keep the paperwork to show the inspector.


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RE: sizing beam for header

Some parts of the country one can get the lumber yard that is supplying the beam to have the LVL company size the correct beam for the load. Some states, not so much. All west coast, FL, NJ...high probability that you will need an engineer.

Sizing a beam, even for well versed professionals, is not a wise thing to do. You are taking a huge liability risk, especially of that size opening. Anything 6' and under, I wouldn't be so worried, The terror factor gets exponential after that. 8'..so so. 10'...yikes. 12'+...you better get the engineer in there to take that liability off your hands.


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RE: sizing beam for header

When a lumber yard sizes an LVL beam the design is actually done by the LVL manufacturer and the document they supply to you will be stamped by an engineer registered in your state so I can think of no reason a building department would reject it. However, the manufacturer must rely on you to provide an accurate description of the loading condition.


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