LVL Floor Span

[Lakeside54]

I am building a 24'x24' Garage with gable roof and above storage. Question will two pairs of 16" LVLs carry the floor load the full 24' Thanks

[ChugiakTinkerer]

Welcome to the forum!

Just to make sure I'm understanding correctly, are you asking about having LVLs support the storage floor?  If that's the case, you can figure that out pretty easily by figuring the total design load for the storage floor.  Design load is a combination of live load and dead load.  The live load is a figure based on the expected use for that area.  Most living space has a live load value of 40 pounds per square foot, abbreviated psf.  The dead load is the weight of the floor itself,  It's best if you can calculate this by adding up the weight of all floor components, but for general purposes a dead load of 10 psf is usually used.  The dimensions for the weight calculation will be the building width less the wall thickness, so assuming you are using 2x6 framing the floor is 23' x 23'.  That totals an area of 529 sf, with a total load of 26,450 lbs.

I would divide this load by the number of LVL pairs that you are considering, which is two.  Each LVL pair will be carrying 13,225 lbs over a span of 23', which works out to 575 pounds per linear foot, abbreviated plf.  Note that one fifth of that is dead load, or 115 plf.  The next step is to look at the span charts for an LVL.  You should see what your local lumber yard carries and find the specific table for that LVL, as engineering properties vary.  Georgia Pacific has a table for headers and girders at https://p.widencdn.net/wmfjdr.  If you scroll down in that document to the labeled Page 41, you see what the load per linear foot capabilities are for various spans and configurations.  Using the 24' span and two 16" LVLs in combination, the max live load is 244 plf with a total load of 352 plf.

In my estimates above, I have made assumptions that err significantly on the side of caution.  Using these assumptions the answer is no, two pairs of 16" LVLs will not support your floor.  That does not mean you cannot build what you are proposing, but depending on your jurisdiction you may need to have an engineer produce an approved design.  At the very least, more details of your proposed garage would be needed to determine how much of the floor load is supported by the walls.  Also, I used a live load value of 40 psf, which is standard for living areas.  A value of 30 psf is used for sleeping areas, and may be appropriate in this case depending on how the storage space is used.  One other way to determine the precise load capabilities of your proposed LVL configuration is to have values for a 23' span.  The table I linked to doesn't indicate if interpolation is allowed, and I suspect not.  A lumber yard that sells LVLs should be able to provide the specs of your 23' span and can probably also provide the equivalent of an engineer's stamp that will satisfy the permit inspector.

[Don_P]

Another way to build it would be using attic trusses. They would span the 24' width without girders, incorporating attic floor framing and roof framing. It's a boom truck job to set them but all that framing is done in one day. If you use cantilevered trusses they rise from the extended joists that overhang the walls to form the overhang framing and widen the stance of the roof, thus giving more useable headroom.

Chugiak, you'll remember me calling this an old transitional method the other day with regards to stick framing. It is also high tech, nothing new under the sun 

[ChugiakTinkerer]

... nothing new under the sun 

It sometimes amazes me how many ways we find to skin a cat.  Keeping the creativity within the realm of safe building practices is the trick, it seems.