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sourdough 08-05-2008 11:28 PM

Replacing existing wall with support beam or I beam
I am in the process of converting a 2 sided garage into an open shop area measuring 24' X 24'. The original structure has a floored open attic which is used for fairly light weight storage and the current mid-support wall is 2"X4" framed. Ideally I would like to support the entire length of the shop (actually 21 feet allowing for the 3 foot wide stairway to the attic) parallel to the ridge board of the roof but I may have to settle for a couple of shorter runs and a post at the ends and midway. Assuming that the total weight of the ceiling/attic would be less than 40#psf live load but more than 20#psf dead load I calculate the total weight to be 12X24X30#psf or 8640 pounds maximum. If my figures are correct what size beam would be required to span this distance? Secondly, if I was to use two manufactured I beams to make the lift easier what size would I need to use. The structure was built in 1980 and is grandfathered so does not require a permit to improve but I do want to stay within safe limits. Thanks for any input.

buletbob 08-06-2008 06:51 AM

I did a job the same as yours and the engineer calculated three 1-3/4" x 11-7/8" LVL's with two 1/2" x 11" steel flitch plates bolted together. with the floor beams Te'code into them.
this is just a guide to let you know what your going to expect.
you must consult with a structural engineer to find out what you will need for you particular project.
and even if you are grandfathered in ,once you start doing any structural changes a permit would be required. here in my part anyway. BOB

Termite 08-06-2008 08:42 AM


Originally Posted by buletbob (Post 146359)
you must consult with a structural engineer to find out what you will need for you particular project.

Absolutely. :thumbsup:

Big Bob 08-06-2008 09:11 AM

A++ advice in above posts. Just because you can crunch the load #s doesn't mean you should. Lots more to it then the right size beam.

Double check how long a beard this "grandfathered in" has.

Most preexisting condition clauses in codes pertain to foot print on your lot.. (local zoning / set back thing) and minor repairs up to $$ % of value of home based on property tax valuation.

Life safety concerns are what the permitting process is all about.

Permits can be a pain, but .... We should all be glad the process is there.

Think about it... the next time you go house hunting or visit a neighbor during a storm.

jogr 08-06-2008 09:42 AM

A good l"real" umber yard will often have an engineer available to spec out beams for no charge if you are buying the beam from them. You must, of course, be able to provide all pertinent information for them to do this correctly.

With the sizes you described a steel beam might well be a better option. Again, your local steel beam supplier will usually have an engineer to spec out the right size beam.

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