Replies

1. 
   Guest_ | Jun 27, 1999 08:47pm | #1

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   Using conventional lumber will require you to need a supported girder in the center. Depending on your specific needs for open space and head clearance, you may be able to span the depth with LVLs, a paralam or steel girders with no intermediate support. Check with your local supplyer for span and load information.

   Where I live in VA, we use SYP for structural members. Joist from 2x8s can span 13'2" for #30 live load per sq. ft. at 16"o.c. For rafters
   at 16"o.c. 2x8s can span 12'8" for a #30 live load with a 7 day snow loading with a design value of in bending "F/b" of 1250.

   Check with your local building official to verify spans, design criteria, and spacing for the species of wood you will be using. This will save you time and trouble in the long run.

1. 
   Guest_ | Jun 28, 1999 06:40am | #2

   *You might want to look at using attic trusses to simplify the whole thing. But with only 22' wide and a 10/12 pitch, you won't have much height to work with anyway.One other option I might mention is a "Storage truss". (This is probably a regional term) By that I mean they take a simple, common truss with a "W" web pattern. Add extra loading in the center bottom chord panel, and use that for storage. It's b muchcheaper than an attic truss, but your storage area is limited.

1. 
   Guest_ | Jun 28, 1999 07:13am | #3

   *Mike:In my building jurisdiction, (we use the Cabo code) another factor that determines ceiling joist size requirements is the access to the attic. Is it walkup (via permanent stairs) or is the access via pulldown stairs or a simple scuttle hole? Here in NC, if the access is walkup, and you are using conventional 2x framing lumber, 2x10s are required. 2x8s are ok if there is not walkup access - assuming that the span is within spec. As far as I know, no dimensional lumber (2x) will span 20' for ceiling/floor joists. 2x8s are sufficient for rafters, but again this is in my area.Here is the URL for a span table that applies to my building jurisdiction: http://www.co.wake.nc.us/inspect/buildinginspections/buildinginspections.htmYou really need to get info that is specific to your area. Perhaps your local government's building dept. (or whoever does your building inspections) can supply you with the info you require.

1. 
   Guest_ | Jun 28, 1999 09:57pm | #4

   *I don't have the tables in front of me to tell you the o.c. spacings and size that you would need, but TJI's or other wood I-beams will do it without a center support. Any lumber yard that sells them will have the tables. You will probably need 11 7/8" depth or more depending on the o.c. spacing.

1. 
   Guest_ | Jun 29, 1999 02:55am | #6

   *Mike:Here are a few span tables for engineered lumber:http://www.cmapc.com/tables/TJIFlrjoistsTable.htmhttp://www.bcewp.com/southspecguide5g2.htmHere's another page that explains all about loads & span tables:http://www.umass.edu/bmatwt/span_tables.html

2. 
   mike_k_ | Jun 29, 1999 02:55am | #5

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   I have a garage that I'm framing and I need help sizing the cieling joists and rafters. The building is 22' wide and will have a simple gable roof on it. the attic space above will be used for storage and the roof will be pitched at 10 in 12". I live in the chicago area and probably need to have 30# psf for the attic floor and rafters sized to accomodate snow load (30# psf) i think
   Thanks in advance for any help.