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Header design information needed
5

Header design information needed

Header design information needed

(OP)
As an architectural technician for an Architect firm I am not as familiar with design criteria as the Architects are.  Sometimes it is necessary to formulate specific notes on drawings in relation to the building structural system when an Architect is not available nor a structural engineer.  This specific instance requires me to formulate a specific note regarding the sizing of headers in interior walls.  Surely there must be a rule of thumb for sizing interior door & window header members per a given span.  For example our Architectural Graphic Standards indicates for rough openings less than 3'-0" to use 2x4's on edge w/ plywood spacers and for rough openings greater than 3'-0" to use 2x6's on edge w/ plywood spacers.  That is all it says regarding header design.  How about rule of thumb for rough openings greater than 4', 5', 6' 8' etc. and also whether or not the header is in a bearing wall or not?  Or if the building has only one story with pre-maufactured trusses for the roof system?

RE: Header design information needed

The 2000 and 2003 IRC have tables for generic sizing of window headers and interior floor support beams.  That is a good place to start.  State that the headers must be sized in accordance with the tables (state their numbers) or be engineered.  I don't have the IRC here in front of me but you can look them up.

RE: Header design information needed

I would caution you from using rules of thumb for header sizes. This can quickly get you in a lot trouble.

I suggest that each header be calculated for the load it supports. If you are unable to do this then have a structural engineer or an architect do it for you.

RE: Header design information needed

I agree with jike to be safe, but those tables are usually good places to start and will prbably work unless you have unusual condition such as excessive load.  In the Florida Building Code for instance, which is based off the old Standard Building Code, Tables 2308.3A, 2308.3B, and 2308.3C give the maximum spans for a certain size header under given typical conditions that are listed in the foot notes.  Note that these specific numbers will changes as time goes by and the referenced code from which these tables are derived will also change.  In the IBC2000 these tables are 2308.9.5 and 2308.9.6.

RE: Header design information needed

http://jan.ucc.nau.edu/~dsl/egr437/class/woodbeams/design.html

This link will provide with the techniques to analyze and design solid-sawn or glued laminated beams. The analysis and design techniques are there but you must also understand load paths, loading, connecting and foundations.  For interior non-load bearing cases typically we use 2 x 2x4 w 1/2 spacer for 3' C.O., 2 x 2x6 up to 6' CO , 2 x 2x8 up to 8' and 2 x 2x12 up to 12'.  For the exterior loads check the truss sheets with typical loading use the code prescriptive method, for highly load cases and spans outside the code see the Engineer...

RE: Header design information needed

I guess I must be building to a different standard. I always use 2x8's for doors and windows and 2x 12's for 8'garage doors. Once you go to the double i pull out my beam design formulae. The cost of acouple 2x' doesn't make much difference when the total lumber cost is over $4,000

RE: Header design information needed

Dick, For exterior windows and doors we use 2-2x12 per FBC.  Typically I would spend more money analyzing,  ordering, checking sill height in designing all the load bearing headers than the savings for reducing to 2-2x8s.  I find a truss load review reviels the high loaded members that require addition review.

RE: Header design information needed

Wood Structural Design Data, 1986 Edition, provides information related to design of typical wood structural members. These data are augmented by reference to the National Design Specification for Wood Construction, particularly on the subject of design stresses. Tabular data in this volume are presented as a convenient aid in design of most frequently encountered elements of wood structural framing.
see http://www.awc.org/Standards/wsdd.html
Chap 2D

RE: Header design information needed

Non-load bearing openings - no problem. But load bearing openings, I agree with jike. Design them individually, often times you will miss a point load or a non-stacking wall above. Don't risk a rule of thumb approach.

RE: Header design information needed

Othere than a few people here in the Phoenix market nobody uses or wants "truss" headers. The exception to that is headers for garage doors and thats only if the wall is 2x4.

 Im just wondering is the market your in big on truss headers?

JP
Truss Designer

RE: Header design information needed

JP, I have only seen them used on appartment complex's and prefabricated walls.

RE: Header design information needed

macroman

Below is what I have used in the past. Go to the row for the span bigger than actual header span that you need. Keep going to the right to an allowable span that is larger than actual "tributary area”. Finally, move up to the header number and read the size of header listed further down. Hope it would the job for you. Avoid rules of thumbs in general. What you see bellow is not a rule of thumb. Every beam listed below is specifically designed and has passed the usual design checks.  Given all that is said above you should do your own due diligence and ensure that these beams are appropriate for the your intended use.

Good lock
Amir Zamanian




MonoSpaced Text
Header    1       2       3       4       5   

SPAN    1    2    3    4    5
4.0    -----    -----    -----    -----    25.00
5.5    -----    -----    -----    22.00    16.33
6.0    -----    -----    -----    20.00    14.20
7.0    -----    -----    21.00    15.50    10.40
8.0    -----    -----    15.00    12.00    7.80
9.0    -----    34.00    12.50    9.40    6.25
10.    43.00    29.00    10.00    7.50    5.00
11.    38.00    24.00    8.50    6.25    4.00
12.    30.00    20.00    7.00    5.00    
13.    25.00    16.50    5.75        
14.    20.00    14.00            
15.    17.00    11.75            
16.    14.25    10.00            
17.    12.00    8.50            
18.    10.00                
19.    8.75                
                    
            
            
MonoSpaced Text
            
Header    size
1    GLB 3 1/8 x 18
2    GLB 3 1/8 x 13 1/2
3    4X12 DF#2
4    4X10 DF#2
5    4X8 DF#2

Designed for DL=21psf, LL=20psf, and no slope (0 degrees)                        

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