Replies

1. 
   Davo304 | May 26, 2004 09:58am | #1

   I wish I could draw you something, for it is way easier than words. Contact the Canadian Wood Council at 1- 800- 463-5091 and ask them to mail you a copy of their booklet titled: The U.S. Span Book for Major Lumber Species.  I have a copy of the 2001 edition and the cost was only $6.50

   This booklet depicts pictorally the header classifications you mentioned , plus a whole lot more.

   In lieu of the book, I'll do my best...

   1. Roof and ceiling.............Header only supports the ceiling joists directly above it and the roof structure ( such as a single story home....or, header is located on second floor of a 2 story only home)

   2. Roof, ceiling, and one center bearing floor......This means the floor joists bear on a center ( load bearing) support such as a wall or a column  near the floor's center or midway point in order  for it to span across the room. Without this support, the joists could not span the distance.

   In this configuration, your header is usually on an outside , load bearing wall, and is responsible for taking up part of the floor load directly above it, plus the ceiling  and roof structure directly above it. 

   3.Roof, ceiling, and one clear span floor.... In this configuration, the floor joists span from outside bearing wall across to the other outside bearing wall . Aside from the joists resting on the outside bearing wall plates, there are no other means of support; such as no middle support posts or bearing walls placed underneath it.  Hence, the space below the floor joists are "clear" of any support obstructions....this type of floor is also sometimes referred to as a "free span".

   Again, the header is responsible for holding up this floor, plus the ceiling and roof structure directly above this floor. Because this clear span has no other means of support, the header in this outside bearing wall must be stronger than the previous type ( No 2)  that has a center support.

   4. Roof, ceiling, and 2 center bearing floors.....This means the header is holding up part of the load of 2 floors ( a 1st story floor and 2nd story floor), plus their respective ceilings, plus the roof structure.    Both floors are supported at their midway point by a single load bearing column ( located on each floor), or by a load bearing wall ( located on each floor). These columns or bearing walls take the load directly straight down to the foundation bearing point.

   The only difference between this (No4) and No. 2 is that you are adding another floor ( story) into the mix. Hence, the header for No. 4 must be beefier than for No. 2 because it has a heavier load to support.

   5. Roof, ceiling, and 2 clear span floors..... This configuration is the same as depicted for No. 3 except that, again, another floor has been added into the mix. ( Example... 2 story house instead of a single story house) Hence header is responsible for taking part of the load of both floors, plus their respective ceilings, plus the roof structure. This header would have to be beefier than all the other types mentioned because it has to support more load than any of the others ( all things being equal that is)

   "Also...girders and headers don't always support these combinations of things...."

   If a window or door is not located in a load bearing wall, then of course the headers will not be load bearing...a couple of 2X4s is all you really need in this example. But, normally, a header is always supporting part of a load if said header is positioned in a load bearing wall. As for girders.....maybe you and I speak a different language, but  to me, a girder is always a support structure. It always is carrying a load of some kind.

   Hope this helps.

   Davo

1. 
   Davo304 | May 26, 2004 10:10am | #2

   As for floor joist dead loads.....usually, unless the floor has a lightweight concrete finished floor topping, the joist dead load is usally rated at 10 PSF. 20 PSF is for said concrete type floors. Of course you know that the "dead load" refers to the weight of the building materials themselves. For floor joists, this would include the weight of the actual joist, plus the weight of any and all flooring products laid ( or nailed) on top of the floor joists. This would include subflooring, and finished flooring.

1. 
   UncleDunc | May 26, 2004 11:01am | #3

   >> For floor joists, this would include the weight of the actual joist, plus the weight of

   >> any and all flooring products laid ( or nailed) on top of the floor joists. This would

   >> include subflooring, and finished flooring.

   Plus any ceiling on the bottom of the joists, I assume?

2. 
   goldhiller | May 26, 2004 05:43pm | #4

   Smoncla,

   See if this is of any help to you.

   http://www.umass.edu/bmatwt/publications/articles/calculating_loads_on_headers_and_beams.html

   Knowledge is power, but only if applied in a timely fashion.