What is the maximum span of ceiling joist?

Question

whats the maximum span of a 2X12 ceilinh joist?

Answer 1

Most homes are now built with truss and the bottom cord of the truss replaces the ceiling joist. I realize that some areas without snow loads do still use ceiling joists and rafters but your queston can't be answered without more info. Is there a center wall? What is ceiling joist spacing? Does the joist also act as a floor joist for attic room?

Answer 2

Depends on several factors:
Wood species (Douglas Fir, Hemlock-Fir, Spruce-Pine, etc.)
Grade of wood (Select Structural, #1 & Better, #2, #3)
Center to center spacing of joists
Dead and Live loading conditions
Maximum deflection condition (L/240 or L/360)

Few people use 2x12 for a ceiling joist. That is a very deep piece of lumber.

Used as a roof rafter, a "2x12" can span as little as 10 ft - 8 in (Western Wood, #3, 24 inch C-C, 20 lb dead and 30 lb live load, deflection of L/360),
to as much as 33 ft - 6 in (DF Sel-Str, 12 inch C-C, 20 lb live/10 lb dead, deflection L/240.)

You need to provide more info about your design requirements. Check with a builder for lumber span tables.

Answer 3

You can probably look on the web - but could also go to a book store and just look it up. I think a 2 inch x 10 inch when spaced 12 inches apart can span about 18 feet according to

http://www.berkleymich.org/web/documents/decks-porches_specs.pdf

Answer 4

My contractor told me the rule of thumb for 1st quality lumber spaced 16 inches on center is 24 feet. You take the depth of the 2x( ) double it and that's your answer.

Answer 5

16 INCHES APART BUT NOT JOIST.
JOIST ARE FLOORS.
RAFTERS OR TRUSSES FOR CEILING.
SOME TRUSSES PRECUT TO 19 AND 3/8 " APART.

MOST PEOPLE SET 16 INCHES APART, NOW DAYS.

IF LENGTH YOU CAN GO 36 FOOT WITH 2x12"
GOING TO BRACE ANYWAY.