how accurate to be with dead loads

huangyhg

how accurate to be with dead loads?
verbage in ibc code says we must consider everything when calculating dead loads.  how accurate must we get? is it ok to say:
beams: 5psf
purlins: 2psf
deck: 1psf
sprinkler: 5psf
other collateral: 5psf
total: 18psf
is this too simplified?
no. that looks pretty close to the way i do it. if this is a roof, don't forget insulation and roofing (particularly if it is a ballasted roof). otherwise, i probably would round up to 20 psf and be on my way.
beams and purlins about 3 each and deck 2 and sprinklers 3.  roofing as it shakes out and mecs (mechanical, electrical, ceiling and sprinklers(already included)) varies from 5 to 15
all adjusted as reqd... the beam and sprinkler load you use may be on the upper end.
dik
when i do house design i do 15 psf dl for all floor, deck and roof (just to safe me time). then if we put gypcrete or veneer, i just add it to the dl. or sometimes for the roof they want to use tile roof, then i just add the load on the top of 15psf i already have.  so my minimum dl is 15.
thank you everyone...this helps much.
if you have wind uplift, then you should remove the sprinkler and collateral loads from the resisting dead loads.
also i was taught that the sprinklers are fixed to every 2nd purlin therefore you would have twice the load on each purlin as a maximum downward load. this would obviously even out for the beams.
csd72... unless you have a real massive sprinkler system, you'd be hard pressed to have a load of 3 psf...
dik
   do an accurate summing of a typical project or two. then your estimated psf rules will have a basis in fact to compare to.
i carry the sig. figs to the tenths for each item.  then i add 5 to 10% of the total (minimum around 5 psf) as miscellaneous dead load to round it to some nice even number.
good advice y'all...from georgia
be careful with the dead loads in asce 7. i have found some of them (e.g. cmu walls) to not be conservative.