2X4 FOR CEILING JOIST

Hi I want to know if i could use 2X4'S for my ceiling span if i double them up @ 16 o/c ? The span is 13'. My framer didn't realise i was putting up 2 layers of drywall :-first layer 5/8'',second layer 1/2'' with green glue between. I did some calculations and it seem 5/8'' is about 70lb so if i did two layers it works out to 7 sheets per layer=490lb so two layers =980lb total. That would make it about 4lbs/sqft since the room size is 13'X17' I AM GUESING THATS WY I AM HERE. I know the best thing to have done was to go 2X6 but now i dont have the space above to put those in. NB; yESTERDAY I DID AN EXPERIMENT ,i double up on one of the joist and i put my body weight on that joisti was just hanging ther and the joist only deflected 1'' or so. And i weigh 180lb aprox. So if the sheetrock's weight is gonna be distributed across all joist DO YOU JUYS THINK I WOULD GET AWAY WITH DOUBLEING UP ON THE 2X4's?

first layer 5/8'',second layer 1/2'' with green glue between.

I can't answer your question about doubling-up your joists, but I can tell you that using 1/2" drywall is not a good idea: Much better to go with two layers of 5/8". - Stuart -

Thanks stuart I was only gonna go 1/2 '' on one layer cause of the weight issue. I already have the 5/8'' but i thought about the weigkt. Plus Stuart i have 2 layers of 5/8'' beef up between upper ceiling joist with green glue and when the saw or air commpressor comes on i hardly hear them up stairs.and thats without insulation and drywall on inner ceiling. I dont know i can do the two 5/8'' i was just worrying about lightening it up a bit. Thank you for responding,you have been tremendously helpfull since i started.

Check this out: http://www.awc.org/calculators/span/cal ... pan#answer

And to add insult to injury, the span of any horizontal framing member is produced from the measurement that you get from outside of framed wall to the outside of the opposite side framed wall. Even if you move the deflection down to 240, which would be more accurate, and move the joist spacing to 12 inches on center which increases the dead load, you can see that you really need to find a way to get 2X6 framing over your head.

Thanks for the response Xspace, I figured out a way to use 2X6 in the ceiling. I am just adding it to the 2X4's that where there and it gives me like 1/4'' of space below some cross member in the truss joist to deflect. Also the inspector showed me where and where i could knotch out a peice of those cross boards used to hold the truss in place vertically. I used #2 2X6 lumber which gives 16' span and my room is only 13.5' each so i should be good.

Pictures?

I will take some new pics tomm and post :wink: I have Electrical and Mechanical inspection tommorow