Replies

1. 
   dovetail97128 | Apr 13, 2009 07:19am | #1

   How "stiff" do you want the floor to be?

   T&G plywood?

   They can't get your Goat if you don't tell them where it is hidden.
2. 
   FastEddie | Apr 13, 2009 04:13pm | #2

   Are you going to have heavy point loads, like a band saw on wheels?

   "Put your creed in your deed."   Emerson

   "When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it."  T. Roosevelt

3. 
   CaptainMayhem | Apr 13, 2009 05:23pm | #3

   will you be driving on said floor? do you plan on laying foam in between your sleepers? If you do lay foam and don't try to drive on it 24 o.c. will work as long as you use rigid foam..otherwise, roll with 12 o.c. with blocking at ends of plywood.

   All I ever wanted in life was an unfair advantage...

4. 
   KenHill3 | Apr 13, 2009 05:42pm | #4

   You didn't say whether your 2x8's are 'standing up' or 'laying down' (sleepers).

5. 
   Ted W. | Apr 13, 2009 07:46pm | #5

   For a shop floor, I'd go with 12" spans. Also, I wouldn't trust exposed T&G joints where a heavy point load may land. Do 12" centers and 2 layers of plywood with the joints staggered, and you'll be able to drive a forklift on it.

   ~ Ted W ~

   Cheap Tools! - MyToolbox.net
   Meet me at House & Builder!

1. 
   BilljustBill | Apr 14, 2009 12:21am | #6

   ....and you'll be able to drive a forklift on it

   I made the mistake of letting a forklift drive over my yard last October....  The roofing company delivered 13 squares too many, so they boy layed down 5 sheets of 1/2" cdx decking that was left over, too.  Even with the plywood butted end to end, and the dirt dry for more than a month, there are still ruts today!!!

   Thin wheels of a loaded forklift, covered with only harden rubber, can take its tole... ;>( 

   Bill ;>)

    

6. 
   user-253201 | Apr 14, 2009 12:41am | #7

   Hi Paul

   I think your question is asking about the 'on center spacing' of your floor joist, based on the thickness of your sub floor (3/4" plywood), in that case others have asked the right questions about point loads and general use.

   As far as 'span' gos, that is the length of the joist from support to support. It sounds like this will be a shop area on top of an existing concrete floor, so if the joist touch the concrete and the concrete is perfectly flat you  have zero span ( or a very short span from hump to hump on a not so flat concrete floor.

   Is this the case or are you thinking of something else?

   Regards Rich

1. 
   GotAll10 | Apr 14, 2009 03:17pm | #8

   Thanks for the correction. The 2x8's will be on end (not "sleepers") on a flat slab. I wasn't planning on foam insulation. Planning on 3/4" plywood on top of them for now, hopefully a hardwood floor on top of the plywood in the future. The heaviest load will be the tablesaw, but it will be stationary and I can put extra support under it. There will be a rolling bandsaw and jointer, probably less than 500 pounds each. I doubt I can get away with 24" OC, but wonder if 16" is OK vs. 12".Thanks

1. 
   Grott | Apr 14, 2009 03:57pm | #9

   Is there a design reason for the 2x8's, duct work, entrance height? If not I'd use 2x4 or 2x6 shimmed to level over the concrete (no effective span). Then add blocking under the TS and any other potential point loads as well as under the sheet joints in traffic areas(in front of the doors, ts, work bench...)Keep us posted,Garett

1. 
   GotAll10 | Apr 15, 2009 02:52am | #11

   The 2x8's are so I can run 6" duct collection duct work under the floor. I have plenty of headroom.

2. 
   FastEddie | Apr 14, 2009 06:12pm | #10

   I am also curious why you need the height of a 2x8.  And why a hardwood surface?"Put your creed in your deed."   Emerson

   "When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it."  T. Roosevelt

1. 
   GotAll10 | Apr 15, 2009 02:53am | #12

   The hardwood surface will be mostly for looks, as well as to strengthen the floor.