floor joist spacing

planning on building a 12x20' studio. 2x8" floor joists running across 3 4x4 skids. should i go with the typical 16"oc spacing for the joists or can i get by with 24"oc. subfloor will be 3/4" tongue and groove acx and floor will probably be laminate or something. will i notice any sag between 24" spacing? thanks.

 

You will need to get a building permit and inspections. To do this you must submit a copy of your plans to your local housing inspector. The local building codes will dictate the minimum (Note: that's not the maximum, just the minimum to get by with.) spacing and size of joists.

16" is preferred. Too much bounce with 24" centers.

There is also some variation among wood species, because different species vary differently under load.

You can play with a calculator here: Maximum Span Calculator for Joists & Rafters

 

For a 12' span, using 2x8's you will need a central beam and support. You can alleviate that by using 2x10's for the 12' span. Check with your local building department for their requirements. You won't be satisfied with 24" spacing. 16"oc will give a more firm feel with less bounce.

 

thanks guys. i figured the 16" spacing would be better. there will be a skid running down the middle. that should be all the support i need right?

 

How will the 4x4 skids be supported?

 

i've laid in four inches of limestone and tamped it down. i was thinking of using deckblocks to hold the floor joists, but i think i'll go with 4x4's on top of 4x8x16 concrete blocks. 3 skids, 2 outside and 1 down the middle. sound reasonable?

 

Not as reasonable as using 2x10's and not having to mess with the supports. And no, you can't use dek blocks. You will have to dig holes, pour footings then install your support members on simpson strongtie brackets.

 

you mean put the 2x10's directly on the limestone or on the skids? i need the floor to be at least 12" off the ground in the very unlikely event of flooding...

 

How much clearance do you have to the rim joist, now? If you use 2x10's you won't need the skids, as they will attach to the rim joist using joist hangers.

 

i haven't done anything except lay in the stone at this point. plan was to put the 4x8x16 blocks down then the three 4x4 skids on the blocks then have the 2x8 joists run across the skids with the rim joist nailed to the outside of the joists. that would give me roughly 15" to the top of the joists right? 2x10's directly on skids with no blocks would be around 13" which is acceptable. should i be concerned about the skids sitting directly on the limestone?

 

or are you saying support the rim joists and not the floor joists? i'm getting confused...

i didn't even consider it that way. having the skids running parallel to the joists and holding up the rim joists. 2x10's can cross a 12' span without support attatched with joist hangers? that seems like a long span?

 

I would definitely worry about wood in direct contact with the ground as you describe. See, we haven't seen your set up yet, so we are describing normal construction methods. Yes, support the rim joists all the way around at least at 8' intervals with concrete block sitting on a footing prescribed by your frost line and your planning and zoning department. You would, then hang the 2x10's via joist hangers on the rim joists. A 2x10 of Spruce, pine or fir (SPF) as we use here in the south will span 15'3" without center support.
And, I'll have to admit, I've done alot of building in my time, but your term "skids" loses me. It may be a local thing, and I just don't know what it is.

 

i am in the deep south too (new orleans), so the frostline is not an issue. skids i think is a term mostly used with shed construction. like a set of ski's that the shed or building sits on. except in this case the ski's would be made of pressure treated 4x4's and there would be 3 of them. make any sense?

 

Not for a permanent structure, mainly from the aesthetic standpoint. Are you attaching it to a shotgun? How will you access the crawlspace in the future if you use these skids?

 

i should have been more clear in the beginning. this is going to be a free standing structure. by studio i meant artists studio. basically it's going to be a glorified shed/workshop. electricity but no plumbing. 12x20' with a wall inside dividing it into a 5x12' area for tools and lawnmower etc., and the 15x20' area to serve as my painting studio. i don't foresee having to access the crawlspace so i am not planning for that.

 

Chandler is right speaking from a builders/contractors point of view. If you live in New Orleans, you would definately be subject to flooding!! However what you are proposing is an out building/shed. Don't know about the codes in your area(I am guessing they have changed since the flood), but I would check to be on the safe side. I built just what you are talking about in Tn. for my lawn mover, tools etc. and it works fine. There is a possibility that if not treated, there will/could be a termite infestation. The electrical part is what will probably determine how you can do it.

The "skids" he is referring to are just like a moveable portable building is built on so it can be loaded/unloaded.