maximum span for solid wood plank or joist and car decking

[Bill E]

Hi folks,

I have a dozen 16' long Douglas Fir logs ranging to two feet diameter in my driveway and a LT-15.

I'm looking to build a removable floor over a currently unused indoor swimming pool that is 11.5 feet across.

I found a span calculator for traditional floor joists ( http://www.cwc.ca/Resources/E-Tools/SpanCalc.htm ) that tells me I could get there with 2x8 joists at 16" centers.

But I'd like to get a much lower profile floor with one of two options:

a.  Just sawing the logs into thick planks.  I'm thinking that something in the four to six inch thick range would work as both the structure and final floor surface.  But I can't find a calculator that would tell me what thickness would be sufficient.  Any ideas?  (The advantage of this approach is I can remove and resaw to wood at a future date if the pool is reactivated.)

b.  A local sawyer suggested 2" think tongue and grove car decking as an alternative -- with the idea that it may need no or minimal joist structure for support.  I did find an article about a house that was built with T&G car decking roof across spans "up to 8 feet."   So I'm guessing that 2x4 joists at some spacing would work.  But again can't find a calculator to refine this.

Any suggestions appreciated.

Bill

[Tom]

Drain the pool enough that you can put the joists below the edge of the pool and make your deck level with the rest of the house.... kinda.  You could use 16" joist then, if you wanted.    You would probably have to connive some kind of ledger board.

[Don P]

With good #2, I would use a 3-1/2" minimum thick "deck" if you go that way. It could be 2x4's on edge nail laminated, or wider planks.

I was using this calculator, it's not "official"
https://forestryforum.com/members/donp/beamclcNDS2.htm
Checking a 2x4 on edge I used these inputs
72 lbs uniformly bearing along the edge of each 2x
138" span
1.5" wide
3.5"deep
750Fb
1.3E
170 Fv

You can vary loads and dimensions. You do get a bump in bending design value (Fb) of 10% at 4" wide becoming 15% at 6" wide, 20% at 10" wide. It'll get stronger in bending but will still deflect the same, which was the limiting factor.

Speaking of defunct, I liked sunken living rooms.

[solidwoods]

Does the pool have water in it?
Can it be filled with rock?
What type of activity and load is going on top?

You can also use concrete block as piers, I'd put treated wood bottom plate, 2ea 4x8x16 solids, then 8x8x16 blocks.  If the pool is dead, rebar/crete fill the piers.

water in the pool- still make the piers sans crete.  I'd chimney vent the air space, or blow air in through skimmer or you could have mold and or mushrooms

You can also make floor panels, hollow core construction, ply/glue/nail each face.
That would be easy remove, lasts long time, sells with the plantation

jim

[Bill E]

Thanks for the feedback Tom, Don and Jim.

That beam calculator is really helpful.  I arbitrarily put in a 900 lb load, and a four inch deep beam passes down to 12 inches wide.  With deflection as the limiting factor, if I make a mistake at least I'll just bounce instead of breaking through. 

The pool is empty.  Five feet deep.  Sand bottom with a vinyl liner.  I could use a wooden plate and pier set up and save some wood.

The room will be used as a recreation room, perhaps including a pool table now gathering dust in the garage, so there will be some weight on the floor.

Bill

[Furby]

I wouldn't use the wood plate/pier system on a vinyl liner, unless you plan to replace the liner if you use the pool again.
The plate will sink through the liner and even if you don't tear the liner, the slight depression will be a bear to keep clean when used as a pool.

[solidwoods]

Hey wait a min. I was pic'ing a crete pool.
You have nothing stoping a side cave in (if I understand right)
jim

[Bill E]

Hi Jim - this kind of in ground pool is made with metal plates forming the sides.

Bill