Floor board calculator

[Ljohnsaw]

I looked in the toolbox and don't see anything that will help me.  I am going to use 2x6 to 2x8 lumber for my floor boards.  I'm just doing one layer for my cabin - no finish floor on top.  The engineer is requiring me to lay it on the 45° angle for structural support.  My joists are 24" on center and I figured, initially, that at that spacing, 2x stock would be plenty stiff.  I have a LOT of flooring to make and was planning on doing T&G for two reasons.  One, to hide the shrinkage/keep from having open gaps and two, to make the floor stiffer.

Since I now have to go on the 45, the effective board length between supports is 34".  I'd like to know what the deflection will be in 2x6s vs. 2x8s (full dimension) and if my Quaking Aspen is still going to work.  Also, I'm considering doing a ship-lap joint rather than T&G.  *Might* be easier to do.  I won't be doing a V-grove on the face - I will butt the boards up and finish sand them when installed.  Is there a way to use the beam calculator to come up with an answer?

Thanks

[beenthere]

If me, I'd make up some test sample floors where I could vary the joist spacing, have them large enough to walk on carrying some weight, and lay at 45° as well as perp to the joists.
Don't nail them down, although nailing will add stiffness in the final product.
Should give you some good information to feed the engineer. As well, ask him to support his decision with some resources. Along with span tables...

45° helps keep the joists from wanting to roll a bit, IIRC. But you are correct that it adds to the span of the decking.

I'd think 16" o/c joists would be best with the 45°

[Magicman]

My question is "does the engineer" have the final say"?  If you "have" to lay the flooring at 45° then my recommendation is 19 diamond floor joist spacing.  Either way, I would stay with T&G.

[justallan1]

I would definitely stay with T&G. Interlocking your decking will add much more strength.

[Ljohnsaw]

My question is "does the engineer" have the final say"?  If you "have" to lay the flooring at 45° then my recommendation is 19 diamond floor joist spacing.  Either way, I would stay with T&G.

MM,
I'm not familiar - could you explain please?

The engineer placed it on the 45 because I'm not using any plywood and he said it was needed to provide the stiffness.  I can't see how it provides stiffness to a concrete foundation that my sills are sitting on!  Anyhow, that is what is on the plans the county approved so I have to go with it.  He approved it with the 24"  joist spacing but I am leaning toward adding a few boards and go with 16" with an effective 25" span.

I guess T&G is the way to go.  I was just being lazy...  I don't have A/C power, just a generator at my site.  Not sure if I want to run my shaper from the generator to process 160 18' floorboards.  I was planning on processing at home and stack/dry in my garage.

[edwin dirnbeck]

Your in the lumber business ,and your going to build with 24 inch center to center joists? Are you making a dwelling or a trampoline?

[beenthere]

edwin
Welcome to the Forestry Forum... you bounced right in..   ;D

[Ljohnsaw]

Your in the lumber business ,and your going to build with 24 inch center to center joists? Are you making a dwelling or a trampoline?

:D :D :D

My "professionally built" house has 4x10 joists 48" on center with 1-1/8" ply floors.  Talk about bouncy!  I just figured going 1/2 the span and twice the thickness ought to be pretty stiff.

[fishfighter]

The camp I'm building, floor joist are 16" OC. I installed 1" TG OSB glued down. Then on top of that, I'm adding 1 By's  that are ship lapped at a 45 degree angle to the floor joist as a second sub flooring. The real flooring will be 100+ year old pine TG.



    

[47sawdust]

ljohnsaw,
The 19 diamond MM referred to is marked on your tape measure,or at least the ones I use.It is metric I believe and is a layout based on 19.2 " increments there being 5 in 8 feet.It is a compromise between the more common 16 and 24 inch centers.
Good luck with your project.
Mick

[warren46]

Someone may correct me but whether your boards are at 90 degrees or 45 degrees, the joists are still at 24" on center.  Most "bounce" in floors comes from deflection of the joists and not from 2" thick floor boards. Particularly if you tongue and groove the floor boards I do not see much difference between the floor with boards at 45 or 90.

[thechknhwk]

You could block your joists, so they function as a unit.

[DMcCoy]

Someone may correct me but whether your boards are at 90 degrees or 45 degrees, the joists are still at 24" on center.  Most "bounce" in floors comes from deflection of the joists and not from 2" thick floor boards. Particularly if you tongue and groove the floor boards I do not see much difference between the floor with boards at 45 or 90.

x2. 
My floor is 4x10 on 36" centers (15' span) with 2x8 T&G at 90 deg. not bouncy, but, I built using D.F.  How Aspen compares should be available somewhere.  I would not go with the ship lap design but full T&G so boards are locked together.  Shiplap would of course allow separation under load.  Deflection will be in your floor joists. Roofs can go L/360.  Floors are (or should be) stiffer but I'm not finding that on the internet.  If you plan tile anywhere you will want it super stiff there.  There are tile sites that are super helpful.

[jaygtree]

i have 4x10 ruff spanning 16 feet on 32 inch centers with 2x6 pine t&g flooring perpendicular to the 4x10s. no bounce that i notice. definitely go with t&g.   jg

[Magicman]

Welcome to the Forestry Forum, edwin dirnbeck.   

MM,  I'm not familiar - could you explain please?

47sawdust is correct.  Look at your tape and you will see the first diamond at ~19" and repeating along the tape.  That is the layout marks for a compromise between 16" & 24" o/c.

In reality, I would consider a 16" layout.  It will be surprising how few additional joist will be needed.

[Remle]

Someone may correct me but whether your boards are at 90 degrees or 45 degrees, the joists are still at 24" on center.  Most "bounce" in floors comes from deflection of the joists and not from 2" thick floor boards. Particularly if you tongue and groove the floor boards I do not see much difference between the floor with boards at 45 or 90.

Yes you are correct, most bounce is from joist deflection. When the boards are 90 to the joist all joist received the load at the same distance from the wall or ends of the joist. Take a 12' wide room for example, at 6' center  90 to the joist the load is applied at 6' on all joist. At 45 to the joist 24" center the load is now 2' offset from joint to joist. The moment arm length from the wall which was a constant 6' from the wall now works it's way from 2',4',6',8'and 10' across the room, you are simply distributing the load at different points along the joist. Where tongue and groove helps transfer the load from one board to the next the 45 transfers the load 2' closer to each end of the joist rather than down the center of the floor, this help's to eliminate the bounce.. hopefully this explains the advantage of the 45 degree placement..

[Ljohnsaw]

Wow, thank you all for the information.

Remle - that is very interesting and coming from an engineering background, it make total sense.  I was thinking the engineer was looking to "stiffen" my concrete walls :D

MM, et al - I noticed the diamonds on my tape measure and they were not exactly on inch marks.  I buy (get for free) HF tape measures since I'm always misplacing them (I generally don't use them for precise measurements ;)).  I figured the marks were off just because it is a HF product.

In my home's case, the bounce is not from the joists (4x10s or 4x12s, 4' OC, supported every 4' to 6') but rather the flooring (1-1/8" T&G ply).  My concern was that my 2x material for my cabin floor might flex under the load.  My joists will be pine, not aspen.  I really hate the bounce in my house so I will go to 16" OC.  The only tile I will have will be my shower.  I've use Wedi Board in the past and really like working with it.  I will use it in my shower.  The board is fiberglass/cement reinforced sealed foam board.  Incredibly stiff, light and easy to work with.  Floor pans come pre-sloped to wherever you want the drain. All joints and screws are sealed with a polyurethane caulk.  That stuff does NOT come off of anything you get it on!  For my shower in my home, I also laid some cement board under the floor section.  I didn't want ANY movement.