How Thick for single layer plank flooring??

[Max sawdust]

I know I could look it up and do the math, but it is much more fun to ask here and learn from others experience ;D

OK,
Considering random width QS Red Oak plank flooring for first and second floor TF structure.  (24x36 structure, 12' bent spacing summer beams, 6' joists on 2' centers.)

So single layer flooring visible from below and above.  WHAT THICKNESS ??? WHAT TYPE OF JOINT ??? GOOD IDEA OR BAD ??? :

Any and all experience would be appreciated.  (My gut is telling me it is not a good idea, and I am not sure why...)

Max

[Don P]

Well then I ain't looking it up either  :D
We've typically used 1-1/2" thick pine or spruce on beam type floors. It's always been 2x6 T&G. They are noisy.

On this one we covered the flooring with 1/2" blueboard foam and 5/8" osb screwed on 8" centers then carpet, its the quietest we've done. Even without carpet the foam and osb had killed much of the noise.

I did do one with 6' maple 2x6's that had been t&g'ed. The short lengths didn't cross enough joists and that was a squeeky floor. They were  made from leftover bedrails from one of the local furniture plants.

[Thehardway]

Max,

I have been tempted to do likewise in the loft area I am building.  I will have 2X10 joists @16 OC.  I have considered putting down 2"X12"X 16' (SYP)  I would drill holes, top screw them down with deck screws and then plug the holes with oak pegs.  I haven't taken the plunge yet for the reasons Don mentioned and a couple others:

1. Dust and dirt filtering through to below
2. hard to pull them tight and eliminate gaps
3. Time consuming to plane, pull tight, screw and peg, then finish.

I have considered getting a T&G head or also doing a shiplap.

Has anyone ever tried glueing?  What was the black, putty like stuff the old timers packed in the cracks of the floors?  I have seen it in some old heart pine floors in churches.

I made flooring for a rec. room with some old pine barn siding I had once, it is 3/4"X 4"W.  I put 15# felt paper under it.  It make some terrible noises when you walk on it (same noise you get when you unroll tarpaper)  :-[ and it was very time consuming. It looks very nice but wouldn't try it again.

[TW]

Edit
Please forget what I wrote here. It was based on an error in converion to metric.

I would cut a groove in the edges of all boards and fit a loose spline to function as tongue. That would make better use of the width of the boards, than ordinary tongue and groove.

I am no expert.

[Thehardway]

TW, That's a great idea, maybe a kerf cut with an edge guide and a narrow strip of sheet metal as a spline would keep the dust from filtering through and should also prevent the squeaking.  T&G does waste a lot of good wood

[TW]

The idea is not mine originally. The oldtimers built the floors in "rian" , the grain drying and threshing buildings like that. Board width was valuable when you had pulled the pitsaw all day. That particular kind of tongue subtitute spline is called "fjeedro" in our dialect.

I would use a wooden spline. Maybe of some harder wood or plywood. Please notice that I have not tested this loose spline method yet, but I have seen it used in many places with no problem.

Another purpose of the spline is to spread a point load to the adjacent boards. Therefore it should have a tight fit.

[Max sawdust]

Well then I ain't looking it up either  :D

OK DonP, where do I go to look it up, I thought it was obvious until I tried : :

Thehardway and TW, that is exactly the kind of knowledge I was looking for.  So far it seems like it would be a suitable method for a second floor workshop in a garage, but not necessarily for second floor bedrooms in a house..

Great info

Max

[Don P]

IRC section R503 Floor Sheathing

Table R503.1 is the right one "minimum thickness of lumber floor sheathing"
16" oc, perpendicular or diagonal to joist,  5/8" minimum thickness
24" oc, perp 11/16", dia 3/4" minimum.

48,54,60" centers all require 1-1/2" min. It specifically states T&G and perp to joist only, so check with your inspector (if necessary) on grading or alternates to T&G, this is structural wood.
at 48" lumber sheathing shall have a min Fb of 675 and min E of 1.1 Mpsi
at 54" lumber sheathing shall have a min Fb of 765 and min E of 1.4 Mpsi
at 60" lumber sheathing shall have a min Fb of 855 and min E of 1.7 Mpsi

For longer spans you can go to the AITC manual for built up wood decks, it starts getting thick.

R503.1.1 End joints
End joints in lumber used as subflooring shall occur over supports unless end matched lumber is used, in which case each piece shall bear on at least 2 joists. Subflooring may be omitted when joist spacing does not exceed 16" and a 1" nominal T&G wood strip flooring is applied perpendicular to joists.

I'm about certain this is where end matching of flooring comes from.

All of those are minimums, guaranteed to disappoint  ;)

[Dave Shepard]

I know of several people that have splined floors in TF construction. One used a hardwood spline, the other used some sort of fiberboard spline. I agree, cutting the T&G is wasteful of the  wood. A friend of mine layed one inch pine boards in one direction, then 5/8 firecode sheetrock, and then 2", splined wide pine planking for the floor. Very solid, no squeeking when you walk over that one.


Dave

[Don P]

It takes 5 more rows to cover 24' at 5-1/2" than at 6". That loss vs the time spent inserting splines is something to consider. An old log cabin I worked on had what must have been 5/4 tulip poplar t&g on 24+" centers and was actually good flooringwise. They were random width up to about 10-11". I removed and replaced them, planed the wood smooth and flat again and used it for wainscot and ceiling in a couple of rooms.
The gaps were packed with dirt and the last century's droppings. As the floor shrank and swelled seasonally it allowed more junk to get in the crack, then packed by the next summer's swell. I tried to clean the grooves with a pressure washer point blank and couldn't. It took a flat bladed screwdriver and alot of elbow grease. You were either seeing that or maybe a lost swabbie caulking with oakum and rosin in the church floors ???
Poplar can develop a velvet nap after years of scrubbing with lye soaps. My neighbors wife has accomplished the same thing with bleach in a much shorter time  :D.

[scgargoyle]

The 200 y/o house i grew up in had two layers of  full 1", staggered to cover up the sizable seams. They wedged old rope down into the cracks; probably because it was built by a sea captain. I always though it was kinda neat. I would guess the span between floor joists was about 4' but that was many years ago. The floors were solid, but creaky. But then again, it WAS 200 years old!