Why did builders stop using planks for subfloors?

tlbean2004June 21, 2014

And what are the benefits of plywood?

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SaltiDawg

Installation cost and cost of material much less.

Many years ago (1973) I bought a new home ion Silverdale, Washington, while stationed at the Navy Yard.

The first floor had joists every four feet - I believe they were 4"X8" - with the sub floor being "car-decking" - like used on ships for shipping automobiles. I believe the car decking was VERY ROUGH tongue-in-groove 2"X6". Big knot holes, etc.

Now that was a substantial squeak proof house.

The second floor was conventional plywood subflooring over 2"X ?

    Bookmark   June 21, 2014 at 4:41PM
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Sophie Wheeler

Ply is more dimensionally stable and a wiser use of resources.

    Bookmark   June 21, 2014 at 4:59PM
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bus_driver

Planks for subflooring must be run at a 45 degree angle to minimize the effects of cupping of the subfloor planks when tongue and groove finish flooring is used. At the angle, the finish flooring rests on the high spots of the subfloor. Cutting and nailing the subfloor is very labor intensive as well as the waste that results from the angle end cuts.

    Bookmark   June 21, 2014 at 5:03PM
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Trebruchet

Laying planked subfloor at a 45 degree angle would decrease joist spacing from 16" on center to 12" on center because an angled plank has a longer span than a perpendicular one.

    Bookmark   June 21, 2014 at 8:51PM
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SaltiDawg

I described my subfloor in a post above... the subfloor was certainly not laid at a 45 degree to the joists.

Indeed, I've not seen one laid that way on any of the TV reality shows dealing with old houses.

    Bookmark   June 21, 2014 at 9:44PM
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HandyMac

Why did builders stop using planks for subfloors?

Money.

Why is plywood beneficial?

Money again.

Same reason sheet rock has replaced lath and plaster for walls.

When planks were in wide use, that was because they were the best material available---no plywood yet.

When plywood was perfected, the planking quickly became more expensive---mostly due to labor costs.

That makes plywood less expensive than planking to install. The 4' by 8' area covered by one sheet of ply would take 6-8 planks. A sheet of plywood can be nailed down in 45 seconds---the same area in planks more like a minute and a half---after more labor to put planks in place.

Plywood is made using materials that would not be viable by themselves. Plywood is dimensionally more staple than solid wood---when manufactured properly. Reason is because the plies used run in different directions in each layer---reducing movement.

Plywood is also less expensive to handle/ship in similar amounts as planking.

    Bookmark   June 21, 2014 at 10:30PM
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snoonyb

Diagonal subflooring was a method used to develop diaphragm shear.
T & G plywood, schedule "C" layout, glued and nailed, also develops this diaphragm shear.

A 4X girder system at 4'oc. used 2-4-1 T & G plywood sheating.

    Bookmark   June 21, 2014 at 10:38PM
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snoonyb

"saltidawg (My Page) on Sat, Jun 21, 14 at 21:44

Indeed, I've not seen one laid that way on any of the TV reality shows dealing with old houses."

In your original response you alluded to 2X6 T & G.
T & G, in and of it's self, because of the design, resists horizontal, IE. diaphragm, deflection.

I suspect the reason it has not been highlighted on the TV programs is that its seldom worth the time to repair in place.

After all, its cheap and dirty TV.

    Bookmark   June 21, 2014 at 10:50PM
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Sophie Wheeler

TV isn't real life. Most especially ''home improvement'' TV shows. They do the whole industry a huge disservice.

    Bookmark   June 22, 2014 at 9:19AM
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Trebruchet

"TV isn't real life. Most especially ''home improvement'' TV shows. They do the whole industry a huge disservice."

C'mon, hollysprings, you mean you can't demolish, install, and get inspection approvals in three days and for $5,000.00?

    Bookmark   June 22, 2014 at 9:38AM
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sombreuil_mongrel

Hi,
Talking of economy; on at least 2 old houses I have worked on, the 1x6 t&g subfloor bore traces of concrete; they used the material as the forms when pouring the foundation walls, then reused it for the subfloor on the ground level. Since at that time (10's-30's) real plaster was being done, it would be no less than 3 months before finish floors went down, and that gave the subfloor plenty of time to dry back out.
It came to me when I was in the basement looking up at concrete-stained boards, and looking over to the 6" horizontal lines (and wood grain shadowing) on the poured concrete walls!
Casey

    Bookmark   June 22, 2014 at 9:40AM
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SaltiDawg

"TV isn't real life. Most especially ''home improvement'' TV shows. They do the whole industry a huge disservice."

Oh for crying out loud. I simply stated that I had not SEEN any diagonal sub floors on any of these shows (nor in any home I've owned.)

I did not give any opinion as to these show's merit or other value and I don't think any of us benefit from pontification about them.

    Bookmark   June 22, 2014 at 10:10AM
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snoonyb

" RE: Stupid (?) question = Quick (?) answer.

Posted by lynn_r_ct"

Schedule "C" layout is a 50% lap, sheet to sheet, row to row.

Since you are "replacing," which I interpret as the walls are remaining, no matter which you select, you are going to be doing a lot of blocking and installing nailers.

Since plywoods grain, on both sides is the long way, plywood is installed with the long dimension perpendicular to the joists, there will be some waste, however accounting for the value of your time.............

Do not reverse a cut-off in an effort to save a little money, because you'll end up with a spongy section. In fact you can try this out by walking on a sheet of plywood laid out in both directions.

You should be using T & G, CDX floor sheating, and if you are not using T & G you need to install blocking for the edges.

    Bookmark   June 22, 2014 at 11:04AM
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airqual_guy

Sombreuil_mongrel: My 1940 house also reused concrete form boards this way. In the crawlspace doing some work, wondered what the heck is that gray dust on the underside of the subfloor? Concrete dust!

    Bookmark   June 22, 2014 at 5:42PM
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bus_driver

It is surprising at the pseudo experts who have posted to this thread.
Quote from the link below: "As far as wood subfloors go, this is what NOFMA (National Oak Flooring Manufactures Association) and NWFA (National Wood Flooring Association) have to say. All solid wood floors should be nailed down (nail, staple/cleat) to an approved wood subfloor. Approved wood subfloors are listed in order; best to least preferable. This is based purely on the materials nail holding capability.
⢠Best: 1" x 6" solid #2 or better Douglas fir or frame grade pine boards installed diagonally across floor joists 16" on center(OC)."

Their stated reason is the nail holding ability of the plank subflooring-- but that was not the primary reason we did it that way long ago.

While diagonal sheathing properly installed does increase the racking resistance of a structure, the racking forces on a floor system are not substantial.

People constantly implore government to make housing more affordable and government responds with more codes, regulations, zoning that increases the cost. Being one of those formerly in poverty who lived in an area that did not (at that time, but now does) have onerous regulations, we bought some property, logged on that property enough to make the lumber required to build a house and moved in with no debt-- mortgage free. The subfloor was boards of various widths and species that were not suitable for finish lumber-- to be painted or stained. Suppose that one had subfloor boards that are 8" wide and place finished flooring 2 1/4" wide on the subfloor board. The finish floor will follow the cup of the subfloor.The result is a roller coaster. And diagonal subflooring has less effect on creating shrinkage cracks in the finish flooring.

We used those boards for the subfloor because they were what we had! The wall and roof sheathing are the type boards.

I stand firmly with my original post above

Garden Web considers the link I tried to post to be spam. Google hardwood installer.

This post was edited by bus_driver on Mon, Jun 23, 14 at 17:23

    Bookmark   June 23, 2014 at 3:24PM
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