Sub floor

daltinator

My inner sub floor is a inch and a half. Two 3/4 inch planks. My outside walls only sit on the bottom 3/4 inch plank.
The house was a bug hotel before I bought it. I have been repairing rot and bug eaten wood. I have to repair the floor under the outside wall. Where do I buy true 3/4 inch sub floor? I found some true 3/4 inch underlayment and used it on some patch jobs inside. Just added two on top of each other to get my 1 and a 1/2 inches. I was just reading on not using underlayment for structural flooring. Why? Seems pretty sturdy to me.
I also have tried adding all the various plywood measurements to add up to 1 and a 1/2 and it does not work. Always short an 1/8th or 1/16th. I am not too worried about using underlayment for minor repairs here and there on the inside.I will be adding another subfloor after all repairs are done. But I am weary on putting it solely under the outside wall if it is not meant for that. Also it would be nice to get away from underlayment. It is pretty spendy.
If I used the 23/32 plywood under my outside wall I would be off a 1/16 from my outside wall to my inside walls. All I want is some 3/4 inch plywood or some planks. Damn metric system.
Thanks for all the people who post on here. I have gotten very good answers. Once I finish my house I will be able to post answers with experience besides just questions. Very good website!

jaydevries

why not use 1x material as planks since you are going to go over the whole floor with under layment

__________________
be careful my advice only comes from general knowledge i know about the 4 rules it takes to plumb and they are
1 poop needs to flow down hill. 2 hot on left cold on right
3 i get a pay check on Mondays 4 do not chew finger nails at or after work.

TarheelTerp

"They all do that Sir"
(it's called platform framing and the interior walls are the same)
The second 3/4" layer is the finished floor (most often oak).

How much do you need?
And what are the 'typical' sizes of the pieces you are installing?
(below the wall sill plates?)

joecaption

Trying to follow your logic. What differnance will it make if the subfloor is off by even an 1/8"? If it's under the wall no one will ever see the differance in height and it will have no effect on the finished flooring.
Subfloor rated plywood will have all voids filled or pluged, and exterier glue. Under layment will have more plys, no voids in the plys, exterier glue but will have a better grade of veneer on the top side so none of the flaws will show through if you use a sheet flooring like linolium.

I like to use 3/4" Advantec instead of plywood as a subfloor.
Personaly I would not use 5/4 planks for a subfloor. Plenty strong enough, but far more chance for squecks and a lot more time cutting every piece.

daltinator

@ jay- I don't know how 1bys would work. I need 3/4 inch

@Tarheel- My interior walls sit on the finished floor. When I installed those I had to cut the studs down a 3/4" to match the exterior walls. I need about 130 to 250 sq feet of 3/4 inch flooring. Depending on how far I cut the floor back from the wall. And depending on how much rot I find. So if i cut a foot back from the exterior wall around the perimeter of my 130' house I will need 130 square foot of flooring. From memory,(do not want to go down stairs and measure right now) the bottom subfloor consist of 6 inch by 6 foot pieces of wood. The top floor, which was a finished floor at one point in the homes life, are just regular tongue and groove flooring. Around one or two inches in width and about a foot or two in length.

@ joe- 1/8 of an inch is a lot. If I put 23/32 plywood under the exterior wall it will not match my interior walls. My joist will be level to themselves but lower at the exterior wall side(1/16th). And then once I put another 23/32 down to accommodate for the top flooring that I removed it will be a 1/8th off to the rest of the floor. Why deal with all that. It is much easier just to match the existing floor.
Tarheels oak comment made me think. I went on the lumber liquidators website and found utility grade flooring that is a true 3/4 inch.

TarheelTerp

By what dimension?
Typically... walls a 3.5" or more.

If it's really just 2" strips you're attempting to install...
(can't imagine how you're clearing out the rotten bits -another thread)
any decent mill work shop can plane boards down to your EXACT required sizes.

hth

daltinator

I will be extending past the bottom plate(3.5 inches). I figured a foot total would be good. So I will extend the repair 8 and a half inches out past the wall. My logic is that I want to clear all the termite damage and also to bring the new joint out a bit so I can cover it with my new subfloor. The termites only got to the outside perimeter flooring. The rest of the floor, being 92 years old, is in great condition.

jaydevries

2x's are actually 1/ 1/2 so 1x's are actually 3/4 and 5/4 are actually 1 inch

__________________
be careful my advice only comes from general knowledge i know about the 4 rules it takes to plumb and they are
1 poop needs to flow down hill. 2 hot on left cold on right
3 i get a pay check on Mondays 4 do not chew finger nails at or after work.

daltinator

Found some 1 bys @ lowes. Very expensive. I will keep looking to see if I can find some cheaper boards. Lumber liquidators are 89 cents for utility grade