Subfloor


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Old 11-06-02, 09:29 AM
J
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Subfloor

I seem to be asking the same questions, but I'm getting conflicting advise. My first choice for flooring is nail down unfinished solid wood but I am willing to consider other alternatives.My subfloor is 1/2" particle board over 1/2" plywood.

The moderator in another forum recommended that I remove the particle board and glue and screw plywood (at least 1/2") to the existing plywood (1/2").

My neighbor nailed his solid wood flooring directly to the particle board. Three different local contractors have told me that the particle board should come up, but that I could nail the solid wood directly to the 1/2" plywood. They saw no need to put down more plywood.

Also, I would like to run the wood lengthwise down a small hallway, but that would run it parallel to the joists. One contractor thought that would be O.K. if the existing plywood was at least 3/4" but not 1/2". As a matter of fact, he recommended running the wood that way in the hallway until he found out that the plywood was 1/2". He recommended running the wood perpendicular to the joists in the other rooms.

My nephew, who is in the housing business, used particle board in the addition that he just added to his house, but he used some type of waterproof or water resistant particle board that he said was now acceptable.

I'm also concerned with the height of the 3/4" wood at the door openings. Is this a major issue or do I just raise the threshold and trim the bottom of the door.Thanks.jdi

Help! Please advise. I need to get at the least the first room down in time to put the Christmas tree up. I want to get started within a few days. Also, is there an inexpensive way that I can measure for moisture in the wood. Thanks.

Confused in Alabama.

jdi
 
  #2  
Old 11-06-02, 12:45 PM
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Installing wood floors

Particleboard is not an acceptable subfloor material. CDX Plywood or OSB (Oriented Stran Board) is recommended. The subfloor should be dry, no more than 13% moisture content. A CDX grade of 5/8" over floor joists 16" on center is the minimum single layer subfloor. CDX plywood 3/4" thick or 23/32" thick OSB can be used singly up to subfloor supports 19.2" on center. Only CDX plywood 7/8" thick can be used singly over supports (truss joists)up to 24" on center. Existing subfloors not thick enough for recommended spacing or supports should be overlaid 90 degrees with 1/2" CDX plywood. The 8' direction of a single layer subfloor should run at right angles to the floor joist, leaving a 1/8" space between the panels and end joints staggered 4' apart.

Thinner materials cannot be recommended as a preferred subfloor material.

It is recommended that you lay the floor parallel to the longest direction of the room and at right angles to the floor joists. NOFMA: The Wood Flooring Manufacturers Association does not recommend installing hardwood flooring parallel to the joist direction because of possible problems with unlevel floors, floor movement and cracks that develop near joists.

Undercut any doorjambs, casing, drywall or moldings where needed before you begin the installation. 1/16" above floor thickness is recommended so that the floor can fit underneath and still allow for the 3/4" expansion space.

A moisture meter can be used to check moisture in subfloor and wood flooring product.

Go to www.installingwoodfloors.com for more installation information.
 
  #3  
Old 11-06-02, 05:01 PM
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Here's the bible -

http://www.nofma.com/installation1.htm

Notice that it says that "subfloor plywood less than 5/8" cannot be recommended".

Why risk it?
 
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Old 11-06-02, 08:34 PM
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subfloor

Thanks. I really appreciate it. Great forum.

jdi
 
  #5  
Old 11-21-02, 02:45 PM
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additional subfloor question

Did I understand you correctly when you say that "existing sub floors not thick enough for recommended spacing or supports should be overlaid 90 degrees with 1/2" CDX plywood." I read this to mean that I should lay the new 1/2" plywood at right angles (90 degrees) to the existing 1/2" plywood sub floor--not at 90 degrees to the joists.

Just want to make sure that I understand correctly before I start tearing up my floors.

My biggest question, however, is how to take up the particle board where it runs under the kitchen counter that separates the den from the kitchen. This counter also has a slight overhang making cutting close to the cabinet difficult. I had not planned to remove the cabinet or to put hardwood in the kitchen. How do I do this--use a chisel?

Also, what kind of screws and glue do I need to fasten these two layers of plywood together. And how many screws do I need per board, etc.

Guess I'm making this way too hard but obviously I'm not much of a handy man, and I'm somewhat nervous about taking on this project. My wife thinks I can do it though so here goes.

Thanks for your help and the great forum as always.

jdi
 

Last edited by jingram105; 11-21-02 at 03:28 PM.
  #6  
Old 11-21-02, 05:42 PM
RealWoodFloors
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Install the plywood in the same direction as the existing plywood. 8' part across the rafters and 4' part in line with the rafters. 1/2"CDX Plywood only has about 1/2 the strength when turned in the other direction. Do not line up the joints of the 8' side. overlap 2' so the new plywood joint centers on the existing sheet.
2.25" sheetrock screws into the rafters is a good length and lots of const. adhesive. See if a rental place has the small circular saw for cutting under toe kicks and close to cabinets. Crain Tool model #785 aprox. $250 new. 3/4" quarter round will cover up to about 5/8" gap. Pulling up particle board is a miserable job, but you'll get through it.
Good Luck, AL
 
  #7  
Old 11-21-02, 09:09 PM
SteveOfloors
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I would tear out the PB, and lay over the 1/2 plywood, with the new hardwood floor running perpendicular to the joists. I run 3/4" hardwood over sleepers on concrete with no problems, so I can't see having any difficulty. Can you get under the house to block the joists under the hallway? I like the idea of running the wood down the hall, (easier to sand) , and it looks right too! The particle board will break off, if you first cut as close as you can with a saw. It's a pain, but anybody who has laid a few floors has suffered through it too. Use a Vaughs prybar, and keep chipping away at it.
 
  #8  
Old 11-21-02, 09:58 PM
RealWoodFloors
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National Oak Floor Manufacturers Association guide lines for installing wood floors states 5/8" minimum thickness for a 3/4" plank floor. Sleepers are to be a minimum of 12"on center. Most rafters are on 16"to 24" centers. I have seen 2 1/4" oak floors nailed directly to rafters on 16" centers and you can't believe the squeking that came from these floors. A burgler never had a chance. Remember you and your wife are the ones that are going to have to live with the floor after it is done.

AL
 
  #9  
Old 11-22-02, 03:27 PM
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Thanks everyone. I really appreciate the response. Wish me luck.

Happy Thanksgiving and Merry Christmas to everyone.

jdi
 
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Old 11-22-02, 05:14 PM
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I apprenticed with a wood installer for some time when I was very young, and he insisted on installing the second layer of plywood at a 45 to the existing plywood.

His theory was that he didn't want the gaps in the ends or lengths to fall on a seam in the plywood beneath. Nor did he want the finished floor edges to fall on the plywood seams. Took forever to install the subfloor, with all the 45 cutting.

Those floors remain gap free today.
 
  #11  
Old 11-22-02, 09:27 PM
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Thanks. I appreciate the advice.

jdi
 
 

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