Damaged, Delaminated Subfloor

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Old 01-23-14, 11:51 PM
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Damaged, Delaminated Subfloor

We are putting oak hardwood floors (3/4" x 1 1/2" T&G) in our kitchen, dining, and living room. The living room and dining room were both carpeted, while the kitchen and entry way in the living room had glued down parquet flooring. I tried to carefully tear up the parquet so I didn't damage the subfloor, to no avail. The top veneer of the plywood subfloor peeled off cleanly in some spots.

Our house was built in the 50's and the subfloor is 2 layers of 1/2" underlayment nailed together with rosin paper in between. I was going to replace the top sheet of plywood in the kitchen where the damage occurred, but today's 1/2" P&T (or 15/32) is almost 1/16" thinner than the existing true 1/2" underlayment.

The top veneer of the damaged sheets actually scraped off relatively easily, leaving a smooth surface with no leftover adhesive. So I was thinking about delaminating the affected sheets and adding a 1/8" luan underlayment to give me a level subfloor. Any thoughts and tips would be appreciated.
 
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Old 01-24-14, 02:30 AM
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Welcome to the forums! I wouldn't sweat the delamination too much unless it was caused from water damage. More of a concern is the structure beneath. Do you know the size and spacing of your joists? What is the longest unsuported span under these rooms.
 
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Old 01-24-14, 06:56 PM
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2x8 joists 16" on center. The beam supporting the joists is directly below the load bearing wall dividing the kitchen and living room. The joists span 10'6" in the kitchen and 12'6" in the living room.

It looks like there could have been some minor water damage at one time where the fridge sits (possibly from the ice maker). From the crawl space below the kitchen I see no water marks on the bottom of the subfloor.

Here are some links to pictures. I couldn't get them uploaded through the forum.

Here I was halfway through tearing up the flooring. You can see places where the subfloor stayed intact and places where it delaminated. The fridge sits on the rights where the subfloor is black.

This is the subfloor after I finished scraping off the top veneer.

Delaminated subfloor where the fridge sits. I'm not sure why the top layer of subfloor was black (it didn't look like mold, as it was in perfect squares the size of the parquet tiles).

Closeup of the delaminated subfloor where the fridge sits.

Transition between kitchen and living room, where the subfloor remains intact.

This is the only spot where I accidentally peeled up some of the second layer of subfloor. I was going to put some wood filler in there and smooth it out with a putty knife.
 
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Old 01-24-14, 07:45 PM
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2x8 joists 16" on center. The beam that supports the joists is below the load bearing wall that divides the kitchen and the living room. The joists span 10'6" in the kitchen and 12'6" in the living room.
 
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Old 01-25-14, 05:13 AM
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You are within specs span wise (barely), so lets go to the delamination. Don't add any luan, as it is not a good substrate. Since you will be using 15# felt under your hardwood, an extra layer in the affected area may give the spacing you need. I just feel the plywood will be too much.
 
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Old 01-25-14, 10:13 AM
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The top veneer of the damaged sheets actually scraped off relatively easily
You should have fought like the dickens to get that layer off. If it was that easy to remove then I question the ability to hold a cleat when you put down your hardwood. I assume that the whole house is the same and all the plywood was put down at the same time.

I would remove the top layer of 1/2" completely and go back with 3/4" advantech throughout the whole area to receive hardwood.
 
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Old 01-25-14, 05:37 PM
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It was a battle in spots, but I meant it was easier than I thought it would be. It took using a small pry bar and hammer to chisel under the top layer, but it was relatively easier than I thought. I ended up with a very smooth surface that I'd be ok with laying flooring directly onto, if it weren't for the fact that the rest of the floor was 1/8" higher.
 
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Old 01-25-14, 05:57 PM
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Flooring cleats are a little like ring shanked nails in that they have striations that grip the subfloor and provide the strength to keep the flooring solid. If the layers are "loosey goosey" then the whole sandwich that make the floor mix is in jeopardy. Your nails will not hold fast and over time you will have issues. If I was to go out in my shop now and try to delaminate a piece of plywood, I would expect to have learned a few new curse words by the time I finished. You definately have an anomaly in your subfloor that I would label as suspect in moving forward. Regardless of the height differential.
 
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Old 01-25-14, 06:03 PM
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I understand luan's ineptness when it comes to acting as a bridge over surface imperfections, as it is very brittle. As long as I have the subfloor completely smooth and flat, is luan good enough? I used Durham's Rock Hard Water Putty to fill in the surface imperfections I linked pictures to above. I just don't think felt paper will make up the gap, as it is a full 1/8" difference.

Here's a link to a picture of the subfloor. They must have cut the furnace vent in the wrong place when they built the house. I found this pieced in underneath where we tore out a built-in bookshelf and it's right next to the vent. I took the pieces apart and they're both 1/2" underlayment with rosin paper in between and attached with ring shank underlayment nails. You can see the veneer is pretty thick. I couldn't find another type of 1/8" underlayment besides luan. Masonite is about the only other think I could find 1/8"
 
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Old 01-26-14, 12:13 PM
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Luan is not an acceptable underlayment for flooring of any kind. What I would do is, remove the flooring in the kitchen and replace with new 1/2". I would then get a large trowel and feather out the 1/8" difference at the door threshold. Run your flooring in the direction so that the planks run parallel to the door threshold. That way, the gradual rise in the flooring will be dealt with over the width of the planks that can hands the rise without leaving a gap. Plan your flooring so that the peak of the rise is at a joint between two planks and not in the middle of a plank. Therefore, no rocking. You may have to bevel cut the transition pieces and use a reversing spline to close the gap that will be created by the height change.
 
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