New Sub-floor on top an old one

By the way, the house has one small room that seems to have been previously used as a laundry room whose door is missing a threshold and thus it accumulates dust inside (the floor of the aforementioned room seems to be wood boards). I was wondering if it would be acceptable to fill the empty space/groove with patch concrete.

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have you considered getting a wooden threshold and installing it under the door?

I would like to install something else besides wood, maybe marble. I would imagine marble would require a special blade (diamond one) to cut it. Would you know any material besides wood that I could use to fill the void there?
thanks!

I cut out the a perimeter around the visible rotten spot on the subfloor. At first, it seemed that the rotten area was rather small, possibly an ongoing leakage unchecked for a long time. But there may be some residue of rotten wood right below the cabinet alongside the spot, but it would very small; same thing with the wall frame (again it would be very small). By very small I would say some fragments. Below is a pic depicting the fact:



The joists are in great shape. I then opened a cavity in the wall in another room beside the kitchen which then gives me a view of the floor under the kitchen cabinet, and it seems to be in bad shape (possibly moisture trapped there for many years):




The top layer of the plywood have unglued itself, and there is a lot of dirty there; but it does not seem to be anything like rotten and such

you're going to have to get that out of there- it looks moldy.

I agree this needs to be dug into, let's talk about why you don't want to move the cupboard, pros and cons.

slownsteady said:

you're going to have to get that out of there- it looks moldy.

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Couldn't I just eliminate the mold with concentrated bleach spread throughout the area?

nealtw said:

I agree this needs to be dug into, let's talk about why you don't want to move the cupboard, pros and cons.

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The kitchen cabinet are not in good shape, but they seemed to be nice ones; and certainly can be brought back to its former glory. Still I could definitely remove them trying to be careful and then rebuild or replace any damage that happens. But then there is the main water valve spot which in hindersight I should have dealt with since day one, the following is the spot of the main water valve for the house (under the kitchen cabinet) with the old main water valve and respective yoke removed (by the way that was the epicenter of my leaking problem):



Then I ripped out the bottom of the kitchen cabinet and installed new plywood for the cabinet itself and a new main water valve coupled with new plumbing. But I probably made a mistake of not replacing the subfloor immediately below it (it was not rotten but in really bad shape). End result:

But that's no problem because you know all about the plumbing . I figured if that was the source of the water problem, there will be mold and rot under the cupboard.
You really need to get under the house and pock at the floor and joists with a screwdriver or something. Best is to prove it's not so bad or bit the bullet before you do the floor. Bleach is not the product for pouruse material. But your not in the kill zone yet.

tk3000 said:

Couldn't I just eliminate the mold with concentrated bleach spread throughout the area?

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Bleach loses it's effectiveness at the surface of the material. Mold spores can be deep in the grain of the wood, so are hard to eliminate. I have heard of (and tried) baking soda & peroxide formed into a paste and applied to the wood. I can't say I have 100% faith in this, but I haven't heard of anything better. Probably easier to just replace the moldy panel.

http://removemoldguide.com/do-it-yourself/remove-mold-from-wood/
First you have to get to the wood remove what is no longer doing any work and replace. You should only be treating wood left when you think you have all the bad stuff out.

nealtw said:

But that's no problem because you know all about the plumbing . I figured if that was the source of the water problem, there will be mold and rot under the cupboard.
You really need to get under the house and pock at the floor and joists with a screwdriver or something. Best is to prove it's not so bad or bit the bullet before you do the floor. Bleach is not the product for pouruse material. But your not in the kill zone yet.

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Sorry about the delay in my follow up. Thanks, I know something about plumbing, but I am willing to learn more, look into different approach, and increment this know-how coupled with practical experience; but overall I am always learning. It certainly can be done, but then I will be deprived of water during the time being and also I will depend on the utility company to turn the water on and off at the curb (I tried different curb tools and none of them work in my case: my water valve is deep down and it is off the center of the hole so the tool would need a certain defection from the center to reach the valve itself and turn it).

The rotten spot I showed before (photo 1 of post #23) does not seem to be related to the water leakage; it probably is related to use during the years from whoever lived there before. Such spot was far from the center of the lekeage and the subfloor surrounding it is not great, but it nowhere close to be rotten.

I took a look at the subfloor behind the kitchen sink (the spot of the main water valve for the house) sometime ago on occasion of putting the new plywood and water valve and I do remember that it was mostly back (mold, so to be expected), but not rotten; it certainly was in bad shape and should be replaced, but again, it did not seem to be rotten. So, I also do not expect the joist to be badly affected (crossed fingers there!). Also, I took a peek at the this joist sometime ago, and from visual inspection only it did not seem to be in bady shape (but I would need to conduct a closer inspection to be sure).

nealtw and slowstead: thanks for the hints and info about mold countermeasures.

Wood is organic, so mold particularly likes wood and moisture. I will try bake soda and peroxide at some point. I usually try to salvage not too wood badly contaminated with mold, but not drywall given that it is very porous if not painted (back side); besides sometimes it is too much work and too little gain for some wood that likely does not preserve all its integrity anyway and is prone to future contamination. And new in this case is always better, especially new stronger treated wood.

So, now I am planning to remove the cabinets and remove whatever is not in good shape there. But it will take sometime given that I have many things going at the same time.

Where is this cupboard in relationship the photo under the house?
Is the cupboard with the meter right next to the floor in question?
I do remmember the problems with the shut off.

nealtw said:

Where is this cupboard in relationship the photo under the house?
Is the cupboard with the meter right next to the floor in question?
I do remmember the problems with the shut off.

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Yep, I posted extensively here on occasion of the shut off valve issue!

The spot that was actually rotten was far from the cupboard wherein the main water valve and plumbing is located. The following is pic taken from the crawlspace showing the joists and plumbing right below the cupboard with the main water meter:



So, now I am planing on removing the most of the kitchen cabinetry to check and replace most of it to be on the safe side. I probably would have to remove the countertops given that they are kind of nasty and ugly (green) anyway. But I hope there is nothing wrong with the joists under the subfloor. The kitchen is the only point in the house with a working sink+faucet, thus I need to finish up some of the plumbing going to the laundry room and bathrooms. On top of that I got some days without rain, so I am taking advantage of it to replace some bad roof sheathing and patch the epdm membrane (check my forthcoming post in the roofing section!)