New Sub-floor on top an old one

[tk3000]

Hello Folks,

In the past, I posted about a small kitchen with sub-floor issues (water damage via a small long leak). At first, I was planing on installing backer board and then install ceramic tiles; but further inspection indicated that a small spot on the sub-floor is rotten. So I would need to reinforced this spot and the subfloor as a whole (to be safer and make it level and square). While it seems easy enough to simply strip the old sub-floor (or simply a perimeter with the rotten part), it is not so given the fact that it would entail removing all the kitchen cabinets together with the main water supply line and main water valve for the whole house (both under the kitchen cabinetry).


Below pic shows rotten spot on sub-floor:

Some wood shims to assist in make the new plywood panels level:

Then the new 1/2" plywood subfloor with proper spacing gaps:

One of the issues with installing the second layer of plywood subfloor in this situation is that -- while I can identify the underneath joists and screw the new plywood panels to the joists -- the joists often do not coincide with the edges of the plywood panel due to the fact that the kitchen cabinets are in place and covering part of the old subfloor.

I am not sure if this approach is ok. So, any insights would be appreciated.

 

[nealtw]

Do you have open access to crawl space or basement?

 

[CallMeVilla]

Simple solution ... sister new joist wood onto the existing to provide a nailing (screwing) edge for your new subfloor patches. You can also run the joist wood perpendicular to the existing joists to provide strength at the seam. Frequently, this can be done from above so you so not have to crawl in the dirt.

 

[Jungle]

Bad advice. Covering up rot just creates more problems, more rot. Rotten wood needs to be taken out never cover up or it will spread into healthy wood. Those cabinets don't look worth saving.

Windex won't help either.

 

[nealtw]

Bad advice. Covering up rot just creates more problems, more rot. Rotten wood needs to be taken out never cover up or it will spread into healthy wood. Those cabinets don't look worth saving.

Windex won't help either.

Not sure telling some one how to affix floor joists after rotton wood has been removed is bad advise.

 

[tk3000]

nealtw: Yeah, I may have access but it is a very difficult and obstructed access through a crawl space with large cast iron sewer pipes and lines. I would have to figure a route through the crawl space avoiding the large cast iron sewer pipes. It would be possible, but complicated... The rotten portion seems to be small (I need to further investigate though). So, I am initially planing on removing the small repair shown on the pics, and try to cut the small rotten portion of the old plywood subfloor (shown above [1ft pic] ) with my mult. vibrating tool and whereon possible (needed clearance present) I will use the circular saw, then I would patch the whole with new 1/2 plywood subfloor and subsequently I would install new 1/2 plywood subfloor on top of all the kitchen subfloor in order to reinforce the subfloor as whole and make it even.

callmevilla: that is a great suggestion, I may do it! But the span of the floor seems to be fairly large, so I do not know how easy it would be. Maybe making small square boxes made out of 2x6 (or 2x4 depending on the size present of the present joist) and fit them into the void would make it stronger.

To make things worse there is a large amount of some large white powder spread throughout the crawl space. At first I thought it was some chemical powder used to neutralize any sewer spillage, but I heard that it may be asbestos. The following pic shows part with crawl space with white powder present (I have small partial basement, lots of crawl space, and the rest of the house seems to seat on a plain concrete slab. All in all, it is a house with over 2100 sq ft):

That is a fairly unobstructed part of the crawl space though. Does it seem like asbestos?

 

[slownsteady]

Don't know how old your house is, but it would have to be about 30-40 years old (?) to have any asbestos anything. A little bit of loose asbestos would not serve any purpose that I can imagine, so i would doubt that it is. However, there is no way of being sure without a test.

I can't see a reason this can't be tackled from above. A recipro saw would be a good investment if you plan on more DIY projects, or just rent one for this.

 

[Jungle]

It's likely mouse rocks or crack rocks. Did a drug dealer live there before?

Should put some typar underneath to protect the house, is probably causing your rot problems. That and the rotten wood. Soon to be 1/2" trampoline. Do you have any subfloor? What's under the rotten plywood?
That wall can go too !

 

[bud16415]

Sounds like you have good advice and a plan.

As to a saw nothing like a sawz all type reciprocating saw except the price. I reluctantly bought the harbor freight version for 19 bucks and a 10 pack of blades for 10 bucks over a year ago thinking it wouldn't hold up. I have worked the tar out of it for a year cutting pipe and wood. I don't recommend many things but it would work great on this project and cost about as much as a rental.


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[tk3000]

slowsteady, bud16416: the house external walls are all concrete and concrete blocks house built around 1955, but I heard that even houses built before the 1990s would still be subject to asbestos issues. Most of my tools are more oriented towards mechanical things (pneumatic, electrical, etc), but I happen to have a reciprocating saw bought at harborfreight few months ago coupled with some nice swiss blades (not the overpriced low quality ones sold at harborfreight); and whilst I can see the reciprocating saw being used in spots whereon the circular could not fit I still feel that the multifunctional oscillating tools (also bought at harborfreight) gives you much more control (thus avoiding cutting or slashing unintending things) in lieu of being much slower. Anyhow, there are situations in which the reciprocating saw would be faster and equally safer as the oscil. tool.

 

[tk3000]

It's likely mouse rocks or crack rocks. Did a drug dealer live there before?

Should put some typar underneath to protect the house, is probably causing your rot problems. That and the rotten wood. Soon to be 1/2" trampoline. Do you have any subfloor? What's under the rotten plywood?
That wall can go too !

Honestly, I do not know what "mouse rocks" or " crack rocks" mean (some type of drug). I believe that a large family with small children used to live there, and it is possible that they were doing drug dealings but unlike.

The exterior of the house is all made out of concrete (no plywood, or otherwise any wood material). The exterior also is complemented with stucco, and has been recently painted. The water damage issue was due to main water valve leak (main water valve happens to be under the kitchen sink); now there is a new main water valve, but the damage has been done.

 

[nealtw]

The wrap around the pipes are questionable, likely fine if never touched but if that is loose asbestos on the ground that is a huge problem and a sample should be taken to a lab, protect your self when under the house or woking over a hole in the floor.
Givin that situation I would do all repairs to the floor from above.
If the rot extends under the cabinet cut out the floor in tha cabinet so you have access. When removing the cab floor cut it out leaving 1 1/2" all around the edges so you can hold up peices of wood under edges and screw them in place and drop in a patch.
You can use the same trick to repair the subfloor. If the rot continues under the walll that should be gone after too.

 

[slownsteady]

I only have very limited experience with a oscillating tool. I know the recipro saw looks daunting but with the right blade (and the right length blade) you can get through almost anything quickly and safely. It won't take long to figure out how to use it effectively and a bit more time to use it skillfully, but I have not seen a tool get through nail embedded wood better than this.

 

[Jungle]

I don't understand why you think it is asbestos, from what? It looks like it was evenly spread for disinfectant or something like that.

I think the best way to cut i out would be a circular saw set at 3/4" or how deep you want.

 

[nealtw]

I don't understand why you think it is asbestos, from what? It looks like it was evenly spread for disinfectant or something like that.

I think the best way to cut i out would be a circular saw set at 3/4" or how deep you want.

You are prepared to say that it is not asbestos, rat poison or some other chemical that could be harmfull to life?

You are going to use a circ. saw to cut out floor that continues under the cupboard or under the wall plate. Read the posts for all the questions before adding to the confussion.:2cents:

 

[tk3000]

I don't understand why you think it is asbestos, from what? It looks like it was evenly spread for disinfectant or something like that.

I think the best way to cut i out would be a circular saw set at 3/4" or how deep you want.

The fact that it was so evenly spread caught me as well (as if it has been deliberated spread). But it can be asbestos or a myriad of other noxious things as nealtw pointed out.

 

[tk3000]

In spite of the unknown contaminant (I will sort it out soon enough) spread throughout the crawlspace I face up a few situation whereby I need to enter the crawlspace: for instance, there is a network of cast iron mixed with galvanized drain/sewer pipes that will require me to go under to then take a closer look. But fraught not, for I will be using one these all body vests equal to the ones used by medical personal dealing with ebola in Africa.

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.

 

[nealtw]

If we can't talk you out of going in there before testing it, may I suggest. Mist the area to dampen down the dust or other stuff down there roll up the poly and dispose of it and replace with new.
The pipe wrap is still questionabe but if in good shape and not disturbed, should be fine.

 

[tk3000]

If we can't talk you out of going in there before testing it, may I suggest. Mist the area to dampen down the dust or other stuff down there roll up the poly and dispose of it and replace with new.
The pipe wrap is still questionabe but if in good shape and not disturbed, should be fine.

Will do it! But soon I will get it tested too. Thanks

 

[inspectorD]

In spite of the unknown contaminant (I will sort it out soon enough) spread throughout the crawlspace I face up a few situation whereby I need to enter the crawlspace: for instance, there is a network of cast iron mixed with galvanized drain/sewer pipes that will require me to go under to then take a closer look. But fraught not, for I will be using one these all body vests equal to the ones used by medical personal dealing with ebola in Africa.

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.

Using the space suit is a must!!... after all there are other viruses down there.
As far as the concrete, not a good idea, but another solution is construction adhesive like pl400 if the gaps are not too big, say under a 1/4 inch. The concrete will just crumble after a while, and the glue is thick enough it should span and not work out too bad. However it too will possibly break off over time.
Installing a floor over it is the best idea.