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Old 09-04-2014, 11:43 AM  
tk3000
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Default New Sub-floor on top an old one

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.



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Old 09-04-2014, 05:38 PM  
nealtw
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Do you have open access to crawl space or basement?



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Old 09-05-2014, 08:38 AM  
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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.

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Old 09-05-2014, 11:10 AM  
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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.

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Old 09-05-2014, 05:32 PM  
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Quote:
Originally Posted by Jungle View Post
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.
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Old 09-05-2014, 09:19 PM  
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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?

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Old 09-05-2014, 09:39 PM  
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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.

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Old 09-06-2014, 06:42 AM  
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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 !

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Old 09-06-2014, 06:51 AM  
bud16415
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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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Old 09-07-2014, 09:35 PM  
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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.



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