Repairing dry rot....

[AmbulanceDriver]

Aight APS geniuses......  Need some help...

SWMBO and I just got our first house.  Been doing lots of work on it, and found mostly pleasant surprises (such as white oak hardwood floors under the bedroom carpets).   Tonight, we found our first unpleasant surprise.

There's a section of dry-rot in the main bathroom that we found when we ripped up the old OSB that was under the vinyl floor tiles.  Pulling up the old floor to put down ceramic tile.  Obviously, we want to repair this.  It's old damage, and the water source has long been removed. 

The subfloor (I've also heard it called cardecking) is 2x6 tongue and goove.  The floor joists run perpendicular to this, I believe at 24" on center.  The area we'll need to replace is 4 boards wide by about 24" long, maybe slightly longer.   

How should we go about repairing this damage?  Best info I've been able to glean (my google-fu is weak tonight) is to cut the damaged sections back to the nearest joists on either side of the damage, cutting the subfloor to the center of the joists.  Then replace the damaged boards with new T&G boards, screwing or nailing the new boards to the joists.

Any other suggestions or better ways to repair this?

[Leatherneck]

Plywood-exterior grade if there's a chance of water getting to it ever again. You may find the rot extends into the top of a joist or two, in which case a :sister" joist should be glued/nailed/screwed against the weakened joist.

Once the plywood patch is in, put down a layer of 30-lb felt paper, then a layer of cement backer board, over which you put down ceramic tile with thinset mortar, and grout a day later. If you want, you can put down heat mat under the tiles.

That will give you a new, durable and attractive bathroom floor. DIY.com has how-to videos of all this. Good luck.

TC

[cassandra and sara's daddy]

http://www.schluter.com/6_1_ditra.aspx
i've been using this to great effect  starting 800 sq ft of it today for a new forum member.  its a lil more expensive than durock but saves on labor and finished results. one important note   you can use the fortified/modified thinset to stick the membrane to the subfoor but MUST use the cheaper non fortified thinset between membrane and tiles or job will fail   in a bathroom it makes underlayment waterproof if you tape the seam.  their shower systems are also the way and the truth.

if you can't find 2x6  tongue and groove you can use multiple layers of plywood to build up to same thickness. i glue between layers and use 3 1/2 inch deck screws to attach it. sometimes its easier to just cut next to existing joist on inside of hole and just sister in new nailer  to it  again i glue and screw

[grampster]

Nothing more needs being said.

[AmbulanceDriver]

Thanks gang

[Leatherneck]

One further thought: are you sure the subfloor is 2x6? That's an unusual choice for subfloor, which in older homes was usually 1x6 at most, in which case a single layer of 3/4-inch ply will replace directly.

TC

[Standing Wolf]

Dynamite. Don't trust anything else. That puny stuff never gets the job done.

[AmbulanceDriver]

Well, ended up going with my original idea.  cut the existing dry rotted subfloor out (and yes, it's T&G 2x6).  Exposing half of a joist on either end of a cut.  Laid in new 2x6, anchored in w/ 3" decking screws. 

Standing Wolf, your idea was next.   

[cassandra and sara's daddy]

nice!  if they used that for subfloor it bodes well for other things. copper waste pipes maybe?

[geronimotwo]

if you haven't closed it up, you might consider washing or spraying with a bleach solution or other anti-fungal solution.  dry rot is a fungi that can grow again if the spores survive.

good luck

[lupinus]

burn it and collect the insurance money, then start from scratch? 

(just kidding of course, don't do it)

[Warhorse]

If it is not too extensive, you might try something called "Git Rot" which is an epoxy with fungicide. It is used to repair wooden boat hulls.

You drill an assortment of holes, mix up the epoxy and pour it into the holes so that it will saturate the wood. It kills the fungus and hardens to strengthen the rotted wood. If done right, then all you have to do is to fill in the holes you drilled. The catch is that it is relatively expensive and the rotted wood needs to be accessible. It's also pretty difficult to use it for an extensive area. In that case, you are better off replacing the wood.

Warhorse

[86thecat]

Have you actually used Git Rot? I built and repaired wooden boats for years and that stuff was considered a joke. It's too thick to actually penetrate into wood. I have used Smiths penetrating epoxy to encapsulate rot and strengthen slightly punky wood on boats though. Properly done the treatment takes days and the solvent fumes are toxic and flammable. But it works. Have also used it to seal the joists when repairing a bathroom floor in an old house with good results.
My best Git Rot story is a masthead repair done by a ""carpenter" that promptly snapped due to the weakening effect of all the little holes that were drilled in the wood. The Git Rot looked like icicles that could be pulled out of the punky wood with pliers. Pulled the mast in the yard (big boat), chopped a few feet off, did a long splice with West System epoxy and a couple of fitted bronze bands and everything was as good as new.

[geronimotwo]

i have used "git-rot". i would recomend it to those with a history of using epoxy or polyester resins. it worked very well for the reinforcement of a small area of plywood decking. the main thing is to make sure the wood is dry, and drill holes (not quite through the repair) about every inch for proper penetration. pre heating the area lends to better penetration but decreases working time.  the big problem is that you would not want to use it where individual parts would need to be taken apart in the future. epoxy tends to fuse things together pretty well.