# Replace Rotted Subfloor



## Kory Beam (Nov 15, 2014)

Hi all!
I have a subfloor question. Hope I have posted in the correct place.

I bought an old tiny fixer cabin in the mountains. It has seen a bit of water damage from years of neglect. Mainly from a bad roof and kitchen plumbing issues. All exterior and interior water issues have been addressed (new roof, plumbing, etc.) and I am ready to tackle the damaged subfloor.

A previous owner, rather than replacing the bad subfloor, nailed 3/8" ply over the original water damaged 5/8" subfloor. Roof and pluming leaks were not properly addressed, so that top layer of 3/8" ply also suffered water damage. Pretty sure the kitchen flooded once or twice, as damage is greatest in this area.

I pulled up the 3/8" top layer in the main living room/kitchen area (22'x11') and the original plywood subfloor is in very bad shape. I want to take it all out and lay down a new subfloor. 

My question concerns the thickness of new subfloor panels.
Joists are 2"x8", 16" OC. They span just under 11'. The majority look to be in very good condition.
5/8" is minimum for code, but I am not sure if 5/8" is the best option?
I am looking into AdvanTech flooring panels.
The cabin is small (about 430 sq. ft. upstairs), so I plan to replace it all with the same thickness (the main living room/kitchen, hall, and the bedroom have all had 3/8" ply nailed over the original 5/8"). Bathroom has already been sorted, and is finished.

Will 19/32" be sufficient over the 2x8 joists, 16" OC, spanning 11'? The other option is to lay the thicker 23/32" instead. I am looking to achieve a level and stiff subfloor. The plan is to use a nice laminate throughout.

The downstairs basement is completely open at the moment(mold remediation left downstairs basement naked), so any joist issues and necessary blocking are easy to address.

Appreciate and advice/info.
Pics of damaged original subfloor (kitchen area):


----------



## Bondo (Dec 8, 2007)

Ayuh,... Go with 3/4" plywood, 'n don't look back,...


----------



## joecaption (Nov 30, 2011)

3/4" Advantech T X G is stronger and far more moisture resistant then plywood and will never delaminate.
The fastest way to cut out that old subfloor is with a Toe Kick saw and an oscillating saw or sawsall with a short wide course blade for the inside corners.
Northern Tool sells a cheap Toe Kick saw or Home Depot rents them. 
Make sure to use construction adhesive on top of the joist.
#8 ring shanked nails will work fine.


----------



## Kory Beam (Nov 15, 2014)

Thank you for the info, gentleman. I was certainly leaning toward using 3/4". 
Joecaption, adhesive and ring shank, rather than adhesive and screw?
Really interested in the AdvanTech T X G, just have to track it down in the valley/city.


----------



## oh'mike (Sep 18, 2009)

Screws will be fine--just take longer than a nail gun----and cost a bit more.


----------



## joecaption (Nov 30, 2011)

Unless you can afford to buy a stand up screw gun it's going to get old real quick having to drive all those screws on your hands and knees.
At least buy an Impact driver and several battery's. 
A cordless drill is about useless for this one.
Going to be screwing or nailing every 6", so that's a lot of fasteners.


----------



## Kory Beam (Nov 15, 2014)

Great points, guys. 

I cannot for the life of me find AdvanTech. Huber website only lists Stock Building Supply as carrying their products around these parts (Los Angeles to Bakersfield). I called a few locations and they had never heard of AdvanTech. Said they stock Sturd-I-Floor for $36 a sheet. Pretty sure Lowes carries that for slightly less.


----------



## Piedmont (Nov 1, 2007)

I had to rip up a rotted subfloor, my house was built before plywood so it was all planks. Fortunately the joists below looked fine. I replaced it with pressure treated 3/4" plywood in the bathrooms after letting it dry. Just an idea. 

I will say 3/4" pressure treated plywood goes on my record as being the heaviest wood I've ever lifted the wettest I'm pretty certain were over 250 lbs a piece.


----------



## joecaption (Nov 30, 2011)

Pressure treated is not even legal to use inside a house except for a bottom plate if in direct contact with concrete!
Why would you use a soaking wet, going to shrink like crazy when it dry's out, full of voids in the core, even in the store it's delaminating, needs all ACQ approved fasteners piece of wood for a subfloor?
Studi is not as good but will work.
All my local lumber yards, Home Depots and Lowes carry Advantech


----------



## Piedmont (Nov 1, 2007)

I've not seen OSB outperform pressure treated plywood, that about sums things up. OSB when it gets wet gets real ugly Pressure treated plywood when it gets wet, dries and not much worse for wear in my experience. I did mention I dried it before installing... 

Before one buys Advantech, it's OSB with a waterproof coating that must maintain this waterproof coating or it will fail. I'm not convinced screws, scratches, cuts, etc. and if it survives all that... that the waterproof coating in 5-10 years will still hold. It only comes with a 2 year warranty whereas pressure treated has proven it can and does last even after repeated and extended watering and if not mistaken the warranty is 15 years.


----------



## Kory Beam (Nov 15, 2014)

Well, the sawzall with a flush cut blade made easy work of the cuts at the walls. Popped a hole through the floor and easy going with that nifty blade. Used a piece of aluminum sheet against the finished drywall, so as not to damage the wall. Had 2/3 of the entire room out in little time.


----------



## joecaption (Nov 30, 2011)

Once you get the outside cuts made make some cuts down between the joist, step down where you made the cut and the pieces will come right out.
I broke down years ago and bought a couple Gutster pry bars.
Makes this type job so much easier.
http://www.thegutster.com/
Bought mine at Northern Tool.


----------



## joecaption (Nov 30, 2011)

Advantech is warrantied for 50 years not 2 years.
Pressure treated has no warranty.
I've gone so far as to take a square of 3/4 plywood, and square of Advantech and drilled a hole in them both to tie a rope to them and threw them off a dock and left them for a week to prove a point to a customer.
The Advantech looked the same with no swelling, the plywood was trash, swollen, and delaminated.
Ever once seen a new house with pressure treated subfloors?
No going to because it does not meet code to use pressure treated inside a house.
If you've never used it, worked with it, seen how it performs, taken the time to read all the good reports on it why keep bringing up how you did your floor wrong Piedmont?


----------



## ron45 (Feb 25, 2014)

Plywood comes in different ratings, and for good reason.
Plywood is rated using a boil test. Most contractors don't even pay attention to the ratings, and here lies the problem. Did you know, the first stealth bomber was made of plywood.?


----------



## Kory Beam (Nov 15, 2014)

Nobody can get me AdvanTech.

Only material available…

• Usual 23/32 T X G OSB (LP Topnotch 250/TruFlor) $17 per @ Lowes/HD
• 22/32 Fir Sturdifloor T X G ply $36 per 
• 22/32 Weyerhaeuser Edge Gold T X G panels (OSB) $28 per

Not quite sure the Edge Gold is anywhere near AdvanTech quality?

Since I am replacing in an already closed home, will I just be better off using the fir Sturdifloor 22/32 Ply? I am in the Southern California mountains (6000 ft.) and we get some snow, but the home is now water tight. Whatchya think?


----------



## Bondo (Dec 8, 2007)

Kory Beam said:


> Nobody can get me AdvanTech.
> 
> Only material available…
> 
> ...


Ayuh,... So long as it's kept_* Dry*_, 'bout any wood won't rot, or delaminate,...


----------



## tstex (Nov 14, 2014)

Here's a link to find your AdvanTech T&G Flooring - by far the best product and bang for the buck - it will adhere uniformily and provide a good foundation for your laminate...make sure you use the right ml thickness under the laminate and to consider the 3/4" + the ml + the laminate under all your door jams/trim and doors...keep the saws handy...BTW, what is your zip code? this is how you can locate your flooring w the link below.

Good luck, tstex

http://www.huberwood.com/locations


----------



## Kory Beam (Nov 15, 2014)

Thanks, tstex. I did use the link. I'm just north of Los Angeles in Southern California.
Stock Building Supply is the only listed . I have called two of their locations... and both said that they could not get it. Neither had even heard of the stuff. 
I guess there is not much use for the product in sunny Southern California.


----------



## tstex (Nov 14, 2014)

Type in 91780 and 50 miles- Lancaster in N. Los Angeles should work...can't go far enough for the right materialZ:

*Stock Building Supply*

*43755 North Division St
Lancaster, CA 93535
*
*Map/Directions »*
​


----------



## Kory Beam (Nov 15, 2014)

No dice with Stock Building Supply. Three locations have told me the same story… can't get it over here in California. They all mention Weyerhaeuser Edge Gold as being the one "similar" product that they can get. There is a Weyerhaeuser Distribution Center in town.

Is the Weyerhaeuser Edge Gold an inferior product to AdvanTech?


----------



## ptspurlock (Aug 14, 2009)

3/4" tongue & groove plywood sub floors is all you need. 2X8's floor joist installed on 16" centers should ok @ 11" span.

You should check the joist for deflection before the plywood is installed. Just stand in the center of the joist and bounce up and down. If you have deflection in the joist, you will probably have deflection in the finish flooring. Some sort of reinforcement may be needed. 

I would glue & screw the subfloor making sure the screws are slightly countersunk and you use a coated screw. A ring shank nail or an non-coated drywall screw will deteriorate over time.

Have fun in the cabin!


----------



## PaliBob (Jun 11, 2008)

It looks like Sturdi-Floor may be over kill for you.
http://www.bc.com/wood/plywood/plywood-products/underlayment.html

But I've ripped Sturdi-Floor to make handicap ramps where they are so *strong* I will never go back to plywood.


----------



## Piedmont (Nov 1, 2007)

joecaption said:


> Advantech is warrantied for 50 years not 2 years.


First read the warranty at http://www.huberwood.com/assets/user/media/AdvanTech-WarrantyResidential-2013-051.pdf we are talking in a possibly wet, at a minimum wood eating bacteria infested area (under sinks, bathrooms, possibly kitchens) where

"Huber Engineered Woods (HEW) LLC warrants that its AdvanTech flooring and sheathing panels will not delaminate nor require sanding due to moisture 
absorption *during installation*"

"Advantech is covered for *500 days* against moisture after purchase". 

Warranty exclusions: "This warranty *does not cover moisture absorption... nor mold and mildew*".




joecaption said:


> Pressure treated has no warranty.


 Actually tell me where because pretty much all the pressure treated I see has a lifetime warranty against termites and fungi at a minimum.



joecaption said:


> I've gone so far as to take a square of 3/4 plywood, and square of Advantech and drilled a hole in them both to tie a rope to them and threw them off a dock and left them for a week to prove a point to a customer.


Which is rated and tested for the extremes of outdoor use?




joecaption said:


> Ever once seen a new house with pressure treated subfloors? No going to because it does not meet code to use pressure treated inside a house.


 First, what are you talking about and where did this come from? We're talking about replacing a bathrooms rotted floor when did it change to something preposterous as replace or build an entire house with it? It has no bearing other than places with moisture like kitchens, and bathrooms.

Second where does it state it can't be used inside a house? Read the FAQ here http://www.culpeperwood.com/index.php/resources/detail/treated-faqs where they recommend it as a subfloor in kitchens and bathrooms. Or this maker http://treatedwood.com/faq/ where they too say it's safe indoors but not counter tops. It's particularly common for window sills. 




joecaption said:


> If you've never used it, worked with it, seen how it performs, taken the time to read all the good reports on it why keep bringing up how you did your floor wrong Piedmont?


I'm not saying it's good or bad, only that the product I feel is NOT the best product for this location nor application. Advantech does not advertise it is protected from decay, mold, or mildew nor does it make claims to be the new pressure treated replacement indoors. It's going to be installed in an environment loaded with wood eating bacteria (since the area already is overloaded with rotten wood) and possibly future water issues all the places PT makes more sense. It does sound like a great product, just not the best product for that spot.


----------



## JazMan (Feb 17, 2007)

Piedmont,

You obviously didn't know that pressure treated was not for indoor use unless we're talking about kiln-dried PT. I've looked and looked and I can tell you it's hard to find. 

Jaz


----------



## tstex (Nov 14, 2014)

I believe from the orig post, the floor was rotted due to yrs of leaks from bad/poor plumbing. No matter what you use in those conditions, you are going to get poor results w anything that is wood/cellulose-based. As we all know: cellulose + H20 = Mold and other.

If the subfloor joists are allowed to dry-out [and will continue to do so over time if no other moisture is introduced], then most any material will work, but a better product will last longer and perform better. No DIY'er wants to redo their sub-floor anytime soon after recently completing the job.

Next, take the proactive measures to eliminate moisture penetration areas, make sure all the plumbing/fittings/etc below are set, and make sure you have access to them incase you need to do so.

Note: good idea on the deflection test and glue will make sure it bites better and provides a cushion too - as noted, if you do use glue, use coated screws, but make sure you have the knee pads.

Send some pics when done and good luck,
tstex


----------



## Kory Beam (Nov 15, 2014)

I believe that the original roof ('73) was wood shingle. Years of leaks, I am guessing. Looked like a new shingle roof had been installed 3-4 years before I purchased, but there were still deficiencies from improper flashing and various satellite dish installs and chimney pipe support brackets screwed into the roof top(no flashing/waterproofing). The roof was still leaking from above and water was coming in and dripping through the T&G.

That stuff is long gone and I had a new roof put on two years ago, right after purchase. She's as tight as a drum. Everything is dry. The place is so small, there is only one wall that contains plumbing… the shared wall between the kitchen and bath. I replaced with copper and rebuilt the bathroom with a Schluter shower, and Laticrete floor warming under the floor tile. There are no more issues with the plumbing. 

So… subfloor in the room is completely removed. A bit of adhesive residue to remove from the tops of the joists.
A joist or two will need to be sistered. Somebody did some cutting/notching to two of the joists… they are a bit springy. I'll fix them. The rest of the joists seem pretty darn stiff with my 140 pound self bouncing on top of them.


My next question… for blocking at the walls, so that the new subfloor has an edge to attach to ( at the wall ends between the joists)… 

Should I add blocking against the rim? Nailing blocking to the rim between the joist ends? I added a pic to demonstrate what I mean. The piece of wood was just a scrap that was handy to demonstrate.

Or… should I float the blocking about an inch away from the rim, and nail to the joists?


----------



## tstex (Nov 14, 2014)

Since you have the 90 metal clips in the corners, you can center a 2 x 6 or 2 x 8 like you have...of course the 2 x 8 gives you a little more spare room. I would also make sure you measure each cut bc some of the lower joists will be off some. Or, cut almost the OC lenght and run a piece the full lenght, no problem there and you would never miss - looks like you can get full leverage to screw it in too.

Next, nothing wrong w being on the lighter side [140lbs], but I am 220lbs. You might want your deflection test done by someone a tad heavier, unless you are going to impose a weight limit.  Nothing like walking across a wooden floor and you hear it squeak when someone heavty walks in a weak spot. Now you can use treated wood in this application, but use coated nails if you do.

Roof sounds good, get to cutting & screwing and then, "just add some people, food, drink & fun".

good luck.


----------



## Kory Beam (Nov 15, 2014)

Thanks, tstex!

Forgive me for not fully understanding… you mean I can place and nail the blocking directly against the rim, as seen in the pic?

Again, appreciated!


----------



## tstex (Nov 14, 2014)

If the integrity of the rim boards are good, then yes. Your main support will be on the joists anyway but by butting an additional 2 x 8 will give your flooring more bite.

You could make cuts to go perpendicular between each joists [a lot of cutting], but you would have 100% coverage on the wall. this would also firm-up the current floor plan too.


----------



## Kory Beam (Nov 15, 2014)

Great! So I can do it either of these ways, shown below. It looks like the 2x8 nailed directly to the rim will provide enough support/bite for the panels at the wall edges.
Besides nailing… would adhesive (glue block to rim) be necessary?


----------



## tstex (Nov 14, 2014)

Pic 1 is much better and preferred...just make sure all the tops are even so you do not have any raised areas or pulled down areas...glue for "Scabbing" boards is not necessry, but on the top of joists when attaching flooring, that is a good idea for: better adhereing and sealing, but mainlly cushion of flooring to joist. Will make it quieter too.


----------



## Kory Beam (Nov 15, 2014)

Well, I have been busy, but I have been able to get up to the cabin on the weekends and have gotten a little bit of work done.
All of the good joists (majority) were sistered... glued, nailed, and bolted (ends only, about 2 feet out from rim/on center). 
Only a few joists needed to be pulled and they were replaced with doubled 2x8.
So... every joist is now doubled. Have also scabbed at the rims (between joists) for complete floor panel support. Should be a darn solid floor.

Now I need to bridge. The joists span 11 feet... so I figure single solid bridging at the middle. 
The bridging I removed was staggered down the center. I could do dead center since the joists are now doubled up... 
In addition to nailing the solid bridging, will using adhesive be a good idea? eliminate possibility of squeaks, etc.? Thanks!
Pic of where I am:


----------



## hboogz (Mar 21, 2012)

Great work Kory. I actually plan on doing the exact same type of work this coming weekend. I have a few questions for you:

Which glue did you use when you sistered the 2x8's to the old joists? PL400?

Did you use rink shank or smooth shank from the new 2x8 into the existing joists?

Did you connect a new joist hanger for the now combined with of about 3" (old joist with new sistered 2x8) 

Did you sister only one side of each joist ?

what kind of bolts did you use on the ends?

Thanks again!


----------



## Kory Beam (Nov 15, 2014)

Thanks, hboogz!
Disclaimer: I am NOT a pro... so do not take any of the methods employed by myself as the 'way to do it'.... or acceptable in your neck of the woods

Liquid Nails Heavy Duty
Nails - 10D hot 
4" x 1/2" carriage bolts - one at end of joist (about 2' from rim), 1/2" bolt hole drilled at center (as seen in above pic)
only one side of joists sistered... with same dimension 8x2
Replaced joists were doubled & installed with new Simpson hangers

Anybody have any advice regarding use of adhesive in addition to nails when center bridging? Guess it can't hurt... just thinking about squeaks.

Thanks!


----------



## tstex (Nov 14, 2014)

I use LOCTITE SUPER Wood Adhesive and it has never failed me. When putting down threshold floor pieces, I use this and not one nail and 225lbs can stand on the edge of it and it does not budge. Good for taking the squeaks out...use a good amt and compress hard, wipe off any excess.

As a note, on thresholds, you do not use nails, but for areas like floor joists, use both. Just remember, once you put this down, the floor is not coming off. If you just want sound-proofing and sealing, use your reg caulk. LOCTITE comes in cartridges w nozzle just like reg caulking used w caulk gun.


----------



## Kory Beam (Nov 15, 2014)

Thanks, tstex. Regarding thresholds... are you saying no screwing subfloor down over the threshold? Glue & screw T X G ply to joists, but just glue at the entry door and slider thresholds(over rim)?


----------



## tstex (Nov 14, 2014)

I was referring to the strenght of the LOCTITE in general, but if you have only a bull-nose threshold w a usual step-down, then a nail looks like crxp so you use locktite. the nose part hangs over the edge while the other 2/3 is glued to the end of the last piece of flooring on finished floors.

For regular threshold transition pieces w even floors on both sides w diff products, usually is it nailed w finishing gun, but you can also apply some loctite. 

re your basic T&G for floors, this would not be a loctite application but more of a mastic flr glue you would trowel down, the pop the upper tongues w your nail gun. The loctite is used for anything you do not ever want to have to separate like sistering two boards or securing playwood to floor joists You use loctite and screws on that application, the plywood is nver coming off....tstex


----------



## Kory Beam (Nov 15, 2014)

Ahh... i see, you were talking about finished flooring, right?
I was referring to affixing the 3/4" T X G subfloor over the rim in the door and slider openings
(since I am removing the doors/slider so that the new T X G 3/4" subfloor continues under the doors).

I would want to glue and screw to the subfloor to the rims (under door/slider) same as glue and screw to the joists. I thought you were telling me not to use nails/screws for the subfloor at the threshold.... my bad.

Thanks again for the info!


----------

