What happened to my floor

I wouldn't pour another thin slab over it, especially so if the old slab is cracking apart. At that point you'd want the new cap to not bond to the old slab anyway and you'd have to reinforce it separately with a bond breaker on the old slab. It's not impossible but it's a bit more work if you ever had to fix the plumbing since it's now in concrete and IMO not needed.

The framing , and the plywood really, should have been pressure treated. Anytime the framing touches concrete, you need pressure treated.

If it was me I'd rip out the old framing and either seal the floor with plastic making sure it's absolutely tight or paint the floor with waterproofing , build the floor with pressure treated, seal the framing with plastic and lay plywood above that. If you are insulating it, use foam board as well.

It's not ideal to seal the framing in moisture rich environment though it'll work if everything is pressure treated. 

Well after some more demo I fear the fix will be rather major.  Floor is no where near flat, several low spots and the floor "joists" were placed directly on the concrete, so most of them are rotted badly.  There are also cracks all over, not big ones but a couple where the rot was the worst.  Here is one of the cracks:

And the worst area of rot in front of the door.  A cutting edge and light illustrate the issue.

The worst is the wall where the garage door was.  I suspect a hole or two in the pour under the sill and would not be surprised if the sill is not pressure treated.  we had a big mouse issue years ago, I dug outside the foundation and poured several bags worth of cement into what looked like openings.  I also made up metal plates to go around the hot water lines going thru the floor.  Instead of a half inch gap it was metal with about a 32nd.  The floor under the sill was pretty loaded with mouse sprinkles.

Regardless, time to call some contractors for quotes and plans to fix it.  Currently 1:00 PM and I need a strong drink!

Dig out all of the old crap concrete and form up the old garage door opening bottom and place a new concrete floor to the top of the foundation wall and using Plasticizer additives (SuperPlasticizers.com: CONCRETE ADDITIVES) to use less water and help self level. Don't forget to cut contraction joints every 8 feet 1/5 the depth of the concrete thickness within 24 hours of the pour.

We still don't know if your house has a basement or is slab-on-grade. Now will be your chance to install some 4" pvc piping in the garage for future radon gas remediation.

In reply to VolvoHeretic :

Sorry, it is slab on grade.  I am not touching the repairs, my skills are limited to demo on this.  I do have a great contractor locally, will get the bad news in a week or two.  I may do a radon test in that room.  Last radon test was 30 years ago and it found nothing.

The concrete cracks don't look too bad, they didn't gibraltar apart so there's at least steel in it. I don't see much leeching around the cracks either so I don't think there's a bunch of water coming thru.

I think the sealing the concrete/pressure treated lumber/sealing the framing is still your best option 

OK first contractor proposes to build a new floor with pressure treated lumber and then spray expanding closed cell foam over the whole thing.  Then cut the foam to joist level and lay down a subfloor.   I am a little skeptical about expanding foam being an insulator and vapor barrier but have no real experience with the product.  Any one care to weigh in?

In reply to porschenut :

Not an expert by any means but wouldn't the lumber still be touching the floor and then allow moisture to wick through the wood to your subfloor?

Stampie's right. The moisture will still wick into the wood. 
 

If wood is completely encased in closed cell foam, it is unlikely to rot.  But the wood won't be full encased as you are describing it. (The top and bottom edges of the wood won't be foamed)
 

As the PT wood shrinks, it could make gaps along the joint between the closed cell and the PT for the vapor to transmit from the slab to the bottom of the floor decking- same problem you started with (with some slightly better materials in place).

It MAY work if he puts down a vapor barrier  first and does his framing on top of it, but he wouldn't be able to penetrate the vapor barrier with fasteners (which means the wood could not be secured to the old concrete)

My suggestion is to go ahead and do the framing and closed cell as proposed, but use a ventilated flooring underlayment under your finished floor similar to this:

AirGuard ventilated underlayment

The concept is that it is a complete vapor barrier that makes air gaps under the flooring. The material rolls up the walls behind the baseboard so air can move under the flooring.

You'd end up with a well insulated floor with pressure treated framing and an ALMOST complete vapor barrier. Then if any moisture does pass through the insulation,  there would be a ventilated layer to prevent the moisture from getting trapped again and enable the plywood to breathe and dry out.

Thanks for validating my thoughts.  Pressure treated has a life span and then it will rot too.  I asked about a vapor barrier under the floor before the foam is shot and he said not necessary.  He also talked about the PEX with baseboard water "squeaking" when it expanded against the foam.  He wants to do a mini split, which I am against as we paid to install ducting to include the room in the central system.  Not a big deal but makes me wonder.

The ventilated underlayment is very interesting but it would require ripping out the drywall, correct?  If it just goes under the molding around the room this could be a winner.

Thanks SV, was hoping to hear your $0.02

In reply to porschenut :

Pressure treated isn't rot proof, it's rot resistant so you are right. Essentially its poisoned so nothing wants to eat into it like insects or fungi. Water will still cause it to become spongy over time.

I don't see any lime leeching so I don't think you have an absurd amount of water coming thru but you need to seal the floor regardless.

In reply to porschenut :

It requires removing the baseboard, but not the drywall. 
 

I think there is a little installation video in the link I sent. 

I just double checked the tech sheet.

The material is intended to be trimmed at the walls after flooring installation, not run up behind baseboard (although I have done it that way successfully)

In reply to SV reX :

I like the product, but have a concern about it venting all the moisture right at the drywall.  The foam should stop most of the moisture, but if it vents right against the drywall it could be another problem in the future.  First guy was not in favor of it but I will continue to research and suggest it to the others.  The floor is floating, so a lot of water vapor can come thru.  I know the foam should stop most of it, but not yet comfortable with this solution for the next 20 years. And the first price came in at 20K, for a 200 sq ft room so right now I am in shock.  Thanks for the info though, keep those comments coming.

Antihero, on the pressure treated it would be ground contact rated which is the best.  First guy is planning to put shims between the floor and the joists so some foam will go underneath.  I am thinking of specifying a plastic material for the shims, not wood.

In reply to porschenut :

The problem is that the floating floor has an impermeable backing. It's a vapor barrier- just like your old floor.

The only place for the floor to vent is at the perimeter (where the flooring ends).  It doesn't actually touch the drywall- drywall is typically 3/4" or so off the floor.

I know it seems like a bad idea at first, but no ventilation is a much worse idea.  Because the product creates a 360* vented layer space, the moisture can constantly migrate to the interior of the building and evaporate into the dryer conditioned air.  The actual moisture you are collecting is minuscule at any one time- it becomes large when it accumulates.  There will never be enough moisture to cause a problem with the drywall.

I had a similar problem to what you are dealing with at my own house. When we removed the old flooring the concrete under was soaked.  I installed this product and a new floating floor about 1 1/2 years ago- no problems.

In reply to SV reX :

I really like this solution, need to find a contractor to use it.  Couple questions-does it still make sense to foam the floor?  I am wondering if it is foamed should spacers be placed between the wood and the floor to allow foam under the joists.  If so how thick?  The spacers would not be wood, I am thinking a HDPE or some sort of plastic.  How much space did you allow between the laminate and the wall?  Spec or did you increase it?

I agree that some ventilation is essential.  When the room had carpet there was no issue and no moisture on the windows so all was good.

"When the room had carpet there was no issue and no moisture on the windows so all was good."

THAT is the key to knowing how to rebuild it. It's the part I am trying to focus on. 
 

Your moisture condition is unusual. More than I have seen. But you already had a solution that worked, so obviously drying to the interior should work for you.

I used standard laminate flooring spacing at the walls.  (1/2")

Your contractor is already planning on shimming the PT framing to get it level. Just ask him to use plastic tapered shims (available at Home Depot).  He could also use metal L brackets to secure the framing to the concrete.

For extra insurance, you could first coat the concrete floor with a vapor barrier sealer.  Then install metal L brackets secured to the floor, then seal over the bottom leg of the L and the fasteners before installing the framing.  The foam will lock everything in place well.

If a gap under the framing makes you feel better, it should be fine.  My only question would be if it expands and could force the framing out of place.  I would consider the foam primarily as insulation.

A gap under the framing would also reduce the thickness of the framing (which weakens it), but a few extra fasteners would help.  The foam would become a structural element securing the PT framing (which is fine).  You'd be surprised how much structural integrity is added to a metal roofing system when we spray it with foam. (It's noticeably stiffer to walk on, and really hard to demo)

It is absolutely essential that you use closed cell foam. If they use open cell, it will be a sponge and do exactly the opposite of what you want.

Nothing lasts forever, and this is an unconventional application. But I'd be perfectly comfortable with it if it was my house.

You shouldn't have any trouble finding a flooring contractor to use the ventilated underlayment.  It's not expensive, and readily available.

Another thought...

If you decide to foam the floor, you may want to check with your pest control service before you proceed. The foam should have pesticide in it, but they may want to consider pre-treating or other approach to make sure your don't have a termite problem later. 
 

Oh, and $20K seems really high. 
 

For that price I'll drive to PA, pay for my gas and hotel, do the job for you, and take you out to a fancy dinner afterwards!

Foam is great, but I get a little nervous about a combo of foam, plumbing and wood. I just had to replace about 40 feet of rim joist, floor joists and sill plate that had been spray foamed because a single, undetected plumbing leak saturated the foam like a sponge and held that moisture next to the wood on the entire wall for years, rotting it out.

Granted, in my case the wood was un-treated, but it has changed how I view spray foam a little in places where a plumbing leak could occur. If you're sticking with the baseboard heat, I'd probably want to avoid contact between the spray foam and the framing lumber. Rigid foam boards could be cut and installed in the bays near the plumbing so that a small gap could be kept between the insulation and framing. If there will be no plumbing, because you're switching over to ducted HVAC, or a mini split, then spray foam to your heart's content.

In reply to STM317 :

That's a valid concern. 
 

But if the pipes are being replaced with insulated PEX, it shouldn't be an issue (assuming NO joints under the floor)

In reply to SV reX :

My leak was caused by a nail being driven through a plastic drain pipe, so even with PEX you'd have to take some precautions to protect it. The thing that makes spray foam such a great insulator/air sealer/vapor barrier works against you if anything goes wrong and traps moisture where you don't want it. Just something for OP to watch for and consider.

If there's already ductwork there, I'd avoid any potential future issues and simply use that for my HVAC rather than the baseboard heat. It's simple, and involves less risk of problems down the road.

SV reX said:

Oh, and $20K seems really high. 
 

For that price I'll drive to PA, pay for my gas and hotel, do the job for you, and take you out to a fancy dinner afterwards!

Literally thought the same thing lol

porschenut said:

A closeup:

Is your old O.H. door to the left opposite your walk door? If so, the last carpenter had to rip the floor taper into each board which sounds like a nightmare. I would turn the joists 90 degrees so that you only need to figure out the depth of each board once using a string line and then rip the entire length to that depth using the highest point for your thickness after subtracting for you shimmed air gap on the bottom. Alternate placing the L brackets on opposite sides of the joist. I'd space the brackets every 4' since you will never get another chance to bolt them down.

If you turn the floor 90 degrees, you could run your PEX inside a floor joist space through a 1" or 1.5" pvc sleeve so it isn't encased in the foam the entire distance.

I also agree about fastening the floor boards to the concrete as is suggested. Treated lumber likes to warp and twist as it dries out. Use stainless screws into the joists and Tapcon screws into the concrete. You should also coat the bottom of the L bracket with some rubberized coating like a spray can of undercoating to isolate the metal from the concrete.

How about a long shot photo of the entire garage space? What are the dimensions of your garage?