How do you do this ? (please read)

[madmax64]

Please see the photograph, you can see that the floor behind the entry door is made of concrete. Between the concrete and plywood is made with concrete leveling (it was done by pro contractor about 12 years ago). I am installing RevolutionPly plywood (5mm thick) over the entire living room, kitchen, hallways and near the entry door. I will be using 1/4 crown staples to secure the underlayment over the wood subfloor (according to Patriot Timber RevolutionPly instructions). The area between concrete and floor is concrete leveling (it was done by the contractor about 12 years ago).

How do I secure 5mm plywood to the concrete area (right next to the entry door). The area is like 4 feet by 4 feet - really small area. I was thinking of using adhesive method to "glue" the 5mm plywood to the concrete floor? No?

I need your suggestions/advice/recommendations.

Thanks.

 

[highup]

Why such a thin plywood? That's like, 3/16" thick. You'd need a staple every 3 or 4 inches and every 2 inches or less on the seams.
Plywood that thin will not hide or span any irregularities in the floor. You'd need to get the floor very smooth before installing that plywood.
What are you installing over it?

 

[madmax64]

I am going to install vinyl planks.

Yes I am aware that I am going to staple every 3-4 inches and 2 inches on the seams. I have watched video about how to install 5mm plywood over the existing wooden subfloor. The existing plywood subfloor is flat and even. Some areas have ridges at the seams, I will have to sand them down - to make them more flat.

I need your suggestions on how to install 5mm plywood over the concrete area (about 4' x 4') right next to the entry door. I can't staple them down because of concrete. I was thinking maybe I can use construction glue (also known as Liquid Nails), but I need your ideas/suggestions.

 

[madmax64]

If 5mm plywood over the existing plywood subfloor is a bad idea. What are the other options? I have COREtec vinyl planks sitting in my office waiting to be installed. These planks come with a layer of cork on the underside (one side). I just want to cover existing subfloor before I'll lay down vinyl planks.

 

[highup]

I assume you have a two component flooring system.....subfloor and underlayment?
If so, that thin plywood will do absolutely nothing to help with any unevenness that you have. It will add zero strength and will not even out plywood seam irregularities. You'd need at least 3/8" plywood, preferably 1/2".
I'd sand the plywood seams and use a cement based floor patch to fill and level whatever needs it. Plywood that thin will follow irregularities in the floor a little better than peel and stick shelf liner.
I can't see what you see, so maybe I just don't understand why you want to add the plywood. It might look nice..... But you are going to cover it up. I'd screed floor filler to make it flat. Renail or screw down the current plywood if need be, sand the plywood seams, then smooth and level with filler.

 

[madmax64]

Good point. Maybe I shouldn't cover my enter subfloor with 5mm plywood.

My subfloor has some "patches" here and there - like old rectangle-shaped HVAC vents. I thought the 5mm plywood would cover it nicely. My house was built in 1958.

There are some gaps around it. Should I fill it with something to "seal" the gap? The picture will help you to understand what I mean. Notice the yellow level in the picture. I was checking for "dips" and "ridges" on the subfloor. Most "dips" are about 1/8" between the plywood subfloor seams at 4' wide. The "dips" are only 1/8" deep, am I required to fill them up with cement lever?

 

[madmax64]

To fill in the gaps, can I use "Fix-it-all" patching compound?

 

[highup]

No I wouldn't use fix all. The last bag of that I bought was probably 20 years ago. It sets up way too fast. There are cement-based products that dry quickly and are made for filling voids and the skim coating surfaces to level them. Ardex Feather Finish, UZIN 886, are two brands. Mapai also makes one but I don't recall what they call that specific product.
You just want to be sure those edges of the patches you have are screwed down so they don't wiggle and flex.
If there's any voids like by that heater vent you would mix up a batch and fill all those in. After that's done you would use some sort of a screed to flatten or blend any depressions in the floor to make the floor flat.
How far out is the floor where you have that level. I don't mean how level is the floor, that doesn't make any difference, because what you're looking for is flat not level.

 

[highup]

I don't know what's inside that vent that the piece of plywood was nailed into. Rather than a row of nails down the center of the vent it would be best to have one on the edges. That would just make it more stable. Basically any seems in the plywood or patched areas like that vent should have new fasteners if you're concerned about any floor movement. Check the floor and place screws where needed. Do all of that first and use a carpenter's pencil or something like that to mark areas that need attention when it comes to using filler.

 

[madmax64]

This one? Henry 547 25 lbs. Universal Patch and Skimcoat-12158 - The Home Depot

Another question: I am somewhat concerned about the moisture from the crawl space. I don't want to go under the crawl space and install plastic sheet over the dirt (approx 1600 sq ft area). I live in Southern California - not much rain except El Nino season and sometimes high humidity during the summertime. The floor salesman said I can use 6 mil poly sheet over the subfloor before the installation of luxury vinyl planks. I think he was wrong because the moisture will trap in there and develop some molds. I understand that there are few options like roof tar paper (no I am not going do that) and kraft paper. What is your opinion of kraft paper? Kraft paper is sort of "breathable" (as opposed to 6 mil poly).

 

[madmax64]

That is how I'm supposed to do that? See short video clip (2:26 - 3:21 only).

 

[highup]

You're correct about the poly. Salesman needs some training.
It's best to put the poly over the dirt.
If you live at the bottom of a hill, you can have more moisture under the home than if you live on top of a hill. Best if the ground slopes away from the house and gutters and drains are working to keep water away from the foundation. I'm betting moisture isn't an issue.
How deep is the crawl space and are there the correct amount of vents in the foundation?
The video is correct, but floor patch material are better than thin set, because they can be screeded to a smoother edge.
I haven't used that Henry patch before, but it ought to work fine. I'd prefer the Henry Feather Finish, but it's more expensive. As long as it screeds out smoothly, the material you mentioned will be fine.
I don't use a board to screed with. I have 3 or 4 sections of heavy gauge 2" angle aluminum, the longest being a 6 footer. No use a scouring pad or synthetic bbq or varnish stripping pad to clean the aluminum after using it. These patches are hard to clean off tools if they dry on them. I also use a concrete finish trowel and 6" drywall spreader to assist my screed results. You don't have to screed things flat in one pass, and don't overfill anything, thinking you can sand it down later.

 

[madmax64]

I have ten 14" x 5" vents (4 vents on the left side of my house, 4 vents on the right, 2 vents in the back. No vents in the front of my house). There is approx 24" x 24" removeable screen door for entry into the crawl space. The crawl space between the dirt and bottom of the house floor is approx 3 feet. I hope I have enough vents to remove moisture.

I really hope that I don't need to do this - cover the dirt with the poly (I really don't like going in there).

I am planning to get a 36" long aluminum screed from Home Depot. I will clean it up immediately after screeding.

What about kraft paper?

Thank you so much for your help.

 

[Jon]

The main point with vents is that you have to have blow through ventilation. If the prevailing wind comes through a large vent/hole under the house the wind can not escape through a small vent opposite, now if the other way around if the prevailing wind comes from a small vent the wind can escape through large vents opposite
I have been known to lay underlayment over concrete using a flooring glue and nailing with small concrete nails used by carpet layers. I would be looking at other ways if a large area

 

[highup]

One thing is, that Coretec is waterproof, so it isn't affected like if you were installing a wood floor.
Mind telling the city you live in? I'm curious about your climate. You might have nothing to worry about.

 

[highup]

The reason I asked where you live might give you some information to ponder.
Click the link in this USDA publication.
It shows each month of the year in different locations around the world and in the US. It shows the change by month in Wood moisture content. In places near the coast it changes very little throughout the year but inland or in the mountains is can change considerably.
The information doesn't tell me if you live next to a lake or on a hill or living in an area where the groundwater table is extremely high, but it's something to consider.
https://www.fs.usda.gov/treesearch/pubs/5913If nothing else is interesting to look at.

 

[highup]

Depending on how bumpy your floor is that 36-in screed might not be long enough. Your level is perfectly straight, so check the floor with that first to find out if you have any major high spots or low spots. Do that before buying a screed.
We have a local steel supplier and they have steel and aluminum in 20 ft lengths and they will cut any size you need. The heavy gauge aluminum angle that I bought isn't terribly expensive. I think a six footer cost me somewhere around $25. It cost twice as much to buy that at a hardware store, pre cut out of store rack.

 

[madmax64]

I live in Riverside, CA. Elevation is around 850'. About 45 miles to the nearest beach. We do get Santa Ana winds (dry air blowing from Utah & Nevada) few times in Fall and Winter. Groundwater table depth I believe is around 50'. The nearest lake is Lake Mathews, about 10 miles from my house.

I have checked subfloor with 6' level (I bought it from Harbor Freight for $17) a couple of days ago, there are some high spots along the plywood seams and some low spots halfway between the seams. The low spots is about 1/8"-1/4" deep.

I can get a 6 footer aluminum from a local metal shop. Thanks for the advice. I am going to start working on my floor maybe tomorrow or Tuesday. My goal is to get it done by Friday.

THANK you so much for your help!!! I really appreciate that.

 

[highup]

On those plywood seams one thing that would be good to do would be to set the nails a little bit deeper and hit them with a belt sander with some coarse grit paper.
It's always best if you take down the hight spots wheneve possible because that will mean less filling.

 

[highup]

You can cut that 6-footer down to make it easier to handle. It all depends on what it takes to do the filling that needs to be done. 5 ft or even 4 ft might still work for you.