# What is this?



## scarymary (Apr 16, 2010)

Yesterday my brother decided to pull up a piece of the particle board in the living room, (which is a converted carport/garage) and found this underneath.  The plan is to install laminate flooring over the entire floor including the stairs.  Don't worry, I only have 3 steps down.  My question is would I necessarily need to install a piece of thick moisture resistant plywood on top of this before laying the laminate or can I get by with something not quite as expensive or thick as 3/4 inch plywood, but just as durable and acceptable for putting down the laminate flooring?  These planks run all the way over the room.  Actually I fully expected to see just 2x4s laid flat underneath the particle board on top of the concrete, but not the case.  It looks like cedar planks to me, but I could be wrong.


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## Nestor_Kelebay (Apr 16, 2010)

Those are fir 1X6's I think (judging by the wood grain pattern).

If that is a converted carport/garage, then someone must have built a wood floor over the concrete garage pad (for a warmer floor).  No one would have built a wood floor expecting to park a car on it.

Before you cover that up, I would inspect the ends of the floorboards carefully to see if they've been cut.  It doesn't look so from the photo.  Those floor boards aren't perfectly flat, so anyone cutting through the particle board with a circular saw after it was installed would have left kerf marks in the particle board and would have scored the crests of the floor boards.  It looks to me that the underlayment (the particle board) was just nailed down with a piece missing, and a small piece of particle board was put in to fill in that spot.  Your brother pryed up that small piece.

You can just nail down a new piece of particle board of the same thickness.

But, if it were me, I would pull up ALL of that particle board and nail down plywood underlayment instead.  The difference between plywood and plywood underlayment is that plywood is allowed to have voids in the inner plies.  These voids would cause problems ("soft spots") on a floor, and so any voids in plywood underlayment have to be smaller than a certain size or filled with a filling material.

The difference between plywood and particle board underlayment is that getting wet won't harm plywood underlayment.  If particle board underlayment gets wet, it swells up and gets soft.  They only used particle board as underlayment because it was cheap.  Fir plywood underlayment is much more durable than particle board underlayment, and you wouldn't have to worry about any large water spills wrecking the underlayment.


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## scarymary (Apr 16, 2010)

Actually, the particle board covers all of that plank style that you see in the picture.  There was carpet on top of that.  We have removed all of the carpet.  What I'm driving at here is would we necessarily need to put something of a thickness of 3/4" plywood or could we go with something thinner over the top of that plank that you see in the pic? Oh, and there are some type of joists underneath those planks there in the picture.  They are nailed to something.


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## Nestor_Kelebay (Apr 16, 2010)

ScaryMary:

Thinner.  You should put the same thickness of material down over those planks as the piece you removed.  That looks to be about 3/8 inch thickness approximately.  So you would use whatever thickness of material that that you took out because that would result in the floor over the planks being flush and level with the surrounding floor.

If someone told you that you need to nail down 3/4 inch plywood over those planks, they simply didn't understand the situation.

You should understand that it's those planks that provide all the strength to your floor.  The "underlayment" that you removed (and now need to replace) doesn't provide any strength.  It's just there to provide a smooth surface over which to install the final flooring material.

You don't need to know the rest:

Normally when the build a house, they have floor joists which are supported by concrete walls of the house's basement.  Over top of the floor joists they will nail down 1X6 plank or 3/4 inch fir plywood, and that layer of planks or plywood is called the "SUBFLOOR".  Then the 2X6 exterior walls and 2X4 interior walls of the house are built on top of the subfloor.  If the subfloor consists of planks, as it does in your case, the planks will be nailed down at an angle to the joists because doing so results in a more rigid construction than nailing them perpendicular to the joists.

Then, they would normally nail down something called "UNDERLAYMENT" inside each "room" of the house to provide a smooth surface to install the flooring over.  In your case, you have particle board underlayment.
One of the benefits of installing plywood underlayment over a plywood subfloor (for example) is that if you ever want to remove flooring that is glued down, like sheet vinyl or carpet, you can pry the underlayment up with the flooring still glued to it, and then put down new underlayment to install the new flooring over.  That would save a great deal of work trying to remove the old flooring.


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## scarymary (Apr 17, 2010)

This is a converted carport.  There are joists under the planks there in the picture which are somehow, I am assuming, attached to the concrete floor of the previous carport/garage.  The particle board we removed from the floor was 5/8".  We measured it yesterday.  We will probably remove the rest of the particle board today.


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## Nestor_Kelebay (Apr 17, 2010)

scarymary said:


> This is a converted carport.  There are joists under the planks there in the picture which are somehow, I am assuming, attached to the concrete floor of the previous carport/garage.  The particle board we removed from the floor was 5/8".  We measured it yesterday.  We will probably remove the rest of the particle board today.



Replacing the particle board underlayment with plywood underlayment is a good idea.  Particle board swells up and gets soft if it gets wet.  The only reason particle board was used as an underlayment was because it was inexpensive.  It's really not a good product to use for anything.

Normally underlayment is meant to be thin, typically 3/8 inch in thickness or less.  It's not necessary to use the same thickness of underlayment, but you may have to remove the baseboards from the walls and raise or lower them if you use a different thickness of underlayment.  Riverside Wood Products here in Manitoba makes a 5/16 inch fir plywood underlayment which you can double up to make 5/8 of an inch.


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## scarymary (Apr 18, 2010)

My husband and I looked around at Lowes yesterday, but we didn't see any subfloor/underlayment material of 5/8" thickness.  I wonder how much difference it would make to use something thicker than that.........


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## Bud Cline (Apr 18, 2010)

The thicker the better.  You are asking for trouble covering those boards when you could replace them with a more suitable plywood. Those boards will expand and contract and move around. Notice how some are cupped and some are crowned now.  You wouldn't notice it under carpet but you will notice it under a hard surface flooring.  You'll never keep the seams together in the finished flooring especially if you use one of those cheap "click" laminates that are being sold today.

Get rid of those boards.

Sorry Nestor but your research has yielded you some erroneous information.

Underlayment plywood's are available in many thicknesses for various reasons.  Underlayments ARE NOT meant to be thin, that is ridiculous.

Remove those boards and use a 3/4" Exposure 1 "Underlayment" product and you'll be fine.

And YES...the particle board was a mistake from the git-go.


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## Nestor_Kelebay (Apr 18, 2010)

I would never remove the plank subfloor to replace it with plywood.

I would replace the particle board underlayment with fir plywood underlayment, and I would put that new underlayment over the plank subfloor.

Scarymary:
     Take your picture down to any of the flooring stores in your area and ask to talk to the Installations Manager.  In my view there's nothing wrong with your existing plank subfloor, and there is absolutely no reason to replace those planks with 3/4 inch plywood.  Speak to the Installation Manager at several flooring stores and see if they agree that the subfloor needs to be replace.  I very much doubt they would.


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## Bud Cline (Apr 18, 2010)

Dimensional lumber in that form is unstable.  It expands and contracts routinely to say nothing of the concaving and convexing going on with seasonal changes. 

The way to stabilize it is to cover it with plywood but even then the plywood install would be rickety rackety because of the condition of the boards. Now is the time to remedy any future problems. 

Seams in laminate flooring won't stay together when the substrate is changing form a couple of times per year. Get rid of that junk while the opportunity has presented itself. It will make good fire wood.


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## Nestor_Kelebay (Apr 18, 2010)

Bud:

     1X6 dimensional lumber will twist and warp as it dries IF IT IS FREE TO MOVE.

     In this case those boards were clamped in place by three (typically) nails per board to every joist.  That held them in place as they dried, and prevented them from warping and twisting.  Take a look at the picture.  If those boards were warped, then you'd see gaps between the boards and the underlayment above.  From what I can see, there are no such gaps and those board appear to be laying pretty darn flat to me.

  I have exactly the same kind of fir plank subfloor throughout my building, and my own experience is that the boards dry flat.  Replacing those planks with plywood would be a waste of money.


Mary:
     Just go to any carpet store and show your picture to the Installations Manager.  He will confirm that your plank subfloor will not present any problems for the installation of any flooring you choose to install over it.  He will also confirm that plywood underlayment would be better than the particle board underlayment you have now, but he may feel that it's not worth the cost to replace the underlayment.  My own feeling is that now that the carpet is out, this would be the time to do that work.
     My own building was built in 1960 and I have 5/16 inch thick fir plywood underlayment over a 3/4 inch thick fir 1X6 plank subfloor.  That's lasted 50 years so far with no indication that it won't last another 50.


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## scarymary (Apr 18, 2010)

These boards are nailed to sleepers secured to a concrete slab.  I'm sure that was the reason for them being underneath the particle board.  All I need is something to lay over top of those boards, and it may appear that the wood is cupping from that picture, but after removing the particle board yesterday, the floor seems to be pretty level in my opinion.


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## scarymary (Apr 18, 2010)

Nestor, the baseboard has already been removed.  This is a complete gutting of our living room.  

http://www.houserepairtalk.com/f39/hi-tennessee-9043/#post43585


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## Bud Cline (Apr 18, 2010)

> Take a look at the picture. If those boards were warped, then you'd see gaps between the boards and the underlayment above.



BALONEY!

Those boards will move with environmental change of every season.  They always have and they always will, that's the nature of the animal. Under carpet its no big deal.  Under a hardwood floor, it's no big deal. Under a laminate floor, it can be a big deal.

If you look closely at the picture you can see the rough edge of the torn particleboard and the crumbled remnants of the fibers piles up.

Look even closer and you will note that (from left to right) board number 1 is crowned, board number 2 is cupped. Boards 3, 4, and 5 are all crowned.

It will never stop. Just because they aren't reaching up and slapping you in the face doesn't mean they aren't moving and aren't distorted.  It happens everywhere.  Millions of homes are built with a similar (diagonal) method and the issues exist in each and every one of those millions of homes.

Now is the time to correct the problem for good by getting rid of those unstable slabs of firewood and replacing them with suitable structurally sound plywood that will take the moisture that is rising from under those boards and will be even more trapped when laminate goes down. The ability for the moisture to dissipate will be greatly diminished now that the carpet has been removed.

Trust me Kelebay.  This is one (more) time you don't know what you are talking about.


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## Nestor_Kelebay (Apr 18, 2010)

Mary:

As for Bud Cline's comments, speak to the Installations Manager at any of the flooring stores in your area.  If there are, or ever were problems installing plastic laminate flooring over underlayment over a lumber subfloor, then the Installations Manager would know about it and would advise you accordingly.

     The way I look at it, your 2X4 sleepers under those 1X6 planks are also lumber and will swell and shrink slightly with changes in humidity too.  And plastic laminate flooring has seams in it that could easily accomodate the tiny amount of movement of the wood we're talking about.  And, on top of all that, wood is a soft material that's easily compressed, and will therefore accomodate a lot of movement on it's own.

     So I simply don't share Bud Cline's views about the need to replace the subfloor.  If it were my house, I would replace the particle board underlayment with either a fir plywood underlayment or 6 mm Baltic Birch plywood.  But I would keep the 1X6 lumber subfloor unless and until someone who's knowledge I trusted told me otherwise.  That's why I say to consult with the Installations Manager on this point.


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## scarymary (Apr 18, 2010)

This is what I know..........I know that it is not recommended by the flooring manufacturer to install laminate flooring over a sleeper constructed subfloor due to not having 18" of ventilation space.  However, they will tell you that you can install laminate or hardwood flooring over concrete, so what is the difference, I ask.


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## scarymary (Apr 18, 2010)

Bud, I will take another picture of the floor from a different angle for you and post it in my remodel album here at the site; perhaps that will give you a better look.


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## Nestor_Kelebay (Apr 18, 2010)

Mary:

Maybe take a picture with something you know is straight laying across the boards to prove they're flat and level.


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## scarymary (May 2, 2010)

OK, we bought some 19/32" plywood to put down over the planks that are on top of sleepers, and I have a question.............the plywood isn't precisely uniform.  Where the seams meet, there is some unevenness.  How should we address this?


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## scarymary (May 4, 2010)

Here is the dilemma...........if I were going to tear out all those existing planks, then I am left with nothing but sleepers on top of concrete.  The room is already framed and had flooring on it previously.  Any deviation from what was there previously will create an elevation change, and that is what I'm trying to avoid.  I can't make any adjustments to the doorways in the room easily.  That is the only reason I am trying to stay within the confines of what was there previously.  I have no reason to doubt your experience or knowledge regarding this.


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## Nestor_Kelebay (May 4, 2010)

ScaryMary:

     I have more than my share of experience installing vinyl composition tiles, but I have never installed plastic laminate flooring.  That's why when Bud Cline insists that there will be a problem with the installation of the laminate flooring if it's installed over a plank subfloor, I can't see any reason for there to be a problem, but if it were my house I would take the time to check on this with someone more knowledgable than Bud, like the Installations Manager at your local flooring store that sells the kind of laminate flooring you want to install.  Their installers would have install lots of this laminate and if there were any problem associated with installing it over a plank subfloor, the Installations Manager would be aware of the potential problem in doing that.  So, just to be on the safe side, I think you should phone any of your local carpet retailers that sell plastic laminate and talk to their Installations Manager to see if he is aware of any known problems installing laminate flooring over what you will have; namely 1/6 diagonal planking for the subfloor and 19/32 inch plywood for the underlayment.  If that Installations Manager is not aware of the problems that Bud is warning you about, then ignore Bud.

Now, for the problem at hand, how much of a discrepancy in height is there between your plywood panels?  Are we talking 1/16 inch, 1/8 inch, 1/4 inch?

You see, the problem here is that if the 5/8 inch particle board nailed down flat on your plank subfloor years ago, then why would there be a problem nailing your 5/8(almost) plywood down flat on those same planks.  (if what Bud is saying is true, and that the boards are warped and twisted, then they'd all be warped and twisted, and the plywood we put on top of those warped and twisted boards would still line up well at the edges and corners).

     I think what you may be encountering is swelling of the particle board underlayment you have.  That is, your existing particle board may be quite uneven.  You say you had a carpet over that particle board before.  Well, if at any time during that old flooring's history, someone overwatered a floor plant or spilled a glass of milk, or knocked over an aquarium, and the excess moisture dripped down through the carpet, through the underpad and got that particle board wet, then it would have swollen (perhaps a little, perhaps a lot, depending on how wet it got) and the result may be that the top surface of your particle board is wavy as a result of swelling.  So, when you set sheets of plywood over that particle board, those sheets wouldn't be expected to meet up well at the corners if the particle board under it is wavy.  But, that problem would be corrected as soon as you pull out the particle board and put that plywood over the plank flooring, which appears to me, at least, to be laying flat and level.

      It may be a good idea to take a bright flashlight and shine it along your floor.  Even a bright light held close to the floor would exagerate the roughness of the floor so that you could see if it was flat or not. That would give you an indication of whether or not the existing particle board is flat enough to do the test you're doing.  I expect you'll find that your particle board is swollen in different places, and so laying flat plywood over it doesn't really indicate if you'll have any problems installing the plywood or not.

     Unfortunately, that's one of the characteristics of particle board that makes it a lousy underlayment for flooring; if it gets wet, it swells up and looses both it's strength and hardness.  And, if my explanation as to why your plywood panels aren't meeting well at the joints seems reasonable to you, then I'm sure you'd agree that your existing particle board wouldn't make a very good surface over which to install your laminate.  That's cuz the plastic laminate "boards" won't be supported along their whole length, but would have a bumpy substrate under them.

     Now, if it turns out that you pull off your particle board underlayment and your plywood panels still don't meet well at the joints and corners, then about all anyone could do in that situation is to use something called a "cement based floor leveling compound" like Mapei Planipatch to "float" the floor.

Essentially, what Mapei Planipatch is is a cement powder that can be mixed with water to form a slurry.  You simply spread that slurry over either the whole floor or just over the joint areas to help smooth out abrupt changes in the floor's surface.







floor patch | MAPEI

Mapei is the largest flooring cement manufacturer in the World, and Planipatch is their leading floor leveling product.  I will be able to explain to you how to use the stuff to level out the surface of the plywood as best you can.  Which won't be very good because we're fundamentally relying on the sleeping 2X4's and plank subfloor to be reasonably flat.  If they aren't, then any plywood we put on top won't lay flat either.

So, if things aren't flat underneath your particle board, then we can expect problems with the plywood as well.  I suspect everything under the particle board is reasonably flat.  My hunch is that the particle board has been wetted in different areas by different amounts over it's history, and isn't flat any more.

But, for the time being, phone the Installations Manager at your local carpet retail outlets and see if any of them have experienced any problems:
#1. installing plywood underlayment over 1X6 diagonal plank subflooring, and
#2. installing plastic laminate flooring over #1.

Finally, the manufacturers of tongue and groove plywood subflooring recommend that a 1/8 inch gap be left between 4X8 panels of their subflooring when it's being nailed down to floor joists.  That is to allow the T&G plywood subfloor panels room for expansion as they absorb moisure from the air after installation.  I have never heard of a similar expansion space being recommended for plywood underlayment.  I would ask the Installation Managers at your local carpet retailers whether you should would provide that 1/8 inch expansion gap around your 19/32 plywood underlayment panels or not.  If it was me, I would provide that space because doing so won't do any harm.  The laminate flooring is plenty strong enough to span such a narrow gap, and in future if you ever want to replace the laminate with a thinner / softer flooring, like sheet vinyl, you can always fill those gaps in with a product like Planipatch.


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## scarymary (May 4, 2010)

All of the particle board has been removed.  We are laying the plywood on top of those planks in the picture I posted earlier.  I don't know how much off from being flush two of the pieces are.  I would have to measure to see.

Actually that particle board appeared to be very dry except for around the edges of it.


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## Bud Cline (May 4, 2010)

Jheeezh!
Plani-Patch is a fine product and can be mixed two ways. 

One way is with water only, in which case it would become hard and brittle and in turn crumble under the strains of expansion and contraction and foot traffic from above on the laminate floor. Under sheet vinyl or VCT it may or may not be a problem because the 100% coverage of adhesive would hold the filler in check.

Another way to mix Plani-Patch is to use their companion additive. This makes the product somewhat more flexible and gives it an adhesive property it doesn't have when mixed with only water. The same additive should be used first to prime the intended surface before installing the filler.



> like the Installations Manager at your local flooring store *that sells the kind of laminate flooring you want to install*.



Therein lies the problem with that theory.  Don't think for a minute a seller is going to tell you anything negative that would kill a flooring sale.  I see it happen every day.


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## Nestor_Kelebay (May 4, 2010)

Bud Cline said:


> Jheeezh!
> Plani-Patch is a fine product and can be mixed two ways.
> 
> One way is with water only, in which case it would become hard and brittle and in turn crumble under the strains of expansion and contraction and foot traffic from above on the laminate floor. Under sheet vinyl or VCT it may or may not be a problem because the 100% coverage of adhesive would hold the filler in check.
> ...



I know.  I spread Planipatch and the Plus additive over 21 apartment floors.



> All of the particle board has been removed. We are laying the plywood on top of those planks in the picture I posted earlier. I don't know how much off from being flush two of the pieces are. I would have to measure to see.
> 
> Actually that particle board appeared to be very dry except for around the edges of it.



Mary:  I am at a loss to explain why your particle board laid flat across those 1X6 planks, but your plywood doesn't.


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## TxBuilder (May 5, 2010)

It's great to disagree guys, but lets keep it civil.


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## Nestor_Kelebay (May 7, 2010)

Can you find one credible web site on the internet that says that plastic laminate flooring should not be installed over a floor with a 1X6 diagonal plank subfloor?

I have advised ScaryMary to ask the Installation Managers at her local flooring stores to see if they have had any problems doing that BECAUSE I am prepared to admit that there may be an issue I'm not aware of.  However, if you claim she should replace those planks, you should be able to find sound reasons for doing so amongst the hundreds of plastic laminate manufacturer's web sites on the internet.

Mary states that the installation instructions talk about the amount of space that's required below the floor, but the installation instructions don't say anything about the TYPE of subfloor that the product should be installed over.


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