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How Much ‘Stuff’ Can Be Under Your Laminate Flooring?

We got a question best answered with some illustrations, so I am once again replying with a full post. The question was a really good one.

In a comment on our What are the worst floors for a basement? post, Dave asks us:

“I have office or Commercial non padded carpeting glued to 1200 Square foot basement. No moisture (Dehumidifier for pool table) I have Pergo flooring and want to (Tile) over the carpeting using the glued (Very thin) carpeting and the attached padding on Laminate. Is there any reason this will not work?”

Hi, Dave and onlookers. Laminate can be installed over many other floors as long as certain conditions are met. One thing that is important for many (maybe not an issue for Dave) is that the main floor under the laminate must be level. Usually the flooring can tolerate a difference or slope of about 3/8 of an inch over any distance of 10 feet. The specific product’s instructions will give the details on this, but I don’t want that to go unmentioned.

The undetailed answer to Dave’s question is, “Yes, it might not work,” but let me give you some specifics so you can determine whether my yes applies to your situation. The biggest issue is the height of anything springy that we put under the laminate flooring. Cement, wood, most vinyl – these things are flat and pretty solid, so we don’t worry too much about them. The soft, resilient stuff, usually padding, must be under kept a certain height or we risk ‘disengaging the locking mechanisms’. Big words for what happens when we step on one plank, and it goes down enough to unlock from its neighbor, like this

6.  Disengage Mechanisms

You can see how, as I press on the left laminate piece, it goes down far enough to pop the two apart.
Now we have a recommended height for our padding, a max of 5mm of thickness. Using carpet as your padding can be a great idea as long as it the carpeting is already well glued down to the subfloor, as Dave’s is, and it meets the height requirements. The thickest pad we sell is usually a felt pad, which is usually 3 mm thick.

Pad heights

Here’s an example. For these pictures, my carpet and pad seemed to be pretty close in size.

Carpet and Pad

Actually, the carpet has two levels. Because we want to limit how far the laminate will move up and down, the higher level is the one that matters. It may actually support the laminate at its height, and then press down when stepped on. For our purposes, this carpet is 6mm high.

2. Carpet height

On top of that, using Dave’s situation, there is some extra padding for our math. Attached to the backs of the laminate planks, it adds 2mm to our total.

Extra 2mm attached


In the end, even with the carpeting compressed by 1mm from the weight of the laminate, we still have 7mm of total padding, which is high enough to risk separating the planks as they are walked upon.
5.  Total too high

The picture above illustrates why we won’t even sell our felt pad to go along with any attached pad product. It is almost universal that attached padding is 2mm thick. Add another 2mm, let alone a 3mm felt pad, and we’re setting ourselves up for a problem.

The thing to do is to measure the height of the existing carpeting and any padding under it. If it is any higher than 3mm, again, assuming that the Pergo padding is already 2mm, then installing directly over the carpeting risks having planks unlock over time.

Dave, I hope this has been helpful, and that you’re able to measure and get your best answer. I also hope your answer is yes! Thanks for asking us. This is a great question, one we have long needed to find a way to answer and illustrate.


– – – –
David is a Writer at Floors To Your Home (.com), as well as the PPC Manager, a Marketing Strategy Team member, a Researcher, Videographer, Social Strategist, Photographer and all around Resource Jitō. In my spare time I shoot and edit video, explore film history, mix music (as in ‘play with Beatles multi-tracks’) and write non-fiction for my friends. Connect with me on W. David Lichty’s Google+

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David is a Writer at Floors To Your Home (.com), as well as the PPC Manager, a Marketing Strategy Team member, a Researcher, Videographer, Social Strategist, Photographer and all around Resource Jitō. In my spare time I shoot and edit video, explore film history, mix music (as in 'play with Beatles multi-tracks') and write non-fiction for my friends. Connect with me on W. David Lichty's Google+

Posted in Customer Q & A, Laminate Flooring
12 comments on “How Much ‘Stuff’ Can Be Under Your Laminate Flooring?
  1. Mike says:

    I have just installed pergo max with pad on top of a silent walk pad and now I have an area that has sperated. I want to know if I need to remove the floor and pull the padding and reinstall the floor?

    • David says:

      Mike, I don’t know the specific thicknesses for your situation, but in general, attached pads are 2mm thick. Also in general, for the thickest laminate floor, 12mm of actual flooring, we don’t recommend that any more than 5mm total of any padding be placed underneath it for this reason. That number would go down with the thickness of the flooring proper. In fact, we will not even sell our 2mm padding to go with our floors with attached 2mm pad. Again, I don’t know how thick your materials are, but it sounds like you might be correct, that the extra underlayment should not be there.

  2. Florri Beckley says:

    Wondering if any padding or underlayment needs to be used under a click plank vinyl flooring on a concrete basement where dogs “eliminate”?
    Is this the best product recommended?

    • David says:

      Hi, Florri,

      No padding needs to go under the vinyl plank flooring, and right now we have not yet found one we’re even satisfied with as a possibility. Padding for vinyl plank is not quite, but close to, not even recommended. The maximum thickness would be 1mm. A vapor or moisture barrier would also not be recommended in your situation. Those are made to keep vapor from coming up through the flooring, not to prevent it from going down. Any downward flow would effectively become trapped between the bottoms of your floor planks and the plastic – probably not what you want in this case.

      That said, yes, this is probably the best product for you, vinyl plank, because it is 100% waterproof. It doesn’t waterproof your concrete, but it is itself waterproof, and while a puddle can seep through the seams between planks, it’s pretty hard to do. No floor will prevent you from having to clean up puddles, but the best one will not be hurt by them. If the elimination issue is regular, then you might consider Loose Lay Vinyl Plank because it is much easier to clean under if that comes up. Those are also 100% waterproof, which is the way I would go for your situation. I wrote a piece called Waterproof Vinyl Flooring vs. Cat Pee where I explained this for another commenter.

      Let me know if I can answer more, or if I haven’t helped enough here!

  3. Diane says:

    We are installing pergo max manor hickory laminate floor with attached pad.Pad is very thin.Do you recommend addino additional underlayment? Like blue hawk premium from Lowe’s?

    • Meredith says:

      Hi, Diane! It looks like you’re installing an 8 mm floor. We recommend a total of 4 mm of padding underneath an 8 mm floor, and the additional pad you mentioned would bring your total padding up beyond the 5 mm limit we recommend for 12 mm thick laminate flooring. You want to be careful with too much padding, because it can add give to the floor and push up the planks until they unlock. Since most attached padding is 2 mm thick, you’d want an additional pad that’s 2 mm thick or less, so your options would most likely be a foam-type pad. Your best bet before deciding on additional padding would be to check your floor’s specifications, figure out exactly how thick your attached pad is, and then go from there. Hope that helps!

  4. Justin says:

    I just bought 10mm laminate from lowes. They had the blue hawk 3 in 1 underlayment on closeout for only 6 cents a foot. I bought it but now I’m wondering is the 3 mill in addition to the plank with the 2 mill will be too much. Do you think I will be ok with a total of 5 mill or should I return the good deal we got on the underlayment? Thanks for your help!

    • Meredith says:

      Hi, Justin, thanks for your question! In our opinion, 5 millimeters is too much for a 10mm laminate floor. One of the great things about buying a laminate with a pre-attached pad is that it’s a 2-in-1 and a time-saver: you’ve already got your padding, so you don’t need to make another purchase. We do not recommend using the additional padding you bought, and we would return it. Hope that helps, if you have any more questions please don’t hesitate to ask!

  5. Stephanie says:

    Hi! I just purchased 10mm with 2mm pad attached from lumber Liquadator. I’ll be installing downstairs on concrete and upstairs on the plywood. I was recommended a 2mm foam underlayment to go along with the flooring but after reading this I don’t know, will it be too much? Thank you

    • Meredith says:

      Hi Stephanie! Upstairs on your plywood you do NOT need any extra padding other than what’s already attached. Down on the concrete, though, you will need a moisture or vapor barrier but NOT that 2mm foam underlayment. That’s too thick. Look for something like the 6mil moisture barrier on the right of this page.

  6. Pat says:

    I will be installing 12mm laminate with 2mm attached pad. Was going to use FloorComfort 1.5mm underlayment for moisture and thermal since it is on concrete. Too much pad?


    • David says:

      Pat, I think you’re going to be fine with that. We used to sell 5mm felt padding for 12mm laminates. Your total would be 3.5mm, and probably consisting of denser material than felt. For a 12mm laminate, you should be well within what the locking mechanisms can tolerate. Always check the documentation for your specific flooring, of course. You never know when some manufacturer is going to be really unique with something.

      – David

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