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