I tore up laminate flooring and the underlayment is still intact and in very good condition. Can I install the new laminate (which has the underlayment attached) on top of the existing underlayment?
I am sorry I don't have time to research this right now but I will give you a quick answer and maybe edit later. First - call Pergo and ask.
Second, I have installed 4 different types of Pergo+underlayment and all of them say to take out old underlayment. I think there is first an issue with the floor becoming too spongy and second if there is spongy/vertical movement it could could splintering or disconnecting of the tiles.
If your old underlayment is "padding" I would remove. If it is just a thin vapor barrier then keep it.
From the Pergo Installation Instructions (Section 10d, page 6):
- If the Pergo Product being installed has an attached foam underlayment then use only a vapor barrier when installing over a concrete subﬂoor.
- When installing a Pergo Product with an attached underlayment foam over a wood subﬂoor no other additional acoustic underlayment should be used.
What Jack said is correct. I'll add some extra comments. Of course you can install over an existing subfloor in good condition. What would be the reason to remove a solid plywood subfloor and replace it with the same material except new? I would advise you to check the existing subfloor to be sure it is secured well. If needed, screw down any loose areas. If there are any dips, use an embossing compound or cement style leveler to fill and level any irregularities. Do not use any additional vapor barriers over the plywood subfloor. The only time a vapor barrier would be appropriate would be over concrete or an unheated crawl space, but then only under the underlayment.