Laminate flooring

[Kilted Ginger]

I'm lifting carpet in a relatives flat to lay laminate flooring. There is nothing wrong with the underlay onder the carpet.
Is there any benefit to leeaving the underlay and laying the white foam sheet over it before the laminate. Or is there reasons I shoud lift the underlay first?
Thanks

[johnnyrod]

If you mean normal carpet underlay that's a lot thicker than the foam sheet, take it up or the laminate flooring will be able to flex too much. The thin foam sheet gives a little sound insulation and evens out small imperfections but basically the laminate needs to sit on the floor.

[Specialone]

The thin foam is crap, get the stuff with silver foil backing, it reflects heat and deadens the sound a bit better.

[SIII]

Carpet underlay too thick. Joints would flex and split.

[-Ralph-]

It's already been said!

Laminate with stronger joints you may get away with it, but you won't know that until it's been down a while, and it'll still compress like soggy grass under your feet.

If your laminate comes with a guarantee, you need to use the right underlay.

If your floor is not completely flat you'll have the same problem with boards rocking and joints splitting as you would have with the wrong underlay. Use a floor leveller compound first.

Really small imperfections you can get away with by using a slightly thicker underlay, but it must be a proper laminate underlay.

Don't use the white foam stuff like parcel wrapping it's crap, either use the denser thicker foam stuff (like a camping mat), or the green stuff with the silver backing that SP1 mentioned.

Don't go round doors, use an off cut as a template for thickness and cut the bottom of the vertical Architrave and slide the laminate underneath it.

Take skirting boards off and refit them over the top, edging strip looks crap.

Leave a 10mm gap all the way round for expansion and contraction of the floor in summer and winter.

Personally I wouldn't look twice at any laminate less than 9mm in thickness, 12mm is my preference.

Get stuck anywhere give me a shout, I did all the floors at Harthill and have replaced quite a few here now.