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It is generally not a recommended procedure. The abrasion of carpet on carpet will cause both layers to wear prematurely. Certain types of glue down carpet can be installed over existing glue down carpet. Check the manufactures installation instructions. I do agree that installing stretch in carpet over existing stretch in carpet is not a good idea.
Yes, because it is a low voltage system, just don't block the lights!
Yes. I'd advise you to make sure the old isn't moldy though
If you have a wood floor that is over a crawlspace or basement, there may not be any insulation. Heat rises. Also, if you have drafty doors or windows, that may have an effect.
It depends on the species of wood, but a good average insulation value is R1.5 per inch. So, you would need 10 inches of boards just to get to R15. Often, making sure to stop the escaping air in this area is more important than the insulation value.
Yes provided the linoleum is still sound (no large sections missing, well adhered to the floor, etc)
It is possible to do but not a recommended practice Carpet tiles are designed to be installed over a stable surface. Even if you use one of the solvent based outdoor adhesives there will be some movement of one carpet against the other. This abrading will result in premature separation of the layers and you will be constantly trying to re adhere sections of the floor as they come loose. The best procedure is to remove the existing carpet, prep the surface & then install the tiles.
Either way, there is a metal strip available that has a groove in one side for the tile and a lip that goes over the carpet. The most common brand name for these metal strips is Schluter.
Home Depot stores sell mats that can be bought by the foot to place over existing carpets. They have nubs on the bottom to help them grip the existing carpet. They generally cost less than $5 a foot.
We have installed carpet on cermic a few times. Please be aware your grout lines will most likely show through into the carpet. The best option is to stretch the new carpet in over cushion. In order to do this the tackstip will need to be glued to the existing ceramic. Keep in mind you will want to glue this tackstrip and let it dry for at least 24 hours prior to stretching in the carpet.
you have to pull the linoleum up to lay tile. . .i would suggest a cement backer board over the existing plywood also