If it's still in good condition there's no reason you can't reuse it, but after a few years it's probably dirty, smelly, and/or no longer very resilient; it doesn't make much sense to install new carpet over an old, dirty, smelly, worn-out pad.
Yes, you can reuse your old carpet pad if it is still in good condition, meaning it shows no signs of damage, mold, or excessive wear. However, it's essential to clean it thoroughly to eliminate any dirt or odors before reinstallation. Additionally, ensure that it meets the requirements for your new carpet type, as different carpets may have specific pad recommendations for optimal performance. If in doubt, consult with a flooring professional.
You may have to remove the carpet pad as well. If it was contaminated, it will have to be replaced, as it cant be cleaned. Just cut a replacement piece to fit, clean both sides of carpet, let dry, and re tuck the carpet.
Carpet is not supposed to be glued to the pad, and I really can't imagine what advantage that would give you.
Gluing splices is the common way to lay pad for carpet.
Yes
A carpet to carpet rug pad provides cushioning, prevents slipping, and extends the life of both the rug and the carpet underneath. It also helps to reduce noise and adds an extra layer of insulation.
It depends on where the carpet is installed. You want a thinner pad on high traffic areas. A thicker pad will give a softer, more luxurious feel.
No, the carpet pad moves far to much and your tile will look loose and crooked in a very short amount of time. Also, the carpet pad will not allow the adhesive to bond to it.
$1550 uninstalled with pad, $2025 installed with pad
you cant
A carpet pad goes under a carpet to provide cushioning and insulation.
Generally, no. The carpet pad will have too much bounce causing the engineered hardwood (or even laminate) to break and split. That being said there are some thin felt carpet pads that could work, but I wouldn't recommend it. I'm not sure why you are asking this question. If it's because you had carpet there and you are hoping to reuse your existing carpet pad, that is a big no no. The carpet pad will be uneven which can cause problems and worse than that, it will already be dirty with germs and potentially moisture and you could develop mold and/or odor issues. Also, if your engineered hardwood is over concrete, you want the traditional laminate/hardwood underlayment which also has a moisture barrier. This, of course, is assuming that you are doing a floating floor. If you are nailing or glueing than it's an even firmer no.