Do I have to buy carpet pad?

Carpet and padding are two separate products. So, in theory, you don't HAVE to buy carpet pad. But, you absolutely should. Here are a few reasons why.

It will make carpet FEEL better.
Every step you take creates hundreds of pounds of pressure per square inch in your floor covering. Carpet padding, or cushion as it is sometimes called, helps alleviate that pressure. The decrease in pressure helps make your carpet feel richer, thicker, and softer.

It will make your room QUIETER and WARMER.
Carpet cushion can significantly improve a carpet's sound-absorption and improve its thermal insulation properties.

It will help you keep your carpet CLEANER.
Dirt can grind down carpet fiber the way sandpaper wears down wood, and thus shortens carpet life. A quality cushion makes cleaning more efficient because it raises carpet off the subfloor and provides an air space underneath, allowing the carpet to "breathe." When you vacuum, that space allows more air to come up through the carpet, carrying more dirt along with it. The result is more effective cleaning every time.

And most importantly, it will make your carpet LAST longer.
Pile crushing can make carpet "ugly out" long before it's worn out. An example of pile crushing is the crushed carpet path where everybody walks, particularly in hallways. A quality carpet cushion helps decrease pile crushing, allowing the carpet to maintain its pile height and stay looking new for much longer. Industry studies have shown that quality cushion can actually increase the useful life of carpet as much as 50%.
Also, placing a quality cushion under your new carpet is often a condition of your WARRANTY.

In most carpet purchases, your carpet must be correctly installed using a pad that meets FHT/HUD requirements. Consult The Floor Store for details.