The easy answer to this question is that pre-pasted wallpaper has paste applied to the back of it. You can wet the back and begin to apply the wallpaper to the wall once the paste is sticky. Non-pre-pasted wallpaper has no paste on it and requires you to buy paste so that you can apply the paper to the wall.
Why People Like Pre-pasted Wallpaper and What to Know
There are several obvious benefits to purchasing wallpaper that already has the paste on it. You don’t have to buy as much stuff to get started and you won’t smear the paste on the wall when you start adding the wallpaper.
You need to read the instructions well when applying this particularly type. The paste needs to be wet enough to stick, but you don’t want to make the paper soggy. You also have to make sure you don’t over wet the paste because it will lose its adhesion if it is too wet.
However, the primary disadvantage to pre-pasted wallpaper is that it tends to start peeling earlier than those papers where you have to apply the paste to the paper. This means that you are more likely to need to redo a particular room in a few years.
Why People Like Non-pre-pasted Wallpaper and What to Know
While it can be messier and a bit more costly, a lot of professionals actually prefer paper that does not have paste on it already because it lasts longer. It is just as important to read the instructions for hanging the wallpaper as it is to read the instructions for pre-pasted wallpaper, there is just less associated risk. You can use too much paste and ruin the wallpaper (just like you can oversoak pre-pasted wallpaper) or you might use too little paste.
It tends to be a bit messier as you have to apply the paste to the paper before you start. Some professions actually apply the paste to the wall, but you need to make sure that is alright before you try it.
The best way to get it right is to take your time asking the sales people any questions you have. Don’t be afraid to go online and ask questions in the forums. Just be aware that they all have an opinion they are likely to share while answering your questions.
In the end, what you choose is up to your time constraints and your skill level. Pre-pasted wallpaper is easier for people who have never worked with wallpaper before because the instructions are all in one place. Just remember it will probably start to peel earlier than non-pre-pasted wallpaper.