Would putting store bought frosting in a pastry bag work for a gingerbread house?

Unless you're buying "royal icing" it will not work. You need something that's going to harden, otherwise the house will fall apart and the candies will fall off.

It will stick, but it will also slide right off if you let the gingerbread house get too warm. Store-bought icing is just not going to harden up enough for this purpose. You really need "Royal Icing". If you can't make that, you might try adding some "meringue powder"--found in the baking aisle--to your store-bought and see if it makes it less likely to melt. But I wouldn't use it at all.

it will stick but the question is not will it harden, it won't! But will it support the walls and stuff you are trying to stick together. Sometimes it will and sometimes it won't! you just have to try!