As a very general guide if the joists are only 2x4s don t plan on storing much in the attic other than very lightweight items.
Boxes in attic.
Heat can damage things such as photographs and wood.
Whether a birds or moths in the attic a raccoon in the garage or mice in the basement critters aren t concerned with taking care of your belongings as a general rule of thumb nothing in your attic.
Think empty boxes and suitcases.
Those cardboard boxes stacked up in your attic could become a veritable buffet for mice and bugs if you re not careful.
If they are 2x6 you can probably get away with some boxes filled with relatively light stuff.
Joists that are 2x8 or larger can likely support more weight.
Pests are attracted to the cardboard and to the glue used in construction of the box says santoro.
Cardboard boxes will deteriorate due to heat and water and animals and bugs will snack on them in the meantime.
In the basement store everything in clear plastic bins labeled and not packed too heavily.
You want to make sure you can lift the boxes easily and if they happen to tumble over they don t hurt anyone.