To get up into the attic, a lot of homes have a pull-down ladder so as to save space in their home. It makes good sense when it comes to space savings, but it does introduce a few more issues for you as a homeowner. Climbing up a ladder is risky at the best of times, but if you are doing so carrying an item, you can easily get hurt, and there is a possibility that you break the ladder as well.
Since the ladder usually has a hinge to allow for folding it as well, this creates a weak point that could break when overloaded.
So, what should you do to prevent this from becoming an issue? One thing to do is to get help when moving things into the attic. If you have someone hand you items while you are in a position to put them in the attic, it will lessen the risk for you.
You should also make sure that the ladder is firmly attached with screws of sufficient length since the ladder only is as strong as the wood it is attached to.