上に: adding benefits or burdens in the same direction
Use 上に to add another evaluation pointing in the same direction. Check accumulated advantages or burdens, connecting forms, and the difference from contrast or action sequence.
Adding an advantage
このかばんは軽い上に、丈夫です。 means that this bag is light and also durable. Both qualities are treated as advantages pointing in the same direction.
By contrast, このかばんは軽い一方で、あまり丈夫ではありません。 presents lightness alongside limited durability. 上に is not the basic expression for this kind of contrast between an advantage and a disadvantage.
Burdens can accumulate too
道に迷った上に、雨も降ってきました。 says that the speaker got lost and, on top of that, it began raining. The expression is not limited to good things; difficulties can accumulate too.
Whether the evaluations point in the same direction depends on context. Rain is not inherently bad, but when someone is lost it can be understood as an added difficulty.
Connecting forms and distinguishing sequence
Verbs and i-adjectives connect in plain forms; na-adjectives use forms such as 便利な上に. A noun can use である上に, as in 彼は専門家である上に、教え方も上手です。, adding teaching skill to his expertise.
内容を確認した上で署名します。 gives the procedure of checking content before signing. 内容が難しい上に説明も短いです。 adds a short explanation to difficult content, so distinguish で from に.
Quick check: Does 家賃が高い上に、駅から遠いです。 explain that distance from the station causes high rent?
Show the answer and why
No. It adds two burdens: high rent and distance from the station. 上に does not express causation in this sentence.