Apart from…: 除了……以外
介词 / prepositions
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
除了……以外 (以外 is optional) has two meanings, depending on the adverb that follows:
1. Exclusion, "except": 除了A，(其他)都… → A is the exception. 除了小王，大家都来了 (everyone came except Xiao Wang).
2. Addition, "besides, in addition to": 除了A，还/也 B → both A and B are true. 除了中文，他还会说法语 (besides Chinese, he also speaks French).
So it's 都 or 还/也 in the second half that decides the meaning: watch for it!
Examples
除了厨房以外，别的房间都很大。
Chúle chúfáng yǐwài, bié de fángjiān dōu hěn dà.Apart from the kitchen, all the other rooms are big.
除了房租，我还要付水电费。
Chúle fángzū, wǒ hái yào fù shuǐdiànfèi.Besides the rent, I also have to pay for water and electricity.
除了周末，他每天都加班。
Chúle zhōumò, tā měi tiān dōu jiābān.He works overtime every day except weekends.
除了我以外，我的同事也搬家了。
Chúle wǒ yǐwài, wǒ de tóngshì yě bānjiā le.Besides me, my colleague also moved house.
Common mistakes
✗ 除了他，我们还没去。 → confusing: to exclude, use 都. ✓ 除了他，我们都去了。
✗ Using both 都 and 还 after 除了: pick one meaning.