How do I form a 'si' clause in French?

In English, a sentence like 'If I were rich, I would buy a house.' is an example of an 'if' clause. It is used to describe a hypothetical situation; something that would happen if a certain condition is fulfilled. In French, this is structured using the imperfect tense after 'si' and the conditional for the second part of the sentence ('Si' + imperfect, followed by conditional). A rule to remember this is "les 'si' n'aiment pas les '-rais'". In other words, 'si' is not followed by the conditional. 'Si j'étais riche, j'achèterais une maison.' is an example of a typical 'si' clause in French. There is one exception (as always!) to the rule that 'si' cannot be followed by the conditional, but not in the same context as this hypothetical 'si' clause. If the sentence exists in the past, i.e. the action has already happened, 'si' can be followed by the conditional. Note the following example; 'I asked him if he would come / Je lui ai demandé s'il viendrait'. This is not the typical 'si' clause which expresses what would happen in the event of a certain situation being realised, but it is useful to know the different uses of the conditional with 'si'.