I'm a bit confused when I use the contracted form of present perfect.
Do you write like this?
My house's just been built.
Or you write like this:
My house has just been built.
Which one is correct? Are there any rules for this?
Unless there is another reason to do so (such as clues from the discourse within which your sentence is part of), a reader will interpret the sentence to have been written in standard English (SE). And in SE, both ways of writing the present perfect are acceptable. However in formal writing, you may wish to stick to not using contractions, especially when indicating the present perfect. On the other hand, in informal English the contracted form might be the most natural way to express the present perfect and so it might be the expected form–especially if the intention is to represent or mimic spoken English.