Causative have is formed by the subject followed by the verb have conjugated in any tense, then the object, and finally the past participle of the main verb. Therefore, the pattern is:
[Subj + have + object + pp]
1) We use a causative construction when arranging for someone to do something for us. In this type of sentences the subject is not the doer of the action, but the one that orders the action on his or her benefit; in other words, it's the one that causes the action.
Look at the following set of examples:
(A) They repaired their car. (active construction)
(B) They had their car repaired. (causative construction)
(C) I cut my hair yesterday. (active construction)
(D) I had my hair cut yesterday. (causative construction)
In instances A and C, the subjects carry out the action expressed by the verbs, that's to say, they repaired their car themselves and I cut my hair myself. However, in sentences B and D, the subjects do not do anything but order someone else to carry out the actions, namely they arranged for the mechanic to repair the car and I arranged for the hairdresser to cut myself.
I am having my room cleaned (I'm not cleaning it myself, I'm making someone else clean it)
My parents have had their house painted (they haven't painted it themselves, they called the painters)
John is going to have his office redecorated (he isn't going to do it, he pays a specialist to do it)
We also use causative have when someone does something to us:
Bill is going to have his money stolen.
I had my computer broken by my little brother.
Like in the passive voice, the agent must be elided when obvious, not necessary or unimportant. Look at these examples of the three sorts of structures, active, passive and causative.
Active: I will build my new house (I'll make it myself, I'm not going to hire anyone to build it)
Passive: My new house will be built by me (same meaning as above)
Causative: I will have my new house built (I won't build it myself, I paid for the builders to make it)
You see, in the passive sentence the by-phrase is present because it's not common that one builds their own house, so the agent is not obvious, thus necessary. However, in the causative example the agent is omitted because it's normal that builders build buildings, so it is an obvious, unnecessary agent.
Get Something Done
Get is possible instead of have, usually in informal spoken English. The pattern is equal to the have one:
[Subj + get + object + pp]
You'll get your hair styled next weekend
I'm going to get my car fixed tomorrow
She got her house painted last year
I get my nails done once a week
Have Someone Do Something
Especially in American English, we can use this construction to talk about giving instructions or orders. In British English make or send is preferred instead of have. The pattern is:
[Subj + have + indirect obj + infinitive + direct obj]
I had my assistant type the report (= in BrE, I sent my assistant type the report)
I'll have my lawyer look into it (= in BrE, I'll make my lawyer look into it)
Exercise1, Exercise2, Exercise3, Exercise4.