I'll have to have the boiler ______ before the weather turns colder.

Have something done
- The causative is used when someone else does something for you.
Example: I've had my hair cut

Form/Structure: 
to have + object + past participle
- The causative is used when someone else does something for you. অর্থাৎ অন্য কেউ যখন আমার হয়ে কাজটি করে দেয় তাকে The causative বলা হয়। 
- এর সাধারণ structure হলো: to have + object + past participle = to have something done.  যেমন:  I need to have my bag repaired. 

Source: BBC Learning English website & Essential Grammar in use by Raymond Murphy