Aircon works, windows and vinyl flooring by home owners.
We have quite a few projects where home owners prefer to source out their own suppliers or sub trades. Something which we are quite opened to. However we do not recommend home owners to source all the subtrades by themselves because then there's actually no "boss" for them to listen to except the home owners. This is quite apparent when things go wrong or when there's no one to finish up the mess or tail end portions of the reno.
Not wanting to pin point any sub contractors but there have been many cases where the subtrades do not listen to the main contractor or even the ID and just do the way they want to do. And there are instances where sub contractors make a mess of the flooring or freshly painted walls or even scratch the parquet. Who is to rectify these defects? Then there are cases where walls are "punctured" and went through some electrical wirings. Again this made both the subcon and electrician very angry at each other.
These can be avoided if all the subtrades are under the main contractor. Should any of the trades makes a defect, the main con is liable for the defect and he can bill it back to his own subcon for the mess that he has created.
That being said, what are the subtrades which we are open for home owners to source on their own?
Windows, rubber tiles, Carpentry and aircon.
Although personally i feel air con is a bit of a grey area, and I usually recommend to go with the main contractor where possible so that the electrical, plumbing and air con can run simultaneously together.