It will not be enought if the insurer thinks the loss may be your fault as opposed to the contractors, e.g. if the facilities or the equipment are the problem. Also, if there is an accident, the first person to get sued is the person who's name is on the title to the premises. therefore you should have appropriate public liability insurance.
You should also have employer's liability insirance if anybody employed by you (including yourself) will be on the premises.
You may also want to get cover for damage caused to cars or equipment through negligence. Public liability may or may not cover this.
Your insurance costs may be reduced if certain indemnities in the nature of indemnities to principals are included in your contractors' insurance.
At the end of the day, you need advice from a good insurance broker!