capital gains

We are about to have approved a second dwelling on a large block of land. We would like to sell the house, land and permit with an anticipated capital gain of 40-50,000. This property is in a company name but not trust.
My accountant tells me, even if the profits are re invested straight away, we cannot get roll over capital gains tax relief on property, ie we have to pay capital gains tax.
We hope to use the money to build and hold a new home on another large land with existing home, which we own.
Has anyone had a similar experience and is there a way around the cap.gains tax issue?
Regina