Interior design contractor breach of contract

Hi. I need your help. I seek the services of an interior designer/architect back in march to do the renovation of my house. Due to delay in permits the construction started on May 2, 2012 but the agreement was entered in March. As stated in the written contract/ agreement the renovation will be for maximum of 60 working days. We also signed a bill of materials for the renovation. May question is what case can i file against him since the construction took 3 months and 3 weeks (15 days over due) and he did not follow the bill of materials agreed. Like he indicated that plywood will be used but he used plyboard. Then he indicated solid mahoganny wood for the furniture but he used cheap wood mix with plywood instead. He also indicated that he will be providing competent persons but the outcome of the renovation is of low quality. I almost lost my job because i was not accepting projects since i was monitoring the construction. Also, do i have a right not to accept the furnitures because it is not what has been agreed and request for a full refund instead? Thank you. Really need your help as i spent a lot already on this renovation project and the contractor is not fulfilling what is written in the agreement.