I have a client who operates his own masonry business. He has no office or shop. He uses a room in his house as an office (filing, paperwork etc) and uses his garage solely for working on preparing for jobs, storing and repairing equipment etc. My question is this, I know he can write off the home office portion of his taxes, mortgage interest, heat etc, can he also write off the workshop in a similar fashion? I have never come across this situation before.