There are going to be several channels open to you. But a few below;
Facebook
Whilst I understand you are looking for commercial work and not domestic, it's worth remembering that you are still ultimately dealing with individual decision-makers. Facebook can be a great platform to target B2B decision-makers, and is cost-effective.
i.e target people within a certain location, who have certain job titles.
Google Ads
Again, it's always going to be tricky to ensure 100% that your ads don't appear in front of domestic customers, however, with the right messaging you can try to ensure that the users who click (and cost you money) are business owners or decision-makers.
You will struggle to find a more effective method of putting your services in front of people, at the exact point they are searching.
There isn't a single answer to your question, but I would advise a methodical approach to setting up your campaigns so that from the second it launches you are gathering data about what works, and what doesn't. You will likely offer many types of joinery services, perhaps covering everything from roofing to bespoke furniture.....so whatever your services are, the campaign needs structuring within to target the right people. Over time proper analysis of the data will allow you to reduce your cost per enquiry, and improve conversion rates.
I just had a quick google of your brand name, and your Google Ads were appearing. Im several hundred miles from you, and you don't have any site links, or call out extensions on your ads... which means they are unlikely to convert very well, and your probably spending a decent portion of your budget displaying Ads to people outside your working area. Google Ads just wont work unless you have your structure, and the Ads nailed (excuse the pun).
Feel free to drop me a msg if you would like assistance
