I think too many people ask several contractors to come over and give them a quote then kinda of say what they want or sketch it out on note paper.
The problem with that is it's hard to get accurate bids, I think what should be done is hire an architect or draftsman to draw up a set of plans and give you ideas of what can be done with a space, they can also make suggestion on materiel to use, some can get you several contractors to obtain bids.
I found a great company
Blue Water Drafting they came out to the house we talked for about 30 minutes and bounced ideas around, they are sending me a preliminary drawing to see if we are happy or to make additional changes.
When finished, I can hand out those plans for competitive bids, the costs depending on the complexity of the work but about $500 - $1000, including the engineers stamp required for permits.
Not a lot money and Drew there is great to work with.
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