You have 3 options if they wont budge. 1. Leave the garage off and add it on as an addition later Go ahead and have them put the beam in now so you just have to knock out the wall under it. This will likely cost you 10-15k later on if you have a contractor do it. 2. Have them build it they way they want and then have the roof ripped off after closing and put in new trusses, you can go with a coffer or scissor truss. Likely would be 5-8k to have it done. 3. Have them build it the way you want and pay an engineer to come out and draw up plans to modify the trusses they install to give you the head room you want. This would likely cost 5k+ Looks like you have a hip roof. Scissor and coffer trusses might not be useble except for the middle section so it might not even give you enough room even with the change depending on how deep the garage is. For an example of how cheap it would be to change now, I built my 40x50 detached garage with the house last year. To go from flat normal trusses 12' ceiling height to coffer trusses (outter 10' of ceiling is 12' high then bumps up to 16' high in the center 20x30 section) cost for the change from the builder was $237. The difference in truss cost to the builder on yours is likely less than 100 bucks, they are just being lazy.