That's probably about right given the work involved in cutting into the slab for new plumbing runs. You didn't mention the length of the pipe runs but that will be a key factor. You can always get additional bids to compare (I always get 3 bids for any project).

Given the overall difficulty and expense of the project as a whole, 5-10% of the project total is darn cheap.

We raised the floor 6 inches above slab to install a kitchen into an area that was the original garage....it evened up the stepping from the old house area to the garage. Worked very well, but the ceiling was only 7'6" but no one ever noticed....we installed cabinets and then a taller soffit/crown trim and it looked great!

Hi Suzzanne11a: I was updating my Pro Listing over the weekend and saw these comments from some time ago. Did you complete your project? There was a few steps down from my dining room into garage so I built a frame over floor and put pluming within the new frame. I am in MA, I cant see where your from, but garage floors here are typically sloped to center and towards door, so if you want a level floor framing level over it is one way to do it, or pouring a pie concrete floor over it to level it. Depending on climate and if a vapor barrier under existing slab, addressing stopping moisture transfer thru slab into new frame or sub floor or selecting appropriate materials that would be compatible with a concrete slab that may or not be transmitting moisture vapor is a consideration, as well as selecting proper insulation for floor. Tom

We did this project on our home when we lived in Stoughton,WI. Later sold the house to our friends and it has been 15 years. No problems at all. We had a kitchen sink on an exterior wall and also a prep sink in the island. Loved that kitchen!

Ok, I must have misunderstood your question? I thought your.post was from 2018 contemplating converting your garage vs 15 yrs ago? Glad your project went well then. Tom

Was browsing this garage topic and had my own questions about the raised flooring for plumbing in garage. Looking into doing the same for a small living space for my mom. How high should the floor be raised and any advise to give me about this type of project please any suggestions well appreciated. Thank you. Have to raise the entire floor so the is not any steps up or down once inside. Garage is 2 car detached from original home. New plumbing in garage is Approx 20 feet from sewer line under main-out in house. How high is sufficient to raise, best barrier on slab, have never seen any rain or moisture get into garage luckily.

I did not see on this thread any mention of what state or climate your in re moisture management of slab which would also raise questions re method and materials to either insulate floor or foundation peremiter. Sounds like your raising framing up to be flush with main home floor? If so that kinda dictates height. Garage floors are not level either way. They slope to center and towards door so a frame minds to be designed with that in mind, for new floor to be levels. if the bottoms of new frame not sitting on new floor, then may need to be sized for span. if hollow block foundation on garage, it may not support new floor.
If your in MA feel free to contact me for design consultation or to bid on job. I do not provide any advice in this type.of a forum and not before viewing the site.

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I accidentally erased post, apologies. I am not in MA, in the north central Texas area. My concern i believe is raising the floor for plumbing to run vs chisel through the concrete. The garage is detached from main dwelling and does need a bit of leveling but none to center just 1-2” lower due south and with several different licensed plumb quotes, 10” will still leave enough height per code. Pros and cons of raising that floor vs digging into slab in your opinion? Thank you for responding, trying to get different perspectives and really would like to keep as much height as possible. Is 10” overkill? Have new bathroom blueprinted to front (closest to main house) to connect. App 20 feet between new bathroom and main dwelling to trench.

I just realized you are hesitant to advise, completely understandable thank you again though for your response, over, lol