Roughing in a "granny flat" / ADU cost...

[lukeiam]

I have an older 1920s house with a detached garage, which is very well built, but small. My town -- Easthampton, MA -- has loosened restrictions on accessory dwellings because we have a pretty bad shortage of available housing. My dream is to convert this small garage to a granny flat in anticipation of my parent needing it. The building, roofing, all the carpentry, I can do...and everything after a plumbing rough-in, but I don't know enough about a plumbing job at this level.

I'd have to tear out the old foundation of the garage and re-pour something. This is the opportunity to rough in the plumbing. But it's only 500 square feet. The garage is like 20 feet to the main house. Obviously I need to trench this to the main house -- which I would do -- and my hope would be run to hot water from the hot water heater in the house (guessing this might not be doable)...and the sewage drain has to connect to the main house and can't be a separate line. So, I'm 1 talking sink - toilet - shower.

My hope would be to GC this, do what I can, and piece together the work wherever possible with friends in the trades. But if I'm trenching and prepping the pad, wouldn't this be reasonable price-wise? I heard some wild estimations over on the garage renovation forum...doesn't seem right. Thanks for reading!

 

[jkl 2455]

I suggest you install a point of use water heater, be it electric or gas, instead of tapping into your main houses water heater.
That way you'll need just 1 water line supplying your ADU...

Insofar as sewage hookup, the main factor would be the condition and size of your existing run to the street.

 

[lukeiam]

I suggest you install a point of use water heater, be it electric or gas, instead of tapping into your main houses water heater.
That way you'll need just 1 water line supplying your ADU...

Insofar as sewage hookup, the main factor would be the condition and size of your existing run to the street.

That's a great point...and it could be small given their needs. The existing sewage line is intact and the actual shi*t pipe in the house to the main line was replaced with PVC. So that's a plus...