We have a small Cape Cod (built 1946) with no basement or garage/workshop. The first-floor BR (roughly 15 x 10) is on one corner, and has a 1/2 bath/laundry room (roughly 8 x 10) adjacent on the other corner. The bath/laundry has a toilet, bathroom-style sink, full size washer and dryer, full size electric hot water heater (50 gal) and the main waste stack that comes from the upstairs full bath (also two bedrooms upstairs).

We were thinking of taking the wall off and bumping out about 5 feet to 1) gain about another 2-3 feet in the galley kitchen (see red line in existing bath), 2) make the first floor BR bigger or at a minimum re-orient it, and 3) make separate bathroom (with stand-up shower) and utility room (washer/dryer, utility sink, HW heater).

Then build a separate garage/shop that would not have any plumbing, but would have electricity and climate control. It could be built such that it might become a real separate residence (think a one BR or a studio apt, so it would get dry plumbed but no actual kitchen or bath installed) or it could be a basic "garage" that would be insulated/sealed so that climate control would work.

OR... build a bigger addition (maybe another 10 feet out) to include a workshop/garage/that is integral with the house.

Our main question at this point concerns costs. Will a bigger addition always beat the cost of small addition plus a stand alone structure? For the sake of argument, let's say that the stand alone would have siding/windows/roof to match the house.

I know one non-cost drawback: dust/noise from my activities in that "uncivilized" space.

I haven't investigated the codes.

Thoughts? Questions? Thanks!

Mark