The cost of building an addition, including simply enclosing a garage, in Austin is between $70 to $120 per Square Foot. This all depends on the contractor you hire, the finish out options, and other items such as electrical.
The cost to install a bathroom can be upwards to $12,000 for a simple bathroom. Depending on the size of the bathroom and finish out for a very simple bath space, it would be between $5,000 to $8,000.
Most homes in the Crestview area have concrete foundations, and could be a Post-Tensioned Concrete Foundation. There is additional cost for cutting into the concrete to reach and connect with the existing plumbing.
Since a good portion of the homes in Crestview have enclosed garages, then you wouldn't loose value and would be able to compete when you decide to sell your home. However, Crestview is an area experiencing some growth due to its ease of access, so it might be worthwhile to keep the single garage (as garage spaces are desired by most buyers) and invest the money into an addition. It may be more cost affective to add an addition to your attic area or off the back of the house, especially if you want an edge when you ever decide to sell the house.
A good contractor or Architect can assist you in determining the best approach. I encourage you to make sure you hire a good contractor.
I hope this information has helped.
Shannon T. Schmitz,
Representing Distinctive Properties
A typical "builder" quality home in Austin costs around $80 / sqft. This would represent, for example, a new subdivision home without upgrades. Due to the lack of economies of scale, a remodel will always cost more for the same qualify of work. So as a ballpark, figure $30,000.
If your home is on a concrete slab foundation, adding plumbing can be expensive if, for example, drain lines are not easily accessible from the garage - it can involve jack-hammering up concrete to tie in. On the other hand, if you already have plumbing in the walls near the garage, it isn't so hard (I moved a W/D to my garage without touching the foundation because there was already a drain line and water supply 10 feet away. Since you have a utility room adjacent, you may not have to dig in the foundation - for drain lines it all depends on whether the plumber can achieve the proper slope so the water drains properly.
If your house is built on piers and beams, it is usually much easier since the plumber can get under the house and access all the plumbing from there - no jack-hammer needed.
You should be able to complete the remodel in a month, give or take, once you have decided what you want to do. Making changes after the work has begun will draw it out longer.
Good luck - contact me if you would like more information!