The general process can be summarized as consisting of the following steps.
1. Understand your local rules and make a plan
2. Get the appropriate permits
3. Get quotes and contracts from any subcontractors
4. Order materials (don't forget beer)
5. Begin construction. Getting periodic inspections as required.
6. Get more materials
7. Continue construction
8. Curse your incompetence
9. Get more materials
10. Repeat steps 7-9 ad nauseam
DISCLAIMER: While this Instructable details my experiences building a garage, your mileage may vary. Use your brain, at your own risk.
Step 1: I love it when a plan comes together!
So step 1 is simply this: do the legwork and get a plan together. Easier said than done.
Key areas to consider:
1. How big do you want the garage to be?
2. How big can the garage be (city ordinances!?!)?
3. Where and how many doors and windows?
4. What type of roof?
5. What parts are you going to subcontract?
The plan will depend on the rules in your local municipality. Since I undertook this project under the rules of a major metropolis, my example will be on the more restrictive end of the spectrum. If you live in the sticks, then you can probably build as big and awesome a garage as you like. Not me. :( So from this point forward I will be presenting the garage-building process from the point of view of a homeowner in the city of Minneapolis, which should transfer in large part to any city in the US of A.
The first thing to do is visit your city's website to learn about the permit and building plan process as well as any special restrictions in your area. Click here to go to the Minneapolis permit page.
Take the time to talk with your neighbors as well to give them a heads up on your plans for dominating the landscape with your new garage. If they don't like it then at least they can get used to the idea while you get underway. If you live in a neighborhood controlled by a homeowners association, you may need to talk to them as well. They really know how to put the ass in association. In general, as long as you do not require a "variance" or exception from city rules on such things as garage height, placement, and so forth you can build regardless of objections from neighbors.
In Minneapolis, we have alleys behind the houses in a lot of neighborhoods and very deep narrow building lots. As a result I didn't have room to expand the existing attached one-car garage. So I decided on building a detached two-car off of the alley in the backyard. The key municipal codes of interest were the required distances that must be maintained between the new structure and the property lines, adjacent structures, the alley right of way, and other urban features. Click here to read the relavant document (PDF).
You will want to draw up a sketch of your lot and your neighbors' lots so that you can get an idea of how things will fit in your yard in relation to the lot lines and other buildings. Get out a tape measure and a friend and take a walk around the yard to get accurate dimensions for the sketch. You also need to locate the metal stakes that mark the corners of your lot. These are often buried a few inches underground and are set 1 foot in from the actual lines. If you can't find the markers on your lot corners, walk around and find your neighbor's. It is permissible to use theirs as a reference point if you know your lot dimensions. I located my neighbor's corner marker two doors down which was very lucky. If you can't find these markers, you will have to commission an official survey ($$$) to locate them in order to draw up the site plan sketch. This sketch is required by the city in securing a permit, you will need to show this sketch and get the plan approved before a building permit will be issued. See my sketches below. The city of Minneapolis requires a top view building site plan with relevant dimensions as well as a series of detail and elevation drawings of the building itself. As you can tell the level of artistry involved does not need to be high.
When making the drawings, be sure to use the wonderous series of tubes we call the Internets to check the city webpage for property line and lot size information as well as using your favorite satellite imagery site to get info on the placement of buildings in your immediate vicinity . While a 3D model is not required by the city, I found Google's SketchUp to be a useful tool for visualizing how the garage was going to look in relation to the rest of the house, trees, neighbors, etc. Download it here. A sample shot of my model is below.
Once you have a set of drawings to your liking you can take some time and head down to the Minnesota Development Review offices at 250 S. 4th St., Room 300, Minneapolis MN. As a first-timer this can be intimidating, but even though this bureaucratic organ qualifies as part of "The Machine" the people there are there to help you out. If you read and understand the rules, bring in a good site plan and drawings, they will happily inform you of any problems, give you time to correct them, and then take your money with a smile. For reference, our 440 square foot detached garage cost $300 for a building permit. I also had to lop off 2 feet of the width since the city of Minneapolis allows a maximum of 676 square feet of accessory building. My existing 1-car attached counted towards that total, a fact I had overlooked. On your way out of the review office, be sure to get a parking token. With the new permit in hand, I was ready to begin purchasing materials, locating subcontractors, and other details.
1. Communication with the building permit office and your neighbors is helpful and important.
2. Take the time to know the city rules.
3. Take measurements of your lot and draw up your site plan on your computer. Experiments here are easier than moving foundations later.
4. Get your plan approved by the city and get your permit.