Critique of initial idea for a garage apartment

   / Critique of initial idea for a garage apartment #1  

TheLorax

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johnDeere
I would like to build a small garage and have a modest living space above it. My idea is for a 24x16 garage, and has 16 foot walls, and an open ceiling, maybe with a dormer window or two.

My idea would be to do a pole barn type foundation using 20 foot posts 4 feet deep in cement. In checking prices on 6x6 pressure treated wood, I had the idea of maybe using 4x4 (true 4 inch) steel square tubing, and found that the steel is about the same price as the PT. The steel would be straighter for such a long post and at 1/8 inch thickness it would be stronger than the wood.

Are there pitfalls to this idea? Aside from the question of whether to use steel or wood is this design reasonably doable?
 
   / Critique of initial idea for a garage apartment #2  
Certainly it is doable. A couple of complications are that the 4x4 steel dimension will require some shimming to transition to wood structure. You may need a lot drilling and bolting to attach the framing. Be sure you have good sealing and corrosion protection where bare steel transitions to concrete embedment. Steel covered by concrete is corrosion protected by the concrete chemistry but, because the concrete will tend to attract some moisture, you can get corrosion problems at the transition.

Finally, are you in a code required area? Some codes have restrictions on living space adjacent to garage space. As a minimum you will need fire barriers which will include code approved covering over the steel. Also, since your construction is probably not directly covered by building codes, a stickler of an inspector would probably require an engineers stamp on the plans.
 
   / Critique of initial idea for a garage apartment
  • Thread Starter
#3  
I'm certain I need an engineer, but my friend uses one that is good and very reasonable.

I thought it would be easiest to buy standard metal brackets for wood and weld them to the steel tube.

I would cap each end of the tube and apply some kind of rust prevention (like raw linseed oil) to the length going in the cement.
 
   / Critique of initial idea for a garage apartment #4  
I am not sure if the rust preventive is going to hold up very long in contact with the concrete.

Not to be a naysayer, but are you covered by any building codes where you want to build this apartment? I am asking because IRC is going to require a fire break between a garage (5/8 sheetrock) and the living space . IRC also prohibits an opening from a garage directly into a bedroom. Also, when you mention using steel tubing and brackets welded to them as supports, there is a good chance your inspecture will require stamped engineering drawings.
 
   / Critique of initial idea for a garage apartment #5  
Check the codes, read the IRC if you aren't sure. Do not weld the brackets but if you must, don't continously weld them. Why don't you laminate the posts like the Morton buildings do? What are you doing for stairs? You do realize that with true 16' posts above ground that you aren't going to get 8' ceilings and that will require cutting alot of drywall.

I really like the idea of an apartment over the garage but you are going to open a can of worms with the project if you don't know what you are getting into.
 
   / Critique of initial idea for a garage apartment #6  
My BIL had a 40x60x16' sidewall approx. high pole shed built. Then in 1/4 of if he made an apartment type dwelling, upper and lower. The lower was living and kitchen, and the upper were bedrooms. This is in the country so I really doubt he had any engineering company design anything, he just got it done.

He used 2x6 walls to hold the upper story and for insulation value. I am sure he used heavy drywall for fire retardation and had doors in the front and back. No dormers but would have been nice for light.
 
   / Critique of initial idea for a garage apartment #7  
I'm a wood king of guy. I recognize that steel has certain advantages over wood, but when mixing them together, you have to take things into consideration that you don't if you just stick with wood.

In every building application, it is always best to stack your wood so each board is resting on top of another board on down to the foundation. If you are going to go with a pole style foundation, the floor for the second story should be resting on top of the posts. Not knowing how much height you need in the bottom garage, I would suggest using 12 foot posts. Then run a header along the length of the posts, then run your floor joists on top of the header spanning the width of your garage. Probably 2x12's every 24 inches with 3/4 tongue and groove plywood for the sub floor. Then I would build up the second floor using standard 2x4 studs.
 
   / Critique of initial idea for a garage apartment #8  
Permit or no permit? If permitted, watch your daylight requirements for the rooms. A single dormer might not provide enough light and air to meet code. Also, the habitable space would need to be separated from the garage. This being an overhead application, you'll need to check the code to see what is required. The system is more complex than just two layers of rock. To be effective it needs to be constructed correctly. You'll also need to watch your fire blocking at the outside walls. Then there is the stair. The stair requirements are well defined by code and must be complied with. The inspector will probably want the stair to be fire rated as well. If you have only one stair, then a second means of egress needs to be provided from the second floor. You can exit out a window, but need to be able to step on something like a balcony or roof. The window also needs to be of a certain size to exit through. Not so much of a problem with casements, but it's tough to get the required vertical height with double hungs. Because this is a habitable space, the footings will need to extend below frost. The community may also want to have sanitary, water and electrical installed. Finally, if the apartment has a kitchen (generally defined as having a stove or the space to put a stove in), then it might be considered multifamily. This could play into zoning and what the community allows.
 
   / Critique of initial idea for a garage apartment #9  
I built my house with heavy steel H posts bolted down to piers. There are 24 piers, most of which are 3' X 3' that go into the ground about another 3'. Then grade beam walls were poured between the piers to allow for the slight slope and to set the perimeter PT plates. These piers are on 12' centers and support posts and trusses that span the width of the house with a 4 and 12 conventional pitch. An entire steel skeleton was built and then framed with wood. The roof went on first, with 2X10 wood perlins running perpendicular to steel roof trusses. Then the walls were all framed underneath it. The transition from steel to wood is simple. Just bolt the wood stud to the frame and go from there, or set horizontal wood blocking into clips welded to the posts and then transition to vertical studs done in a conventional manner that stand on a PT sill plate. My structure is 60 X 60 with a 900 sq ft garage. and a 700 sq ft covered porch. Since the walls don't support the roof, even though they are tied to it, I had complete freedom to do any floor plan I wanted and make changes as we went along. Since I like steel I went ahead and built an oversized glass and steel front door and opening. The ceilings are mostly at 10' except the Great Room that is at 14'. After the roof was on I did all the underground plumbing and electrical, then poured an 8" slab with full radiant heating including the garage. Heating is done with a large thermal solar system and 650 gallons of stored hot water. Backup heating, if required is done with an oil fired boiler.

This place was so unconventional that the building inspectors marveled and gave me no trouble at all. Of course, the plans were signed by an engineer and certified by the steel company, but I went way beyond the original design by eliminating all diagonal bracing and instead sheeted the whole house and roof. This made it even stronger and allowed windows wherever I wanted.

If you want a rigid long lasting structure with lots of open space and freedom of interior design, go with steel. There are also lots of tricks to make a rather conventional rectangular building look more interesting from the outside. Ways to get away from the boxiness, such as overhangs, porches, decks, window seats and siding treatments. I did all of those. My land slopes about 5' diagonally across the house footprint, so I can drive right into the garage in back, but have a porch about 5' high in front to take advantage of the view.

I think steel on concrete footings is a great way to build. Corrosion was mentioned as a possible problem, but we've had none of that. Steel gets along just fine with concrete.
 
   / Critique of initial idea for a garage apartment #10  
Cord makes some good points about how to have habitable space in a garage. But you can satisfy the codes with design tricks that make it work. Build a good rapore with the inspector and he'll be on your side with useful suggestions and some leniency. Issues like fire separations, bedroom access from the garage, etc., can all be worked out. That's why you need an engineer to help present all of that to your building department for the permit, if you plan to get one.

It's really a matter of degree. You might want a simple apartment upstairs, or a whole house above the garage or a garage in the house, under the same roof. Really, all the same thing, just a matter of degree. Around here a lot of my neighbors have airplanes and runway access. They mostly like to put a "convenience apartment" in the hangar somehow. Then maybe live there as they build the main house, live there permanently or rent it out.

We have a guest house that we finished and lived in while building the main house. I never put in a permanent stove to avoid it being called a house. I just set a camp stove in the kitchen until we moved. Now that there will be no more inspections, I might put one in.

If you're touchy about inspectors and assessors, you can finish things out after you get your final. It's VERY common and as long as you follow building codes and common sense safety, it's fine.
 

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