I would like to add a second story to my garage for a hobby room. The problem, of course is whether the foundation is sufficient for it.
The garage is 50 years old and was built as a grain bin with 10 foot tall 2X6 walls and measures 26′ by 36′. The foundation was a monolithic footing and pad. It appears to be below frost line and built to the width standards of the day, about 10″ to 12″. I can only assume that the rebar is tied into the pad and footing. There are no cracks other than hairlines. The same standards were used to build my two story house that is attached.
The house has not settled, although the footing width does not meet today’s standards of 16 to 20 inches. I will be removing the garage trusses and asphalt roof, adding I-joists ( with girder support in the center), then a four foot kneewall, and then installing new trusses (perpendicular to the floor joists) and fiberglass shingles to form a 26′ by 36′ room with a sloping wall up to an 8′ tall ceiling.
My question: There are no building inspectors to deal with here in rural Iowa, so should I proceed on the assumption that the two story house built on the same basic foundation is holding up well? The only added weight to the existing garage would be the floor joists, the knee wall, and the live load and it would be a very nice addition compared to other alternatives.
TIA
Replies
Just a thought to throw out, since I'm the unofficial resident "truss guy".
I absolutely can't stand posts in garages. So I always look for ways to eliminate them.
Using attic trusses would give you a smaller upstairs room, but would simplify framing and eliminate the need for posts.
Clear span floor trusses would also work, but would have to be fairly deep.
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No posts. I plan to support the middle with steel that is supported at the sidewalls.
I will check into attack trusses also.
I wanted to get a feel for whether this was a bad idea before I pay someone to engineer the structure for me. I greatly appreciate your help.
Do you know anything about what the soil is like that the garage is in? I'd tend to agree that if the house has stood without problems, then the new 2-story should be okay.
I'm not sure what the soil will hold here. All garages I am familiar with have trenched footings with the floor poured at the same time. My addition built 7 years ago was spec'd for 16 inch footings, 8" poured basement walls and 10' ceilings and lots of live and dead load. I know I'm taking a chance, but I am confident that this system has worked locally for two story structures. I was hoping to catch a resounding NO or YES from those who read my post before I spend the bucks on someone to spec the building. Thanks for your input.
You're welcome. Looks like your structure and those like it have a proven "track record" so that's good. Much better than you being the first to try it kind of thing.
You use the word assume more often than i like for a problem of this sort.
Without seeing some evidence of it, I would never assume that rebar was used. Bosch makwes a metal finder specifically for finding rebar in crete for under a hundred bucks.
To your advantae, If the roof currently loads onto the same walls that support the joists, then by switching directions for the new trusses, you change the laod to the alternate walls with the result that the load on the original load bearing walls is similar or possibly less, while the flanking walls that previously had little load now take on the roof load.
So, if this and if that and if something else - yeah, you're fine to go, assuming of course, that I presumed everything just right.
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I'll check on the rebar. I didn't think to verify that. The assumption was that since this building was once used to store a large volume of grain, the floor was well reinforced, since that was the way it was done back then, according to the old timers.
When I added a second story to my house, the engineer looked at my footings and said "if you are anywhere close to modern standards you will be fine". And he's ultra conservative.
I hope you are planning on using steel to clear span that garage area so you don't have posts to bump your car doors into.
MERC.
Yup, I-beam across the middle with the ends supported at the sidewalls. I will tear up the floor and run some footings under the I-beam supports, since they will be concentrated loads.