Pouring New Footings???

frostbitten1

I have a customer up here in central Michigan who wants me to stack a second story on her wood framed house. No problem except the foundation is about 18" deep and I am not sure if it will support a second story.
The home is about 30 years old and is in very good shape. It sets on a 3 block crawl space very near the river but up on a bank so unless we get a large thaw (not beyond the realm of possibility) water will not be much of a problem. The house is pretty small 24x32' and she wants a chalet style 12/12 pitch stacked on top to dress the little place up and give her more living spave on this cramped little lot.
Short of enlisting the services of a structural engineer, what are your thoughts?? Any experience with pouring footings under a structure? I would be very interested in any insights anyone could provide.

firemike

Footing depth here in Michigan is 42", so you are losing the battle right from the start. I would definetly hire an engineer, as you will be liable for EVERYTHING you do from here on out if you try to take shortcuts around doing the right thing.

I have looked at doing 2nd story additions like yours, and the very first thing I do is dig down to the footing, verify it's size, soil conditions, and have an engineer certify that it will or will not support the intended load. There is too much at stake to guess, and with an existing 18" deep footing, she's lucky that it hasn't failed.... yet anyway. She might be high enough and dry enough that there isn't a lot of ground movement during the freeze/thaw.

Instead of adding to what is there, you would be farther ahead to have the structure jacked up, tear out the old footing completely, and install a proper one for the addition.

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Jason Whipple

You might want to ask your customer to consider a finished basement if you need new footings. I think the cost would be far less and it would add the space they need. No siding to do, no tearing off the roof and replacing, and the best part; no working in the rain and snow

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frostbitten1

Jason, the problem there is the close proximity to the river, I think we would have problems with the water table.

cleveman

These guys are onto the solution-lift it up, remove 18" footing, put in proper footing.

The real problem will be finding some skinny-assed guys to dig these footings. I suppose you could figure out how tall a trencher is and get the house up high enough to accomodate the trencher.

The engineering question regarding the footing is, "If I don't want to have 8x16 at the bottom of the trench, what is the alternative"? Maybe the building dept. will let you just pour an 8" wide trench, maybe they'll require 10", who knows before you ask/hire an engineer?

Here we're allowed to just pour 6" up for a slab on grade. This slab on grade could have concrete block walls with a brick veneer. That's a lot of weight. Your framed story and a half wouldn't have nearly that much weight on the footings. After all, we're talking about a glorified garage.

neolitic

She is probably "grandfathered"
on the footings, and it sounds like
story-and-a-half rather than two
story, which should be okay
for existing footings.....BUT
Since the builders cut corners on depth
you really need to excavate,
find out all you can, and get
an engineer to sign off on it.
Like Firemike said, as soon as you touch
it, you've bought all the old mistakes
as well as your own!

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concretemasonry

If you add on, you are increasing the load on the footings. Grandfather clauses are then out he window since you have created a new situation that should be up th code (the worst you can do and still be legal/out of jail).

If you make changes, you will be responsible for all problems.

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kevjob

thats how it is here grandfathered till you add on.

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Tom R

Same here (in Jersey) . . .

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frostbitten1

I appreciate all of your help, I will talk with the building department tomorrow and see what my friendly building official has to say about it and take him over for an inspection. I tried to talk her into a demo and rebuild, but her father built the cabin and she is very attached to it. That being said I am certainly not going to get myself into a situation I am not completely confortable with. Rather lose the project than lose sleep (and hair) over doing it the wrong way.
Thanks fella's

Tom R

Maybe it's an option to build outward instead of upward??

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frostbitten1

Tom, there is no room. This is a lot in a subdivision which has been built up on canals that lead out to a big lake. We have about 9' one way to go on one side and still maintain the township mandated setbacks. There is a garage at the back and the river at the front, all restricting where we can go.

neolitic

You really need to excavate the footing.
Some old timers "cheated" them another
way.
They would dig to frost then fill 'em
with concrete to save block laying.
Instead of 4 courses of block and 8"
of footer, they might pour 24" of
concrete with 2 courses of block.
It's worth checking, high water table
is one reason I've heard for doing that.
Just a thought, if you haven't seen the
bottom of the footer.
Sometimes there are good surprises too.

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