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Convert patio to shop?

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pbesong

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I have a 12' x 25' patio in the back of my house that is poured concrete (about 4" or so). Is that enough of a foundation to put a roof over it to connect it to the back of my garage and turn it into a wood shop? I need a place where I can leave a mess when I'm working. Right now I have to back the cars out of the 2 car garage so they don't get covered with sawdust, then make sure i have enough time to sweep up when I'm done working that day. Makes it tougher during winter. I was thinking if I enclosed the patio behind the garage I might be able to make a nice space that I can put my power tools in and have heat there too in the winter. Would the 4" concrete slab heave up at all in the extreme cold here in PA? Not sure if it would be possible to tie into the roof if that's the case.
 

nealtw

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I have a 12' x 25' patio in the back of my house that is poured concrete (about 4" or so). Is that enough of a foundation to put a roof over it to connect it to the back of my garage and turn it into a wood shop? I need a place where I can leave a mess when I'm working. Right now I have to back the cars out of the 2 car garage so they don't get covered with sawdust, then make sure i have enough time to sweep up when I'm done working that day. Makes it tougher during winter. I was thinking if I enclosed the patio behind the garage I might be able to make a nice space that I can put my power tools in and have heat there too in the winter. Would the 4" concrete slab heave up at all in the extreme cold here in PA? Not sure if it would be possible to tie into the roof if that's the case.
A deep foundation on a footing is to spread the load below frost depth.
What you describe might be fine for a shed but if you are tying into the house with a shed roof, any movement cause by frost would not be good.
 

pbesong

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yeah i just don't know if it would raise up or not, so I was wondering if it were possible. I'd hate to tear out the concrete to put in new footings. I probably wouldn't do it at all if that were the case.
 

nealtw

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yeah i just don't know if it would raise up or not, so I was wondering if it were possible. I'd hate to tear out the concrete to put in new footings. I probably wouldn't do it at all if that were the case.
You could cut a hole and dig in a post support and build a post and beam style with floating walls.

That said I built a cover over the basement door which is entrance into my suite. One post sits on a rock wall the other has a saddle in a 3" thick sidewalk.:rofl::rofl:
 

bud16415

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Build a pole barn construction slightly larger than your slab. Go down 4 foot with your poles. If the slab isn’t connected to your building it can move if it wants without disturbing the building. If you want to heat it you can insulate the pole barn construction. I would fill the gap in the floor around the edge with crushed stone.
 

pbesong

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thanks. that might be my best option. i put a deck around our pool and the furthest I could get down was 30" due to heavy clay underneath. that was using a power auger too! I'm assuming it would be the same with a pole construction as it would be near the pool deck. PA calls for 36", but I only got down 30-32". The building inspector was understanding, however, and okay'd the deck.
 

nealtw

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There is video somewhere of a guy digging down to the clay layer, using a electric drill and a shop vac to dig the hole.:hide:

You can argue that the water never gets to that depth but once you dig a hole the water will have access.

Cheating on the depth is betting on the weather. It is the length of the cold spell the deeper the frost.:)
 

pbesong

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if the power auger can't get thru it, i doubt water will either.
 

nealtw

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if the power auger can't get thru it, i doubt water will either.
Right but the water will get to the soil just above your clay and the post or pier is at that depth.

I would not spend a lot of time worrying about it.
If in fact in a bad winter it froze to 36" and your post is at 32 inches. How much of a lift will 4 inches if ice give you. And then how much will that change the angle of the roof against the house. Then would that be enough to actually pull nails to the point where the roof could fail.

Just found where, water expands 10% when it freezes. So if you had 4" of water below the post it would rise about 1/2" in one year. It may or may not go back down.

But if you shed is 10 ft wide, the angle of the roof changes by 1/2" /10ft.

So if you had a roof built at a 6/12 pitch at worst it would be 6.2/12.

So a rafter cut at 6/12 leaning flush against the house and if the outside wall lifted 1/2" the bottom of the rafter would pull away from the house no more than 1/10"
 
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