Shed Foundation


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Old 05-11-07, 06:39 AM
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Shed Foundation

Questions about 2 different projects

1) Shed

I'm thinking about building a shed, probably 10 x 10 or less. I know I could use lumber on blocks, but I think I would rather have a concrete floor. I have some experience with sidewalks and curbs. I live in MD, frost line is several feet down. Should I just do a floating slab, or do I need footings? Shed location is not flat, so shed foundation wall will need to be around 10" above yard grade to keep all the shed walls away from the dirt. I was originally planning to install J bolts in the slab before it sets (for attaching the wall base), I but need to revise that plan b/c of the foundation wall height. Should I pour the slab and raised foundation wall as a single pour, or is there a better easier way?

2) Everything in my garage rusts. I suspect moisture may be coming thru the slab. If I do a test and determine that it is, is there any down side to sealing the floor to hold down the moisture? Will sealing the moisture into the slab harm the slab or make it deteriorate?
 
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Old 05-11-07, 09:43 AM
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P.S. Garage floor is 20 years old
 
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Old 05-11-07, 04:02 PM
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Shed= pour it all at once, foundation and floor, since I have no clue as to how deep the foundation for this shed will be, I suggest adding some #5 rebar around the perimeter so the foundation floats with the slab. It is actually not a foundation but more of a retaining wall, if I follow your information correctly.

I think there should be a new rule here where one has to specify their location so frost can be assessed.
 
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Old 05-12-07, 07:18 AM
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Thank you. I have a few more questions.

(Because frost line is 2 to 3' deep, I just want to float the whole floor and foundation.)

To confirm your answer: To do a slab floor and raised foundation wall that will extend above the slab, I should do it as a single pour and should use #5 rebar to support perimeter of slab and foundation wall. How do I run the rebar? As 2 sets of crosshatched rows running all the way across the slab from one side to the other, or just one way like stripes, or just as 4 lengthwise pieces around each perimeter edge? If I run as rows, how far apart? Also how thick should slab be?

I've seen several guides on how to do this. Most said slab should be same depth in center area and perimiter. One said dig a little deeper on perimeter edge to make perimeter deeper. Seems like single depth is best if I'm going to use rebar and want it to float, right?

Lastly, can you answer question #2 from my first post about sealing my garage floor.
 
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Old 05-13-07, 11:41 PM
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Ok… first remove all the grass from the area where the slab will be 10’ 6” X 10’ 6”. Than nail together 2” X 4” and make a 10’ X 10’ box and place it in the area you just cleared the grass from… square it. You know how to square a box, measure from corner to corner making sure the measurements are exactly the same. Stake all four corners and check for square again. Raise the boards to the height you want and be sure they are level, than nail to the corner stakes. Finish staking around the forms, at least two in the middle for each ten-foot side. Now dig your trench around the perimeter where necessary, if you dig your trench before the stakes are driven in they will collapse the trench. Have your trench the same depth all the way around and the width of a digging spade will be wide enough.

If I understand correctly, your yards un-even so at one side you will not have to dig much at all and the other side you will have to dig the full ten inches. Fill with stone and compact, at one end the stone will be only 3” in depth (minimum depth for stone) and the other it will be 6” in depth. The stone will taper from the top of stone grade to where it meets the ground so the top of your trenched perimeter will be wider than the bottom.

Since the top boards are on grade you must use filler boards on the end where the ground slopes, work your way down to the ground where necessary and nail them to the stakes… be sure to use kicker stakes on the side that has the filler boards or it will bow.

Now you will have a 4” slab with a 10” trench perimeter. Prepare the trench rebar by cutting to 10’ lengths and bending for each corner, let them overlap 6” at the middle of each side and tie them with bailing wire, all around the perimeter. You want double rebar around your perimeter for your trench, the lower rebar’s 2” from the bottom and the top rebar’s 2” from the top. To hold them in place cut 8 rebar’s about 12” –14” in length and stick them in the ground about the middle of the trenchs width vertically, at each corner and one at the middle of each side, about where you tied the horizontal perimeter rebar’s together. Tie your horizontals to your verticals at the depth I described above, 2” from the bottom and 2” inches from the top. For your slab reinforcement just crisscross from corner to corner two rebar and tie to the top perimeter horizontal rebar.

Now your slab and trench will float together… I would not pour a solid 10” slab for this shed, do you know how heavy it would be? Small thick heavy slabs have a tendency to sink at one side when floating.

If you don’t know how to square a box or how to use kicker stakes I have drawings at the following link under the framing chapter.
http://h1.ripway.com/ConcreteMan/

As for your other question, hard to say without looking at it.
 
 

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