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dclay79 11-04-2012 06:02 PM

Shed - Out of square concrete pad
Hey all,

Shotty concrete guy poured our 10' x 20' pad out of square. Diagonal corner measurements SHOULD be 268 3/8" (ish) but instead we have the following:

268 1/2
270 5/8

We'll also be using 2x6's for framing the sill plates since the anchor bolts were put in about 3" in from the edges. Additionally I'll be using that pink foam underlayment under the plates.

Any advice on how to frame this guy? My assumption is to square the framing and have the sill plate hang over up to 1" on two opposite sides. I'm just not sure how to seal this opening so its water tight and my shed doesn't rot from underneath.

If its relevant - pad end 6" above grade, vinyl siding was intended to hand down about an inch below. Shed will be divided into two 10x10 sections with two doors centered on each area of one of the 20' sides.

sixeightten 11-04-2012 06:08 PM

Since there will be no finished flooring, you could actually flush up the walls and let the overhangs be slightly out of square.

dclay79 11-04-2012 06:10 PM

Good point - and I've considered this, but a framer buddy of mine said that would create gaps when I tried to put on siding and build the roof.

While he does have a lot of experience, and I like to get his input, I know he speaks of of his butt sometimes.

Another thing to note - one of the 10' sides actually bows out, instead of staying in a straight line. My assumption is his concrete forms bowed from the weight of the concrete. In the last 5 feet it archs to about an 1" out.

funfool 11-04-2012 07:05 PM

Just build square off of it.
I understand the forms were not perfect, slightly out of square in 20', also bows out in the middle, forms were not strong enough to hold the concrete.

If were bigger issues then this I would be concerned, what you describe I would simply frame square starting at the bottom, will save many headaches further down the road.
If foundation sticks out a little here or there, not a catastrophic issue.

To avoid this in the future, you actually hire a company that pours foundations, but what you posted so far ... couple boo boo's but not show stoppers.

TheCamper 11-04-2012 07:22 PM

Frame your building square, it just goes easier and faster. Let the plates hang out over the slab. It's a shed. You should be able to find treated lumber rated for "ground contact" , you may wish to use that since part of the plate will be extending beyond the concrete. Make sure you use non-corrosive nails into the plate. Good Luck.

hand drive 11-04-2012 07:34 PM

maximize the amount you set the plate to the edge of the concrete at the far side and let the plate extend out past concrete where the concrete sits in. you do not want the concrete sticking past the plate more than one half inch because of water intrusion, even if you think it is sealed it is not. Another way is to follow the out of square pad with the walls and take the difference out of the rafters bird mouth making the overhangs take up the out of square difference. A central bow in the finished pad is normal and I've seen it on many pads and sometimes that involves framing the wall flush at the middles while the ends hang out over the pad,or a variation of all the above.

shedbuilder 11-04-2012 07:36 PM

You got it!
Use the shortest diagonal, build the shed sq., cut off any anchor bolts that don't work drill and re-apoxy new anchors. If the crete sticking out is a conserning factor hide it with a correlating aluminum or stainless steel flashing.:)

AtlanticWBConst. 11-04-2012 08:18 PM

As others have stated (TheCamper) = square it off, essentially; build your square structure ontop of the slightly off-square pad.

Although every slab and foundation "should be" poured square and to the actual plan dimensions, they are not always done that way, and you will have to make adjustments for it, when building.
That can include (on a rare occasion) humps in the frost walls.

Regardless of the slab, make your adjustments to frame-it (build-it) so that the framed-structure is square and plumb.

Gary in WA 11-04-2012 09:50 PM

The sheathing should not have any concrete slab in front of it to disrupt the WRB plane. AL and PT don't mix...


picflight 11-04-2012 10:01 PM

I am with funfool.

Sent from my iPhone using DIY Forum

brockhouse 11-05-2012 10:27 AM

Go with what most people are saying; frame a square building over the out of square foundation. With our code we can have 1/3 of the framing not supported to if you are framing with 2x6 you aloud about 1-3/4" unsupported which is enough to build square on your foundation.

dclay79 11-05-2012 12:32 PM

Thanks for everyone's replies. I'm almost certainly going to build the shed to hang over the out of square portions of the slab. My primary concern at this point is the approx 1" open gap between the slab and siding. It will be PT wood, but is it ideal to just have this open to the elements? Or should I be putting in some kind of sealant to fill the gap? I'd hate to make sure this shed is built well, but then have an Achilles heel type weakness :)

woodworkbykirk 11-05-2012 03:08 PM

brocks right. theres no issue with overhanging your plate.. if your worried about seeing a gap between framing and the foundation.. you can cheat your other plates so they overhang slightly.. this way you can hang your sheathing by 1/2" which can keep water run off from the walls from running in under your plates

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