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Posted by C & E on June 1, 2007, 11:34 am
>> On Fri, 18 May 2007 12:20:47 -0500, wrote:
>>
>> >>Hi-
>>
>> >>The previous owners left us with a 9x12' slab they had poured for a
>> >>dog kennel; it happens to be in the same place I want to build a shed.
>> >>The slab is 7" deep and though it's an obvious DIY job it has held up
>> >>for 10+ Minnesota winters. Assuming I want to build an 8x12 shed on
>> >>PT sills atop this slab, what's the best way to anchor the sills?
>> >>With a new pour I'd just use bolts but I'm not sure what the best
>> >>method is in this case. FYI, we're in tornado country and do see
>> >>gusts in the 50-60 MPH range during thunderstorms or blizzards a few
>> >>times a year, so I want to make sure this shed stays put.
>>
>> >>thanks,
>> >>kiwanda
>>
>> > Check some anchor bolt catalogs such as Hilti or the like. They will
>> > explain the loads and how to install the different type bolts. I
>> > think you will have to drill into the concrete and use a bonding agent
>> > in the hole with the bolts set in.
>>
>> > You might also want to check the stability of the entire structure in
>> > wind.
>>
>> The last poster has it spot on,
>> rotary hammer drill and set in epoxy threaded rods where you think
>> they are required. Expanding masonry anchors are great but close to the
>> edge of a slab they could split the concrete. Manufactures have tables
>> specifying edge distances for this reason.
>>
>> A length of threaded rod is cheap so I'd go for 12mm. (half inch,) set
>> in a minimum of 4 inches.
>> Put your threaded rod, or hold down bolt, near a stud at each corner, and
>> say maybe a couple spaced equally to each wall, but close to a stud. Say
>> 10-12 bolts in all.
>>
>> Fix a strap or timber connector from the bottom plate to the stud
>> (vertical) near each HD bolt and also tie in the top plate to the same
>> studs. Get the picture, a link from the concrete to the plate to the
>> stud
>> to the top plate. Then strap down your roof, same way.
>>
>> All this is a fair bit more work than maybe you want to do Kiwanda,
>> but the material costs are nothing compared to the rest of the shed.
>>
>> Do you want feel responsible if your shed blows through you neighbours
>> living room window?
>>
>> What with all the global warming and extreme weather stuff going on, you
>> never know what the next storm will bring. Build it strong and sleep
>> easy.
>>
>> --
>> Billhttp://www.builderbill-diy-help.com/
>
> Thanks again to all for the advice-- it's very helpful. I'll take it
> all into account as I plan the project this summer, but it seems quite
> reasonable to build this thing as solidly as possible since I plan to
> finish it to match the garage and it will be a permanent part of the
> property. Really high winds are rare here (nothing's gonna stop a
> tornado but we do get big downdraft gusts from t-storms on occasion)
> and if the cost/design issues aren't that great it makes sense to do
> everything I can to make sure it will stay put when my neighbor's shed
> (which is just sitting on railroad ties) blows away.
>
> -Kiwanda
>
I would use Tapcon screws. They aren't cheap but you wouldn't need many for
your size shed. I believe that they come with a drill. They also have a
large washer to prevent the screw head from sinking into the wood. I've
used them with good results, not hard to use and I'm no carpenter.
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