On May 20, 2:35 am, Bill wrote:
On Fri, 18 May 2007 12:20:47 -0500, wrote:
On 18 May 2007 09:41:44 -0700, Kiwanda 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