Re: Holding garage to floor?

Posted by Billy NY on April 14, 2015 at 07:21:23 from (104.228.35.235):

In Reply to: Holding garage to floor? posted by Whiskey Bent on April 13, 2015 at 19:53:15:

Thats just a missed coordination and or detail, happens, but this one is kind of obvious, should have been done prior, but.... LOL !

You can look at fastener manufacturers information and obtain pull out and shear values of fasteners that are installed into concrete. Mind you the concrete design mix needs to be known, 3000, 4000 psi etc. To prove it, technically speaking you would still have to do a pull test, but if your concrete is good, it should be no issue.

For ease of installation, I would suggest a mechanical fastener, Hilti sleeve or wedge anchor, or the current equivalent. Red Head,(which I used exclusively on one 15 story building) and others like Powers or similar should have mechanical fasteners for concrete. Powers used to offer a fastener with a certain thread designed to perform like a thick tapcon, so its possible you may be able to do that. I recall when these were new, I was hesitant to use them on commercial buildings, having worked with wedge, sleeve and epoxy anchors/fasteners, they were new at the time and I questioned thread engagement, given concrete, steel reinforcing, aggregate etc. Powers had a failure in one of the tunnels in Boston, Mass., don't recall the details or what fastener, thought it was the epoxy type. Specific to that job more than likely.

With a mechanical fastener as mentioned above, drill the correct diameter through the sill plates, drill a larger hole to recess a washer and nut if you like, just partially into the top plate of the multiple sill plate. Get a hammer drill, match the bit size to a 3/8" or 1/2", (probably best) sleeve or wedge type anchor, mark the bit for correct depth, so you know where to stop, allow for the bottom sill plate thickness. Drill the holes, clean with compressed air, drop and tap the fastener into the hole, then install the nut, washer and tighten it down, the wedge or sleeve will expand as the end of the fastener is tapered or is designed to expand when tightened, don't over tighten, there is likely a torque value if you want to get fancy.

Details of the concrete are important. You are on the edge of slab with the wall, so edge distance with mechanical fasteners is important, you need a certain amount of concrete both depth and what surrounds the fastener, and the manufacturer should provide the acceptable tolerances for each fastener. You don't want to violate that specification, the fastener will either fail or the concrete will spall, fracture when you tighten it, causing failure. 1/2" fasteners will need more edge distance, 3/8" may need less, so if 1/2" does not coordinate with the slab detail, see if 3/8" will. You may be able to get the same overall values, pull, shear and whats transferred from wind loading, using smaller fasteners, but more of them. Just make sure the spacing allows the correct edge distance. Epoxy anchors are often used when edge distances won't allow a mechanical fastener, also for many other reasons, like Dr Sportster said about the G.W.B. where they were used and it seems for dampening purposes given vibration.

If there is reinforcing in the slab, probably no bigger than #4 deformed bar, or much smaller 6"x6" woven wire mesh, its best to avoid steel with masonry drill bits. So if you have any idea that if the edge of slab is tapered on the bottom, like an Alaskan slab, thicker on the perimeter, there could be a pair of deformed bars all the way around. We can't always predict where we will find rebar in concrete on high rise jobs, but do try to avoid it as much as possible, wears bits quickly, even Hilti ones which are good quality. I would look at structural details and approved shop drawings to locate reinforcing, then detail the structural connections for our work, often times submitting details based on field conditions after doing a mock up of an installation, even if just with fasteners, it saved me lots of headaches, and one job I redesigned the connections because it was grossly mis coordinated per the design, we could hardly get a fastener in the original location. Well thats for big jobs, but the priniciple applies. A little careful planning and layout goes a long way no matter what you build.

As a general rule of thumb with mechanical fasteners into concrete, concrete block or C.M.U., it should be coordinated in advance with that work, makes the job so much easier and the fasteners will perform. I did some repairs to a fancy stable in Wellington Fla, years ago, all of the stall gate hardware was mechanically fastened into CMU walls, problem was they left the cells hollow, and the fasteners were failing in the thin wall CMU. At some point that hardware should have been located, marked on a drawing and it made so when the CMU went up, filling those cells to provide adequate structure and depth for these kinds of fasteners. Just an example that would have made a big difference if someone had taken the time to coordinate these details, the remedial work is much more costly.

Click below, I did a search on Hilti epoxy and sleeve anchors, lots of photos and product data, you could refine your search for sleeve anchors if you like, you'll see charts for values and typical details.

Many if not most fasteners like you get at HD or Lowes, will not provide any values, like deck screws, for example, have no shear value at all. One needs to use care when selecting fasteners for any structural component.

• Hilti

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