Concrete Screw Anchors with Epoxy
Concrete Screw Anchors with Epoxy
(OP)
I'm having a steal storm shelter anchored to my garage floor with the 3/4" Hilti HUS-EZ screw anchors.
Does any one know if there is a concern about adding epoxy to the holes before we screw them in?
I dont have any other anchor options because that is what the engineering drawings require. I was thinking of adding epoxy to the holes just to add holding power and possibly help with corrosion. I asked Hilti about it and they just replied that they didnt have any data on it. Obviously removing the anchors would require me to zip the heads off.
Thank you
Does any one know if there is a concern about adding epoxy to the holes before we screw them in?
I dont have any other anchor options because that is what the engineering drawings require. I was thinking of adding epoxy to the holes just to add holding power and possibly help with corrosion. I asked Hilti about it and they just replied that they didnt have any data on it. Obviously removing the anchors would require me to zip the heads off.
Thank you






RE: Concrete Screw Anchors with Epoxy
If you are going to epoxy just use threaded rod anchors (much cheaper than the HUS-EZ). No point in paying for 2 specialty products.
RE: Concrete Screw Anchors with Epoxy
RE: Concrete Screw Anchors with Epoxy
Does one else on the forum have any experience or knowledge of this?
RE: Concrete Screw Anchors with Epoxy
either the existing design is acceptable or not. why would you assume it is not?
RE: Concrete Screw Anchors with Epoxy
I've decided to not do the epoxy, come back and inspect one of them in 10 or 15 years, and put epoxy or wedge stainless steel anchors in if needed at that time. If I do the epoxy now, I wont be able to back them out to inspect.
I don't understand why the epoxy wouldn't add strength though, it should created a bond between the metal and the concrete.
Thank you
RE: Concrete Screw Anchors with Epoxy
Why would they specify a 7" long anchor when there isn't 7" of concrete. You don't gain any capacity past the thickness of the concrete. Don't pay for anchors that are too long for the use. Do not allow them to core completely through your concrete slab. This all seems sketchy. If you need the higher capacity put in epoxy anchors and threaded rod at the correct depth for your application. And if you don't have enough concrete to get the capacities you need then you need to figure out a way to get more anchors.
RE: Concrete Screw Anchors with Epoxy
for a 7 inch anchor you need 8 inch thick concrete. these anchors will not reach the maximum design load if your slab is thinner. They do make a 5 inch anchor which might work if your slab is 6 inches. These are not designed for cored holes, use a hammer drill.
unfortunately, adding epoxy will not help gain additional capacity. regardless of the type of anchor, most anchors rely on concrete breakout strength. they do not rely on bond strength. the assumption is that the bond strength between the anchor and/or epoxy to the concrete is adequate for the load. so failure occurs when an anchor pulls out a chunk of concrete.
RE: Concrete Screw Anchors with Epoxy
Ground radar showed I have approximately 6" of concrete and some of them will be going into the grade beam which is much deeper. Perhaps I would be better just using the 4.5" or 5.5" anchors?
I believe you use a impact driver into a 3/4" cored hole. If the installers use a drill, is that a problem? I know there is a maximum torque rating which must be observed. I'll try to keep an eye on them, but I don't have any experience with anchoring.
RE: Concrete Screw Anchors with Epoxy
https://www.hilti.ca/medias/sys_master/documents/h...
RE: Concrete Screw Anchors with Epoxy
Good research! Your instincts paid off by asking questions. Probably only 1 in 100 homeowners did the checking you did.
How did you do the concrete radar depth checks? It sounds like a neat idea.
RE: Concrete Screw Anchors with Epoxy
Does any one know how to do the calculation for the force the shelter can tolerate?
Wind Speed- 250mph
Concrete psi -3000
Shelter length - 80"
Shelter height - 75"
I'll probably only get 6 HILTI 3/4" HUS-EZ anchors on each side, so 12 total. Hilti says at 4" embediment, each can handle a tension of ~4800 lbs.
Thank you
RE: Concrete Screw Anchors with Epoxy
FEMA 320
FEMA 361
My experience has been solely with FEMA 361 designing community safe rooms so I am by no means an expert.
If you are looking for a way to convert the wind speed to wind pressure so you can determine your required anchorage capacity, you can use ASCE 7 and the basic wind speed (v=250 mph) to determine a pressure.
RE: Concrete Screw Anchors with Epoxy
If the safe room can take this kind of forces, I would say your post-tension slab will fail first.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Concrete Screw Anchors with Epoxy
RE: Concrete Screw Anchors with Epoxy
PS. The shelter weight about 2600lbs.
RE: Concrete Screw Anchors with Epoxy
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Concrete Screw Anchors with Epoxy
RE: Concrete Screw Anchors with Epoxy
its not a shed, its a tornado shelter, of course we cares if it stands up in a hurricane. otherwise, see ya Dorothy... the tensile strength is far more than 4 kips per anchor and so is the shear strength
perhaps you should bury this thing
RE: Concrete Screw Anchors with Epoxy