Concrete Mechanical Anchors - Exterior Use
Concrete Mechanical Anchors - Exterior Use
(OP)
I am looking at a few exterior deck failures in which ledgers have been inadequately attached to concrete or masonry walls. (These connections were horrible and not worth discussing here.) The wood requirements generally govern anchor spacing (i.e. 2-rows of 5/8" anchors at 16" o.c. or similar). I need to specify a concrete anchor for ledger attachment. I want to specify screw anchors (i.e. Titen HD or HILTI HUS-S). But the ICC literature says they are only approved for interior dry aplications. This seems to be the case on every mechanical anchor I've looked at. Are epoxy anchors the only anchors we can specify for exterior applications?
Another side of this argument is that since there are so many anchors required by the wood ledger, the actual bolt to concrete loads are very small (25% of design load). In my head, I divide by a safety factor of 5 to imagine in the worst case, I load these bolts to about 5% of the load it would likely take to pull them from the wall. Thoughts? Experiences? Anyone seen actual failures by exterior use mechanical anchors? Ever considered using them and specifying a sealant or epoxy just to keep water out of the hole?
Tony Krempin
TopKnot Engineering
Another side of this argument is that since there are so many anchors required by the wood ledger, the actual bolt to concrete loads are very small (25% of design load). In my head, I divide by a safety factor of 5 to imagine in the worst case, I load these bolts to about 5% of the load it would likely take to pull them from the wall. Thoughts? Experiences? Anyone seen actual failures by exterior use mechanical anchors? Ever considered using them and specifying a sealant or epoxy just to keep water out of the hole?
Tony Krempin
TopKnot Engineering






RE: Concrete Mechanical Anchors - Exterior Use
I have never been a fan of any type of screw bolt into concrete, and this is just a gut thing. It seems like it would be easy to mess up in the field. Tap cons for light loads I am fine with, but when the loading is above a few hundred pounds I go with epoxy.
RE: Concrete Mechanical Anchors - Exterior Use
RE: Concrete Mechanical Anchors - Exterior Use
It seems like a CYA limitation. Has anyone actually seen a failure of an exterior mechanical anchorage attributed to moisture?
Does anyone know specifically of a mechanical anchor approved by ICC-ES for exterior use?
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Tony Krempin, PE
TopKnot Engineering
RE: Concrete Mechanical Anchors - Exterior Use
I believe this was blamed on corrosion of the anchorage
RE: Concrete Mechanical Anchors - Exterior Use
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RE: Concrete Mechanical Anchors - Exterior Use
Clarke Engineering Services, PC
Jobsite Engineering and Consulting
www.anchorengineer.com
RE: Concrete Mechanical Anchors - Exterior Use
Use Hilti epoxy anchors with SS threaded rods or hot dipped galvanized rods. For CMU block Hilti has special screen caps that get inserted in hole first and then epoxy is extruded through the back side when rod is inserted.
Best of luck.
RE: Concrete Mechanical Anchors - Exterior Use
It is not true that hot dipped galvanized and stainless steel mechanical anchors do not exist. They are not available in all sizes, and may be more difficult to procure in some locations, but they exist.
RE: Concrete Mechanical Anchors - Exterior Use
I was told that due to the gringing nature of their anchorage, There is a good possibility that the galvanizing will get stripped leaving the steel will corrode at the most vonroble pressure point.
They are simply not worth the risk.