Hilti Anchors to CMU
Hilti Anchors to CMU
(OP)
I need to attach plates to an existing cmu wall, my loads are in the 400# range per anchor in tension and about 150# shear. These plates will support cantilever tubes so I want to have a good factor of safety in there. I have some questions about how people typically handle the following:
- Most likely the anchors will hit a mix of solid and hollow cells. If I go with Hilti they recommend a different anchor for each condition - do you spec both and make the contractor switch back and forth?
- Hilti anchors are shown as not applicable at or near the mortar joint, I can't really control the location of these anchors. Do you typically deal with this by adding additional anchors assuming that some will be ineffective?
thanks
- Most likely the anchors will hit a mix of solid and hollow cells. If I go with Hilti they recommend a different anchor for each condition - do you spec both and make the contractor switch back and forth?
- Hilti anchors are shown as not applicable at or near the mortar joint, I can't really control the location of these anchors. Do you typically deal with this by adding additional anchors assuming that some will be ineffective?
thanks





RE: Hilti Anchors to CMU
2. Yes. Whenever I can, I actually design a Post-installed anchor for double the anticipated load precisely because of the situation you are talking about.
RE: Hilti Anchors to CMU
RE: Hilti Anchors to CMU
In the US, the typical safety factor required by code is 4 for this type of anchorage....further, you have to check unity with shear and tension.
RE: Hilti Anchors to CMU
RE: Hilti Anchors to CMU
RE: Hilti Anchors to CMU
What you should do is assume all block is hollow. If you are using an adhesive anchor with a screen tube it really will not matter if you hit a solid block (your capacity will be higher). Also, if you are just penetrating one face of the brick make sure your anchors are short enough. When anchors are too long they tilt up and don't mushroom out behind the block face correctly. If you use Hilti, go with the HIT-A rods. They have squared ends and make a big difference in performance. Finally make sure the guys installing these anchors know what they are doing.
For such small loads you may want to consider a mechanical sleeve anchor. I would only use this if the block is new. Also, once this anchor is set you can not remove the nut because the threads get damaged when you hammer it in and you tend to spin the anchor in the hole which loosens the whole thing.
Good luck!