Do Hold-down anchors count towards sill plate anchor requirements?
AdamPNW
| Posted in General Questions on
Hi all, I’m in seismic d2 zone, I see that the IRC requires sill plate anchor bolts <6’ OC and within 12” of plate ends.
However I also have quite a few hold-down anchors that could take the place of some of those sill plate anchors. Is that allowed?
Adam
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Adam,
I think the question may be the other way round: Will your engineer accept the hold down anchor also having the additional function of being an anchor bolt. There is nothing in any code I've seen that precludes adding hold down anchor hardware to anchor bolts as long as they still have the required washer and nut.
Thanks Malcolm, I see what you mean. Sounds like it’s easier to just keep their functions separate.
Adam,
I have the locations of anchor bolts spray painted on the forms so I can quickly put them in as soon as the top is troweled.
For hold downs, where the exact location is a lot more important I do one of two things:
- Fasten the threaded rod onto a block screwed to the top of the form.
- Drill and epoxy the rod in once the concrete has cured for a few days.
Great. Ever used the plastic Anchormates?
Adam,
I don't level my forms, instead using a pour-strip, so the distance to the top varies, which would make using the Anchormates difficult.
I also like having the top of the forms unimpeded while I level and smooth them.
If an HD anchor is located where a sill plate bolt would normally be (or at least within 12"), it would definitely be acceptable as a replacement since the HD anchor is normally much stronger. However, the engineer has last say on this since they are liable for the design. Regarding epoxy anchors in holdowns, it's not recommended. I believe that research done to date shows that these anchors can only develop 1/3 to 1/2 the strength of anchors that are set in concrete. This could be critical in a high seismic zone, depending on the actual loads. A new holdown location should be calculated and new concrete poured that is sufficiently tied to the existing concrete.
KD928,
The method of attachment of hold down anchors is specified by the engineer, or in more generic situations the manufacturer. If they show epoxy anchors I don't second-guess them.
Correct. Some engineers don't have a problem with it and some do.
KD928,
Temperamentally I'm with you in being more comfortable relying on concrete embedding, rather than adhesive if there is a choice.