Hello,
I am looking for some help with Hold-Downs.
I know hold downs should be installed on the corners of shear walls, and typically face so that the nailing surface faces the corner.
Is it OK to face hold downs the other direction?
The name Hold-Down seems to convey that it keeps the shear wall down, while the sheathing / blocking provided lateral stiffness.
It seems like it would be common for the Hold-Downs to be slightly off, how do framing contractors deal with this?
E.G I want to have a corner just nailed to the sill, and then attach the Hold-Down to a separate beam.
Replies
P.S Simpson Strongtie website is no help.
http://www.strongtie.com/products/connectors/HDU.asp
I usually do a lot of layout for holddowns at the foundation stage before we pour concrete.
The inspectors require the holdowns in the forms for inspection. You need to know how your going to frame your structure and what your engineer will allow for framing members in the corners and at the ends of each shear panel.
It maybe double studs nailed together in a certain nail schedule or 4x material (typ) at each end. Flipping the hold down to one side or the other usually doesn't matter but you still need to check with your engineer.
On a large home I would spend the time and make layout sheets for each panel or corner
so that when I do layout for framing I know what the offset for each particular holddown was suppose to be. During the concrete pour they almost always seem to get moved around a bit.
Howie
Howie, thank you for your reply.
I thought I had the layout perfect, but I was wrong haha.
I have 2x6s doubled attached to the hold-downs, which is what is required.
I'm just hoping the inspector doesn't have me flip them around : X
I'll find out tomorrow, I figure might as well find out the good / bad news now.
It's been hard to find any info on this, but I did buy a book that is supposed to help.
http://www.shearwalls.com/ has a book from the ICC about wood shear walls; the Journal of Light Construction said it was "an essential reference for framing crews" or somesuch.
I looked through the California Code, but couldn't find anything on it today.
Of course the inspector is coming tomorrow and the book won't be here for 2 weeks, oh well.
Kevin,
You should be fine ,but , then again it sometimes depends on your inspector and how they interpet code and the engineering. Usually having the HD on one side or the other of the post dosen't matter.
I have had many times been able to set the holdown up to a max. of 6" above the bottom of the post . This allows for a little flexability to get the STB angled a little to go through the holdown. If it's to far off the you'll need to drill and epoxy in a new all thread.
Most of the time STB's end up in the wrong place because they moved during the concrete pour or you left it up to the concrete guys to set all the HD's. Not that the concrete guys don't care but they will set them in the corners, somewhere, according to plans.
I always suggest that if your the framer... you allow to layout and set all the HD's at foundation stage. Your the one framing it and it will save you a ton of time. You will always miss it here or there but it's way better than fighting every HD.
I've built some projects with 100+ HD's... that a lot of time!
Good Luck!
Howie
Howie,
Thank you for the advice. This is my "learning project" so I'm doing everything.
If I ever do it again I will definitely be very, very, careful on the Hold-Down layout.
It's my first "addition / whole house project" as opposed to just gutting an existing and retrofitting.
I like gutting and retrofitting them better, but I wanted to try "doing it right the first time" or some other bad idea like that.
I'm going to have my architect come kick around and make sure.
He seems like the most knowledgeable person.
The inspector really didn't answer, he said to talk to my architect and keep going.
The only thing he said is I'm missing my Anchor Bolts at the hold downs (I thought the H.D counted as a A.B in those locations). He said it probably can if I get an addendum from my architect so they do.
I'll tell you how it goes.
My architect told me to call the structural engineer. : X
I have a feeling this is going to be an expensive lesson...
I assume the holdowns are for a shearwall. FYI, a shearwall transfers wind or earthquake lateral forces from the roof to the foundation. The forces that a shearwall resists are in the plane of the wall. The holdowns resist uplift from the wall "tipping" for lack of a better word. So on one end of the shearwall the holdown is in compression. On the opposite end the holdown is in tension. If the holdown doesn't have an anchor bolt to the foundation, it is doing no good.
You'll need an engineer to come up with a solution that will accomplish the structural requirement to transfer the uplift forces into the foundation. There are simple solutions, but will probably require the engineer to get it approved by the building department.
Good luck.
Thank you for the reply.
The Hold-Downs DO have anchor bolt, actually they have special anchor bolts.
They are connected with Simpson Hot Dip Galvanized SSTB 5/8 anchor bolts.
The inspector said that H.Ds do NOT replace the need for having a Separate anchor bolt within 12" of the end of the bottom plate.
My structural engineer said that he wasn't sure of standard practice, but that the hold downs are for uplift and not lateral sliding.
Could a H.D work as both? > nobody knows, the inspector wanted both or an addendum.
The structural engineer is taking a look (hopefully, I emailed him all the info / pictures).
Honestly it seems that nobody really understands shear walls, the city inspector had no clue (who can blame him).
I should post a picture, it's just a 1 story bump out. My existing house doesn't even have anchor bolts.... (although with this project I'm going to eventually retrofit the whole thing)
I really don't understand the need for like 5 anchor bolts and a hold down in an area of maybe 6 square feet at the corner.
Especially since my house has made it 60 years without any hold downs or anchor bolts.
Of course I'm also having to get an addendum for framing in 2x6s @24" as opposed to 2x4s @16", I know the sheathing has to be upgraded, but come on.
I remember that as long as the HD was on the sill and had a nut and washer it counted as an anchor bolt. Some are mounted higher up and would not count. Maybe if you used a bearing plate as a washer he would pass. I think 3" bearing plates are the code in Ca. now for anchor bolts, I don't live there anymore.
Of course it's pretty easy to just put in a bolt and move on.
John
Since you've already contacted your engineer, you might ask him to do a site visit to see if your work is done to his expectations. If it is, ask the building inspector if he will sign off with a letter of acceptence/approval from the engineer. If not, ask him for the corrections required, in writing,make the corrections then call for a re-inspect.
I agree with the other posts regarding involving the framing contractor. A competent frame can locate the hold downs and anchor bolt locations for the foundation contractor and usually will be glad to since it makes his job easier when he gets there.
The jurisdiction I work in requires us to have the structural engineer to inspect the structure and provide a letter stating all work has been done to his provided plans. We have to have the letter on site, for our framing inspetion.
HV
Having seen all the homes that have slid off of their foundations in the Whittier earthquake (which was not a particularly large earthquake), I would definitely advise anchoring the house to the foundation by retrofitting if you are in an earthquake area. Simpson has some products, and the City of LA has some standard plans to do this.
Most homes in the LA area built prior to about 1933 are not anchored. It was the 1933 Long Beach earthquake that caused codes to implement earthquake standards, including anchor bolts.