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Earthquake retrofits

Vincerama2

Vincerama2

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Hi guys, since I've been poking around the crawlspace creating a plan for reinforcing the floor (I've decided to add a beam and 2 posts, and also to sister the joists up to the new beam) I decided that I might as well do whatever earthquake-proofing I could.

Has anyone done this? Yes, I could hire a pro, but the new bathroom we added killed my savings (me and 3 ladies, 2 of which are now potty trained. Well, OK, the older one was potty trained decades ago ;) in the house couldn't survive with just one bathroom!)

Do to the setup of my house, I'm thinking of using Simpson "Universal Fountation Plates" to anchor the mudsill where I can, but there are places (ie where the big tank will go) where the mudsill is actually embedded in the foundation, such that there is no edge to attach the UFP. (Maybe it doesn't need it?) And I'm going to add some shear walls on the downhill side of the house where there are cripple walls.

I just picked up a Harbor Freight (yes, yes, I know!) SDS rotary hammer (it got good reviews as a HF product that doesn't suck!) so that will make sinking anchors easy. Also will come in handy for breaking the rat-proofing for installing my reinforcing posts.

OK, I'm just rambling now, but I was wondering who else has done this, so I know who to "ping" for questions!

V
 
Incidentally, I'm using this as a guide, obviously it suggests Simpson Strong-Tie products...but that's OK because that's what HD and Lowes sells http://www.strongtie.com/ftp/fliers/F-PLANS07.pdf

V
 
No clue myself.
But I can say this: A friend did it.
Afterward, he sold me his hammer drill cheap, not really wanting to see it ever again.
He said It was a ton of work, and miserable under the house.
Only advice is to get the right-angle attachment for your hammer drill.
 
interesting read their Vince... I'm curious about my house now after reading through that :D... Being as my house most definitely isn't less than 20 years old and I have living space above the garage :D

That said, maybe Jon will chime in.. I always thought the best earthquaking you could do is to attach those straps to the studs of your walls.
 
Your on the right track. Bolting and shear wall are great upgrades.
My guess is that there are some bolts in the sill plate but they may only be 1/2 inch and further apart than today's standards.
I end up usually putting 12"X 5/8 or 3/4 inch bolts with a BP washer every 3-4 feet on retrofits. If you can't get the drill in then the Simpson UFP works well.
 
Kind of a related subject, but I have one of those high efficiency washers and when it's going into one of its super spin cycles the whole house vibrates. The wife claims it didn't do it before it moved, but I still think it did. Would beefing up the flooring its under help at all?
 
Beefing up the floor would probably help if it's not real firm but that's kinda what happens.
Stronger is better.
If your washer is on a concrete slab then no worries but once you put it on a framed floor that is part of the house your going to get some vibration in the house.
 
I can't see a hammer-drill ever working with a 90 degree attachment, the "hammering" is inside the drill and it's along the axis of the drill a 90 degree attachment will not work because the hammering will in fact hammer the (now at 90 degrees) bit sideways!


Yeah, I think I'll use the UFPs.

I think I'll go back down and try and draw a proper diagram of the crawlspace, this will help me plot out where to put the new beam/posts and where to put the UFPs.

By the way, the UFPs seem to sell for $19.99 everywhere except Lowes, which sells them for $14.88 (and is all out of them at the moment). Well, I should say "everyplace that showed up on google search".

What other local stores might have them? Ace?

Shoot, where do you get Simpson products other than HD and Lowes!?

V
 
Vincerama2 said:
I can't see a hammer-drill ever working with a 90 degree attachment, the "hammering" is inside the drill and it's along the axis of the drill a 90 degree attachment will not work because the hammering will in fact hammer the (now at 90 degrees) bit sideways!


Yeah, I think I'll use the UFPs.

I think I'll go back down and try and draw a proper diagram of the crawlspace, this will help me plot out where to put the new beam/posts and where to put the UFPs.

By the way, the UFPs seem to sell for $19.99 everywhere except Lowes, which sells them for $14.88 (and is all out of them at the moment). Well, I should say "everyplace that showed up on google search".

What other local stores might have them? Ace?

Shoot, where do you get Simpson products other than HD and Lowes!?

V
Click to expand...

The right angle hammer drill probably works well for like 1/4 inch holes but I tried one to drill 5/8 and it overheated and died quickly.
Try a local lumber yard or builders supply for Simpson and ask for a contractor discount.
 
Does someone sell a foundation plate similar to the Simpson UPF10, but is 90 degrees? I ask because the UFP10 will work if you can fasten it to the mudsill from the SIDE, but I have a large section of mudsill that is flush with the foundation, so there is no accessible side of the mudsill, and yet there is no headroom to drill down into it either. Since it's embedded, does it need an anchor?

I found a UFP at Home Depot and tried to imagine it fitted to the top of the foundation with screws angled downwards. I think it might work, but would it be effective at all with the sds screws screwed in at an angle, reaching down to the top of the mudsill? even if I used longer sds screws, would it be effective? (Well, OK, it's better than nothing!) I'm thinking a simple right angled plate would work, if I could find such a thing rated for retrofit!

V
 
Yes, the right angle attachment even says it reduces force by 40%.
Never tried it myself on large holes.
--
The engineer in me is wondering how it works as well now.
Sure seems like it should not. Never really thought about it before.
May have to take it apart an see.
:)
 
so Mr contractor ... what kind of discount do you get? ;)

I'm actually going to also try a lumber yard near my place, I think they had some stuff there. Empire Lumber I think it is.

V
 
You know, I thought you mean "HD IS FOR contractors" that had me puzzled for a second! THanks for the heads up, I'll check them out.

V
 
Wow, my earthquake paranoia spidey sense must reach to Japan!

I picked up some UFP10 plates from my local lumber store. Price is about the same everywhere (buy locally to save shipping!). Home Depot sells the plates for $14.88 BUT they don't include the 5 SDS screws that COME WITH THE PLATE. Yes, they removed the screws! I don't know about Lowes yet, since they also sell for $14.88 (but don't have them in stock often). If Lowe's sells the plates with the screws, then it's the best deal, otherwise, you have to buy the SDS screws in a pack of 50 for $15 or so. So it's a wash if you buy 10 plates.

I bought 10 UFPs and 20 Titen HD 1/2" bolts for $198. That should cover the part of the crawlspace that I can reach.

I found the following information, by the way, for those interested;

There is a "BASE SHEAR FORMULA" that tells you what approximate amount of shear your hardware must resist. I could only find the coefficient for Berkely, but having nothing else to go on, I'll use it. The formula is

Shear = 0.185 x Weight of the House.

reference : http://www.bayarearetrofit.com/RetrofitDesign/RetrofitEngineering/retrofitengineering.html

So ... how much does your house weight? Estimate that it's about 50 lbs/square foot for a 1 story house or (I think) 80lbs/sqft for a two story house. So my house, for example is about 1120 sq ft, that means;

Shear = 0.185 x (50 x 1120)
Shear = 0.185 x (56000)
Shear = 10360

So in each direction (including UP!) needs to resist 10,360 lbs of shearing force. Since you have (in general) two walls in each direction, each wall must resist half the load, so in my case 5180. Each UFP can resist 1340 (I think) so I need 4 per wall.

That's the highly guestimated math. However, building codes state that each wall needs to be anchored by 5/8" bolts with bearing plates every 6 feet. And Simpson states that to replace anchor bolts with UFPs, you need UFPs spaced at MAX 6' apart. So that completely ignores the weight of the house, etc. My house doesn't exaclty have a square foundation either. That bay area retrofit site admin wrote a memo stating that he thinks Simpson 1/2" titen bolts suffice based on the shear rating of the bolt actually exceeding the bolt to wood strength (which is like mid 1100's).

So it' bamboozling enough that I am certain that going every 6 feet max with UFP plates (due to low clearance) I'll exceed the estimated shear resistance required to keep the mudsill connected to the foundation. I have crappy shear walls on the two walls that have cripples walls (I'm on a hill) but I might take those out and do it properly ... at another time.

Oh yeah, once you do that, you now have to connect your floor and rim joists to the cripple walls or mudsill. You can use the shear value to find out how much harware you need (I'll use Simpson L90 brackets) but again, the rule of thumb is every 12", regardless of your calculated shear value.

So at a minimum, calculate your required shear resistance and use at least that much hardware (each hardware has a rating, just add them up top match or exceed your shear load, which is an estimate anyway) And at best, follow building codes that state distances between hardware.

That's a moutfull, but I thought I would spew out my research so that you guys have a place to start. And of course, Simpson Strong Tie has that excellent PDF that everyone posts, and that you can pick up at most hardware stores!

Do the work and sleep better at night!

For "The Big One", cross your fingers and pay your earthquake insurance! Oh yeah, the hardware guy told me that his insurance broker suggested to him that if the big one ever hit, insurance companies will just declare bankruptcy and not pay anyone...however after seeing the AIG bailout, I'm not so certain that will happen.

V
 
good luck with that Vince... I too have been peeking around downstairs, and have not liked what I've been seeing, looks like some beams pulling away from support structure, vertical supports (good ol true 6x8 posts) which look cracked vertically. Not sure if these were like this, or if the front of my house is pulling away from the back... or if I can just run a bolt through those beams to prevent them from splitting any further... or if I'm just borked. But I think I might need to get someone to come over who has a bit more expertise if anything just to look at everything and recommend a plan of action.
 
When I was looking into retrofitting the house, I found the City of San Leandro website very helpful - http://www.sanleandro.org/depts/cd/bldg/retrofit/home.asp
 
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