Replies

1. 
   joeh | Jan 04, 2004 09:54pm | #1

   Step one, get a Bosch Bulldog hammer drill.

   Step two, get a Simpson catalog.

   There was an article in FHB long ago about retrofitting seismic hold downs into a house just as you describe.

   Probably 15 years back, only Andy E knows.

   If you are anywhere near as old as your house is, hire someone 30 years younger.

   Joe H

1. 
   JohnSprung | Jan 07, 2004 03:52am | #6

   Measure carefully to find your tightest place, and be sure that there's room enough for the Bosch Bulldog with the bit.  If not, the Milwaukee Hole Hawg is another good choice, although it's a straight rotary drill with no hammer action.

   -- J.S.

1. 
   Mooney | Jan 07, 2004 04:45am | #7

   We always strap down with bailing stap and a ramset . Oh yea , sheet rock screws? [kiddin]

   Tim Mooney

1. 
   joeh | Jan 07, 2004 05:15am | #8

   After quake pictures show houses off the foundation, a lot of them with a little knee wall with all the studs sitting at an angle & the house off to the side.

   CA is, or was, full of houses built like that.

   Joe H

1. 
   Mooney | Jan 07, 2004 05:37am | #10

   I will ask a  question . We have tornados , others have hurricanes and strapping like that is called hurricane ties . They go down the foundation wall to the footing . Simpson only attaches at top of wall. How do you build quake proof?

   Tim Mooney

   Edited 1/6/2004 9:46:11 PM ET by Tim Mooney

2. 
   joeh | Jan 07, 2004 07:23am | #11

   Tim, if you look through a Simpson catalog you'll find page after page of stuff that you just flip past. If you read all the little notes you can figure out how to tie the whole thing together.

   Some of thoes things that look like baling strap with twists go from one level to the next, to continue the load path.

   You're right, the things called Hurricane clips hold the roof to the top plate, or some twist down onto the wall studs. More at the bottom will tie it to the bottom plate and that is hopefully secured to the footing well enuff to hold it all down when the wind blows.

   Or a length of all thread from J-bolt through the top plate. That really stiffens things up.

   Lots of ways of doing it, but I suspect the wind or the earthquake will win eventually.

   Recent events indicate mud is not the answer, but it did last 2000 years. Many of the adobe building in Southern Cal have survived many years and many earthquakes, but sooner or later there's a big one.

   Joe H

   Joe H

3. 
   Mooney | Jan 07, 2004 04:20pm | #12

   I know about wind and have worked it . Earthquakes shake the ground I understand. Different set of rules would apply it seems to me , but I dont have any earthquake knowledge.

   Tim Mooney 

4. 
   skids | Jan 07, 2004 08:48pm | #13

   they are changing the codes in cali all the time by adding this and that, but the basic premise of earthquake retrofiting requires a belt and suspenders type of aproach. it could be shakin sideways, it could be up and down, or a combo. everything needs to be tied together in two directions so it stays were you put it. if you were to put ply on all cripple/pony walls, and strap from joists through to foundation, alternating from vertical to horizontal foundation bolts you would have it. simpson makes both kinds of brackets. a similar approach all the way up through the rafters/trusses and you got it. 

5. 
   Mooney | Jan 07, 2004 11:43pm | #14

   Thanks for that explanaton . I learned something today .

   I figgured on force in all four directions really or at least three . If it comes up it hammers down .

   Anyway , nothing I knew of in tornado ties were going to be much good or hurricane either I figgured . Ive only got a lot of experience with tornados as they rip through here every year. About the only difference in a bad one and one that doesnt do damage is how high they are when passing through and where their path cuts through. They down firewood every year in this forestry state .

   Tim Mooney

6. 
   kaorisdad | Jan 08, 2004 06:21pm | #15

   Actually, wind can act in all directions, including uplift or suction as the air passes over the roof.  High and low pressure differences cause suction or uplift on the roof.  This also occurs on the leeward side of a building wall, while the windward side is towards the building.

   Generally, earthquake codes focus on design in the lateral directions.  While emphasis is placed on properly tying the building components together, design is mainly in the horizontal direction.  Most earthquakes accelerations (g's) are measured in terms of horizontal accelerations.  Vertical components are about 20% less than horizontal.  To simplify design, codes consider mostly horizontal accelerations.

   Continuity in another important aspect of earthquake design.  But really, it is designing for lateral forces.  As an example, a rod or tie from one floor to another seems like it is there for vertical forces.  And it is, but as a result of lateral loads placed at the upper level - it will want to rock a house or wall, and this results in vertical components on either side of a wall element.  One side will be in compression and the other in tension.  So a tension tie is added to resist the rocking forces caused by lateral loads.  Shearwalls are there for lateral forces or 'shear.'

7. 
   JohnSprung | Jan 08, 2004 11:38pm | #17

   Making the structure stronger is all well and good, but there's another important way to make it safer in a quake:  make it lighter.  For instance, a one pound per square foot metal roof puts a lot less stress on the structure than a 12 psf clay tile roof.  When the ground goes sideways, there's less inertia up there making shear forces on the walls.

   -- J.S.

8. 
   kaorisdad | Jan 09, 2004 12:12am | #18

   Generally, for residential construction, weight is not really an issue if properly designed.  In high-rise construction, weight is important, but even then, properly analyzing and engineering the structure is key.  I've seen high-rise buildings designed that actually add inertial counterweights to offset earthquake and wind-induced displacements and forces.  I think it was in the tallest building in the world - it has a massive steel ball suspended with cables at the mid-height of the building.  It dampens lateral forces by 'tuning' the building's mass and dynamic characteristics.  Interesting stuff - highly theoretical though.

   I have seen a barrell-tiled roof on a patio structure where the structure was not properly designed or sized and was in imminent danger of collapse.  The roof ridge beam was severely undersized and had cracked and split.  I noticed this at a kid's birthday party, and I quietly informed the owner that the structure was unsafe.  Later, analysis showed the ridge beam to be extremely overstressed.  So weight is important, but properly sizing and designing structures - even simple ones is critical.

2. 
   caseyr | Jan 07, 2004 05:31am | #9

   Bailing strap - that must be similar to the baling wire we use here rural Oregon to tie down our houses, right...

1. 
   Isamemon | Jan 11, 2004 04:49am | #23

   Bialing wire, good idea, thats probabally cheeper then rebar tie wire

   I wonder if the orange bale twine will work

   got plenty of that here in the willamette valley

   Edited 1/10/2004 8:50:50 PM ET by silverhammer

2. 
   davidmeiland | Jan 04, 2004 11:13pm | #2

   There are various Simpson hardware items that connect the mudsill or joists to the concrete, using bolts, nails, screws, epoxy, etc. You can get a catalog from almost any lumberyard and see what they have. What you end up doing depends a lot on how the house was built. For instance, it's not much good to attach the mudsill to the concrete if nothing attaches the house to the mudsill. Typical construction these days has sheathing panels nailed to the mudsill and to the framing above, so that the structure is nicely fastened together. Don't spent the time putting in a bunch of anchor bolts if you don't have hold-down paths above to make those bolts useful. Consulting a structural engineer is always a good idea for these issues.

3. 
   AaronRosenthal | Jan 04, 2004 11:41pm | #3

   My house is 73 years old, also not bolted to the foundations when built.

   When I started fixing the place, I got lag bolts with anchor sleeves and started drilling through the sill into the concrete.

   Works fairly well. Mind you, we have not had an earthquake to test it, and I hope we never do.

   Quality repairs for your home.

   Aaron the Handyman
   Vancouver, Canada

4. 
   rez | Jan 05, 2004 12:25am | #4

   FHB #29 pg 34

    

    

5. 
   kaorisdad | Jan 07, 2004 12:47am | #5

   I'm in Los Angeles, and the building department here has some guidelines to properly anchor your house.  It's not just anchoring the sill plates to the foundations, it's also about adding shear panels to the cripples at the crawlspace.  You should have plywood shear panels on all sides.  This prevents the house from collapsing at the cripple walls at the crawlspace.  It's really not that hard - just properly nailing plywood sheets to the interior side of the cripple walls in the crawlspace and properly anchoring each end of the shear panel.  (The shear panels are small shearwalls.)  There might even be details on Los Angeles Department of Building and Safety's website.

6. 
   TrimButcher | Jan 08, 2004 07:59pm | #16

   As Joe said, get a Simpsons Strong-Tie catalog and start looking.

   One of the world's premier earthquake research centers is at Univ. of British Columbia (UBC); primary researcher is Dr. Carlos Ventura. Some of their research is funded by Simpsons.  They have the world's largest "shake table".  They built two typical North American housing structures, one with Strong-ties, and one without, and shook'em at 6.7 Richter (similar to the last big California quake).

   The structure without Strong-ties was an insurance write-off (structural failure).  The one with Strong-ties had cosmetic damage.

   Regards,

   Tim Ruttan

7. 
   reinvent | Jan 10, 2004 12:49am | #19

   As has been sugested I would get the simpson catalog. But I would sugest you go one better and contact simpson. They are very helpful and depending on your exact location a simpson rep might come out and give you some recomendations. If you can not get some one to come out you could maybe email them some pics and if they have enough info to go on they will send you a complete take off list of what you need from their catalog.

1. 
   geoffmurray | Jan 10, 2004 07:00pm | #20

   This is an interesting thread. Lots of good info. I have gone through a SImpson catalogue and found an FJA connector, which seems to be what I am after. But intuitivly, it seems I should be putting some connectors at angles. The simple vertical connectors won't prevent racking or twisting.

1. 
   joeh | Jan 10, 2004 07:50pm | #21

   The connector is to attach the structure to the foundation.

   The shear forces have to be dealt with during  construction.

   Joe H

   Edited 1/10/2004 11:51:09 AM ET by JoeH

2. 
   reinvent | Jan 11, 2004 03:38am | #22

   JoeH is right. If your house is shethed in plywood your ok. Otherwise you will need to do a retro fit on the wall either inside or out. However what you are planing on doing is far better than nothing. Good luck.

1. 
   JohnSprung | Jan 13, 2004 11:40pm | #26

   > If your house is shethed in plywood your ok.

   Per City of LA, 1/2" Struct #1 plywood with 8d commons at 6" on the edges and 12" in the field is what it takes. 

   -- J.S.

3. 
   kaorisdad | Jan 12, 2004 07:53pm | #24

   The FJA's are mainly for uplift.  I assume you want to keep your house from sliding off the foundation - alot of houses in Whittier, CA did this after the Whittier earthquake.  What you really need is a combination of several items.  To keep your house from sliding off the foundation, drill epoxy-anchors through the sill plate at 4-feet max spacing.  To keep the cripple walls from collapsing, install plywood sheathing to your cripple walls to act as shearwalls.  You also need Holdowns at either end of the shearwall panels.  The Holdowns can be epoxy-anchored.  You need the cripple shearwalls panels on all four sides of your house, although they don't have to be the full length of your cripple walls.  Assuming your house is square or rectangular in plan, I would put the cripple shearwalls at each corner in each direction.  You'll end up with two shearwall cripple panels on each wall.

   As several of the posters have mentioned, you can contact Simpson for assistance.  I notice that on the Los Angeles Department of Building and Safety's website, they have typical details for retrofit foundation earthquake anchorage that you can download.  The link appears to be broken right now, but I would check back in a few days. 

4. 
   Rachel | Jan 13, 2004 09:34am | #25

   Spend a little money and get an engineer in to give you a retrofitting plan.  Here in California it can cost as little as $300-400 (US).  The reason it is worth it:  you can over-stiffen one part of a building which, as it has been explained to me, means that the less stiff parts of the building can blow out during an EQ.  In other words you want to make sure that each part of the building is going to respond equally to the energy/force of the EQ.  The plan can be detailed or not.  I've got a friend who, after looking at the Simpson products went overboard and created his own tie-down and straps from angle-iron.  But, before doing so, he did talk with an engineer.  Good luck.