Since there have been a couple of recent threads regarding the proper fasteners for ACQ lumber I started wondering why steel bolts with diameter >= 1/2″ are exempted from the galvanized/stainless requirement in the IRC.
Edited 11/6/2005 11:43 pm ET by Soultrain
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All I can think of is it would take a long time for rust to eat through them.
I do believe that your rationale is correct. Pretty weak though, if you ask me.
I still see regular 1/2" steel J bolts on most foundations I frame on. I keep a can of spray primer or two in the truck and we'll usually blast them real quick. Better than nothing I guess. We also drill out the holes in the PT a little over size so there isn't a ton of contact. The second KD plate then gets drilled tight and we use an oversize washer to really clamp the plates down. Best I've come up with, so far.
Yeah, my feeling is that 1/2" are okay because they may only rust down to say, 3/8" in ten years, why don't they allow 3/8" on non-PT? (Maybe tehy do--I'm not that familiar with codes). And who's to say where the rust stops? In Michigan the highway dept. required Cor-Ten steel on bridges and highway overpasses and such because it was supposed to get a thin layer of "protective" rust, then the rusting process was supposed to stop. Well, they found out that in structures exposed to road salt and so on, that process did not stop after a thin coat and things that were supposed to last twenty or more years were falling apart after a few years.
That's what I figured, but if you need 1/2" bolts, wouldn't you want them to remain 1/2" thick? My only guess is that for foundation anchors, they feel that the compression from the weight of the house holds the top of the wall in place. That seems pretty silly to me because hydrostatic pressure (especially if you have a full basement) can be pretty intense. Also what if you live in a seismic or high wind region?
Right (concerning wanting half inch bolts to stay half inch), see my reply to Dieselpig. But I think the foundation bolts are mainly to keep the house on the foundation in an earthquake (might be wrong). In Michigan (not many earthquakes) we were told in drafting class that they prevented the house from being lifted off the foundation in high winds. Most of the time, the weight of the house will hold it to the foundation.
Up until 2002 foundation bolts were not required here in NC, except where you had a wall sitting on top of a wall. An example of a wall on a wall would be a garage wall sitting on a masonry stem wall foundation, or a step down foundation "pony wall" sitting again, sitting on top of a masonry/concrete wall. So, prior to 2002, thousands and thousands of houses were built with no anchor bolts. Of course there were extra requirements in high wind and seismic areas (the costal counties & some mountain counties) which did include anchor bolts. Now anchor bolts are required everywhere in NC (IRC 2000 adopted in 2002) although I have never heard about houses coming off their foundations except in situations where the house was a total loss anyway - usually the roof goes first...
Besides, just think - it Dorothy's house was anchor bolted down she probably would have died in Kansas as the house tore apart and she would have never met the Wizard of OZ.
With respect to deck construction, the flavor of the IRC2000 we use here in NC has been modified to require HD galvanized bolts. Here, for this application, HD gal bolts have been required for at least 10 years that I can remember. Not the case though for J bolts (anchor bolts). HD galvanized J bolts are becoming available in home stores, but our local masonry suppliers still don't stock them.
Just out of curiosity, what version (year) of the IRC do you all use? Does your state modify the code you all use, or do they just adopt it as supplied?
Remember though, building codes are minimum requirements.
Here is another thought: why aren't all masonry and concrete anchors HD galvanized? I mean it's almost a given that they will be installed in damp environments. I've wondered about this for years.
Edited 11/7/2005 7:54 am ET by Matt
Can you tell the difference between HD galvanized & electorplate galv (are these the same as Zinc plated?) by appearance? or do you simply assume it is not ACQ rated unless you actually pull them from a box that is labeled "rated for ACQ" or "HD galv"?
From looking in the hardware store, it seems that the HD galv fasteners are more of a dull gray whereas the electroplate galv seem to be more of a silvery color.
HD galvanized are dipped in molten zinc, usually twice to get the HD rating.
Electrogalvanized are just what you say-electroplated with zinc. Its a much thinner coating of zinc.