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Old 05-28-2009, 06:49 AM   #61
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Originally Posted by DecksEtc View Post
Please show me where in the Building Code that it states that the above method is required?

I have NEVER once had a building dept./inspector tell me to put clear stone at the bottom of a deck footing, EVER.

Until this happens, I won't be wasting any time/money on dumping clear stone at the bottom of my footings.

All of my decks are plenty safe, thank you very much.

Piers for decks and such via sono tubes are supported by surface friction around the concrete column and support as little to do with support carried to the bottom of the pier. If it was as GBAR states, then we would be using a footing like we do with foundation walls.

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Old 05-28-2009, 11:03 AM   #62
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Piers for decks and such via sono tubes are supported by surface friction around the concrete column and support as little to do with support carried to the bottom of the pier. If it was as GBAR states, then we would be using a footing like we do with foundation walls.
Bob, sorry. I don't follow what this means.
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Old 05-28-2009, 11:49 AM   #63
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The condition at the bottom of a sono tube is not that important. The load that a pier can support is based on the total surface area (friction) around the pier. This is why some areas want 12" not 8" tubes for decks.
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Old 05-28-2009, 01:23 PM   #64
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I had to doubt that most support is from friction
Considering that these holes are backfilled & probably not tamped down tight by most people

But appears to be true, provided soil is tamped down

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But the real solution is to make larger and deeper piers, so they do not sink. Larger (as in larger diameter) piers will have greater end bearing capacity on the soil on their bottom end, however, most pilings (you did say they were 8 feet long, so I would call that a piling instead of a pier) get their support from surface friction with the earth.

Let's say that the soil will support a load of only 1500 pounds per sq ft, take a piling which has a diameter of 8 inches, that's 50 sq inches end bearing, which is 1500 / 144 x 50 = 520 pounds of bearing support.

Now, let's take skin friction of the piling, let's say the soil has a skin friction support of 300 pounds per sq ft, take that same 8 inch diameter piling, which has a circumference of 25", with an embedded length of 78" (96" piling with 18" above grade) for a surface area of 1950 sq inches, which means 300 / 144 x 1950 = 4062 pounds skin friction support. Total bearing support = 520 + 4062 = 4582 lbs.

The end bearing support (520 lbs) is very limited when compared to the skin friction support (4,062 lbs). Make that piling a 12" diameter piling and the end bearing goes up to 113 sq inches or 1,175 pounds support bearing ... BUT ... the skin friction goes up too, because the circumference is now 37.7" x 78" = 2940 sq inches of skin area for 6,124 pounds skin friction support. Total bearing support = 1175 + 6124 = 7299 lbs.
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Old 05-28-2009, 01:59 PM   #65
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This exterior surface friction that is supposed to be holding this pier in place as opposed to the end support of the concrete on a tamped base. How is that achieved with a homeowner with a post hole digger? These holes are often(always?) rather larger then the hole the sonotube goes into. The tube is centered and the hole is backfilled. Is it tamped every 6" or so ,so it's packed in? Doubtful. It's more often filled to the top and stepped on a few times and soil added until it doesn't compact any more.
I can't see too much side friction in this scenario.
Does it build up over time as the soil wets and compacts naturally?
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Old 05-28-2009, 02:06 PM   #66
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I actually pack mine down with a sledge hammer
But that's just me
With rain etc I would assume the dirt settles
My last house I put 4x4 PT in the ground & used a sledge to compact rock around them. I didn't use any concrete & they never moved. They were used to build an 8' high lattice wall around my patio
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Old 05-28-2009, 02:29 PM   #67
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I actually pack mine down with a sledge hammer
But that's just me
With rain etc I would assume the dirt settles
My last house I put 4x4 PT in the ground & used a sledge to compact rock around them. I didn't use any concrete & they never moved. They were used to build an 8' high lattice wall around my patio
Dave, for every Extreme DIY guy there are hundreds of Fast Eddy's who barely let the concrete fill the tube before they're throwing load on these piers. The deck is built before the pier concrete has cured and definitely before the dirt surrounding the piers has had a chance to settle.
So initially it's the bottom of the pier that does the support. Unless I'm missing something.
This side friction must build up over time, varying due to soil composition and tamping vigilence.
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Old 05-28-2009, 02:36 PM   #68
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Yeah, that's why I kinda doubted it & searched the web for info
I was sort of surpised to find the info & the amount of support provided by friction
I wonder if this also comes into play with a foundation
I know (most) foundations have footers
Just wondering if this is taken into account somewhere for load bearing

My main reason for tamping was that I didn't want the cement piers to fall over

Actually the info I found (re-reading) was on pilings - which are driven into the soil. So I can see how that has friction support
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Old 05-28-2009, 07:13 PM   #69
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Take a soup can in the yard and step on it. Then remove the soup can's lids, step on it. Hmmmm. Anyway's I did some research on gravel under the footing and piers. Wow, I learned a lot. The gravel prevents the capillary water action from saturating the soil under the sonotube or footing, which in turn can freeze, from contact with the freezing water above the frost line. Called frost heaving, or jacking.

Even the size of gravel makes a difference. Page 32, in Pro Hint:

http://books.google.com/books?id=1gg...num=3#PPA31,M1

And diagram 28- gravel for drainage. Did you read how to size a sonotube rated on load, cool.

Redibase says their tubes need footings, and gravel:

http://www.redibase-form.com/pages/frost.html

Those are just some articles that say tubes need a footing base to protect against frost heave.

Just google "frost heave" or "ice lenses". I did not know this:http://www.oikos.com/esb/43/foundations.html

Gravel under decks, outbuilding footings: http://www.sustland.umn.edu/implemen..._footings.html

I hope everyone learns something, I did. Be safe, G
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Old 06-09-2009, 03:09 PM   #70
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well,stairs almost done. (I'll post some pix when actually finished) time to think about the railing. the one I removed and plan to re-use has a slight problem: the "balusters used 30 years ago were rough and around 1.75 square. I can't seem to find those, only the newer kind which are 1.5 square and finished. that newer kind won't match the rest of the deck. some of the old balusters are split. (not rotten but split) can I rescue those split balusters by pouring a generous "glob" of waterproof glue into the split or are they gonre for good?

tnx,
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Old 06-09-2009, 04:19 PM   #71
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you can try mixing sawdust and titbond glue to use as a glue/filler to fix these. Just fill, clamp, let dry then sand smooth. Use titebond type III glue and another exterior water based glue.
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Old 06-09-2009, 05:34 PM   #72
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If the split pickets are not next to each other, you might try glue. The handrail/guardrail assembly is supposed to withstand 200# of side force to it, as per safety code. When mine split, it is always the grain in the nail or fastener, which greatly compromises the holding power. Be safe, G
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Old 06-09-2009, 06:54 PM   #73
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Originally Posted by GBAR in WA View Post
If the split pickets are not next to each other, you might try glue. The handrail/guardrail assembly is supposed to withstand 200# of side force to it, as per safety code. When mine split, it is always the grain in the nail or fastener, which greatly compromises the holding power. Be safe, G

well,that's interesting. kinda wondered about that. so,how would one know if his railing is up to snuff force wise? is there a "rule of thumb"? is that 200# number something the building code guys made up or is it real? maybe if a 200# guy can't break it it's ok? I weigh almost 200 so if I fall against the railing and it doesn't break,it's ok?

tnx,
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Old 06-09-2009, 10:08 PM   #74
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well,that's interesting. kinda wondered about that. so,how would one know if his railing is up to snuff force wise? is there a "rule of thumb"? is that 200# number something the building code guys made up or is it real? maybe if a 200# guy can't break it it's ok? I weigh almost 200 so if I fall against the railing and it doesn't break,it's ok?

tnx,
The building code guys made it up. They do this stuff all the time.
I once saw two of them get in a car and laugh their asses off after they told this guy building a deck that he had to use metric lag bolts to hold the posts to the deck.
Maybe the KCtermite will pop in, I'm sure he has a few stories.
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Old 06-10-2009, 08:19 PM   #75
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I worked two months in same development building houses. One local Safety and Health Safety Inspector would stop at my house every week on his rounds to unload on me instead of his wife. Twice he investigated deaths on different job-sites, for fault citations, during that period.

Yes, it is a minimum safety code: (opposite the picture of rail failure that killed a young man)

http://www.nadra.org/industry_news/april07_woodbits.pdf Be safe, G

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