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Old 06-25-2011, 09:32 PM   #1
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To bury or not to bury deck posts with Simpson Strong Tie brackets


I see that this is a much debated topic, but here goes. We have a front porch that was built about 3 years ago by a pro. For the support posts, they poured a concrete footer, attached a Simpson strong tie post bracket then buried the whole thing under 6-8 inches of soil. We recently dug out around the posts to apply waterproofing and discovered that the brackets, although galvanized, have rusted terribly. Our question is this: should we worry about this? It was inspected by the city inspectors and passed at the time. What would be a recommendation to fix this? Put rocks around the posts instead of soil? Replace them? Or it it OK as is?

Kathy
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Old 06-25-2011, 10:37 PM   #2
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The purpose of a Simpson plate attachment is to keep the post out of the soil and allow the air to dry it.

There are two reason for the bad installtion:

1. They did not comprehend where the soill eventually would be.

2. They ran out of concrete to build the concrete portion at the right height. - Very common when you have to haul and mix bags within the available time.

Dig out the soil around the post to a at least a foot below the top of the existing concrete that is too low and slip a larger Sonotube (12" or so would be a skimpy guess). Support the deck and cut off the post and cast the new Sonotube post at a height at least 6" above where you "think" the soil may be in the future. Embed a new Simpson connector and connect the post in a day or two.

You got code approval (the worst you can do be leagal, but not necessarily the right way), because there may have been no sign where the eventual fill would be placed.

Correct it now with concrete at the right height or wait and do it later. The brackets may last for a while depending on the moisture and the soil chemistry. Eventually. the buried portions of the posts will be gone in any case.

The worst area is the areas subject to wetting and drying and air exposure. If you ever look at the old piling in a mariana, the several feet near the tidal/wave levels are the first to go and that is for serious wood treatment of old growth wood and not DIY caliber materials. The slight gap provided by the Connector maintains a air gap and separation to protect the wood, because the concrete does quite well at or below the soil level.

Dick
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Old 06-25-2011, 10:58 PM   #3
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Ok, I have a couple questions.

When these "pros" did the concrete pour, did they embed the saddle leg into the wet concrete or did they hammer drill a hole and drop it in?

Even though your post is pressure treated lumber it should NEVER touch earth.. Can you keep the posts away from the dirt? Can you re-grade the ground lower then your concrete posts?

Joey
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Old 06-26-2011, 06:19 AM   #4
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Thanks, Dick and Joey, for the information.

Joey, in answer to your question they drilled a hole into already dry concrete and installed a bolt then bolted the bracket to the footer.

Where it is, it should have been obvious that there would be a fill in with soil to the inspector, in my opinion, but I don't know what they told him as I wasn't there at the time of the inspection. Looking at the footers, it appears that they intentionally poured them at that height as they're all about the same.

The guys that built the porch were very good carpenters and took great pains in every other aspect to make this a wonderful addition. In fact, if the house ever blows down, the porch will still be standing. That was what was so perplexing. They did such a good job otherwise I wonder if they misunderstood the purpose of the bracket, for some reason.

We were hoping for a simple solution as I'm afraid this is going to be an expensive endeavor and beyond our DIY capabilities.
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Old 06-26-2011, 06:50 AM   #5
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Quote:
Originally Posted by joeyr View Post

Even though your post is pressure treated lumber it should NEVER touch earth..
You're right, but wrong as well. Normal PT lumber should never touch the ground. However, I imagine the posts they used (I would HOPE anyways) are PT posts MADE for ground contact. 2 different critters, 2 different treatments. I have a lot of the latter in 6" X 6" posts, 2" X 6" and 3/4" PT plywood all touching ground and/or concrete.

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Old 06-26-2011, 08:30 PM   #6
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And even if they install the correct p.t. wood, they should have used "ZMax", brackets or post bases with thicker zinc coating for the new p.t. wood, scroll down the list for post/column caps and bases-ZMax; http://www.strongtie.com/products/categories/zmax.html

The existing may not have enough coating to resist the chemical leaching out the posts which shouldn’t really be buried (the bases). Slide your cursor over the selection to find yours to compare: http://www.strongtie.com/products/ca...ost_bases.html


Gary
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Old 06-28-2011, 10:34 AM   #7
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Thanks for all the information. As far as I can tell, they used the "new" PT wood and supposedly ZMax brackets, but should these brackets EVER be buried, is our question? And should they show significant rust in 3 or 4 years? We're concerned that these brackets, with the 1" standoff" will eventually rust out and allow the posts to drop down that one inch.
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Old 06-28-2011, 11:01 AM   #8
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The Simpson catalog contains extensive discussion about corrosion induced by various conditions, including soil contact, and contact with pressure treated lumber. The majority of this discussion may be found on pages 10 and 11 of the Strong Tie catalog. I am not going to paste the discussion here, it is too extensive, but you can read it on line if you want to.

Simpson divides exposure into five categories, ranging from interior dry (lowest risk of corrosion) to higher exposure (the worst condition). Brackets in contact with soil are considered higher exposure. The same bracket in a wet condition, not exposed to soil, but in contact with ACQ standard treated lumber, would be a medium condition. If the ACQ lumber is ground contact rated (higher chemical content), then the bracket condition becomes higher exposure.

Here is the point. For medium exposure conditions, Simpson recommends the Z-max bracket, which is what you probably have. For higher exposure conditions, Simpson recommends a stainless steel bracket with stainless fasteners, which you probably do not have. I have never seen stainless Simpson hardware, it certainly is not commonly available at the big box stores. So the bottom line is that covering a Z-max bracket with soil would be contrary to Simpson installation guidelines, and therefore rusting and deterioration of the brackets could have been anticipated.

As previous posters have noted, the solution is either to remove the soil, or raise the concrete footer. Unfortunately the brackets have begun to rust, indicating that the coating is damaged, so the bracket should probably be replaced, but you are going to need to do that anyway if you raise the concrete footer.
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