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Sealing Posts That Go Below Water Table

 
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Old 12-30-2019, 10:29 PM   #1
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Sealing Posts That Go Below Water Table


These are 6x8 x 12' w.r cedar posts for a structure I shipped to the gulf coat of Texas. They'll be going 4' in to the ground, and the water table is at 3'.

what's the best way to seal the bottom 4' of those posts? I'm thinking epoxy or epoxy paint, but I've never dealt with this water table issue before. We already used an oil based stain on the part above ground.
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Old 12-30-2019, 10:45 PM   #2
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Re: Sealing Posts That Go Below Water Table


ipe ends are covered with a wax covering, can cedar be covered in the same way?

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Old 12-30-2019, 10:54 PM   #3
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Re: Sealing Posts That Go Below Water Table


The end grain is the most important but I'd like to seal the sides also.
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Old 12-30-2019, 11:30 PM   #4
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Re: Sealing Posts That Go Below Water Table


I’ve used Anchor seal for end grain. No reason it won’t work on the edge grain.

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Old 12-31-2019, 07:55 AM   #5
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Re: Sealing Posts That Go Below Water Table


Be careful about sealing the wood under the water table, you'll lock it in and it will start to rot from inside out. Best to seal the bottom and the first foot or so underground with a waterproof coating.

Our water table a lot times is 12-18" below ground. The place posts will rot out here is at 6" above, below, and at soil level. Water really isnt as bad as moisture/dry condition. It's why pilings on docks rot at the waterline and not at the bottom.

If the water table is at 36" then the post will always be wet at 24" too. If you were to paint everything from 30" below soil level, and then take care of soil level, it should be fine. Put some kind of drainable rock at the first 6 inches below ground and it should work perfect.

It's not uncommon on the Gulfcoast to replace post every 5 or 6 years if they arent done correctly.
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Old 12-31-2019, 09:00 AM   #6
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Re: Sealing Posts That Go Below Water Table


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Originally Posted by Deckhead View Post
Be careful about sealing the wood under the water table, you'll lock it in and it will start to rot from inside out. Best to seal the bottom and the first foot or so underground with a waterproof coating.

Our water table a lot times is 12-18" below ground. The place posts will rot out here is at 6" above, below, and at soil level. Water really isnt as bad as moisture/dry condition. It's why pilings on docks rot at the waterline and not at the bottom.

If the water table is at 36" then the post will always be wet at 24" too. If you were to paint everything from 30" below soil level, and then take care of soil level, it should be fine. Put some kind of drainable rock at the first 6 inches below ground and it should work perfect.

It's not uncommon on the Gulfcoast to replace post every 5 or 6 years if they arent done correctly.
Same with cedar fence posts here, always at ground level at 5-6 years
Cedar is useless here
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Old 12-31-2019, 09:30 AM   #7
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Re: Sealing Posts That Go Below Water Table


What would you use to seal it Deckhead?
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Old 12-31-2019, 09:47 AM   #8
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Re: Sealing Posts That Go Below Water Table


I would paint some penetrating wood preservative onto the sides, especially at the ground level and above. And finish with gravel around the top of the base instead of soil.
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Old 12-31-2019, 12:37 PM   #9
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Re: Sealing Posts That Go Below Water Table


Why do anything if it's in water and there is no way to keep it dry
We NEVER put wood post in the ground here. I guess you don't have the termite problem we have here.
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Old 12-31-2019, 01:02 PM   #10
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Re: Sealing Posts That Go Below Water Table


yeah I never put posts like this in he ground either but that's what the engineer called out as this is in a high wind hurricane danger zone.
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Old 12-31-2019, 01:16 PM   #11
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Re: Sealing Posts That Go Below Water Table


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yeah I never put posts like this in he ground either but that's what the engineer called out as this is in a high wind hurricane danger zone.
Add Seismic to that and that's is what we build for here. Engineers
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Old 12-31-2019, 05:05 PM   #12
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Re: Sealing Posts That Go Below Water Table


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What would you use to seal it Deckhead?
I've used the stuff they use to seal concrete for tile crack suppression and it worked well. Honestly you just dont want it weeping up water through the bottom and getting to where it dries quickly. I'd epoxy the bottoms. Anchor seal is okay but it's a wax and wont last as long and has a tendency to melt (doubtful it will melt under water) but doesnt seal completely as it doesnt go into the wood pores. Really you just want protrusions covered. You arent going to keep water out of it.

The idea is to let the water out and in at a slow pace. Too quickly either direction and you end up with dry rot or fungal growth.

If you have a good oil on it there is no reason it wont last as long as the bottom end grain is sealed beyond expectation. WRC on our coast is a tough one.
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Old 12-31-2019, 05:08 PM   #13
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Re: Sealing Posts That Go Below Water Table


The owner is going to use an epoxy paint which is what I'd do also.
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Old 01-01-2020, 10:03 PM   #14
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Re: Sealing Posts That Go Below Water Table


Q8 log oil would be my preference for water repellent. You will never really stop water intrusion of cut ends but this stuff is good.

If you're concerned about fungus or bugs I'd go with Woodlife Copper Coat or Boracare. If it's deep down then you're unlikely to really have issues with either of those until you get to the top 12" of soil.

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