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Keeping porch posts from rotting

Started by BrentRobinson, December 19, 2015, 07:56:26 AM

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BrentRobinson

Hey Guys,

I'm framing a new house right now and I have cut and planed 8X8 Douglas fir posts and beams for a porch that will wrap around two sides of the house. I'm curious to hear what people have for ideas on keeping the bottoms of the posts from rotting. In this case I poured concrete piers on footings with the foundation and was planning on having some steel under the post so it is not directly on the concrete. The post will not have full bearing on the steam so air can get under around the outsides. In my case 8X8s are way overkill as they are holding up a porch roof that spans 6' so I'm not worried about taking away from it structurally by not having full bearing.

What have others done in the past?
If you don't make time to do it right you'll have to make time to do it again.

beenthere

Best is to keep the bottoms dry.

Finding ways to do that will be the trick.   ;)
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Roger Nair

One of the methods found on old houses is to have hollow posts either bored through or built up hollow with openings top and bottom to enable air to pass through.  Sorry I do not have a suggestion of how to bore through an 8 x 8 end to end.
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canopy

Steel may not be a good choice due to condensation. A timber frame engineer I have worked with recommends 3/8" thick plexiglas plates fitted under the posts. I use these under all posts, not just exposed ones to block any moisture from wicking up from the slab to the post. I also wax the end grain.

landscraper

I did something similar recently, and I shimmed up my posts on 2 - 2" wide PVC shims, and I routed an "X" across the base of my 6x6 posts to allow water to drain away and air to move under/around.  I crowned my sonotube piers to shed water, my untreated SYP 6x6's are locked down with foundation brackets that are anchor bolted into the piers.  Time will tell.
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SLawyer Dave

Here in California, generally you use a post bottom plate.  It is a steel box, open on the sides, about an inch and a half high.  The top plate of the box has some small spikes that go up into the wood of the post to keep it from slipping off.  The box bolts to the pier through the bottom where a hole exists, then you use an open end wrench to sink the nut down, tightening the box to the pier.  The "plate" is smaller than the diameter of the post, so that it does no capture any water that may run down the side of the post. 

witterbound


fishfighter

Quote from: SLawyer Dave on December 19, 2015, 10:56:36 PM
Here in California, generally you use a post bottom plate.  It is a steel box, open on the sides, about an inch and a half high.  The top plate of the box has some small spikes that go up into the wood of the post to keep it from slipping off.  The box bolts to the pier through the bottom where a hole exists, then you use an open end wrench to sink the nut down, tightening the box to the pier.  The "plate" is smaller than the diameter of the post, so that it does no capture any water that may run down the side of the post.

This is what we do here too! I would wax the end grain after cutting a X across the bottom just in case for air to pass thru. Other then that, you could add a piece of treated lumber to the bottom of the post till it is to were the post itself is clear to any chance of getting wet at the bottom. Say 1' or so.

Magicman

 

 
Here is a picture of the poly ones that I used on the Cabin Addition.  I also have used the metal ones which work fine.
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BrentRobinson

Thanks to all of you that replied. Will try and incorporate a few of these ideas and as has been said, Time will tell.
If you don't make time to do it right you'll have to make time to do it again.

Jim1611

I've heard of asphalt shingles being used for the bottom of the post to sit on. 
"Let every man be swift to hear, slow to speak, slow to wrath."

fishfighter

Quote from: Jim1611 on December 21, 2015, 09:39:13 AM
I've heard of asphalt shingles being used for the bottom of the post to sit on. 

I do that when I install treated post into the ground/concrete.

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