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Cedar/Redwood safe for inground post?

emaxxman00's picture

My mailbox and post (plastic cover over 4x4 pressure treated) got vandalized.  I want to build something nicer and sturdier.  I have some cedar (or redwood...not sure which but it's definitely one of them)  4x4 posts (~8ft long) that a neighbor gave me when he moved.  I would like to build a post similar to "The New Englander" at the following link:

I plan on getting some cedar stock and building out the post base like in the pic.  My plan was to make a sleeve for the base that would fit around the 4x4 post.  I would build the sleeve so it had about 1/16 to 1/8" of room for water drainage so water isn't held between the two pieces of wood.  
I would have ~3ft of the 4x4 in the ground.  Is the cedar post safe for ground contact?
If it isn't safe, can I join the cedar post to the existing 4x4 PT post with a Simpson tie (they have one that mates 2 4x4 posts together) and then put the PT post in the ground?  The PT post has been in the ground at least 15 years and shows no sign of rotting.
I would build the base sleeve so it could slide over the Simpson tie (to hide the union of the two posts).

A man who owned the local (post #190281, reply #1 of 11)

A man who owned the local cedar mill told me you could get an extra 10 years out of a post by covering the end with the plastic bag before planting it. Jus cut off the excess at ground level where you don't want it to show. Some people will also treat the buried end with something like End Cut in order to retard rot.

So is rot induced by water (post #190281, reply #4 of 11)

So is rot induced by water wicking up through the end of the post?  I was thinking of using a wood preservative for the submerged portion.  I've also seen where people pour some preservative into a bucket and let the wood sit in it overnight. 

water travels several times (post #190281, reply #9 of 11)

water travels several times farther and faster through end grain then through edge or face. That's why the instructions with some of the preservatives like End Cut suggest you put the end in the bucket and let it wick up. Overnight will do just fine. Depending on the soil type, you can sometimes get preferential rot near the soil line. A good combination of organisms and oxygen is available for "action"

emax (post #190281, reply #2 of 11)

Fill me in-You have a 4x4 already in the ground.  Are you talking mating a cedar post to the top of that?  Can you salvage that in the ground vandalized post in such a way that some will stick up above ground?  A foot or so?  Your sleeve would then go over that stump and really give the whole thing more stability.

As far as joining one to the other at ground level-I've never seen the post joiner from simpson.  Do you have a link to that thing?


A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Hi Calvin, Here's what I (post #190281, reply #3 of 11)

Hi Calvin,

Here's what I currently have:

1) 4x4 pressure treated post in the ground.  Post sticks out of the ground about 3 feet to 3 1/2 feet

2) Vinyl mailbox post sleeve over the 4x4 PT post.  Mailbox sleeve is the vinyl kind found at Home Depot.

3) Vandals broke the vinyl post sleeve (support that holds/supports the mailbox is broken)


Yes, I was wondering if you could mate the redwood post to the PT post.  Here is the connector that I found at Home Depot:

My thought was to connect the two posts together.  Then the base sleeve would cover the joint and more rigidity.  

Obviously if the cedar post was rot resistance enough, I would just put 3 ft of it in the ground directly.

If it would stand up to a snow plow.......... (post #190281, reply #6 of 11)

then you should be ok.  I'd be tempted to carve out the post in the ground (above the ground) and do the opposite to the add on post.  Bolt that lapped joint together-glued too I would.

Way more rigid than what the coupling hardware would do.  It would lengthen the connection.

The sleeve would add some structure-but it's main purpose would be cosmetic.

I've had to repair cedar and redwood due to poor water management and would shy away from sticking it in the ground.  What old growth might have been able to endure I don't think exists as much anymore.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


I'd fill the plastic sleeve (post #190281, reply #5 of 11)

I'd fill the plastic sleeve with concrete, put it back together and let the vandals have at it!

Since you have vandals in the (post #190281, reply #7 of 11)

Since you have vandals in the neighborhood, the cedar post will last at least until they ruin your piece of art.

Probably longer.

I have replaced foundations where homes were built on cedar poles that were a hundred years old more or less. The rot was always in the part about 2" to 10" below surface of the ground. That is where there is both moisture and oxygen to support insects and microscopic wood destroying organisms. Wrap that with saran wrap and you are good to go. No need to end treat to prevent wicking. Wood that deep that stays wet will not rot.



Oh Well,

We did the best we could...

Just curious...would wrapping (post #190281, reply #10 of 11)

Just curious...would wrapping the submerged part of the post in the same rubber adhesive membrane that you use around door and window installations provide enough protection?  I don't remember the proper name for it but I have a fair amount left over from when I installed my front door.  

Vycor (post #190281, reply #11 of 11)

Yes, that'd be good



Oh Well,

We did the best we could...

contact your local poco.  (post #190281, reply #8 of 11)

contact your local poco.  they often have 'pole butts' from old and trimmed new power poles.  typically pressre treated beyond anything available at big box.

I put in an 10 in. dia pole butt for mail box after a vandalization - dope tried to run it down, whoever succeeded in busting their radiator

- evidenced by tranny fluid and antifreeze pool the next morning- 


a little while later, box had an M80 attack, so now have a 3/8" steel plate mail box - still mounted to the pole butt, no problem since then