cover treated lumber with tar?

going to use 10 treated 4x6 posts as foundation for 10x12 shed.....guy at menards sugested coating with tar to extend life. sounded like good idea to me...also building inspector guy advised me not to concrete posts in ground or frost will be problem.....dig holes 48" then concrete in bottom of hole and posts sit on the concrete....sound OK? Thanks
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snipped-for-privacy@home.com wrote:

4 x 6 posts?
Are they square? Do you mean 4 x 4 or 6 x 6 posts?
So you're not going to have a poured concrete pad or floor for this shed?

He might mean creosote. Paint the in-ground portion with creosote (several coats) - let it dry in the sun between coats.

I've done it. Wood posts (6" x 6") set into 1-foot diam. concrete posts (piers) set 4 feet in the ground.

What is the frost line in your area? 4 feet is about the deepest you need to go in northern US and Canada except possibly Alaska.
You can do 10" holes (12" if necessary), get cardboard sono-tubes, set your creosote-painted posts in the holes and then pour concrete. Have the top of the concrete come to at least 2" above grade - 6" is better. Throw some 1/2" rebar into the concrete (2 or 3 pieces, each one 4-ft long). That will make it indestructable.
Mix the concrete properly. NOT TOO SOUPY. USE AS LITTLE WATER AS YOU CAN. CLEAN SAND AND CLEAN 1/2" CRUSHED STONE.
Use a tamper (or rent a vibrator) to properly place the concrete (important when you minimize the water content).
All concrete shrinks when it cures. The more water you use, the more it shrinks. A concrete pier shrinking around a wood post will result in cracks radiating from the corners of wood post. The rebar will help hold the pier together if that happens.
The concrete will also protect the wood post from rotting. But only if you properly mix and place the concrete. If you just throw some cement, sand and stone in the hole (or the pre-mixed concrete stuff) and pour some water on it, you'll just end up with shit.
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4x6 posts have been available for as long as I can remember.

Creosote, and most tar related products, are now restricted use pesticides. You have to be licensed to buy and use it.
KC
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KC wrote:

I've never gone out to look for 4 x 6 posts at the local big-box stores but I've never seen any there while looking for other things.

I bought a 5-gallon drum of the stuff about 7 or 8 years ago from a farm supply place (TSC - Tractor Supply). I'd imagine that it's still available - if only at farm supply stores.
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Many farmers have restricted use licenses in order to buy & apply chemicals to their ag products, so restricted use chemicals are out there. However the business can be fined & lose their business license if they sell to Joe Public. All sales have to be recorded. All applications have to be recorded also and are subject to state & federal review. I have a license and have to renew it every few years.
The current list of EPA restricted use pesticides include coal tar, coal tar creosote, creosote oil, and creosote solutions, because of possible oncogenic and mutagenic effects.
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I can vouch for 15-20yrs ago availability. Needed a long one.
But today I go to the damn Blue Borg to get some regular 5/4 for cornerboards (not decking). Nope. Don't stock. And I wanted to get some 10d galv finish. Nope. 8d then next is 16d. Not even a hole or label for them. WTF?

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snipped-for-privacy@home.com wrote:

It is a little more concrete to mix, but correct answer is to pour rebarred concrete piers (probably using the cardboard Sonotube forms), and drop a big J-bolt in the top to anchor a metal standoff plate from Simpson or similar. You then put the 4x6 posts in the standoff plates. Once shed is framed and squared up, you lag the posts in place through the holes on the standoff plates. If the piers are down into undisturbed soil, they should last essentially forever, and your timbers will probably never rot. Piers don't have to be tall- just want them higher than the rain splash/snow line, and tall enough to make it obvious if any termites start building tunnels up to the wood.
If that sounds like too much work or bother, just put gravel in the bottom of the hole, set and square the the posts, fill the sides with tamped gravel, and maybe put a small concrete cone on top to shed rain. Idea is never to trap wood in a concrete pocket- always give the water someplace to go. IMHO, tar will do more harm than good, and tend to keep the wood wet.
And unless you have strange local conditions, inspector guy sounds clueless- if the hole is below frostline and into undisturbed soil, and properly sized, frost heave shouldn't be a problem. Maybe he meant to not put a big concrete mushroom on top at dirt level- that can heave enough to yank even a deep post out of position.
-- aem sends....
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wrote:

Why not jusy build it on 6X6 PT skids and put it on blocks??? It is just a shed and it will be a heck of alot easier to move when SWMBO says it would look better over there or you decide to build on an addition or garage in that spot...LOL...See the thread below about moving a shed...LOL....
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wrote:

Right, good advice, don't listen to the inspector.
Around here, if the inspector says a concrete footer, gravel won't do.
Here they inspect the holes b/4 the pour & after. Here, when the inspector says a 6" concrete footer, they don't want to see gravel. If they do, the red tag comes out.
Footers are not something unusual. I guess it is if you don't have building codes.
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Cabot wrote:

For a shed?
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What the inspector says, goes. Whether you like it or not.
When you're talking a permanent structure, going below frost line, yeah, footers are mandatory in this neck of the woods.
The idea behind codes, are to eliminate shoddy practices.
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First time I ever heard of getting a permit for a shed too. Peerhaps his definition of a shed is different than what I am used to
Jimmie
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JIMMIE wrote:

versus just sitting on loose blocks or sleepers, it needs a permit, if they notice. Foundation makes it a 'permanent structure'. Permanent structures also can raise your taxes, so up-on-blocks is the usual method here. Not sure how they would regard cast-in-place concrete piers. Although it seldom gets real windy around here, I would at a minimum use those mobile-home tiedown thingies on the corners, for a shed not bolted to concrete or built on buried wood posts.
-- aem sends...
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First time I ever heard of getting a permit for a shed too. Peerhaps his definition of a shed is different than what I am used to
************************************************
In my town, anything over 100 sq. ft. needs a permit. It must also be 10' away from the property line.
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On Jul 17, 5:59pm, snipped-for-privacy@home.com wrote:

You're way over-engineering a small shed. Post frame contractors simply dig the hole, toss in a bag of premix formulated for the job, install posts, and back fill the holes. A Morton building (larger than your shed) in our neighborhood was finished in 1972 and still is in service in good shape defying the Illinois winters.
Joe
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Listen to your inspector.
Make sure you get _ground contact_ 4x6's. They do make several different kinds. Forget the tar.
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When I built my Dads 10 X 12, I set the finished PTL 2 X 4 frame floor on 3- 12 ft PTL 4X4's lying flat on the ground (I put a 2-3" gravel base underneath).
Put One in the center and the "outer" two set about one foot in from the sides. If it needed moving, I'd just drag it on these skids. It hasnt needed to move and so its been sitting there for ten years now, just fine. Nothing "Dug-In" or buried in the ground.
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