Does setting posts in foam give them some protection from dry rot?

[Stephen Tashiro]

Does setting treated wooden posts in foam (the kind that's designed for setting posts) give them some protection from rotting?
Is it easier to replace a post that's been set in foam that a post that's been set in concrete?

I want to build a pergola and I'm debating how to set the posts.

Options:
1. Bury in the ground
2.. Set in concrete
3. Set in foam
4. Pour a concrete pad and set the post on a post anchor on top of the pad

My experience with cedar and treated lumber in this climate is that it dry rots in about 10 years when buried. I think posts last longer when set in concrete, but when they must be replaced, it's a pain in the neck. Posts set in post anchors on top of a concrete pad hold up well, but they must be temporarily supported during construction.

[Jamie Buxton]

Last week I watched a crew replacing a wood utility pole. They bored a hole with a truck-mounted auger, dropped the creosoted wood pole in, and backfilled with gravel. They used a vibrator to compact the gravel as it was poured in. Done. No footing, no concrete, no foam. There's a lesson there.

[Mike Henderson]

When I built one, I poured a slab then used those Samson devices. It's been a while but I think I drilled into the concrete and then used bolts set in construction epoxy to attach the Samson thing to the slab. Then you put the post into the Samson, drill some holes and attach it. The problem is that you have to make some skirts to hide the Samson. These only have to be about 18 inches high.

The Samson device supports the post about an inch from the slab so water doesn't wick into the bottom.

I'm going from memory here. Of course this approach assumes you're going to use a slab.

Mike

[Frank Pratt]

Are you talking about Simpson post anchors? They make all manner of brackets for joining lumber.

[Bryan Lisowski]

Last week I watched a crew replacing a wood utility pole. They bored a hole with a truck-mounted auger, dropped the creosoted wood pole in, and backfilled with gravel. They used a vibrator to compact the gravel as it was poured in. Done. No footing, no concrete, no foam. There's a lesson there.

There is no lesson to be learned, the utility company sends its customers a bill each month, so since you and the others are paying for present and future replacements, they don't care how long they last.

[Rich Aldrich]

I built one for my daughter and did not sink the posts in the ground. We used the sonotubes from Menards. We were down to bedrock at 30" so we poured concrete in the tube and used a simpson post anchor like Mike did. Both the tubes and the post anchors are available at Menards and something similar if not the same at the other box stores. That was 5 years ago.

[Lee Schierer]

There is no lesson to be learned, the utility company sends its customers a bill each month, so since you and the others are paying for present and future replacements, they don't care how long they last.

Maybe there is something to learn. The utility pole in front of our house was several years old when we moved in 1977! It is still the same pole. That's at least 43 years. How many fence posts last that long?

[Eric Arnsdorff]

20 years ago I built my deck and poured concrete footers with piers and used the Simpson brackets.
The only issue I had with my posts are the Simpson brackets are rusting out.
I added onto my deck and resurfaced it this last year. I decided to try a different approach.
I left rebar and galvanized all thread sticking up out of the piers. I coated the ends of the posts with primer and then bed-liner. I crossed drilled the holes for the rods so I could epoxy them in place.
This was a lot of work but seems to have worked well. Hopefully they will last well beyond 20 years.
440609

[Andrew Seemann]

Maybe there is something to learn. The utility pole in front of our house was several years old when we moved in 1977! It is still the same pole. That's at least 43 years. How many fence posts last that long?

Plenty, if they have been doused in that much creosote:)

A post will rot if water gets trapped around it, like if a post is set in concrete and is completely surrounded, including the bottom. For a fence post you can set the post in the hole touching the ground (needs to be rated for ground contact) and then pour concrete around it.

For anything bearing a load or that needs to resist uplift, it is best to pour a footing in concrete, and use one of the concrete to post anchors. Ones that you set in wet concrete are easier, but you need to get them located right, since you can't adjust them.

[Mike Henderson]

Are you talking about Simpson post anchors? They make all manner of brackets for joining lumber.

Yeah, it's been a long time and I couldn't think of the exact name. I drilled holes in the concrete and epoxied in threaded rods. Used that to anchor the Simpson brackets with nuts on the threaded rods. The Simpson brackets set the post up about an inch.

Mike

[Bruce King]

I rent a two person auger, dig hole at least 30 inches, more up north. Put some bricks in the bottom to keep water away and set the post on it. Fill with concrete to a few inches above grade.

[Bill Dufour]

Modern ground contact lumber should be rated at 50 years or better. I assume it does not rain that much in new Mexico so they should last longer. The two telephone poles at the family home are at least 70 years old but they came by every 5-10 years and drilled a hole and poured in more creosote then pounded in a dowel to seal the hole. Utilities have a department of actuaries to determine when to replace a pole. Growing up our neighbor was one.
Bill D

[John Gornall]

Fence on 1 side neighbor insisted on concrete. The other 2 sides my way - compacted sand. Dug 30 in deep, put in and plumb pressure treated post, pack sand in 6 inch layers. Concrete posts lasted about 15 years - wind blew fence down, rotten posts. Posts in sand still good over 30 years

[roger wiegand]

I was always told that water was the enemy and that concrete was an efficient way to wick water into the wood. With untreated or above ground treated posts (the only kind they seem to sell at the Borg) posts set in concrete seem to last in the 7-10 year range. Posts set in gravel last several years longer; wood treated with the underground rating lasts near forever. I stopped using concrete decades ago and have only used gravel since.

It's also easier to jack out a post that's been set in gravel than concrete. I've never noticed any increased rigidity with concrete.

[Thomas Colson]

#4: Set on top of concrete using an anchor that keeps it 1" high. OZCO has an amazing interactive catalog with at least 20 different post anchors that IMHO will outlast and outperform the Simpson. At least in my county, inspector will not approve any wood in the ground, for any use, reason, type of wood/treatment, or method of construction. I think it was UVA that demonstrated that even posts set in concrete can rot, and most jurisdictions amended their code shortly after. With the set on top method, you can, with some difficulty and approval of an engineer and the inspector, use specialty concrete grouts and adhesives to remove a post/bracket, drill a hole, and get another one in there without having to replace the concrete. Be careful how you orient the brackets: They only resist movement in one direction so you have to get creative with a free standing structure and plan to resist movement in both directions with your posts. In my office building, lots of exterior posts 8 X 8 set on these giant 3/4 inch galvanized steel brackets with the mounting part kerfed up into the middle of the post all secured with 1" stainless bolts. On my list to ask our buildings guy where those were spec'ed because that's what I'm going to use on my deck.

[Carl Crout]

Been farming and ranching for over 40 years. My dad taught me to not put concrete around a wood post as it will make it rot faster.

Since creosote was outlawed treated lumber . I used some landscape timbers treated with CCA and they were just laying on top of the ground to hold gravel in place. They didn't last twenty years

[Frank Pratt]

There are different grades of pressure treated lumber. Most of what the home centers sell is not rated for ground contact. That's why pressure treated is getting a reputation for rotting quickly. The stuff rated for ground contact is supposed to last 50 years minimum.

My fence posts were set in concrete almost 30 years ago & it's still as sturdy as it always was.

[roger wiegand]

For foundation piers I agree completely that they should be set above ground either with a gap or a very high quality water barrier to stop wicking from the concrete into the wood. (standoffs work great for posts, harder for sill plates and such, trickier for sill plates and such). I always avoid wood in direct contact with concrete. I thought we were talking stuff like fences and mailbox posts.

[Mel Fulks]

I've seen some stuff about using gravel and all the users are happy. I have to replace a post box 4x4 ,gonna use new
SHARP gravel. Gonna treat post with my copper naphthenate ,if I can find it.

[Rob Damon]

Utility poles are infused with some real nasty chemicals that you are not going to find in big box store lumber. They are meant to last 70 plus years direct buried in the ground. All of our structural engineers and architects design a concrete foundation with an L-anchor bolt bolted to steel plates or simpson plates to keep the wood post off the ground .

[Warren Wilson]

I’ve used several methods, from compacting plain dirt (bad idea), concrete, concrete with a galvanized bracket on top, and most recently I used the foam.

Around here the key is to keep the place where the post emerges from the ground as dry and clean as possible. I found it easy to expand the foam above ground then sculpt it down away from the post. (In fact the directions stipulate that you pour some foam down the sides of the post like that). It adheres well to the wood, and I am hoping that the protective foam cone will shed water and keep dirt from contacting the wood. Of course I used treated wood, but belt and suspenders.

One thing I was dismayed at was how much more foam I needed than the directions said — even though I used the specs as to hole and wood diameter and depth of hole. It certainly sets faster than concrete, so you want that post held plumb and correctly positioned before you start: there’s not too much wiggle time.

[Brice Rogers]

Simpson makes a variety of 4 x 4 and 6 x 6 fasteners to attach wood to concrete. The wood sits on top of a raised platform of metal and is not in contact with the ground. The metal bracket is bolted into the concrete with an expanding anchor or epoxied bolt.

https://www.decksdirect.com/media/catalog/product/cache/b8d45b4f9d6eeb8cac81a950e24c1a61/a/p/apb1010__1_600.jpg

https://www.dhcsupplies.com/resize/images/simpson/Outdoor_Accent/simpson_apb66.jpg?bw=1000&w=1000&bh=1000&h=1000

[Steve Rozmiarek]

No ones answered the question about the foam yet. As long as it's closed cell foam, it'd offer the similar protection as concrete, so not much. Water can still get in where the foam stops, and wick anywhere it wants. Foam would then hold the water in better than concrete, so your post would always be in moisture. If you have freeze/thaw, it's wetness could introduce another dynamic. Use brackets. Temp braces are your friend, and you'd have to use them on posts set in concrete while it dries to.

[Bill Dufour]

Foam or concrete will rot the post where it touches. I have removed several rotten posts that were sound above and below the concrete. difficult to get the lower portion out.
Bill D

[mike stenson]

Foam or concrete will rot the post where it touches. I have removed several rotten posts that were sound above and below the concrete. difficult to get the lower portion out.
Bill D

This. The only posts I'll concrete in (and these days I just dry pack it) are vinyl or steel.

[Neil Gaskin]

We always use Simpson CBPC cast in place post bases for pergolas as well as for post at the bottom of the stairs on decks. I believe these offer the best up-lift resistance and are attractive.

The problem with anything set in the ground is that it is going to rot at some point in the future and replacement is a bear. If you do decide to set the post in the ground, or even if you don't coat the bottom and sides with Anchor Seal. It can be applied over stain. It forms a protective wax like surface over the wood. We treat the first foot or so that above grade.

I cannot speak to the foam, I've never seen it?


https://www.strongtie.com/classiccollection_architecturalproductsgroup/cbpc_base/p/cbpc

https://uccoatings.com/products/anchorseal/

[John C Bush]

I built a pergola using the Simpson Outdoor Accents hardware system that Brice shows above in his #7 reply.
I is a great system that made the build very simple and solid--for the posts as well as all the other joinery. It is spendy but I volunteered to supply the cedar stock and build out for our small town so they paid for the hardware. We poured footers and used the bases/anchors shown above to attach the posts and all the other fixtures for the other joints. I'm not a construction guy and was concerned about the 12' X 20' structure racking but I used knee braces everywhere I could and the structure is very solid. There is no lift issue with an open pergola and no significant racking. The stock is joined with long lags with "washers" that look like large hex bolts. Great look, easy to install and really solid. I would use them even if I had to pay!!440727
Good luck.

[John Grossbohlin]

There is no lesson to be learned, the utility company sends its customers a bill each month, so since you and the others are paying for present and future replacements, they don't care how long they last.
The poles on the street my parents live on were installed when my grandfather bought the property with 1000' of road frontage. That was about 78 years ago. The poles are being replaced now not because they have failed but because the power company is hardening their distribution network with bigger, taller poles in addition to adding redundancy to sub-stations and more distribution lines. The original poles were set in ground that is clay and shale as are the new ones... back-filled with crushed stone. The poles in my neighborhood have been replaced too and based on the age of the houses there is a good chance those poles were closer to 95 years old. At some point the cross bars were removed from almost all the poles in the area when new wire was strung. One of my back-fence neighbors worked for the power company when that was done and he framed his garage and fence posts from the old cross bars. Collision damage is the biggest problem around here... an astounding number of poles are hit by vehicles! Within a 1/4 mile of my house I know of three poles that were broken by collisions in the past two years... and 6 within a 1/2 mile in the past 10 years. The bigger poles, and metal poles, they installed to replace them may not break!

[Andy D Jones]

There is no lesson to be learned, the utility company sends its customers a bill each month, so since you and the others are paying for present and future replacements, they don't care how long they last.

The monthly payment is set, so if they can avoid replacing poles for longer, they get to pocket the extra money. On the flip side, the less they have to pay to replace it, in labor and materials, the more they pocket as well, all else (longevity, etc.) held equal.

The pursuit of profit will balance the cost and longevity of the method of installation to maximize said profit.

That said, the precision with which a power pole retains its position and angle is probably significantly less than that of a support for a rigid structure. I believe the poured footings for transmission line towers (single base or multi-footed) would bear this out. Thus the power pole method may not be applicable to that of a column supporting a pergola.

Andy

[Thomas McCurnin]

Some county inspectors recommend "Post Guard" (a plastic product which goes beneath the grade and surrounds the post) and/or "Grade Guard" (a product which goes slightly below grade and slightly above grade).

https://www.postprotector.com/post-protector-grade-guard-post-decay-protection/

[George Makra]

When i was a kid i dug thousands of fence post holes. Back filling with gravel was the best way to secure the post since once packed the gravel locks together and allows for drInage.
Concrete will retain moisture and will slowly deteriorate the wood even if it is treated.

[Tom Bender]

So much depends on your local soil moisture and on the species of wood.