Fence Building: Soaking cedar fence posts in preservative?

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Mrs.Feeley
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Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

Any fence builders here? Here's a question from my better half about planting posts: He's re-doing a section of our cedar rail fence. He built the fence and planted the posts years ago, and for years helped his granddad build fences on the farm. For the most part farmers would simply plant posts in the ground, maybe slathering some tar around the post at ground level. That's how he's always planted fence posts in the past. But doing some Googling he discovered that it's recommended that fence posts:

* Be planted in backfilled gravel. He's skeptical. Wouldn't dirt eventually settle in amid the gravel and make all the hassle of using gravel useless?

* Be soaked in preservative. What kind of preservative? Does it really make the post last longer? And how do you get rid of these chemicals after you're done soaking your posts?

Any insights would be appreciated!
JoinToday
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by JoinToday »

FWIW: I put up a fence in the late 80's. I had no experience when I built it, but read up on it. This is what I did:

Hole was 6 inches deeper than the bottom of the post. Gravel at the bottom of the hole (6 inches), plus a little more (couple inches) around the side after the post was in the hole. Then concrete filled the rest of the hole, with a little slope away from wood post so water wouldn't collect and stand against the wooden post. Redwood posts were painted with some sort of preservative, the entire post was coated, not just the bottom. Stunningly, the fence is still standing and the posts are intact. I used to worry when we have big winds, but haven't had any problems to date. It is a solid fence (for privacy), 1x6 cedar planks. Posts were 8 feet on center.
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Mrs.Feeley
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

JoinToday wrote:FWIW: I put up a fence in the late 80's. I had no experience when I built it, but read up on it. This is what I did:

Hole was 6 inches deeper than the bottom of the post. Gravel at the bottom of the hole (6 inches), plus a little more (couple inches) around the side after the post was in the hole. Then concrete filled the rest of the hole, with a little slope away from wood post so water wouldn't collect and stand against the wooden post. Redwood posts were painted with some sort of preservative, the entire post was coated, not just the bottom. Stunningly, the fence is still standing and the posts are intact. I used to worry when we have big winds, but haven't had any problems to date. It is a solid fence (for privacy), 1x6 cedar planks. Posts were 8 feet on center.
Thank you so much! I've passed on your recommendations. Would kind of gravel did you use? Pea gravel? We have lots of gravel gathered from gardens, but it's mostly larger chunks. We've been debating whether to buy a bunch of pea gravel.

DH originally build this particular cedar rail fence about 15 years ago, but some of the posts, especially those by gates, are getting a bit wobbly. He had been planning to plant the posts in concrete but one of the things he read on the net was that small spaces could develop between the concrete and the post, bacteria could take hold and quickly eat away at the wood. But one would think concrete would be essential for keeping the posts stable over time. A fence that's been up since the '80s is VERY impressive! :beer
letsgobobby
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by letsgobobby »

JoinToday wrote:FWIW: I put up a fence in the late 80's. I had no experience when I built it, but read up on it. This is what I did:

Hole was 6 inches deeper than the bottom of the post. Gravel at the bottom of the hole (6 inches), plus a little more (couple inches) around the side after the post was in the hole. Then concrete filled the rest of the hole, with a little slope away from wood post so water wouldn't collect and stand against the wooden post. Redwood posts were painted with some sort of preservative, the entire post was coated, not just the bottom. Stunningly, the fence is still standing and the posts are intact. I used to worry when we have big winds, but haven't had any problems to date. It is a solid fence (for privacy), 1x6 cedar planks. Posts were 8 feet on center.
This is how it's done around here (a wet area). If dirt is in contact with the wood, even pressure treated cedar, it will eventually rot. Gravel, then concrete, and make sure the concrete is just above ground level so dirt doesn't slowly cover the concrete and come in contact with the post.

also occasionally brush away dirt that piles up and touches the bottom of the fence boards, or those will rot, too.
Last edited by letsgobobby on Thu May 05, 2016 1:06 am, edited 1 time in total.
JoinToday
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by JoinToday »

I probably used the cheapest small gravel sold in bags from home depot. Smaller than what is used in concrete. Probably some sort of pea gravel. For gate posts, you have to have the concrete, and consider putting the posts a little deeper than normal. The forces on a gate posts will cause them to wobble over time if you dont. And make the hole at the top bigger than normal so the concrete spreads the force over a larger area.

I have heard the same thing about concrete & fence posts. The previous owner of my house put up a fence. The top of the post at ground level was in concrete, the bottom was dirt. Termites ate the bottoms in dirt.

Consider galvanized steel posts, with wood for the rest, if that works for the fence. It never rots, and with enough galvanized coating, I think it would outlast wood.
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Leeraar
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Leeraar »

I doubt that any home treatment would be effective and not very toxic. Just put the posts in the ground. Where do you plan to be in 15 years?

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onmyway33
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by onmyway33 »

I am planning to DIY install a wooden fence at my house in the coming weeks and have been researching this exact topic, so your post is very timely for me and I will be following this thread for any helpful feedback from others.

Your post install plan is very similar to mine, and I am planning to use a wood preservative with Copper Napthanate. Here is an example:
http://www.homedepot.com/p/1-qt-CopperC ... 9C1D0D3F50

I would use something a little bigger than pea gravel in the base of the hole, maybe a 1/2 - 1 inch aggregate.
I am also planning to apply a bead of exterior caulk between the post and concrete to help maintain a water tight seal.

Here is a good overview, from a pretty decent source :
http://www.familyhandyman.com/garden-st ... t/view-all

How are planning to dig your post holes? I am expecting my soil to be somewhat rocky and was planning to rent a towable post-hole digger with a 6"augur. If anyone has any experiences with this piece of equipment, I would love to hear.

Admittedly, I often over-engineer my projects, but I want this fence to stand the test of time and be a potential asset if/when I sell my house in the future. Best of luck to you!
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likegarden
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by likegarden »

My experience with cedar was that the planks started to rot in horizontal spots in 10 years even with staining it every 2 years. I agree with the gravel at the bottom, fill in hole with concrete and slope it away from post. I have a pressure treated 9 ft high 40 ft long blind towards neighbors for 20 years and have no rotting at all, without staining. It naturally grayed. I exchanged the cedar fence with aluminum 5 ft pickets- no rot, no staining, wonderful.
vested1
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by vested1 »

I've built many fences using treated posts and they will rot eventually regardless of all your efforts. An alternate choice would be what I did on a 70' redwood fence I just installed in my backyard. I used galvanized metal fence posts, sunk in cement. I also placed pea gravel in the bottom of the post holes and a 2" x 12" treated (brown) plank at the bottom of each section, topping the plank with 12" wide redwood boards. No dirt is touching the wood as I back-filled 6" along the base of the fence with pea gravel as well. The posts are reversible and have non-threaded holes every inch or so for the length of the post, making horizontal leveling very easy. I cut the excess of the posts off with a porta-band saw.

My nephew who is a licensed contractor and my son-in-law who has his own cabinet shop helped me and they both were very impressed with the posts, which should last indefinitely. The posts aren't visible because the boards and planks are screwed (my choice) or hammered to the horizontal rails, which are screwed to the posts, and a 4" wide redwood board is attached to the back of the fence at every post. Home Depot and Lowes stock the posts in 7.5' lengths, which were too short for my needs so I bought the 10' ones, which I was able to pick up in person at the Hayward, Ca warehouse location. They sell the posts directly much cheaper than you can get them at any store.

It costs a little more but if the fence is going to be there for a long time I wouldn't use any other product.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by jharkin »

Somebody mentioned "pressure treated cedar"? never heard of that. Normally pressure treated lumber is pine or doug fir, and the stuff rated for ground contact can last 25+ years in dirt. There is a lot variation in cedar and it might last only 5 years or as long as 15-20 depending on the quality (old growth dense heartwood lasts longer than new growth farmed wood and is correspondingly more expensive). Untreated pine,etc might rot in less than 3 years.

Traditionally the methods for installing fence posts where just to bury the posts in dirt or set them in concrete. Concrete is the most rigid mounting and is what fence companies usually do for gate posts, but it also causes the post to rot the fastest because the concrete basically forms a bathtub around the post holding water in the wood.

I have used the gravel method, an I like it. The idea is that by having the base of the post in grave l and not touching dirt you allow water to drain and prevent the post from staying waterlogged all time. I did this method with both a cedar lamp post and a cedar mailbox. What I did was dig the hole about a foot larger than the post and 6 inches deeper. Then line the entire hole up to grade with landscape fabric. Pour a 6 inch layer of gravel in te bottom and tamp it down. Set the post and then fill in with gravel up to a depth of 3 inches or so. Tamp that down again, then fold the landscape fabric over the top of the gravel and top it off with dirt. This lets the bottom of the post drain and the landscape fabric keeps dirt out of the gravel. I just used plain old blue stone, nothing fancy.

One thing I came across recently is cedar posts with a PVC pipe extension on the base. The PVC is what sets in the dirt and you only see cedar above grade. This could be an ideal solution to get the natural cedar without the rot problem. My lamp post is this style and its holding up well so far.

Or you can just use full on Azek (cellular PVC) plastic posts. I dont personally care for it but it will last forever.

Preservatives - You could add an extra preservative soak to the post but I cant say how much protection it will add. There should be a number of formulas available at building supply centers, probably ranging from copper based formulas similar to whats used in pressure treatment to the traditional boric acid. Boric acid has been around for centuries and is very effective and also protects against termites and carpenter ants and is less toxic to people than the harsher chemicals. The downside of boric acid is that if you leach a lot into the soil plants wont grow.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by saladdin »

Times have changed... We would (and still know those that do) soak the post in old tractor oil (collected in barrels) for days to make it "water proof". These fences are still up after decades upon decades to weather. So, I would put gravel in the hole and use whatever the current equivalent preservative on the end of the post that is going into the ground and the top of thepost that will get rained on.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by barnaclebob »

My pressure treated 4x4 posts sunk straight into dirt lasted about 15 years in the pacific northwest in the wettest portion of my yard that gets no sunlight and is damp year round. The posts on the well drained portion of the yard are up to 20 years now an still going strong. This assumes the fence was built when the house was.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by lthenderson »

jharkin wrote:Concrete is the most rigid mounting and is what fence companies usually do for gate posts, but it also causes the post to rot the fastest because the concrete basically forms a bathtub around the post holding water in the wood.
This has been my experience as well. Rot resistance posts placed directly in tamped dirt last a lot longer. Also, if you live in a place where you get deep freezing during the winter, the concrete will crack into two pieces inside of a few years as water soaks down between the post and the concrete. As the post dries, it shrinks and the gap just gets wider.

I spent a summer building fence on my father's farm 30 years ago and the fence is still standing to this day. Nothing but tamped clay holds it up.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by gmc4h232 »

If you just have a handful of posts to install, I would avoid using concrete. Yeah it's easy and quick, but after a few years of freeze/thaw cycles, you have a wobbly post in the ground with concrete on the end of it. Also, it is a royal pain to replace a post if one should rot on you. We always set posts using alternating layers of good compacting fill (non-topsoil) and fist sized rocks. Drop a layer of rocks in the hole around the post then set them in place using a tamping bar, then a few inches of fill dirt, compact with tamping bar, and so on and so forth. In doing this, you are essentially making a concrete style mixture, but using dirt instead of portland cement. Using this method, you don't have to worry about water getting trapped against your post, and the post will stay tight in the ground through freeze thaw cycles.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by ddurrett896 »

Skip wood posts.

Instead, use chain link fence posts in concrete with OZ post fence brackets and wrap in wood. Easy, looks the same and will never need to be replaced.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Helodriver »

I started installing fence using Simpson strong tie column bases. The Galvanized metal is roughly in the shape of an H. Your 4x4 post attaches to the top and the lower portion is embedded in concrete. The post never comes in contact with soil and decay is greatly diminished. I have one fence that is 12 years old and shows no rot. Why is that a big deal? I used non pressure treated Douglas fir posts.

Your cost will increase some because the bases cost about $15 and you will also need two lag bolts two nuts and four washers per column base. So about $20 additional per post over traditional methods.

The only drawback has been after the wood shrinks after a dry summer I need to get a socket and tighten some of the bolts.

Good luck!
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Ninegrams »

Pressure treated posts are generally recommended over cedar. Gravel ( with fines ) instead of concrete will work fine and make it easier when you need to replace the posts (they all will rot eventually ), just make sure to tamp well with a 2x4 every couple of inches or so. On a heavy gate either slightly cant the post to allow for the gate's weight or use a wheel to help support at the other end.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

lthenderson wrote:
jharkin wrote:Concrete is the most rigid mounting and is what fence companies usually do for gate posts, but it also causes the post to rot the fastest because the concrete basically forms a bathtub around the post holding water in the wood.
This has been my experience as well. Rot resistance posts placed directly in tamped dirt last a lot longer. Also, if you live in a place where you get deep freezing during the winter, the concrete will crack into two pieces inside of a few years as water soaks down between the post and the concrete. As the post dries, it shrinks and the gap just gets wider.

I spent a summer building fence on my father's farm 30 years ago and the fence is still standing to this day. Nothing but tamped clay holds it up.
Thank you for the advice. We live in the north with lots of long sub-zero stretches in the winter and for that reason have been leery about concrete. Looks like we'll probably skip the concrete.
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Mrs.Feeley
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

gmc4h232 wrote:If you just have a handful of posts to install, I would avoid using concrete. Yeah it's easy and quick, but after a few years of freeze/thaw cycles, you have a wobbly post in the ground with concrete on the end of it. Also, it is a royal pain to replace a post if one should rot on you. We always set posts using alternating layers of good compacting fill (non-topsoil) and fist sized rocks. Drop a layer of rocks in the hole around the post then set them in place using a tamping bar, then a few inches of fill dirt, compact with tamping bar, and so on and so forth. In doing this, you are essentially making a concrete style mixture, but using dirt instead of portland cement. Using this method, you don't have to worry about water getting trapped against your post, and the post will stay tight in the ground through freeze thaw cycles.
What a great idea! Thank you for the advice! We do have lots of fist-sized rocks laying so this would be easily doable. When you mention compacting fill.... Around our house where the fence gate is located there's lots of highly sandy soil filled with teeny tiny gravel. Strange stuff unlike other soil in the area. We thought the builder may have brought it in when the house was built 50 years ago. On the other hand we are located in an area where glaciers rolled through. Is this what you mean by compacting fill?
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

jharkin wrote:Somebody mentioned "pressure treated cedar"? never heard of that. Normally pressure treated lumber is pine or doug fir, and the stuff rated for ground contact can last 25+ years in dirt. There is a lot variation in cedar and it might last only 5 years or as long as 15-20 depending on the quality (old growth dense heartwood lasts longer than new growth farmed wood and is correspondingly more expensive). Untreated pine,etc might rot in less than 3 years.

Traditionally the methods for installing fence posts where just to bury the posts in dirt or set them in concrete. Concrete is the most rigid mounting and is what fence companies usually do for gate posts, but it also causes the post to rot the fastest because the concrete basically forms a bathtub around the post holding water in the wood.

I have used the gravel method, an I like it. The idea is that by having the base of the post in grave l and not touching dirt you allow water to drain and prevent the post from staying waterlogged all time. I did this method with both a cedar lamp post and a cedar mailbox. What I did was dig the hole about a foot larger than the post and 6 inches deeper. Then line the entire hole up to grade with landscape fabric. Pour a 6 inch layer of gravel in te bottom and tamp it down. Set the post and then fill in with gravel up to a depth of 3 inches or so. Tamp that down again, then fold the landscape fabric over the top of the gravel and top it off with dirt. This lets the bottom of the post drain and the landscape fabric keeps dirt out of the gravel. I just used plain old blue stone, nothing fancy.

One thing I came across recently is cedar posts with a PVC pipe extension on the base. The PVC is what sets in the dirt and you only see cedar above grade. This could be an ideal solution to get the natural cedar without the rot problem. My lamp post is this style and its holding up well so far.

Or you can just use full on Azek (cellular PVC) plastic posts. I dont personally care for it but it will last forever.

Preservatives - You could add an extra preservative soak to the post but I cant say how much protection it will add. There should be a number of formulas available at building supply centers, probably ranging from copper based formulas similar to whats used in pressure treatment to the traditional boric acid. Boric acid has been around for centuries and is very effective and also protects against termites and carpenter ants and is less toxic to people than the harsher chemicals. The downside of boric acid is that if you leach a lot into the soil plants wont grow.
Thank you for all the great recommendations! Landscape fabric...yeah, we can do that. Where did you find the cedar posts with the PVC extensions in the base? We just buy cedar posts and rail at the nearby big box store. You're right that there must be a wide variety in quality as some have lasted only a few years, while some have lasted fifteen years. Haven't heard of treated cedar posts.

There are gardens on both sides of this fence gate that we're replacing. Along with some very big trees and bushes. I would hate for any preservative to leach off into the soil, so my vote on this will be to use just gravel, fill soil and landscape fabric. Thank you!
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by lthenderson »

Mrs.Feeley wrote:
gmc4h232 wrote:When you mention compacting fill.... Around our house where the fence gate is located there's lots of highly sandy soil filled with teeny tiny gravel. Is this what you mean by compacting fill?


It probably won't make good fill. If the gravel is rounded, it won't pack well. You want crushed gravel that is highly angular and the smaller the better it packs. Clay also works if you have it around underneath the top soil away from the house. You can easily test it by trying to pack it with a tamping rod. If it doesn't pack, your tamping rod will just keep sinking and moving the material around instead of making it into a hard unyielding surface which is what you want.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

Thank you everyone for all the wonderful comments and advice! I've been forwarding them on to my husband and he is grateful for all the advice offered. This cedar rail fence is a very low fence circling our yard and running mostly through gardens. Don't think it would be possible to replace the posts with anything but cedar. It's the sort where you buy the cedar posts with the holes pre-cut and place the rails in the holes when you plant the posts. It's held up well, but after 15 year it's starting to show its age in spots. Again...thank you for all the help, folks! This is great! :beer
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Mrs.Feeley »

lthenderson wrote:
Mrs.Feeley wrote:
gmc4h232 wrote:When you mention compacting fill.... Around our house where the fence gate is located there's lots of highly sandy soil filled with teeny tiny gravel. Is this what you mean by compacting fill?


It probably won't make good fill. If the gravel is rounded, it won't pack well. You want crushed gravel that is highly angular and the smaller the better it packs. Clay also works if you have it around underneath the top soil away from the house. You can easily test it by trying to pack it with a tamping rod. If it doesn't pack, your tamping rod will just keep sinking and moving the material around instead of making it into a hard unyielding surface which is what you want.
Ah! Thank you for the clarification! This soil looks like it came from near a beach. Clearly wont' work.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by jharkin »

Mrs.Feeley wrote:Where did you find the cedar posts with the PVC extensions in the base? We just buy cedar posts and rail at the nearby big box store. You're right that there must be a wide variety in quality as some have lasted only a few years, while some have lasted fifteen years. Haven't heard of treated cedar posts.
The post with PVC was a lantern post that I bought from a company called Historic Housefitters. Looks like so:

Image

We were at the showroom of Walpole Woodworkers a couple years ago and I recall seeing a similar system for fence posts. Granted these are both higher end companies that cater mostly to the New England region so you might not find it elsewhere and I kind of doubt a box store would have it. A dedicated fence supply house might have more luck.
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Re: Fence Building: Soaking cedar fence posts in preservative?

Post by Green Nut »

as far as fence building you'll get as many opinions as people that respond, so i'll add what i did last year.

I used all pressure treated pine, panels and posts. 6' panel and 10' posts. Painted the bottom 1/3 of the post with driveway sealer, used a powered one man hand held 8" auger and put in a 36" deep hole. Put a couple inches of trap rock or native rock at the bottom, put the post's painted end in the hole and added 6"-8" at a time of removed soil and tamped, continued until I filled the hole...if you have leftover soil you didn't tamp enough. This allows water to filter by, I didn't want trapped moisture like a chunk of concrete would allow. After year one all is good...I'll report back after 15 more.
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