7 ft wood fence - do I need concrete posts and if so how deep?

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Posted by: from Ottawa
4/24/2013 at 2:55:04 PM


I plan to build a 7 foot wood fence to close off my back yard. The fence would connect my house to my garage and have a 2 X30" double gate (wide enough to bring anything through since it would become the only access to the backyard). It will be "L" shaped, with the gate in the centre of the long side.

I've read up all I can about how to secure the posts and the advice is to put 4 foot concrete posts under each wood post or to sledgehammer in steel supports into the ground and attach the posts to them. 4 feet of concrete seems excessive.

What if I dug a 1 foot trench where the fence goes and sunk rebar 3 feet further down in the ground and put brackets in the concrete. Would that be good?

I can connect the posts that would be against the house & garage wall to the wall but I am not sure if that is a good idea.

I've looked around at fencing in my neighbourhood, and no one seems to have concrete at all nevermind from concrete form tubes like I have seen online. Just posts buried in the ground (and some sitting on the ground).

Any advice?

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Richard from DK Land And Home in Bradford
Date/Time4/24/2013 at 3:19:53 PM


The reason behind the four foot concrete footings is the frost line in canada. If you only dig a foot or so and pour some concrete the first or second winter the earth will literaly spit out your fence posts and knock them down.

The reason you don't see any concrete at neighboring homes is most contractors will allow for a small amount of sod to sit right up against the post so you don't see the concrete, this looks nice but can lead to your wood rotting, the steel post ties are garbage most of the time they bend and hit a rock or something on the way down an shift a weird way strongly don't recommend them.

The best way to build a fence is to pour four foot concrete footings and place the post right in the concrete and level the post, then angle the concrete away from the post for water and once it's hard even a little caulking around the post where it meets the concrete is best to provent any water from rotting the wood.

I hope my information was helpful.

Thank you


DK Land And Home

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Dustin from Silica Tiling in Peterborough
Date/Time4/24/2013 at 3:24:18 PM

Yes 4 ft. concrete pads buried in the ground is definitely excessive for a basic fence.

Best thing to do in my opinion and the easiest is to make sure you're using pressure treated wood

posts for you fence. With pressure treated wood you could just bury the end in ground and it would last

decades without rotting.

But I would dig atleast an 18 to 24 inch hole for each post, position your posts and level them for plum,

brace them in place, then pour concrete into each hole around the posts and let it set up. You don't need much, just enough to anchor the posts in the ground. You could also use a forming tube in the ground for the concrete to pour into and around the post end.

Pouring concrete into a trench with rebar is really excessive and a waste of time in my opinion.

Good luck.

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Date/Time4/24/2013 at 3:25:05 PM

First of all I'm going to fly in the face of tradition and tell you not to use concrete at all. I bore holes 4' deep by 8"-10" dia. and put 'chips and dust" or limestone screenings around the post in layers about 6" deep and tamp each layer well with a piece of 4x4 up to ground level. Be sure to dampen the gravel as you go to allow it to be packed in tight. You will never get frost heave with this method and if for some reason you need to remove a post you can do so without hiring a backhoe to excavate. Hydro uses this method to install their poles in the ground so you know it works.

If you use concrete, melt water in late winter can and will get underneath the concrete and freeze and push your posts up out of the ground even 4'down. The concrete will transmit the cold below the frost level in very cold weather.

Never ever ever use super spikes on a fence this height unless it is in a location that makes digging a hole impossible or you only need one post between structures and never put 2 side by side. A strong wind will fold a 7' fence built on super spikes. Also be sure that a 7' fence is allowed in your municipality...many places limit the height and materials for fence construction. Have fun!

Rob Maguire

Maguire and Sons

Renovations and Steel Roofing

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Date/Time4/24/2013 at 3:35:23 PM

Hello Fence Builder,

In short, any time that you are installing a post for fencing where there are dramatic cliamte changes (winter/summer), best practice it to have a 4ft footing. The reason is that during different seasons the ground shifts. Here in Canada, the frost line in winter has a penetration of 3ft, Because of the contraction during the different seasons, the concrete will shift and eventually pull your fence appart, Proper anchors will provide added stability as well.

Your Contractors,

Home Boys Contracting.

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Date/Time4/24/2013 at 3:35:40 PM

Hello Fence Builder,

In short, any time that you are installing a post for fencing where there are dramatic climate changes (winter/summer), best practice it to have a 4ft footing. The reason is that during different seasons the ground shifts.

Here in Canada, the frost line in winter has a penetration of 3ft, because of the contraction during the different seasons, the concrete will shift and eventually pull your fence appart. Proper anchors will provide added stability as well.

Your Contractors,

Home Boys Contracting

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Date/Time4/24/2013 at 4:09:11 PM

Hi Andy,

As per the popular vote so far...bury the posts in at least 4 feet of concrete. You can use a tube or just dig out the hole.

DO NOT listen to what Dustin is suggesting, unless you want your fence to come apart.

If you want it to last, follow the guidelines and go below the frost line with the concrete.

Hope that helps,

Bill Clawsie

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Date/Time4/24/2013 at 4:38:03 PM

First off contact your cities by-law department. Most have a 6' max. height restriction. You have to dig at least 4' deep to get below the frost line. The deeper you go the more stable your fence is going to be.

The reason you use concrete with sonotubes is that the frost has nothing to grab onto with the smooth sides of the tubes. If you just poured concrete in the hole, then the frost has the jagged edges of the concrete to grab onto and lift the post out of the ground.

Build it right the first time and then you don't have to worry about it.

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Date/Time4/24/2013 at 11:00:33 PM

It always depends on how long you want the fence to be standing sturdy. Putting the posts in concrete is the way to go, you may not need to use forms, however it would be easier. As long as the holes are 4 ft deep. Just leaving the posts in dirt and they will rot in no time.

The biggest problem you see with older fences is the posts bottoms rooting and falling over. The base of any outdoor project takes time.

Good luck

Brian L.

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Deck Works in Ottawa
Date/Time4/24/2013 at 11:14:27 PM

Depending on the depth of frost you get in your area, the holes must be 3-4 feet. I recomend against using sonotube for fence post. Simply cover the bottom of the hole with gravel, put in your post and fill the whole 1' of concrete. Once set fill the rest in with the dirt you removed, pack it good and your done.

What you have done is given the post a footing, as the earth settles on top of it it makes the post firm and solid.

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Andy in Ottawa
Date/Time4/25/2013 at 9:32:50 AM

Thanks for all the replies. Didn't think there would be so many, so fast.

I didn't think to check city by-laws assuming it didn't matter since this fence isn't along the border of my property. Anyhow I just checked and Ottawa tells me 213cm/7ft is the max so I am good.

Alright, 4ft concrete seems to be the way to go. I don't want to do it twice.

3 more short questions then:

Should I brace the fence to the house - or would I be asking for trouble with wind vibrating the fence and then cracking my stucco?

Is it better to embed a steel bracket into the concrete and then bolt the fence post into it or to embed the post into the concrete (or does it not matter)?

Guess I'll rent a power auger. I've never used one. 2 of my posts are going to be right up against the wall of the house/garage. Can you get a power auger right up against a wall? The handles on a 2 man auger look like they would get in the way. What about a 1 man one?

Thanks all

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Date/Time4/25/2013 at 10:40:39 AM


As a gardener and landscaper I come across a lot of rotten fence posts, and gate posts. True to the fact that over time anything put in the ground will rot and cedar vs pressure treated is almost about the same for length of time they will survive in the ground.

I would recommend putting the posts directly into the ground and using a cement paste designed for that use in the ground. Products like 'Post Paste' or Post Cement are quick setting cement type mixes that allow you to continue building in just a few hours. They are really easy to mix up in a wheelbarrow and then pour around the post in the ground. I even mix directly in the ground with the water. Usually you will need two bags per post, and set your post approximately 2 feet into the ground.

Setting the post directly into the ground will give the fence and gate more strength, especially for the gate, if its set on top and then attached to concrete post will not have the same strength and even flex too much to cause the gate to overlap and not close properly. Sometimes though the ground is not so easy to work with, ie, underground lines, or large boulders buried where you want the post to be and this may be a alternative solution. If you use the concrete post method in the ground and attach the post to it, you can use a larger L bracket to attach.

Don't wrap the post in plastic when using the Post Paste method, I have seen this and I would only say it will trap water and speed up the rotting process. If done right you should expect the posts to last about 10-15 years.

Hope this helps.

Michael Davison

Rain Forest Gardens and Landscaping

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Chastity in Ottawa
Date/Time5/7/2013 at 1:50:38 PM

I too am in the Ottawa area. You may want to call the city to double-check on the height. I haven't checked recently, but it used to be a maximum height of 6 feet with allowance for up to 1 foot high of lattice for a total of 7 feet.

As for the posts, we built our fence 3 years ago to a height of 6 feet. We dug down 2 feet and used the rapid setting concrete. After the first winter we noticed a little shifting. After the second winter all of the posts had shifted, twisted, etc. The concrete is completely cracked and we can pull chunks out of it. Last year we wedged the posts as a temporary stop-gap. After this past winter, all of the wedges have heaved up and the fence is worse than ever.

We spent last night dismantling the fence. The fence posts pull straight out of the ground. After researching, this time we plan to dig down 4.5 - 5 feet. Fill the bottom .5-1 foot with gravel to allow for drainage and fill the rest with concrete (NOT the quick setting kind). Stopping the concrete about 4 inches from the ground level. Once the concrete has all been poured, we will thicken the concrete and create a slope from the outside up to the post so that water will drain away instead of pooling. Once the concrete is completely set we will then place soil over top and seed. As well, we will paint the posts with a waterproofing agent to deter rotting. (Creosote is the old agent; there are newer ones, but I cannot recall at this moment.)

I hope that helps a little. Best of luck to you!

FYI - In case you are wondering, my yard is clay and has very poor drainage.

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Marc in Moncton
Date/Time7/20/2013 at 5:47:58 AM


I would not dig a hole close to your house. Simply attach a 2x4 to your house with galvanized lag bolts. If you've done your posts properly (4feet sona tubes concreat ) you will be ok. To be sure when you attach your fence panel to the 2x4 at the house use a method of fastening that will allow for some movement as usuall your house will always move differently from anything attached to it even if only a small amount

Hope this helps.

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Shawn in Ayr
Date/Time7/31/2013 at 7:53:39 PM

You need to dig a hole 4 feet deep due to the frost in Ontario. You can fill it with concrete, or you can fill it 2/3's of the way with concrete, or you can fill it with gravel or stone dust. All will keep it in place as long as the other.

If you use gravel, make sure to wet and pack it. It is key that your hole is round and smooth. The frost will still grab any edges and heave your post. Gravel or stone dust works great and allows water to drain away from the post. They will last longer.

They never used to use concrete around posts, but the four foot depth is not negotiable in our area.

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Date/Time11/10/2013 at 7:38:44 PM

Hi there,

As a fencing company in Ottawa I can tell you that the City of Ottawa bylaw states that the maximum residential fence height is 7' without a permit. They will on occasion allow a higher fence in specific situations.

4' deep is definitely deep enough, the frost line is said to be at 34" in Barrhaven. It's common practice in the fencing industry to bell the bottom of the holes which makes a Bigfoot shaped hole. You don't need to use sono tubes, they are generally only used in special situations. If you put the posts 4' deep your fence will be there until the posts rot. Don't use any metal brackets on the posts, put the posts right in the concrete


NewFound - Land, Fence & Decks

7 ft wood fence - do I need concrete posts and if so how deep?
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Date/Time5/2/2014 at 7:02:47 AM

The only problem I find with setting posts directly in concrete is the wood expands and contracts in diameter with weather conditions, and that eventually cracks the concrete, which allows more water into the cracks, freeze thaw, eventually the posts become loose. The fence acts as a big sail in winds, cracking the concrete further.

My own preference is to set the posts on heavy duty post anchors. Keeping the post bottoms above grade from degradation and wicking water up from the bottom of the post.

Definitely go below the frost line for your area, using 8" diameter sono tubes otherwise you can have ad freezing where the pier is lifted out of the ground. We have all seen fences leaning because the piers have been lifted out of the ground after the winter months.

Pay the extra costs for better installation and for longevity.

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