8 ft fence post requirements

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Posted by: from Minesing
5/1/2016 at 7:35:59 PM

When building an 8ft fence what size posts would be required and how deep should they be set?

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Date/Time5/2/2016 at 5:49:20 PM

Hi Jen,

For a wood fence you can utilize 4" X 4" posts in ACQ Pressure Treated Spruce, Pine, or Fir, or Western Red Cedar, or Imported rot resistent Hardwoods such as Ip.

Your fence posts have to be bearing on undisturbed soil below the frost line, which in are area for argument sake is 4'. Because fences are subjected to a lot of lateral pressures, it is prudent to sink the posts into the ground to this depth to provide resistance to these forces.

Having said that, you should check with your local Building Department as to the height to which you can construct a wooden fence. In the Toronto area you are limited to about 6' above average grade along the fence line. So while an 8' fence might make for good neighbours, you don't want to be in a situation where you are later required to either take it down or cut off the top 2'. Either way, it is cheap insurance to check with your local Building Department to make sure.

Typically a 6' fence would use 10' posts with 4' being set in concrete or gravel below grade, however if you ever walk through a sub-division that is having its fences done, it is not uncommon to see the tops of the posts at all different heights. This simply means that they are not in the ground far enough. It also likely means that the people (Owner or Contractor) may have hit a rock that was too time consuming to dig out. Regardless of whether or not the post is that deep, it is imperative that the holes were both dug to below the frost line and that the bottoms of the holes were cleaned out prior to pouring concrete. If they are not, take a walk through the same area after the first winter and you will start to see all kinds of leaning posts and wobbly fences.

It is also a good practice to dig a little deeper and place at least 6" of clean clear 3/4" gravel at the bottom of the holes prior to the placement of the posts. This allows for added protection by providing drainage for ground water to drain away from the end cut of the wooden post prolonging the life of your fence.

Lastly, despite it being less attractive and slightly more costly, you should ensure that the concrete on your fence post holes is finished with a smooth trowel at least 1" above grade and tapered to permit water to drain away from the bottom of the post. Many homeowners and Contractors will cut corners here to save a bit of money on concrete and a bit of labour to finish the tops. Even though the wood you used should be resistent to rot, you will find that often the concrete is filled to an inch or two below grade for a clean look. This will lead to standing water being trapped at the posts most vulnerable point, where it is submerged in the concrete. It will not take long before these posts experience serious rot at this point and can often be snapped off by hand in just a few years.

Hope this helps. Best of luck with your project.


Jason Irving

Cedarfalls Building Consultants Limited

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Date/Time5/2/2016 at 9:55:47 PM

Hi Jen,

Using a 6" by 6" post would be recommended for a fence of that height. Check with your local building department for maximum height allowed. The 6 by 6 is a bit more expensive but will provide added stability as well as a more substantial looking structure.

Best of luck,


BBbuilds, Cochrane

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Matthew from Matt of All Trades in Kitchener
Date/Time5/4/2016 at 7:28:31 AM

6x6 for sure.

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Jen in Minesing
Date/Time5/6/2016 at 11:56:39 AM

Thank you for the replies. We have checked with our township and are able to build an 8 ft fence.

Here is my current problem. I have had a fence built and am not happy with the way it looks. They installed an 6ft gate (doesn't match style of fence) and can only be opened from inside. My question is what size gate would be appropriate and should it not be able to open from both sides?

The fence that was built does not have any type of staggering pattern to it. Instead the builder has each section of fence at varying levels in height. Is this normal (it does not look very appealing to the eye)? How can this be fixed? Should there be additional support added (cross pattern etc.) to keep the boards warping?.

I have attached 2 pictures of the fence that show some of the concerns.

Any advise you have would be greatly appreciated.

8 ft fence post requirements

8 ft fence post requirements

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