Backyard Fence:
A Heavy-Duty 6x6 Post
For A Wide Gate
The Weight Of An Extra-Wide Gate
Requires A Special Post
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In This Article:
A 4-foot deep hole is dug
and the bottom compacted. A 6x6 post is set in the hole and
backfilled. Gate hardware is installed.
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Related Articles:
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Skill Level:
3 (Intermediate)
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Time Taken:
About 2 Hours
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Author:
Bruce
W. Maki, Editor
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Project Date:
November 2010
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[See Tools and Materials]
[Add your comments below the article]
As part of my backyard fence project, I needed to build a gate between the green shed on the right and the white garage on the left.
I decided to build an 8-foot wide gate next to the shed, so I needed to
place a heavy-duty treated lumber post in the ground in the area marked
in red.
I used a flat-blade shovel to dig a rectangular hole about 24 inches wide by 18 inches front-to-back.
I placed a 6' x 8' tarp on the lawn to contain the dirt. The flat-blade shovel works well for cutting the sod into squares. I set aside the sod on the tarp.
I kept the topsoil separate from the light brown sand below, so the topsoil could be placed back on top.
In my area, the soil is mostly beach sand, and the "native" soil (the stuff below the topsoil) has no nutrients. You can't grow much of anything in the stuff, but it's easy to work in.
I used the shovel to dig as deep as possible, then I used a pair of post hole diggers to continue digging until the hole was almost 4 feet deep.
My gate post is 8 feet long, and I plan on having about 4'-2" of post above the ground.
Tree Roots: To cut smaller roots, I used a pair of pruning lopers. Any roots bigger than 1 inch wide were cut with a reciprocating saw and a pruning blade. There are hand saws available for this task.
This is an 8 inch tamper, which is used to pack down soil.
I reached into the hole and tamped the soil on the bottom of the hole, while trying to make sure the bottom was flat and level.
I placed the 8-foot long 6x6 post in the hole.
At this point, the only important task is getting the post base in the right position. I wanted the post to be 2-3 inches from the shed.
I used a 4-foot level to adjust the post until it was plumb. Then I moved the post sideways until it was in the right position.
Actually, this big 6x6 would stand up by itself, because the bottom of the hole was fairly flat and level.
I backfilled the hole with about a foot of dirt, then I used the tamper to pack down the soil.
The first foot of back-fill keeps the post base from moving around. At this point the post can easily be leaned a bit to make it plumb.
The benefit of digging a wide hole is that there's enough room to use the 8 inch tamper to pack down the dirt.
Once the post base was stabilized, I used a big sledge hammer to pound on the top of the post. This helps compact the soil under the post to resist settling.
Soil Compaction Is Very Important:
An 8-foot gate puts a lot of "torque" (bending force) on a post. To minimize leaning, the soil around the post needs to compacted tightly.
My approach:
- Place 6 to 10 inches of soil in the hole.
- Pack soil with tamper or piece of 4x4 post.
- Pour water in hole, at least a couple inches deep. Soil needs to be damp to pack down properly.
- Allow water to soak into soil for a few minutes, then tamp again, if the water drains into the soil. If water remains in the hole after 3 to 5 minutes, I skip this tamping, because it splashes mud all over.
- Continue with this procedure until the hole is filled.
When the back-fill got within a foot of the top, I filled the hole with 6 inches of water to help settle the soil.
Counteracting The Expected Lean:
I expected the post would lean a bit after the gate was hung, so I made the post lean backwards (towards the shed) by about 1/8 inch.
In hindsight, it would've been better if I'd made the post lean 3/8" to 1/2".
I nailed a scrap of treated 2x4 to the post, about a foot below grade.
This will act as a brace to help the post resist leaning from the weight of the gate.
This board was longer on one side than the other, because my hole was against the shed.
Then I added more backfill and tamped it until the soil was even with the top of the cross-brace.
I nailed another brace to the post. This board was about 22 inches long.
I fastened these braces so the top of the upper board would be about 4-5 inches below the surface. This will allow me to place the sod back in the hole with no trouble.
Concrete Around The Post?
Many people insist on pouring concrete around a fence post. Some people pour concrete around the bottom of the post, some pour concrete around the post near the surface.
Concrete at the bottom makes it really difficult to lift the post out of the ground, and that's about all. Unless you use a lot of concrete, it doesn't improve the resistance to leaning, from my experience.
Concrete just below the surface helps the post resist leaning by effectively making the post wider, so it has a larger area to push against the soil.
I've been using these wood cross-braces for several years, and they seem to work as well as concrete, but are quicker and cheaper. If you ever see a treated lumber retaining wall being built, you might see wood "tie-backs" being placed behind the wall. These are large T-shaped horizontal "posts" that are held in place by the weight of the soil. The bottom of the T-shape is bolted to the retaining wall, and these hold the wall from tipping over under the lateral force of the soil.
I suspect that some people use concrete around a fence post instead of compacting the soil. If you ask me, there is no substitute for properly compacted soil.
I filled in the hole up to the top of the upper brace and tamped it.
Then I placed some topsoil in the hole and arranged the squares of sod around the post.
I find it best if the sod is slightly lower than the surrounding grade by about a half inch. Then I rake some topsoil on top of the sod and tamp it lightly.
If the sod is too high, it's difficult to tamp it lower. But if the sod is too low, it's easy to cover it with a thin layer of soil, and the grass will grow through the dirt in no time. This works best if the blades of grass show through, and the soil covering is less than an inch deep.
Gate Hinge Peg-Bolts:
This piece of hardware is part of a heavy-duty gate hinge. I bought these at Menard's for about $5 each.
These are sold separately from the strap hinges, because there are different lengths of straps available. There are also other sizes of peg-bolts sold.
The strap hinges I fastened to the gate just slip over the peg on the end, like this.
To drill the holes for the peg-bolts, I used a 3/4 inch augur drill bit with a long extension.
It's very important to keep the drill bit level.
I made a mistake here. Note how I drilled the holes in the center of the post...
If I had drilled the holes about an inch to the right, the gate would've swung in both directions. After my gate was installed, it could swing against the shed (my main intention), but it wouldn't swing the other direction very far, because the edge of the gate would hit the post.
Making The Gate Swing Both Directions:
This is the gate shown in this article.
When I try swinging the gate so the hinges are on the outside of the gate, the edge of the gate hits the post (red arrow).
When the gate is swung the other direction (when the hinges are facing the post) there is no problem.
When I built the second gate, I located the holes for the peg-bolts about an inch off-center.
When the gate is swung with the hinges on the outside, the gate doesn't pinch the post until it has moved beyond 90 degrees.
With one nut and washer on the peg-bolt, I placed the bolt in the hole.
Then I put the washer and nut on the other end, and tightened the last nut while holding the first nut (near the peg) using a pair of 15/16" wrenches.
With these peg-bolts, it's possible to adjust the distance between the peg and the post. Menard's also sells a lag bolt with a peg on the end. Those wouldn't be so easy to adjust.
The heavy-duty gate post after the hinge hardware was installed.
A Note About The Post Top:
I left the top of the post just flat. To prevent water damage to the post, the top should be sloped to let water drain off. When I built this fence I figured I would build some type of cap for the posts, but I haven't settled on a design yet.
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A closer view of the gate hardware. It's important to leave enough space between the post and the building so the end of the bolt doesn't hit the wall. Of course, the entire bolt could be adjusted so the peg was farther away from the post.
Then I set the gate on the peg-bolts. (Read about building this gate.)
One tricky aspect of my construction methods is the difficulty in getting the peg-bolts spaced apart just the right amount.
An easier way might be: Install just one strap hinge on the gate (I'd do the top strap), then set the gate on the peg, using some blocks of wood to hold the gate level. While a helper holds the gate from falling, you could set the lower strap on the peg and mark the holes on the gate.
Read about building the 8-foot wide gate shown here.
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