• Last Updated:
  • Apr 9th, 2019 11:10 pm
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[OP]
Newbie
Feb 8, 2019
21 posts
7 upvotes

Rebar in sonotube

I'm replacing gates at the rear of the garden due to sagging issues.

I'm planning on setting two 8 or 10" sonotubes approximately 12' apart, dug to 48" for Calgary frost line, plus another 6" for gravel.
I have 4 pieces of 1/2" rebar @ 48" inside two circles of 6" circumference, tie wired 12" up/down from each end, with no J or L bend on the bottom.

4 pieces of 1/2" threaded bar, not ready rod. 14" lenghts, set 12" into the concrete to hold the post holders.

Post holders are 1/4" angle, 4x6" bolted to the concrete. They will be painted with tremclad, with either an epoxy or bitumen coating at the bottom where it contacts the cement.

Gates themselves will be 3/4" angle iron frame welded 6'sq with a flat bar brace spanning 2 opposing corners of each gate.

Piers will be 6' 4x6" PT bolted into the post holders, with similar moisture barrier at the bottom asthe post holders .

Aside from it being possibly over built, is there anything I should be doing better with the rebar?
27 replies
Deal Expert
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Feb 11, 2007
16025 posts
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Oakville
I didn't think rebar was normal for a fence/gate post? I thought typical install was just post surrounded by cement?
[OP]
Newbie
Feb 8, 2019
21 posts
7 upvotes
I want this to last and be adaptable for other possible uses in the future if necessary.

Wood rots, technology and usues change. I want it to be repairable or upgradable for the next 20+ years

Not looking for the bare minimum or cheapest I can get away with.
Deal Expert
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May 10, 2005
36156 posts
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Ottawa
Delete your other post on this identical subject.
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[OP]
Newbie
Feb 8, 2019
21 posts
7 upvotes
Sorry, not sure what happened there, it just double posted for some reason.
Jr. Member
Feb 28, 2018
152 posts
99 upvotes
Waterloo region
Mrbishi wrote: I'm replacing gates at the rear of the garden due to sagging issues.

I'm planning on setting two 8 or 10" sonotubes approximately 12' apart, dug to 48" for Calgary frost line, plus another 6" for gravel.
I have 4 pieces of 1/2" rebar @ 48" inside two circles of 6" circumference, tie wired 12" up/down from each end, with no J or L bend on the bottom.

4 pieces of 1/2" threaded bar, not ready rod. 14" lenghts, set 12" into the concrete to hold the post holders.

Post holders are 1/4" angle, 4x6" bolted to the concrete. They will be painted with tremclad, with either an epoxy or bitumen coating at the bottom where it contacts the cement.

Gates themselves will be 3/4" angle iron frame welded 6'sq with a flat bar brace spanning 2 opposing corners of each gate.

Piers will be 6' 4x6" PT bolted into the post holders, with similar moisture barrier at the bottom asthe post holders .

Aside from it being possibly over built, is there anything I should be doing better with the rebar?

Will the tops of the gate posts be tied together.
If I’m understanding this correctly, the posts are not set into the ground, just fastened to 4x4 brackets on top of concrete.....
There’s nothing to stop the posts sagging.....
Deal Fanatic
Jan 25, 2007
9965 posts
5250 upvotes
Paris
I am not an expert by any means, but the saddles typically used at the top of a sonotube arent great for side to side force (as in the case of a fence, gate, etc) which would act on them like a lever. I think they are just meant for posts that are held together at the top as in the case of a deck.

I would think building a gate on top of this construction would result in sag as there is not enough holding the post from moving at the base. Maybe I’m not visualizing correctly?
Jr. Member
Feb 28, 2018
152 posts
99 upvotes
Waterloo region
Jerico wrote: I am not an expert by any means, but the saddles typically used at the top of a sonotube arent great for side to side force (as in the case of a fence, gate, etc) which would act on them like a lever. I think they are just meant for posts that are held together at the top as in the case of a deck.

I would think building a gate on top of this construction would result in sag as there is not enough holding the post from moving at the base. Maybe I’m not visualizing correctly?


Ditto ^
Deal Expert
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Jun 12, 2007
16177 posts
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London
The gate opening is 12 ft wide?
These are 2 gates, each 6 foot wide (that meet in the middle) ?
Deal Fanatic
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Oct 19, 2008
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GTA
That rebar better be powder coated, and get a rattle can for the cut ends. Rebar causes many issues as it corrodes, if eng doesn't spec no one would use it. There is no need for rebar added strength in the piers you are pouring, and the planned threaded rod to attach post holders is another concern as it ages.
Just go with good concrete for the piers, belled bottom under sono tubes and ground contact rated PT posts sunk into the sono tube as suggested for lateral strength. Design the gates with a crossmember between the posts to stiffen everything up and keep the important size of the gate opening consistent.
Deal Expert
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Dec 26, 2005
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Thornhill
Yow - over-designed but good. I would embed the fence post into the concrete, not just supported by the saddle. Saddles are only designed to support a vertical weight, not something like a fence - it’ll snap after a few wind storms.

About the rebar, you can also get epoxy(?)-coated rebar. Also, bell-out the bottom of the post hole. You can do that with a digging bar and a clam-shell shovel.

bjl
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Jan 6, 2002
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Toronto
I've no professional knowledge in this area, but I don't see rebar giving you any net benefit here. Rebar is designed to give you strength in concrete under tension, whereas your situation is mainly compression and a bit of localized shear.

I would think the wire cage reinforcement would be a better situation for this, if your worry is the concrete fragmenting. All your pieces of rebar are just more ways for bits of moisture to wreak havoc around each point of egress.

If what you want is vertical rigidity out of the ground, I would instead embed a galvanized tube deep into the concrete and have it stick out 3-4-5-6' (whatever is needed.) And then tie the opposite sides together as needed -- that's the only way to prevent sagging if you have any sort of cantilevered weight on those poles.
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[OP]
Newbie
Feb 8, 2019
21 posts
7 upvotes
Thanks for all the input, exactly the feedback I was looking for.

I hadn't thought about tying the posts together with a beam, wood or steel, definitely something I'll need to consider as obviously a proper frame will be stronger than 2 individual uprights.

I figured straps from 1/4" steel angle iron would be strong enough as I don't want to set the post in the concrete due to eventual rotting, but I may consider using galvanized pipe, would 4" gas pipe as the post work instead?

Epoxied on the bottom and cap welded at both ends for moisture.

The reasons for the rebar are that I have it and if I wanted to install a sliding gate or decking by the garage in the future there would be strong footings for it already.
Deal Fanatic
Jan 25, 2007
9965 posts
5250 upvotes
Paris
Mrbishi wrote: I figured straps from 1/4" steel angle iron would be strong enough as I don't want to set the post in the concrete due to eventual rotting, but I may consider using galvanized pipe, would 4" gas pipe as the post work instead?
What kind of lifetime expectation do you have here that 10 years or more for wood isnt enough?

Water will still penetrate the top of the concrete and rust out the pipe in the embedded concrete.
Jr. Member
Feb 28, 2018
152 posts
99 upvotes
Waterloo region
Mrbishi wrote: Thanks for all the input, exactly the feedback I was looking for.

I hadn't thought about tying the posts together with a beam, wood or steel, definitely something I'll need to consider as obviously a proper frame will be stronger than 2 individual uprights.

I figured straps from 1/4" steel angle iron would be strong enough as I don't want to set the post in the concrete due to eventual rotting, but I may consider using galvanized pipe, would 4" gas pipe as the post work instead?

Epoxied on the bottom and cap welded at both ends for moisture.

The reasons for the rebar are that I have it and if I wanted to install a sliding gate or decking by the garage in the future there would be strong footings for it already.

We use 4” pipe as baracades, sunk in the ground 4’.. for corrosion protection below grade we wrap with a tar tape applied with a torch... ( also use this on actual gas mains & services ) there’s baracades out there 30+ years old and still in good condition. Heavy duty & strong.. https://www.chasecorp.com/products/hot- ... pecoat-20/
[OP]
Newbie
Feb 8, 2019
21 posts
7 upvotes
I'm from Europe, where buildings last hundreds of years, slate rooves, masonry walls, much higher quality windows and doors, water boilers, radiators etc.

Not to shit all over the North American system as I understand the different environmental requirements and availability of raw materials etc, but if you told someone back home that the building envelope on a new house was only warrantied for 5 years or they'd need to replace their roof or exterior finish every 15 years or so, they just wouldn't buy it.

So I want anything I build to last as long as possible, and be as easy as possible to replace or repair when it wears out.
I have gates at home on the farm that are steel and concrete that are 50+ years old, some sagging alright due to animal or tractor impacts but still lining up within an inch or so of the bolt hole to close them.

I definitely look into the gas pipe as well, I had thought about wrapping it in soprema or blueskin, but torch on would probably be better alright.

Any issues using weld on hinges with pipe like that?
Jr. Member
Feb 28, 2018
152 posts
99 upvotes
Waterloo region
Mrbishi wrote: I'm from Europe, where buildings last hundreds of years, slate rooves, masonry walls, much higher quality windows and doors, water boilers, radiators etc.

Not to shit all over the North American system as I understand the different environmental requirements and availability of raw materials etc, but if you told someone back home that the building envelope on a new house was only warrantied for 5 years or they'd need to replace their roof or exterior finish every 15 years or so, they just wouldn't buy it.

So I want anything I build to last as long as possible, and be as easy as possible to replace or repair when it wears out.
I have gates at home on the farm that are steel and concrete that are 50+ years old, some sagging alright due to animal or tractor impacts but still lining up within an inch or so of the bolt hole to close them.

I definitely look into the gas pipe as well, I had thought about wrapping it in soprema or blueskin, but torch on would probably be better alright.

Any issues using weld on hinges with pipe like that?

Our welders weld it every day... new pipe and also live in the ground pipe... those guys make it look easy..
Deal Fanatic
Jan 25, 2007
9965 posts
5250 upvotes
Paris
Mrbishi wrote: I'm from Europe, where buildings last hundreds of years, slate rooves, masonry walls, much higher quality windows and doors, water boilers, radiators etc.
Labour is much more money in Europe and home ownership is longer. It accounts for a lot of the difference.

In Japan they apparently tear down the homes every 5-10 years so longevity isn’t any concern. There is no DIY market there.
Deal Expert
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Feb 11, 2007
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Oakville
Jerico wrote: Labour is much more money in Europe and home ownership is longer. It accounts for a lot of the difference.

In Japan they apparently tear down the homes every 5-10 years so longevity isn’t any concern. There is no DIY market there.
I wouldn't be surprised if they do that in Japan because of improving earthquake standards.

Certainly in the EU they have better regulations and minimum standards for builders as well.
Deal Fanatic
Jan 25, 2007
9965 posts
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Paris
engineered wrote: I wouldn't be surprised if they do that in Japan because of improving earthquake standards.

Certainly in the EU they have better regulations and minimum standards for builders as well.
After the quake and resulting tsunami a few years back they talked about changing standard for the rebuilds. We thought they were going to murder the North American lumber trade. And they didn’t. Just rebuilt to the same standard they had.

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