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bow slayer

pergola building....best way to secure post? NF

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I am about to build a backyard pergola,but I keep getting conflicting opinions on how to secure the post. Some tell me to dig and set in concrete ,others say sono tubes, others say use post spikes,and again heard dig and set in just pea gravel. So to start I need to set post,so what is the best way to set the post. Also I have been told set them down 3ft and 4 ft. I live in southern Ontario close to lake erie shore we usually don't get a deep frost? thanks in advance.

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If you want to be sure it doesn't move dig and concrete; you'll use less cement with a sono tube. Set the sono tube in place and then dump about 3-4 inches of cement into the bottom of the tube for a footing; let it set up over night. The last thing you'd want, is the post to let go of the cement and start sinking down; especially in sandy soil.

Yes a minimum of 3 feet deep (4 is better); you don't want any form of frost getting under the footing and pushing it up.

 

Dan.

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I would do sonotube/concrete as well. If your looking for something permanent anyway! For the amount of concrete your talking about it's an easy job with a wheelbarrow. We did a large atv shelter at our hunt camp and put in tubes and concrete. That things not going anywhere! 3 feet should be plenty!

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Sonar Tubes is the way to go. 46" minimum depth in On. some areas it's 48" even though they don't make 48" augers, maybe they do now, but there are times you just can't get that deep. 4" post= 8" Sonar tube. The wooden post must not touch any concrete, it will rot the wood, it is set on a post anchor set and leveled into the top of the concrete. Concrete touches metal not wood, it is best to put some Ice and Snow wrap on the bottom of the post so the wood doesn't touch the steel.

 

Dig the post hole.

 

Set the tube and level it horizontal and vertical.

 

Find the level of all tubes, mark and cut them off with a kill Saw

 

Reset them and shovel crushed stone into the bottom. 4"'s and tamp down hard.

 

Check level and plumb

 

Pour concrete to top of tube

 

Crown top slightly to let water drain away

 

Set in anchors and plumb and level

 

Install posts and secure with proper deck screws for the type of wood

 

I've done many hundreds if not more, now I watch it being done and only use my finger to supervise.

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Sonar Tubes is the way to go. 46" minimum depth in On. some areas it's 48" even though they don't make 48" augers, maybe they do now, but there are times you just can't get that deep. 4" post= 8" Sonar tube. The wooden post must not touch any concrete, it will rot the wood, it is set on a post anchor set and leveled into the top of the concrete. Concrete touches metal not wood, it is best to put some Ice and Snow wrap on the bottom of the post so the wood doesn't touch the steel.

 

Dig the post hole.

 

Set the tube and level it horizontal and vertical.

 

Find the level of all tubes, mark and cut them off with a kill Saw

 

Reset them and shovel crushed stone into the bottom. 4"'s and tamp down hard.

 

Check level and plumb

 

Pour concrete to top of tube

 

Crown top slightly to let water drain away

 

Set in anchors and plumb and level

 

Install posts and secure with proper deck screws for the type of wood

 

I've done many hundreds if not more, now I watch it being done and only use my finger to supervise.

I agree with this. I cringe when I see wood set in concrete and buried. PT or not it's going to rot away. Sure the sonotube and the portion of the post in the concrete aren't going anywhere, but you've made a weak spot right at the ground.

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Ensure the concrete anchors are about 4" above finished grade which will make your wood posts above finished grade. Water & snow against your wood is a sure way to have the wood rot over a short period of time.

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Go google " Pylex adjustable foundation screw". Rona and Home Hardware carry them in a variety of lengths and capacity. I used them to hold up my Pergola, so far 2 winters and no movement.

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Sono tubes are meant for vertical bearing. That means they are designed to be put in plumb, and carry weight straight down. For lateral strenth, which is what a post is, you don't want to use a sono tube. Same thing as a fence, no sono tubes.

 

A sono tube will carry a lot of weight, but a post in a sono tube can easily be rocked side to side, and will eventually fall over if its not tied into something solid.

 

For your purpose, no sono tubes, 8" holes (assuming 6x6 posts), and fill with concrete. Dig the holes 4 ft, trust me on this. I've seen 3 ft deep holes push a post out a foot! Done deal.

 

S.

Edited by Sinker

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it helps to flare the bottom of the hole a bit to stop the frost heave... I have heavy clay at my place and everything heaves that isn't 4 feet down..

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