Concrete for deck post depth

[fireman32]

Replacing the deck on my house. It will be 8x16. The one I just tore down lasted 14 years before it rotted. Height will be 3 feet to the floor. I’m wanting to rebuild this one to last. My plan is to pour concrete for the 4x4 posts with a bracket installed to hold each post. How deep should I pour the concrete for each post. Or is setting the post in concrete with gravel at the bottom a better option? Main goal is to delay rot as long as possible. Decking will be trex. Also I’m in S. Ga so ground freeze isn’t a concern.
Also figuring to use 8 inch forms.

 

[paulito]

I'm not a builder so can't advise you on what you Should do or need to do per any code. The deck i had build on my house tho has 6x6 posts and most i've seen these days have them as well. You may want to consider upgrading your 4x4 to 6x6 which should make it last that much long. Shouldn't be that much in a cost difference.

For my posts they did a 2 foot square footer and i believe they are at least 18 inches deep of concrete. They also did the bracket with the 6x6 sitting on top not "in the concrete". Putting the post in the concrete actually makes it rot out faster I believe as it promotes extended water to wood contact.

Hope this helps a bit.

 

[WayneB]

footing and post mounted on top with bracket.
footing should be wider rather than deeper for bearing the weight, but also needs to be deep enough not to slide or shift.

 

[Duff]

18'x18'x1' should be more than enough Farman. Post on top of concrete with bracket. Keep the dirt off the post. Today's treated wood isn't what it used to be.

 

[ol bob]

Build the deck out of Locus, it will out last you.

 

[DannyW]

For my posts they did a 2 foot square footer and i believe they are at least 18 inches deep of concrete. They also did the bracket with the 6x6 sitting on top not "in the concrete". Putting the post in the concrete actually makes it rot out faster I believe as it promotes extended water to wood contact.

This^^^^.

Whoever built my house put the 6x6 directly into the concrete. After 28 years, I see a little rot where the wood meets the concrete. Nothing concerning now, and probably none for the next 60-80 years.

But when it comes time to sell, I'm sure some inspector is going to report to the buyer that it's a dire situation.

 

[Crakajak]

Not sure where you live at,but codes for footings will vari from the north to the south end of Ga because of types of soil.
I would call some local contractors to see what is required.
Some counties require a permit ,even for a deck replacement.

 

[Mike 65]

If you put the post in the concrete make sure you use ground contact.

 

[hopper]

What is the benefit of putting post on footer vs post in concrete. I've always dug a hole 18" to 24" twice the size of the post, concrete and domed the top for a deck. I have only built 4 in my days for myself definitely not a builder but haven't had any problems.

 

[fireman32]

What is the benefit of putting post on footer vs post in concrete. I've always dug a hole 18" to 24" twice the size of the post, concrete and domed the top for a deck. I have only built 4 in my days for myself definitely not a builder but haven't had any problems.

Post in concrete tends to hold moisture unless the post is sealed, post on top stays dry.
The deck I tore down had 3 posts rotten below ground, and carpenter bees had done a number on several posts and joists. The post were not in concrete, just dug a hole and tamped them. It was considerably smaller than the one I’m fixing to build.

 

[paulito]

I checked mine last night and they are 18 x 18 not 2 foot but big none the less.

 

[westcobbdog]

Replacing the deck on my house. It will be 8x16. The one I just tore down lasted 14 years before it rotted. Height will be 3 feet to the floor. I’m wanting to rebuild this one to last. My plan is to pour concrete for the 4x4 posts with a bracket installed to hold each post. How deep should I pour the concrete for each post. Or is setting the post in concrete with gravel at the bottom a better option? Main goal is to delay rot as long as possible. Decking will be trex. Also I’m in S. Ga so ground freeze isn’t a concern.
Also figuring to use 8 inch forms.

4x4 is not what I would use, go with 6x6. Can't tell you how many shaky 4x4 supported decks I see. Be sure and properly flash and use hangers too.

 

[notnksnemor]

Use sauna tube to pour the concrete in and mount the post bracket on top with "J" bolts.

 

[Crakajak]

I would also recommend joist tape over the joist.
Have had a lot of people wanting the deck boards replaced because of age only to find the joist had rotted on the top 1/2-3/4" because of debris build up between the floor boards.

 

[Ugahunter2013]

I always set my posts 2ft or 2 1/2 ft down with concrete, but I am also not a builder.

 

[fireman32]

I would also recommend joist tape over the joist.
Have had a lot of people wanting the deck boards replaced because of age only to find the joist had rotted on the top 1/2-3/4" because of debris build up between the floor boards.

I’m either going to use joist tape, or paint all the joists with tar because of that very issue. That and the carpenter bees.

 

[Crakajak]

I’m either going to use joist tape, or paint all the joists with tar because of that very issue. That and the carpenter bees.

If you paint, cut the framing members,dry fit,then paint the ends of the joist.

 

[Spotlite]

We used to build decks. We used a 12 inch auger and went down 48 inches. Poured a concrete footer in 12 inches deep. Set the post on the footer and tamped dirt in. Post was 36” in the ground. We never had any issues. My parents was built in 1991 and it’s still in place.

Overkill but how many times do folks grill out and have twenty extra people hanging out on the porch?

 

[Crakajak]

We used to build decks. We used a 12 inch auger and went down 48 inches. Poured a concrete footer in 12 inches deep. Set the post on the footer and tamped dirt in. Post was 36” in the ground. We never had any issues. My parents was built in 1991 and it’s still in place.

Overkill but how many times do folks grill out and have twenty extra people hanging out on the porch?

10 -12 big adults and you can have close to 3000 lb load.
Lots of decks were failing because of attachment to the house in the 1990,s early 2000,s
Codes were changed to thru bolts and not lagged into the home rim joist because of deck failures.unwanted?
Better to be safe than a lawsuit.

 

[westcobbdog]

10 -12 big adults and you can have close to 3000 lb load.
Lots of decks were failing because of attachment to the house in the 1990,s early 2000,s
Codes were changed to thru bolts and not lagged into the home rim joist because of deck failures.unwanted?
Better to be safe than a lawsuit.

Some years back in W Cobb on a large new construction home for sale multiple groups of buyers happened to meet on the back deck touring a home, they all took about a 20 ft plus ride to the ground together when the poorly built deck failed.