Post bases, what's your preference?

[BK777]

I'm working on a lean to shed project. Posts/anchors will be placed in new concrete (on a gravel pad) that I would likely be pouring. I was leaning towards one of the StrongTie cast in place options like the ones below.

But there are also J bolts and L bolts which would then be attached to a base. Considering I am not a concrete pouring expert, which is harder to screw up? I've heard the bolts are out of fashion with a lot of people, due to failure rates and/or poor installation (example here).

What do you guys usually use?

 

[theoldwizard1]

Depending on the size of your shed and the wind loads in your area, that is total overkill !

Start by removing the sod. You want to be about 4"-6" below grade. Fill with gravel (not pea gravel or river rock) and tamp down. Use concrete "deck blocks". You may want to set them on top of solid concrete 4" "cap" blocks. The important thing is to get the floor a good 4" above grade so that light and air can get underneath (critter won't nest there if the is light and air flow).

Check with your local zoning. This won't pass code in some areas.

 

[BK777]

Shed will be about 12x20. I attached a drawing. There is no floor. It's more of a carport/storage area than a walled shed. But I planned to dig holes for the posts and set in concrete to avoid frost heave and account for wind load.

This will sit on a bit of a rise facing down hill on the windward side of the building and it does get pretty windy here. But I thought what I described was standard practice. I'm not sure what you mean by not passing code because it's overbuilt. I didn't know that was a thing.

 

[tarmy]

I use the upper one you posted OP. We are in earthquake country so uplift is an issue. That and I tend to overbuild the **** outa things.

That base will keep the wood off the ground and make sure you slope the conc away and you should be good...

 

[nadogail]

Your local codes will apply and may vary according to your local jurisdiction.

 

[BK777]

Tarmy, any tips on setting it? Did you place it first & then pour the concrete? Or the other way around? Any suggestions on minimizing voids in the concrete & things like that? The Simpson instructions are pretty vague.

 

[joey1320]

.

What do you guys usually use?

I used this style when I built my deck. I poured the concrete footers/piers and placed them on. All you have to do is wiggle them about so that the wet concrete shapes around the legs. Super easy to use.

Annnnndddd just cause I said wiggle...
<iframe width="560" height="315" src="https://www.youtube.com/embed/34r4-yzCyVw" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

 

[Bretny]

Are you going to put bracing or any type of sheer brace on the posts to keep them vertical? These post bases arnt really designed for that if I remember right.

Considering your only doing 4 posts in a line and a specific distance off the current building theres really not alot to screw up. Run some string lines or even better would be a lazer level with 90* line.

 

[theoldwizard1]

It's more of a carport/storage area than a walled shed. But I planned to dig holes for the posts and set in concrete to avoid frost heave and account for wind load.

That is just an open lean-to so you have no wind load. You are over thinking it. Dig the holes below the frost line, set the posts and back fill with gravel. Tamp it down.

 

[joey1320]

That is just an open lean-to so you have no wind load. You are over thinking it. Dig the holes below the frost line, set the posts and back fill with gravel. Tamp it down.

I'm doing this for the 8' x 12' lean to I'm building next to my shed, but I'm adding a 60lbs bag of concrete to each just because.

 

[BK777]

Are you going to put bracing or any type of sheer brace on the posts to keep them vertical? These post bases arnt really designed for that if I remember right.

Yes I plan to put wood braces on the corners at least. Also not fully drawn is the decking and composite roof I plan to add. That should increase the stiffness against shear.

 

[BK777]

That is just an open lean-to so you have no wind load. You are over thinking it. Dig the holes below the frost line, set the posts and back fill with gravel. Tamp it down.

I won't deny that I'm overthinking it, that's what I tend to do. But I'm not sure how you can say there will be no wind load. My battered Costco carports beg to differ. I'm thinking of the upward load when the wind that whips through here catches the roof like a sail (or just creates lift).

Setting the posts in gravel would mean it's only the weight of the shed keeping it from lifting (and I suppose the friction of the gravel). My rough calculations estimate about 15psf dead load with a composition roof. I don't know if I'd trust that against a 60mph wind over a 200sq ft surface area - although I haven't attempted that math yet.

 

[tarmy]

Tarmy, any tips on setting it? Did you place it first & then pour the concrete? Or the other way around? Any suggestions on minimizing voids in the concrete & things like that? The Simpson instructions are pretty vague.

I dig a hole big enough to hold 150-200 lbs. min of conc. More in your case. I put a layer of 3/4-1” stone/gravel in bottom of hole. Cut enough chunks of rebar to place in the hole vertically around the sides...several inches from the edge. I weld or wire tie 1 1/2” piece of rebar in that center bottom hole in the Simpson piece. Drop the mixed conc in enough to start making sure the rebar is properly situated...keep filling hole to the approx point of where that lower strap sits...rodding/tamping the conc to settle it properly. Set the Simpson w/ rebar attached in the middle...keep filling hole until desired height...crown the top of conc. Away from bottom of that plate. Double check plumb and location to make sure it is where it needs to be.

 

[Firebrick43]

That is just an open lean-to so you have no wind load. You are over thinking it. Dig the holes below the frost line, set the posts and back fill with gravel. Tamp it down.

Lean to and open pavilions are actually the worst for wind load. They have no walls to add strength (shear diaphragm) and the wind gets under neath them causing serious up lift issues.

To the OP, the post bases you have listed have no place in a post taking shear and uplift loads.

You need a post base like these

https://permacolumn.com/products/sturdi-wall-brackets.html

https://www.amazon.com/Sturdi-Wall-Plus-Bracket-Post-SWP66/dp/B07VFPY698?th=1

Dig a 4' hole and insert a sonotube. fill with concrete and set the bracket.

You can also buy precast post base from a permacolumn dealer and if available I would do it as the concrete is cured correctly(probably submerged) and is 10K strength.

Make sure you use the uplift anchors.

 

[nadogail]

IMHO; Find out what your local authority having jurisdiction requires, then use that as that as the minimum. Exceeding the minimum, when feasible is generally considered "Good Practice".

 

[Git]

OP - Your building basically what would be called an ' Attached Patio Cover' in my area. A lot of jurisdictions have pdf file on line that lay everything out for you. Here is an example, just google around cities in your ares

Note - they even spec the column base "USE SIMPSON CBSQ, PBS OR EQUAL W/BOLTS/ SCREWS/NAILS PER MFG"

I have used the Simpson PBS which looks like the first one in your first post
https://www.homedepot.com/p/Simpson...t-Base-for-6x6-Nominal-Lumber-PBS66/202092496

They also have footer details

https://temeculaca.gov/DocumentCenter/View/258/CD21-Attached-Residential-Patio-Cover-PDF

 

[Hank11]

Unless you have regulations to meet, just put your 6x6s in post holes about 30-36" deep with a bag of concrete mix per post. I'd line them all up, brace them well and then pour the holes full. Buy good quality ground contact posts.

Come back in a couple of days and build the roof section. Through-bolt 2x10s to the outside of each post at a height that allows you to put your joists on top and extending out your desired overhang. Use proper ties to fasten the joists and joist hangers to attach to the ledger you bolt to the building. Deck, roof and done. A gutter might be nice.

 

[BK777]

Thanks for the advice everyone. I did find some local code info but not nearly as detailed as the one above. But I was also thinking the PBS looked good. It has some extra support for uplift too. Firebrick43's suggestions made me think maybe I don't overbuild as much as I thought. That is some hefty hardware! I may consider that stuff if I get around to building an even bigger shed in the future.

I feel pretty good about the design and have done this once before (with previously installed bases on a concrete slab). I mainly wanted advice on the actual setting of the base in wet concrete. Tarmy's response was helpful in that regard. Not a whole lot of YouTube videos on that but I can certainly see how it would be easy to do incorrectly. In fact I've seen it suggested that it is better to just pour concrete & after it cures, hammerdrill some holes for a retrofit which leaves less room for error.

As for setting posts directly in concrete, we have enough broken fenceposts out here and a large deck (built before I bought the place) that may soon need some major repair due to weak or rotting posts. I'd prefer to avoid more of that in the future (though yes I realize there's a right and a wrong way to set posts directly like that).

 

[joey1320]

OP - Your building basically what would be called an ' Attached Patio Cover' in my area. A lot of jurisdictions have pdf file on line that lay everything out for you. Here is an example, just google around cities in your ares

Note - they even spec the column base "USE SIMPSON CBSQ, PBS OR EQUAL W/BOLTS/ SCREWS/NAILS PER MFG"

I have used the Simpson PBS which looks like the first one in your first post
https://www.homedepot.com/p/Simpson...t-Base-for-6x6-Nominal-Lumber-PBS66/202092496

They also have footer details

https://temeculaca.gov/DocumentCenter/View/258/CD21-Attached-Residential-Patio-Cover-PDF

I wish my city had that type of information.